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Home My WebLink About2009-283B -- ---- -- --- ----- ---- ------ o � l �t� ;��s 10 GGcz2a E , 0 � FLORIDA INLAND NAVIGATION DISTRICTe \,,`��\ /{l C AND Z of INDIAN RIVER COUNTY LEASE AGREEMENT C (OPY This LEASE AGREEMENT ( " LEASE ") is made and entered into this day of 2009 , between "the Parties " , the Florida Inland Navigation DISTRICT , an independent special district existing under the laws of the State of Florida (the " DISTRICT' ) , and INDIAN RIVER COUNTY , a political subdivision of the State of Florida , (the " COUNTY ") . WITNESSETH : WHEREAS , DISTRICT is the owner in fee simple of a parcel of land in Indian River County , Florida , designated as Dredged Material Management Area IR- 14B which will be used by DISTRICT and the United States for the improvement and maintenance of the Intracoastal Waterway from Jacksonville to Miami , Florida , and the DISTRICT holds title subject to a future easement that will be granted by it to the United States of America for such use ; and WHEREAS , the DISTRICT and the COUNTY desire to provide benefits to the citizens of the COUNTY and others by providing passive recreational opportunities ; and WHEREAS , COUNTY desires to lease from DISTRICT a portion of Dredged Material Management Area IR - 1413 , a description of which is attached hereto as Exhibit "A " and made a part hereof, for passive recreation purposes subject to said rights of DISTRICT and the future rights and easement of the United States of America and . to the terms and conditions of this LEASE ; and WHEREAS , DISTRICT desires to collaborate with the COUNTY in the proper use and management of DISTRICT ' s property ; and WHEREAS , DISTRICT is of the opinion that such use by the COUNTY pursuant to the provisions of this LEASE is in the public interest ; and WHEREAS , DISTRICT is agreeable that this LEASE should be executed for a limited x r terry 1t a nommal, rental:tsubject to the terms and conditions stated herein . NOW THEREFORE , in consideration of the promises and mutual covenants and agreements contained herein , the receipt and sufficiency of which is hereby acknowledged , it is agreed by the parties hereto : 1 . RECITALS : The recitals contained herein above are true and correct and incorporated herein by reference . 2 . LEASE : DISTRICT hereby leases to the COUNTY the property hereinafter known as the " Leased Premises " as described in paragraph 4 below , subject to the terms and conditions set forth herein . 3 . PROJECT MANAGEMENT : The Project Manager for the DISTRICT is its Executive Director and all correspondence and communications from the COUNTY shall be directed to him /her . The Project Manager shall be responsible for overall coordination and oversight on behalf of DISTRICT related to the performance of this lease . 4 . DESCRIPTION OF THE PREMISES : The Leased Premises is situated in Indian River County , State of Florida , as described in Exhibit "A " , attached hereto and made a part of this LEASE . In general the Leased Premises is a strip of land consisting only of an existing dike system around a wetland mangrove area on District property known as IR - 148 . 5 . EXISTING CONDITIONS : The COUNTY agrees to accept the Leased Premises in " as is " condition subject to any existing easements and deed restrictions that may be placed on the Leased Premises by the DISTRICT or others with DISTRICT approval . 2 6 . TERM : The term of this LEASE shall be for an initial thirty ( 30 ) year period with one ( 1 ) option to renew for a twenty-five ( 25 ) year extension . Rent shall be one ( 1 ) dollar per year and shall be paid in advance . Prepayment of the rent shall not affect in any way the DISTRICT ' s rights under paragraph 24 below . The initial period shall commence on the date of execution , and continue for a period of thirty ( 30 ) years . A second term of twenty-five (25 ) years shall automatically commence absent written notice of termination by the DISTRICT or the COUNTY at least ninety ( 90 ) days prior to the end of the initial term . 7 . PURPOSE : COUNTY shall manage the Leased Premises solely to provide a pathway or trail for passive public outdoor recreation . 8 . QUIET ENJOYMENT AND RIGHT OF USE : COUNTY shall have the right of ingress and egress to , from , and upon the Leased Premises for all purposes consistent with paragraph 7 above that do not conflict with the DISTRICT ' s and the United States of America ' s Dredge Material Management Program . 9 . UNAUTHORIZED USE : COUNTY shall , through its agents and employees , make every reasonable effort to prevent the unauthorized use of the Leased Premises or any use thereof not in conformance with this LEASE . 10 . ASSIGNMENT : This LEASE shall not be assigned , except as noted in Paragraph 13 , in whole or in part without the prior written consent of DISTRICT . Any assignment made either in whole or in part without the prior written consent of DISTRICT shall be void and without legal effect . 11 . PLANS : The terms of this LEASE shall guide the passive recreational use and the associated management of the Leased Premises in accordance with the schedule and methodology stipulated below . A . DEVELOPMENT PLAN : The COUNTY will develop a passive recreational 3 pathway or trail plan for the Leased Premises . This plan will be reviewed and approved by the DISTRICT prior to the solicitation for contractors for the preparation of the COUNTY passive recreational pathway or trail for passive public recreational use . B . COUNTY PLAN FOR PASSIVE RECREATIONAL PATHWAY OR TRAIL : COUNTY shall develop and implement , subject to approval by the DISTRICT , an Operational Management Plan ( OMP ) for the property . The OMP shall provide general background data on the property , contain information on the properties resources , set forth general and specific management goals , objectives and guidelines and outline the specific procedures , funding requirements , staffing levels and management practices necessary for their accomplishment . The OMP shall be submitted by the COUNTY to the DISTRICT at the same time as the development plan is submitted . The OMP shall be submitted for approval to the DISTRICT' S Board of Commissioners . In the event the parties are not able to come to agreement on the OMP within one hundred eighty ( 180 ) days of submittal , this shall be sufficient cause for either party to terminate the LEASE pursuant to Paragraph 26 below . The Leased Premises shall not be developed or physically altered in any way without the prior written approval of DISTRICT until the OMP is approved . The COUNTY shall not proceed with development of said Leased Premises until the OMP required herein has been submitted and approved by DISTRICT' S Board . After the COUNTY pathway has been constructed , the COUNTY and the DISTRICT will meet at least once annually to review and discuss the management activities authorized by this OMP and to agree to any changes in the OMP and/or additional rules and regulations governing public use of the lands covered by the OMP 4 that may be deemed appropriate . The COUNTY shall prepare and submit for discussion at the annual meeting a_yearly summary report to include : 1 . COUNTY ' S management program and activities on the property . 2 . Status of visitor use . 3 . Review of special problems and concerns encountered over the previous year . The approved OMP shall provide the basic guidance for all management activities and shall be reviewed jointly by DISTRICT and COUNTY during the annual meeting and updated as necessary . The COUNTY shall not use or alter the Leased Premises except as provided for in the approved OMP without the prior written approval of DISTRICT . C . DISTRICT SITE MANAGEMENT PLAN : The DISTRICT and the U . S . Army Corps of Engineers will utilize and operate the site during Intracoastal waterway dredging operations. in accordance with Exhibit " B " which may be amended from time to time without prior notice to COUNTY . 12 . EASEMENTS : This LEASE is for the purposes specified herein , and easements of any nature are prohibited without the prior written approval of DISTRICT . Any easement not approved in writing by DISTRICT shall be void and without legal effect . 13 . SUBLEASES : This LEASE is solely for the purposes specified herein , and subleases of any nature are prohibited without the prior written approval of DISTRICT . Any sublease not approved in writing by DISTRICT shall be void and without legal effect . However , the DISTRICT acknowledges that the COUNTY intends to enter into an agreement with the 5 Indian River Land Trust to develop and manage the Leased Premises . This sub - lease and any other approved sub - leases shall contain this LEASE as an at and the sub - lease shall require that the sub - lessee abide by all conditions of this LEASE . 14 . RIGHT OF INSPECTION : DISTRICT or its duly authorized agents , representatives or employees shall have the right at any and all times to inspect the Leased Premises and the works and operations of COUNTY in any matter pertaining to this LEASE . 15 . PLACEMENT AND REMOVAL OF IMPROVEMENTS : All structures , improvements , and signs , if any , associated with the Leased Premises shall be constructed at the expense of COUNTY and /or DISTRICT in accordance with the park development plan and the OMP approved by the DISTRICT . Further , no trees , other than non - native species , shall be removed or major land alterations done without the prior written approval of DISTRICT . No permanent equipment or non - removable improvements shall be placed on the Leased Premises by COUNTY ; provided , however , the DISTRICT and the COUNTY agree to cooperate with regard to and coordinate the placement of park benches , regulatory signage , and other similar types of objects that are typically associated with passive recreational uses within the Leased Premises ; provided , further , however , that the DISTRICT ' s determination relative to such placement shall be conclusive and final . Removable equipment and removable improvements placed on the Leased Premises by COUNTY which do not become a permanent part of the Leased Premises will remain the property of COUNTY and may be removed by COUNTY upon termination of this LEASE , pursuant to Paragraph 27 below . 16 . INDEMNITY BY COUNTY : To the extent and limits permitted by Florida law , COUNTY hereby covenants and agrees to investigate all claims of every nature at its own expense , and to indemnify , protect , defend , and hold and save harmless the DISTRICT from 6 any and all claims, bodily injury , personal injury , property injury , actions , lawsuits and demands of any kind or nature arising out of any action taken by the County or its sub - lessee as related to this Lease or the COUNTY ' s use of the Leased Premises . Nothing contained herein shall be construed as a waiver of sovereign immunity enjoyed by the parties hereto , as provided in Section 768 . 28 , Florida Statutes , as amended , or any other law providing limitations on claims . Further , nothing herein shall . be construed as a waiver of the limitations on liability enjoyed - by a landowner providing land to the public for outdoor recreational purposes , provided in Section 375 . 251 , Florida Statutes . 17 . INSURANCE : A . The COUNTY shall procure and maintain , throughout the term ( including any extended term ) of this LEASE , Worker' s Compensation insurance as may be required by Florida law . The COUNTY shall provide an insurance certificate demonstrating such coverage prior to the commencement of this LEASE . The Worker' s Compensation insurance policy required by this LEASE shall also include Employer' s Liability . The COUNTY shall require all COUNTY contractors working on the Leased Premises to procure and maintain Worker' s Compensation insurance . B . The COUNTY shall procure and maintain , through the term of this LEASE , comprehensive general liability insurance or be self- insured under Florida law (the " policy") . This policy shall provide coverage for death , personal injury , or property damage that could arise directly from the performance of this LEASE . The policy shall have minimum limits of $ 1 , 000 , 000 . 00 per occurrence , combined single limit for bodily injury liability and property damage liability . This minimum limit may need to be reviewed and increased during the life of this lease . This shall include the following endorsements : i . premises and operations , ii . independent contractors ' ; products and completed operations ; and iv , contractual liability C . The COUNTY shall provide insurance certificates as proof of insurance prior to the commencement of performance . All such insurance shall name the DISTRICT ( and the United States of America once the DISTRICT has conveyed an easement to the United States of America ) as an additional named insured , and be written by a financially sound company authorized to do business in the State of Florida . The policy shall contain a provision requiring the certificates to shall be countersigned by a registered Florida insurance agency or broker . The insurance policy shall contain a provision that the insurer shall notify the DISTRICT at least thirty ( 30 ) Days prior to cancellation or modification of any insurance policy required by this LEASE . 18 . PAYMENT OF TAXES AND ASSESSMENTS : COUNTY shall assume full responsibility for and shall pay all taxation liabilities that accrue to the Leased Premises and/or to the improvements thereon , including any and all ad - valorem taxes and drainage and special assessments or taxes of every kind which may be hereafter lawfully assessed and levied against the Leased Premises . 19 . NO WAIVER OF BREACH : The failure of DISTRICT to insist in any or more instances upon strict performance of any one ( 1 ) or more of the covenants , terms and conditions of this LEASE shall not be construed as a waiver of such covenants , terms or conditions , but the same shall continue in full force and effect , and no waiver of DISTRICT of any of the provisions hereof shall in any event be deemed to have been made unless the 8 waiver is set forth in writing and signed by DISTRICT . 20 . NON - DISCRIMINATION : COUNTY shall assure and certify that it will comply with Title IV of the Civil Rights ACT of 1964 ( PL 88 - 352 ) as amended and , in accordance with that Act , shall not discriminate against any individual ' s race , color , creed , sex , national origin , age , handicap , or marital status with respect to any activity occurring within the Leased Premises or upon lands adjacent to and used as an adjunct of the Leased Premises , 21 . UTILITY FEES : COUNTY shall be responsible for payment of all charges for the furnishing of gas , electric , water and other public utilities to the Leased Premises and for having the utilities turned off when the Leased Premises are surrendered . 22 . COMPLIANCE WITH LAWS : COUNTY agrees that this LEASE is contingent upon and subject to COUNTY obtaining all applicable permits and complying with all applicable permits , regulations , ordinances , rules , and laws of the State of Florida or the United States of America or of any political subdivision or agency with jurisdiction over the Leased Premises . 23 , NOTICE : All notices given under this LEASE shall be in writing and shall � be served by certified mail to the last address of the party to whom notice is to be given , as designated by such party in writing . DISTRICT and COUNTY hereby designate their address as follows : TO DISTRICT : Florida Inland Navigation District 1314 Marcinski Road Jupiter , Florida 33477 Attn : Executive Director TO CO !eNTY : Indian River County, Government 1801 27th St . Vero Beach , FL 32960 Attn : Environmental Lands Director Facsimile transmittals shall not be an acceptable means of providing notice . 9 24 . BREACH OF COVENANTS TERMS OR CONDITIONS : Should COUNTY breach any of the covenants , terms , or conditions of this LEASE , DISTRICT shall give written notice to COUNTY to remedy such breach within thirty ( 30 ) days of such notice . In the event COUNTY fails to remedy the breach to the satisfaction of DISTRICT within thirty ( 30 ) days of receipt of written notice , DISTRICT may either terminate this LEASE and recover from the COUNTY all damages DISTRICT may incur by reason of the breach including , but not limited to , the cost of recovering the Leased Premises and attorney ' s fees ; or maintain this LEASE in full force and effect and exercise all rights and remedies herein conferred upon DISTRICT . 25 . DAMAGE TO THE PREMISES : COUNTY agrees that it will not do , or cause to be done , in , on , or upon the Leased Premises or as affecting said Leased Premises , any act which may result in damage or deprecation of value to the Leased Premises , or any part thereof. 26 . HAZARDOUS MATERIALS : COUNTY agrees that , during the term of this LEASE , it : A . Shall keep or cause the Leased Premises to be kept free of hazardous wastes or substances except those permitted to be utilized in the normal operation of a passive recreational pathway or trail which substances shall be used only as permitted by law . In no event shall the COUNTY store or mix any such substances on the Leased Premises . B . Shall not cause or permit , as a result of any intentional or unintentional act or omission on the part of COUNTY or any assignees , a release of hazardous wastes or substances onto the Leased Premises . C . Shall comply with and ensure compliance by its employees and all others under its direction with all applicable Federal , State , and local laws , ordinance , rules , and regulations . " , " hazardous substance " , " disposal " , " release " , and D . The terms " hazardous waste 10 ( 30 ) days following the termination of the lease , remove the same . Upon final termination , the Leased Premises must be left in essentially the same condition as when first leased to the COUNTY , save for ordinary wear and tear , unless otherwise approved in writing by the DISTRICT . 28 . BEST MANAGEMENT PRACTICES : COUNTY shall implement applicable Best Management Practices for all activities conducted under this LEASE in compliance with Rule 18 -20 . 004 , Florida Administrative Code , which have been selected , developed , or approved by DISTRICT or other land managing agencies for the protection and enhancement of the Leased Premises . 29 . PROHIBITIONS AGAINST LIENS OR OTHER ENCUMBRANCES : Fee title to the Leased Premises is held by DISTRICT . COUNTY shall not do or permit anything to be done which purports to create a lien or encumbrance of any nature against the Leased Premises including , but not limited to , mortgages or construction liens against the Leased Premises or against any interest of DISTRICT therein . 30 . PARTIAL INVALIDITY : If any term , covenant , condition , or provision of this LEASE shall be ruled by a court of competent jurisdiction to be invalid , void , or unenforceable , the remainder of the provisions shall remain in full force and effect and shall in no way be affected , impaired or invalidated . 31 . DUPLICATE ORIGINALS : This LEASE is executed in duplicate originals , each of which shall be considered an original for all purposes . 32 . ENTIRE UNDERSTANDING : This LEASE sets forth the entire understanding between the Parties and shall only be amended with the prior written approval of the Parties . 33 . MAINTENANCE OF IMPROVEMENTS : COUNTY shall maintain the Leased Premises and the improvements , if any , located thereon in a state of good condition , working 12 order and repair including , but not limited to , keeping the Leased Premises free of trash or litter , meeting all building and safety codes in the location situated , and maintaining the Leased Premises in accordance with the approved development plan and the OMP . As may be mutually agreed to by the Parties , any removal , closure , etc . , of the above improvements , if any , shall be acceptable when the proposed activity is consistent with sound goals of conservation , protection , and enhancement of the natural and historical resources within the Leased Premises and with the approved OMP . Maintenance of any and all existing dredge material management structures is reserved to the DISTRICT . 34 . GOVERNING LAW : This LEASE shall be governed by and interpreted according to the laws of the State of Florida . 35 . SECTION CAPTIONS : Articles , subsection and other captioned contained in this LEASE are for reference purposes only and are in no way intended to describe , interpret , define or limit the scope or extent of intent of this LEASE or any provisions thereof. 36 . SPECIAL CONDITIONS : The following special conditions shall apply to this LEASE : A . COUNTY shall ensure that the area is identified as being publicly owned and operated as a public outdoor recreational facility in all signs , literature , and advertising . COUNTY shall erect signs identifying the Leased Premises as being open to the public , as a DISTRICT assisted project and as a DISTRICT property which will be used from time to time as a dredged material management area . All such signs are s . bjoc+ + o the L� lDistrict appy^ iia ' which shall not be unreasonably withheld ; and B . The COUNTY agrees to install and maintain all required entrance and informational signage for its management activities ; and 13 C . The COUNTY shall not in any way restrict access of the DISTRICT and/ or the United States of America to the property as needed during periodic use of the dredge_ material management area , as both parties recognize that such use is to be the paramount use of the Leased Premises . D . The COUNTY shall comply with any public access restrictions required by the DISTRICT and/or the United States of America during the periodic use of the property for dredge material management . 37 . VENUE/ATTORNEY' S FEES : In the event of any litigation arising out of or resulting from this LEASE , the venue of such litigation shall be had only in the State courts in Palm Beach County , Florida . The prevailing party in such litigation shall be entitled to its costs and reasonable attorney ' s fees ( at trial , appellate , and post-judgment proceeding levels ) . IN WITNESS WHEREOF , the parties have caused this LEASE to be executed on the day and year first written above . COUNTY : INDIAN RIVER COUNTY ATTEST : J . K . BARTON , Clerk of Court Ci j 1 Clerk ( Deputy ) Chairman ; Wesley S . Da is for : J . K . BARTON CLERK CIRCUIT COURT BCC approved : - ,A.1 '/-3 0 9 APPROVED AS TO FORM AND LEGAL SUFFICIENCY , .. , fc.- County Attorney 14 DISTRICT : LEGAL FORM APPROVED FLORIDA INLAND DISTRICT CWUINSEL NAViGA i i0N DIS T RIC T BY : BY : ( SEAL) Chairman ATTEST : Secretary 15 'y IBM Y - . 1 ' 4 � , 1` .aP,�y Y%9$ i �rt • { � � � � A � pro. • 1 � t , IX 0 f t I t ;t x x ( R9 . 3 tl 7 rbsr z 5. ... c . r . ,¢,✓ x� ` a f`r� k+r+ t t a t • .y.F7 f? r 7 tI ll k''ir .- kei ,, (M� RIN PI�Illr `t�.��.s: � a .. � fi °�j1 �yjjy" ° 4 `�' ( yl �f " tllrl { f$ if '�kkrrR i' t "+ll� < �u(. �` ,t•'i 's° 1r yt�. # ti x '*'`ef 'x ' t t � ,s tux t� r iYrr i • t N `� -' a e 4x �' __. __— r5`; • 1�Jt3x 3k' , -ilkz�? � A r'f;,}.1`'� s�E"�•¢ ,j w5 a ° ✓ f ; n 4 � nt�f•v t , { > tS y er htn ir6t `t '00 fill ,� - 3e s a �. 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Ue r � c l ` �` '" 1 � . - � 3'�` � _ : , � . . yrs. � �1'ti Cox Ohs .. �"rzt � d 'i. , • .^+*' k' - ;O1rI kIV 12 KNIGHT McGUIRE & ASSOCIATES INC • INl )T CONkLT!ING ENGINEERS AND PLANNERSI T , Ai til T) "I'l TZ , Attachment ABROYAL8POINE569-16 MRO BEACH, n PHONE: (772) FAX: (771) 569.1455 EIMA1v8@KM6 `M ( ;u4em I. CEAITF9CATOF AU710M9EA0NUMBER - 000003]5 i Exhibit A " text " The existing mosquito impoundment road on the FIND tract will be used for part of the greenway trail system and for establishing a small picnic area on the eastern edge of the property near the shoreline of the Indian River Lagoon . The pervious road leading east from Indian River Blvd . will be available for trail maintenance vehicles by county officials and emergency access vehicles only . Fencing and/or gates will be installed and maintained to prevent public access to the dredge management containment area and private properties to the north . _ - .�.-- 6 i t 1 LEXH B Management Plan IR- 14 Dredged Material Management Area May 1999 Management Plan 11144 Dredged Material Management Area Prepared for FLORIDA INLAND NAVIGATION DISTRICT by R. Bruce Taylor, Ph .D . , P . E. William F . McFetridge Taylor Engineering, Inc . 9000 Cypress Green Drive, Suite 200 Jacksonville, Florida 32256 (904) 731 - 7040 TABLE OF CONTENTS iiiLIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 .0 PRE-DREDGING SITE PREPARATION AND DESIGN FEATURES 1111 . . , . . . . . . . . . 5 2. 1 Site Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. 1 . 1 Containment Basin Capacity and Configuration Requirements . . . . . . . . . . . . . . . 5 2. 1 . 2 Containment Basin Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 .2 Facility Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2. 2. 1 Clearing and Grubbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 11 2. 2. 2 Excavation and Grading . . . . . . . . . . . . . . . . . . 8 . . . . , , . , . . . . . . . . . , . , . . . , , 11 2.3 Additional Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 1 1 , . . . . . . 1 12 2. 3. 1 Inlet . . . 11 , 1 * 1111 , 1100 , 0 0 a 11 1 1 BW8091 . 111 14 , It I DID I I I 1 11 1 1 1 1109 a - 1 . 12 2. 3. 2 Weirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2. 3. 3 Ponding Depth and Basin Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2, 3. 4 Interior Earthworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2, 3. 5 Ramps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2. 3. 6 Perimeter Ditches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2. 3. 7 Dike Erosion and Vegetation 1 1 1 1 . . . . . . . . . . . . . . . . . . . . I , , . 1 4 1 6 . . . . . . , , . 23 2. 3. 8 Site Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.4 Groundwater Monitoring 1 0 0 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2 . 5 Migratory Bird Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1111 . . . , . , 25 2 .6 Cultural Resources . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3 . 0 OPERATIONAL CONSIDERATIONS DURING DREDGING . . . . . . . . . . . . . . . . . . 1 0 0 0 27 3 . 1 Placement of Pipelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3 .2 Inlet Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3. 2. 1 Monitoring Related to Inlet Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3 .3 Weir Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.4 Effluent Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.5 Groundwater Monitoring . . . . . . . . . . . . . . . . . poll ' , , . . . . . , Isla . . . . . . . . . . . , . 34 i 3 . 6 Migratory Bird Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4 . 0 POST-DREDGING SITE MANAGEMENT . . . . . . . . - 1 11 1 11 . . 1 . 1 . . , . , . 36 4 . 1 Dewatering Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 4. 2 Grading the Deposition Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I , . 38 4. 2. 1 Control of Stormwater Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 4. 2. 2 Topographic Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4 .3 Material Rehandling/Reuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I . , . . . . . 39 4.4 Additional Environmental Considerations 1111 . . . . . , 1111 . . . . . . . . . . . . . . . . . . . 40 4. 4. 1 Biological Monitoring . 10 11 . . . of . . . . . . . . . . . . . . . . . . o , . , . . . . . . . . . . . . . . . 40 4. 4. 2 Migratory Bird Protection . . logo 111 11 11 41 4. 4. 3 Groundwater Monitoring . . . , 0 1 0 1 . . . . . . . . . . . . . . . . 1 . . . . . . . . . , . . . . . . . . . 41 4. 4. 4 Mosquito Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4 .5 Site Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 . . . . 1 . . . . . . . . . . 42 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 APPENDIX A ii LIST OF FIGURES Figure 1 . 1 Location of IR- 14 Dredged Material Management Area, Indian River County, Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I . 4 . . . . . . . . . . . . 2 Figure 1 .2 Location of IR- 14 , Within Reach III , Dredged Material Management Plan , Indian River County, Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 2 . 1 Site Plan , IR- 14 Dredged Material Management Area , Indian River County, Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 2 . 2 Land Use and Vegetation of IR- 14 , Dredged Material Management Area, Indian River County, Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 2 . 3 Typical Dike and Ramp Sections, Vegetation Plan , Dredged Material Management Area, Site IR- 14, Indian River County, Florida . . 1 6 1 . 0 . . . . 10 Figure 2 . 4 Grain Size Distribution , ICWW Sediment, Reach III , IR- 14 Dredged Material Management Area, Indian River County, Florida . . . . . . . . . . . . . . . . . . 1 . 1 18 Figure 2 . 5 Zone Settling Velocity of Intracoastal Waterway Sediments ( based on Taylor and McFetridge, 1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 iii 1 .0 INTRODUCTION Site IR- 14 (Figure 1 . 1 ) , one of three sites in Indian River County, Florida , selected for development as dredged material management facilities, will provide long-term capacity for the management of sediments dredged from adjacent segments of the Intracoastal Waterway (ICWW) . The site-specific management plan for the IR- 14 dredged material management facility, outlined in this report, provides guidance for the development and operation of the material management area so that it efficiently processes , temporarily stores, and ultimately transfers material dredged during scheduled channel maintenance operations . To that end , this plan document addresses those facets of site design and operation which directly influence site efficiency or reduce off- site conflicts . These include elements of site preparation and facility construction , techniques ofdecantingand dewateringthe dredged material during and immediately following maintenance operations, and guidelines for post- dredging site operation and maintenance . Throughout, the goal of each phase of site management is to ensure that the site not only achieves its minimum 50-year design service life, but that it also fulfills its potential as a permanent operating facility for the intermediate storage, processing, and transfer of maintenance material dredged from the ICWW . Site IR- 14 was selected as the primary site to serve that portion of the ICWW in Indian River County defined in Taylor et al . ( 1997) as Reach III (Figure 1 .2 ) . Reach III extends from a point near Vero Beach ' s northern boundary , opposite the community of Gifford ( Cut IR-24 , station 28+00, ICWW mile 210 . 19) southward 8 . 27 miles to the Indian River/St , Lucie County line (Cut IR-35 , station 31 + 50, ICWW mile 218 .46) . A comprehensive evaluation of Jacksonville District Corps of Engineers ' archival records confirmed that this segment of the Waterway has not been dredged since its 1959 deepening to the present - 12-11 MLW project depth . Nevertheless, the most recent examination survey ( 1996 ) documented a total in situ reach shoal volume of 57 ,498 cubic yards (cy) within the authorized channel . The projected 50-year storage requirement for Reach III ---- 162 ,658 cy — represents extrapolation of the documented in situ shoaling volume multiplied by a bulking plus over-dredging factor of 2 . 15 . Thus, the IR- 14 containment basin must provide a capacity of about 163 , 000 cy . r Golf • • � . ~G es • S v �# flg.�. L• 1,'fl " a 1 • course LE IQ r • t -•• :tom — 0 . . ` •�.SY%jkb• �"hb �'".e! ' 1 J e .'!Z .• � lion nii r�._•a�yy Y Y Y % � • . . • tf � , � ceE a r� , I ( g � - � l.�.s"rx `� Rk ,4 *5 Ya 'v.�' c . • . • . • • 9, • n,° ' e. • - to tri . �5 C Is` ° ' 9h 1 'sn .° a ' . sr ^ ' f . 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Y - � � �.� � L y R' � _ � F,` a'n < 2"' 1"' w fir. � '$< °=�, � �;�� . ;� .. $v �aL zw" ��,r`s r^" � � ' ;�.;_• � a�g�`t�"�` <5s;� ��€, '�- ~<.., µ *b�• � y[�, a �,yy �( �*� . ,a d nsi � "' ' .A�. ,. t, M � 'V '�L .f Y' � H ,,;¢'�. w l' _ d j 8 . - •J � I 1 I � I I I The absence of a maintenance dredging history for Reach III precluded projecting the frequency of future dredging operations . However, an assumed frequency of once every 5 to 10 years appears reasonable, based on operational considerations such as scheduling and contract procedures, as well as present shoaling patterns . Thus , depending on the interval between successive dredging operations, each maintenance operation in Reach III should produce a bulked material volume between 16 ,300 cy and 32 , 600 cy for placement in Site IR- 14 . Beyond satisfying a minimum capacity requirement, the management objective for the 1R- 14 dredged material management area is to process ( i . e . , decant and dewater) the dredged material efficiently and to operate the facility so as to extend its usefulness beyond the design service life. The design and construction of the containment facility establish the site ' s potential long-term efficiency, while its operating procedures intend to ensure the realization of this potential . Specific elements of site design and operation during and following dredging activities will be discussed in turn as they relate to site efficiency and local impacts . Accordingly, Section 2 . 0 begins the management plan with a discussion of site preparation and design . Section 3 . 0 presents operational considerations during dredging . Section 4 . 0 addresses post- dredging site management. 4 2 .0 PRE-DREDGING SITE PREPARATION AND DESIGN FEATURES 2 . 1 Site Design The present discussion addresses only those aspects of site design which directly influence site construction and operation as they relate to the facility' s long-term objectives . All other design elements (e .g. , construction details, materials , etc . ) derive from specific information not yet available and thus are necessarily deferred to the facility ' s final design phase . 2. 1 . 1 Containment Basin Capacity and Configuration Requirements The containment basin constructed within Site IR- 14 (Figure 2 . 1 ) must satisfy four criteria : ( 1 ) provide sufficient material storage capacity for the projected 50-year material storage requirements of Reach III of the ICWW in Indian River County , (2) provide adequate separation from adjacent properties , (3 ) minimally impact sensitive on - site habitats , most notably the wetlands that comprise most of the site ' s eastern one-half, and (4) minimize the excavation depth required to obtain adequate dike material . First , to repeat, Site IR- 14 is designated as the primary site to serve the maintenance needs of Reach III of the Waterway in Indian River County . Thus, Site IR- 14 must provide adequate capacity for the projected 50-year material storage requirements of Reach III . A comprehensive evaluation of Jacksonville District Corps of Engineers ' archival records confirmed that this segment of the Waterway has not been dredged since its 1959 deepening to the present - 12- ft MLW project depth . Nevertheless, the most recent ( 1996 ) examination survey documented a total in situ reach shoal volume of 57,498 cubic yards (cy) within the authorized channel . The projected 50 -year storage requirement for Reach III — 162 ,658 cy — derives from this documented volume and includes a bulking plus over- dredging factor of 2 . 15 . Thus, the IR44 containment basin must provide a capacity of about 163 ,000 cy . Second , the basin ' s placementon the site must provide adequate separation from adjacent properties . As shown in Figure 2 . 1 , the containment dike ' s outside toe lies 250 ft from the eastern right-of-way of Indian River Boulevard on the site ' s western side, and 100 ft from a proposed wetland mitigation area to the north and 5 O Access Road d I n 00 ell Al ,+ j ; 5 Discharge n Outley, Culvert Weir 1 d /— Existing Graded Road Outlet - _ - Pipeline Inlet o 25 Route of C I - 1 73 i` < ro .�-_._ ......- --- - - ,r 0 NOTES : 1 . Total Site Area : 53 . 39 Ac 4. Weirs : Three 8ft , Diameter CM Half— Pipes GRAPHIC SCALE 2 . Containment Area : With Removable Flash Boards Adjustable o , so 3w Within Outside Toe of Dike : 15 . 54 Ac From + 1 . 8ft NGVD to + 12 . 7ft NGVD . Within Outside Toe of Dike: 10 . 18 Ac Capacity: 178 , 051 cubic yards ( IN FEET ) 3 . Elevation Datum : NGVD of 1929 1 inch = 300 ft. Figure 2 . 1 " C9716 TAYLOR ENGINEERING INC . Site Plan , IR - 14 9OSS CYPRESS GREEN DRIVE Dredged Material Management Area _ JACKSONVILLE . FLORIDA 32226 Indian River County, Florida °"" April , 1999 from a passive- use county park to the south . Although less than the established 350-ft program optimum , these setbacks provide adequate separation , given the intended uses of the adjacent properties . Third , basin construction must minimally impact sensitive on-site habitats , most notably the wetlands that comprise most of the site ' s eastern one-half. As shown in Figure 2 .2 , the containment dike ' s outside toe lies a minimum of 50 ft from the nearest wetland edge along the basin ' s eastern side and at its northeast corner . However, establishing a similar setback was impossible in the central portion of the basin ' s western side where construction will impact up to 0 . 10 acres of disturbed wetland . Classified as a mixed wetland/Brazilian pepper community, this former hammock area now qualifies as predominantly wetland, based on hydric soils and periodic standing water. However, the dominant vegetation does not support this classification as previous clearing has promoted a dense regrowth of Brazilian pepper. Within the disturbed wetland, a formal wetland delineation would likely classify some isolated areas as upland . Avoiding this area and providing an appropriate dike setback would unduly constrain the basin ' s total area. Notably, the extensive mangrove impoundments within the site ' s eastern one- half offer ample opportunity for on- site mitigation . Fourth , because of low upland elevations, the likelihood of a seasonally high water table, and the possibility of a shallow limestone strata in portions of the site, basin construction must minimize the excavation depth necessary to obtain the required dike material . Qualitative information presented in the county soil survey (Wettstein et al . , 1987) provides the only available data describing soil and groundwater conditions on site . Native soils include ( in order of decreasing areal coverage) McKee mucky clay loam , Riomar clay loam , Jupiter fine sand, Chobee loamy fine sand, and Perrine Variant loamy fine sand . Characteristic of mangrove islands and swamps and thus confined to the wetlands within the site ' s eastern one-half, the McKee mucky clay loam and the Riomar clay loam soils avoid all construction impacts. The site ' s western one-half, predominantly upland and including those areas historically planted in citrus, contain the remaining three soil associations . Typical of low, broad flats , depressions , or poorly-defined drainways , all three upland soils are characterized as nearly level and poorly- drained to very poorly-drained . All three soils typically maintain a water table within 10 in . of the soil surface from four to more than six months each year. Because of the poorly-drained conditions, these soils become suitable for citrus production only if a water control system (e . g. , ditching and bedding) maintains the water table at a depth of 4 ft or greater . Relic evidence of such water control methods remains in portions of the former grove areas of Site IR- 14 . Notably, 7 s ntJ`P�`^z��,'i�th1 �A. a '" ate. � y; L { rf "'IY .+�" y v ; •. t / lOr�, '�r1 - � � t t q'- 3.� SL! I ..� � �i S 4�i , �I r 1 - to -10 4 , r .r r I�1 r' k�` tr ., w' a i �•' ,� � % X31 ! , oqllll A . . I �A,`.� le, l C 1• r y f s �� 7�1}*` ��'C}Y` .k• 4 �6" • r \I 1. k� 4V " � / � �� . • __ ��'S6. .i.�i'�4tL!'1ti � • j _ i ) W i i 1 /F t tA Ad to V r .d_®rte r �7. '• 1 1 � IC •. ✓ e {i �, ) t ssl • 1'. . ' . • • • 1 .. I � 1•; .-) � lc be • • • • . � : both the Jupiter fine sand and the Perrine Variant loamy fine sand typically possess a hard , continuous to fractured limestone strata within 12 to 24 in . of the soil surface . If present, a shallow limestone strata could require non- standard excavation methods for containment basin construction , could limit excavation depth, and could dictate obtaining some dike construction material off site . However, inspection of the banks of the large east-west ditch that bisects these soil groups failed to reveal the indicated limestone strata. A detailed subsurface survey will provide more specific geotechnical information before final design and construction of the containment basin . As shown , the basin ' s preliminary design provides the maximum footprint within the bounds set by the two preceding criteria and thus minimizes the excavation depth needed to provide the required dike material . 2. 1 . 2 Containment Basin Design With the optimal basin footprint thus determined , the resulting containment basin design is specified as follows . Within the 15 . 54 -acre containment area, dikes will be constructed to a crest elevation of + 14 . 7 ft NGVD, or 11 . 0 ft above the existing mean site elevation of +3 . 7 ft NGVD (Figure 2 . 3 ) . The dike cross- sectional design , including side slopes of 1V : 3H and a dike crest width of 12 ft, will require 54 ,945 cy of material for construction . Ramps to provide equipment access to the interior of the containment basin for material dewatering and transferwill require an additional 1 , 667 cy of material . Excavating the basin interior to a mean elevation of - 0 . 4 ft NGVD — 4 . 1 ft below the existing mean grade elevation of the basin footprint — will provide material for dike and ramp construction . An interior slope of approximately 0 . 2% will provide drainage from the inlet point to the outlet structures . Thus the excavated grade within the basin will range from +0 .4 ft NGVD at the inlet to - 1 .2 ft NGVD at the weirs . Excavation set back 20 ft from the inside toe of the dikes will maintain the IV : 3H side slope of the dikes . With the containment basin filled to capacity, the surface of the deposition layer will lie a minimum of 4 ft below the dike crest, comprising 2 ft of freeboard and 2 ft of ponding above the maximum deposition surface . The resulting basin capacity — 178 ,051 cy — exceeds the projected 50-year storage requirement for Reach III by 9 . 5 % . 2 .2 Facility Construction Construction of the IR- 14 facility will occur in two phases . The first phase — to be completed as soon as practical following site acquisition — will include clearing and grubbing all vegetation from within 9 BORROW FOR PERIMETER DITCH, DIKE CONSTRUCTION SEE NOTE - 12' 14 + 11,7 ft NM NOTES SIDE SLOPES Jct DIKE HEIGHT 11 .0 fL rIm r D ' 20' Perimeter Itch : 20' Side Slopes 1 V: 2H . .. Bottom Width 1 ft. " � 0 4 Ncw Mean Invert Elev. — 0. 5 ft. NGVD DMNG BADE Slope Bottom as Required for Section A—A' Drainage BORROW FOR PERIMETER DITCH, SIDE SLOPES 3c1 DIKE CONSTRUCTION SEE NOTE t2' J, + 14.7fL NGw RAMP ' . .. .. . .. . . .. ..:c: :. .... •: 12 : ::: •::.-:. .- DIKE Hf]GHT 11 .Qft 20' 20' p DOSTTNG GRADEoil Section B—B' PERIMETER DITCH NATIVE GRASSES PERIMETER SERVICE ROAD BORROW FOR DIKE CONSTRUCTION 20'........ ... ... - . 00STING VEGETATION 100-250 IL BUFFER Dredged Material Management Area — Vegetation Plan SECTIONS NOT TO SCALE pawl TAYLOR ENGINEERING INC. Figure 2 . 3 Typical Dike and Ramp Sections , Vegetation Plan v000 CYPRESS orza=EriSHITE moo JACKSONVILLE. FLORIDARIDA 32256 g Dred ed Material Management Area , Site IR - 14 Indian River County , Florida the planned basin footprint, construction of access roads, and installation of security fencing around the site ' s upland perimeter , The second phase will include containment basin construction and related earthmoving operations and the installation of outlet structures and other design features . This phase, subject to the scheduling and budget priorities of the Jacksonville District Corps of Engineers, may not immediately follow completion of the first phase. However, perimeter fencing and in- place security procedures will secure the site before excavation , grading, and dike construction begin . The remainder of this section discusses each site preparation element in more detail . 2. 2. 1 Clearing and Grubbing The first phase of facility construction begins with clearing and grubbing of site vegetation . Although adding significantly to the initial facility construction cost, the removal of all woody vegetation from the basin interior will promote efficient settling within the basin . The trees and other woody vegetation that dominate the upland areas of Site IR- 14 (Figure 2 .2), if allowed to remain , would constrictor channelize flow through the containment basin . Cutting the trees, but allowing the roots to remain , would preclude the uniform excavation and grading of the basin interior . Either omission would necessarily restrictthe required excavation to the perimeter of the basin interior and thereby result in short-circuiting, reduced retention times, resuspension of sediment through increased flow velocities, and the deterioration of effluent quality . Moreover, a failure to clear existing vegetation will make the periodic removal of the dewatered dredged material more difficult. Therefore, clearing and grubbing the area within the containment basin footprint, as well as the areas of the access and perimeter service roads ( Section 2 . 3 . 5) and the perimeter ditch (Section 2 . 3 . 6) , should take place before construction . 2. 2. 2 Excavation and Grading The second phase of site preparation includes all earthmoving operations required to construct the containment dike and basin to the design geometry . Preliminary site design ( Figure 2 . 1 ) specifies excavating the containment basin interior to obtain the material required for initial dike and ramp construction . Excavating to an average elevation of - 0 .4 ft NGVD, or 4 . 1 ft below the existing mean grade elevation within the basin footprint (+3 . 7 ft NGVD ; Figure 2 . 3 ) will provide the needed 56 ,612 cy . Excavation set back 20 ft from the interior toe of the dike will ensure dike foundation stability . Excavation of the perimeter ditch 11 ( Section 2 . 3 . 6) will produce an additional 7,200 cy of material . Should some material excavated from the basin interior be unsuitable for dike construction, the ditch material can make up the deficit. Alternatively, the material excavated from the ditch can contribute to the dike requirement to reduce the excavation depth in the basin interior. The final excavation depth and distribution of material , determined in the final design phase, will reflect the results of detailed subsurface investigation. The interior of the containment basin must also be graded following excavation . Construction efficiency may initially dictate taking dike material from a perimeter trench inside the containment dike. However, before dredging operations begin, this trench must be eliminated and the site interior regraded to avoid flow channelization and unacceptable effluent quality. if left ungraded , the irregular topography within the basin will produce nonuniform flow and deposition patterns which , in turn, will result in isolated surface water ponding. Ponding will inhibit drying of the deposition layer and make initial attempts at surface trenching more difficult . For these reasons, a uniform grade with an adequate slope (about 0 . 2%) must be provided from inlet to weir as part of initial facility construction . Thus, although the basin interior will maintain a mean excavated grade of 44 ft NGVD, the floor of the basin will slope uniformly downward from approximately +0 .4 ft NGVD near the inlet to approximately - 1 . 2 ft NGVD at the weir. Once dredging operations begin , differential settling of varying grain size fractions ( i . e . , rapid precipitation of the coarser fractions nearerthe inlet with increasingly finer sediments deposited nearerthe outlet) will maintain a rough downward slope from inlet to weir. 2.3 Additional Design Features 2. 3. 1 Inlet The number and locations of the dredge slurry outfalls, or pipeline inlets, govern the pattern of deposition within the containment basin . A single, moveable inlet offers several advantages over single or multiple fixed designs . A single, fixed inlet would produce a mound of coarse material at the fixed inlet point. If not mechanically redistributed, the mound would effectively reduce the basin ponding area . A multiple inlet manifold could overcome this disadvantage . However, the infrequent maintenance projected for this portion of the ICWW, once every 5 to 10 years, cannot justify the cost of a fixed , multiple inlet manifold system for the IR- 14 containment basin . More cost effective, a single inlet, periodically 12 repositioned as dictated by the deposition pattern , can effectively distribute the coarse sediment over the basin floor . A flow-splitter or a spoon to break the jet ' s momentum will also help the single inlet distribute the slurry . Regardless of the inlet design or operation , maintenance of optimal basin performance will require regrading the dewatered sediment to reestablish the initial uniform slope of about 0 . 2 % ( Section 2 .2 . 2) from inlet to weir before each successive placement operation . Preliminary analysis of the settling characteristics of the dredged material to be placed in the IR- 14 containment basin ( Section 2 . 3 . 3 ) indicates that the available distance between inlet and weirs will afford adequate solids retention . Moving the inlet for more even material distribution must not significantly reduce this separation distance without additional precautions . To ensure continued compliance with water quality standards , these additional precautions may include increasing the ponding depth or installing turbidity screens surrounding the weirs . 2. 3 . 2 Weirs The IR- 14 facility will use weirs to control the release of the clarified surface layer of the water ponded within the containment basin . Adjustment of weir height controls ponding depth within the containment basin which in turn controls basin retention time . Weir height and ponding depth are discussed in more detail in the next section . However, several additional aspects of weir design affect the flow of water inside the basin and thereby strongly influence the efficiency of solids retention and the quality of effluent released from the site . These include weir crest width , weir crest length , weir type, and the location of the weir within the containment basin . Each of these design aspects and its effect on basin efficiency is discussed in the following paragraphs. The first two weir design parameters , -weir crest width and weir crest length , affect weir performance by determining its withdrawal depth. The withdrawal depth is the depth at which gravity forces on suspended sediment particles exceed the inertial forces associated with flow over the weir. It therefore represents the depth of the surface layer of ponded water that is drawn over the weir crest and released from the containment basin . Maintaining the withdrawal depth less than the ponding depth reduces the possibility of resuspending sediment which has settled out of the upper water column . Moreover, since the concentration of suspended sediment increases with depth, minimizing the depth of the withdrawal layer 13 maximizes the retention of suspended solids. Specific expected performance characteristics of the weir system are discussed later in this section . As mentioned above, the width of the weir crest affects withdrawal depth . Weirs typically employed in dredged material containment facilities are described as sharp-crested or narrow-crested based on their crest width relative to the static head over the weir. A weir is described as sharp- crested if the thickness ( T) of the weir crest is significantly less than the static head (H) over the weir, typically HIT > 1 . 5 . Under specific conditions, sharp- crested weirs may result in a shallower withdrawal depth than weirs with a broader crest, that is, for weirs with a value HIT :g 1 . 5 (Walski and Schroeder, 1978 ). To withstand hydrostatic pressure and reduce deformation and seepage the proposed weir design specifies the flashboards (discussed below) to be nominal 6 in . X 6 in . timbers . The timbers ' finished dimension of 5 . 5 in . , combined with the design static head overthe weir of 4. 9 in . , yields H/T = 0 . 89, a ratio within the range of a narrow-, rather than a sharp -crested weir system . However, in the present application, the use of a narrow-crested weir should be adequate (Gallagher and Company, 1978) . The weir parameter that most directly influences withdrawal depth and effluent quality is weir crest length . The Selective Withdrawal Model (Walski and Schroeder, 1978) developed by the U . S . Army Engineer Waterways Experiment Station ( WES) under the Dredged Material Research Program (DMRP) relates weir crest length to withdrawal depth through the parameter ofweir loading. Weir loading is defined as the ratio of the liquid discharge of the dredge (Q) to the effective weir crest length (B ) . Project planning guidelines used by the Jacksonville District Corps of Engineers indicate that an 18 - in . O . D . dredge will likely be used for future channel maintenance in Reach III of Indian River County . Given typical design output specifications for a 244n . dredge (discharge velocity of 16 ft/sec, a volumetric discharge of 3 , 560 cy/hr, and a 20/80 solids/liquid slurry mix), the Selective Withdrawal Model indicates that a weir crest length of 24 ft should produce a 2 . 0-11 withdrawal depth, based on a design weir loading (QB) of 0 . 89 ft'/ft• sec . As discussed in the next section, this depth falls below the recommended minimum ponding depth at the weir (2 . 8 ft) and thus should not result in the release of effluent with a high suspended sediment concentration . Moreover, DMRP research indicates that under field conditions, the actual depth of withdrawal may fall significantly below that predicted by the WES Selective Withdrawal Model . Therefore, the use of the WES Selective Withdrawal Model provides a conservative containment basin design . 14 Three corrugated metal half-pipes, each with an 8 -ft weir section , will provide the required 24 - ft total crest length . The three half- pipes connected by a common manifold will provide drainage from the containment basin via a single culvert under the dike . During dredging and dewatering operations , the return water pipeline will connect to this culvert and transport the clarified supernatant to the Indian River . Pipeline placement and retrieval is discussed in Section 3 . 1 . Removable flashboards will allow adjustment of weir heightover a range of 10 . 9 ft — from the initial elevation of ponded water within the basin following construction (estimated as + 1 . 8 ft NGVD) to a maximum elevation of + 12 . 7 ft NGVD . Setting the weirs at the minimum elevation permits the immediate release of ponded water at the start of dredging operations . The maximum elevation provides a 2 ft mean ponding depth and 2 ft of freeboard above the maximum deposition surface . The 5 . 5 in . x 5 . 5 in . flashboards (finished dimension) provide an adjustment increment roughly equivalent to the projected depth of flow (4 .2 in .) over the weir crest at the point the weir discharge approximately equals the liquid inflow to the containment basin , a balance reflected by the design weir loading, QB = 0 . 89 ft'/ft-sec . This design provides adequate adjustment resolution to maximize weir performance and effluent quality throughout the dredging operation and subsequent release of ponded water. The final weir design parameter considered is the location of the weirs within the containment basin . First, to reduce the likelihood of flow constriction , sediment resuspension, and dike instability the weir crests must be offset a minimum of 100 ft from the dike ' s inside toe . Second , the weirs must be placed to maximize their distance from the dredge pipe inlet and to minimize the return distance to the receiving waters . Providing the maximum inlet-weir separation also maximizes the basin ' s effective area and ensures that the effluent released from the basin meets the weirs ' performance criteria. Hydraulic analysis ( Section 2 . 3 . 3 ) indicates the 800-ft separation distance shown in Figure 2 . 1 to be adequate. In addition, locating the weirs to minimize the return distance from the weirs to 'the Indian River provides the most efficient effluent transport from the containment basin . Gravity flow will be used to the greatest extent possible. However, one or more dredging operations may be required to sufficiently raise the elevation of the basin interior such that all ponded water will drain by gravity flow . Until that time, auxiliary pumping may be required . Analysis of weir performance based on nomograms developed at the Waterways Experiment Station under the Dredged Material Research Program (Walski and Schroeder, 19 78) indicates that the weir design 15 described above will produce an effluent suspended sediment concentration of less than 0 .45 g/I . Relating suspended solids concentration to Florida effluent quality standards — based on the turbidity of the effluent relative to the ambient turbidity of the receiving waters — is problematic since turbidity depends highly on the physical characteristics and concentration of the suspended material . However, WES guidelines (Palermo et al . , 1978 ; Walski and Schroeder, 1978) indicate that this 0 . 45 g/ I falls well below typical standards for effluent discharged into estuarine waters . 2. 3. 3 Ponding Depth and Basin Performance Ponding depth refers to the height ofthe water column (with its suspended sediment load) maintained above the depositional surface during dredging operations . It is regulated by the height of the weir crest and, to a lesser extent , by dredge plant output. Given the initial slope of the basin interior (about 0 .2%), ponding depth will vary within the basin . The ponded water, most shallow nearest the inlet, will increase to its maximum depth nearest the weir . Conceptually, ponding depth is typically discussed in terms of its mean value over the entire basin interior. However, as a practical operational criterion , ponding depth is more usefully specified at the weir where it can be measured directly. At the weir, the excavated grade of the 1R- 14 basin is - 1 . 2 ft NGVD , or 0 . 8 ft below the average basin depth . Therefore , ponding depth at the weir exceeds the mean basin ponding depth by approximately 0 . 8 ft. In the remainder of this report, ponding depth will be given in terms of the mean depth over the basin and, where appropriate, related to the corresponding depth at the weir. Ponding should be maintained at the greatest possible depth during dredging operations . Increased ponding depths produce increased retention times and decreased flow velocities through the containment basin and therefore improved solids retention and effluent quality . The limiting consideration for increased ponding depth is the amount of hydrostatic pressure the dike can withstand without loss of structural integrity . Analysis of sediment settling characteristics established whether the 2 . 0- ft minimum mean ponding depth produces a basin retention time adequate for acceptable solids retention and effluent quality . The fine- grained sediment component, because it requires the longest time to settle out of suspension , determines the required basin retention time and therefore the required ponding depth . 16 Data characterizing channel sediments in Reach III were obtained in a program of sampling and analysis conducted during the plan development phase . As documented in the Phase I report (Taylor et al . , 1997 ) , sediment samples were taken at nine locations within the Indian River segment of the ICW W channel including three locations within Reach III . In an effort to sample worst case conditions, each sampling station was located near a potential source of fine sediment. Analysis determined that sampling location IR-3 -2 , located at ICWW mile 213 . 93 (Cut IR-30 , station 14+25 ) south of Vero Beach and opposite Prang Island near channel marker R- 150 , produced the finest- grained sediment of the three locations within Reach 111 . Silt and clay-sized particles (particles passing a #200 sieve , or with diameters less than 0 .074 mm ) comprised 80% of the sample (Figure 2 . 4) . Based on this conservative design criterion , an associated zone settling velocity was then determined from an empirical relationship between the percentage of fine- grained material and settling behavior. This relationship was developed from U . S . Army Corps of Engineers (COE) sediment data characterizing the silt content of a variety of ICWW channel sediments and the corresponding settling behavior of slurry concentrations similar to those typically encountered in dredging operations (Figure 2 . 5 , Taylor and McFetridge , 1989) . From these data the characteristic zone settling velocity for the sediment to be placed in Site IR- 14 was determined to be 0 . 25 cm/min , or 0 .49 ft/hr . This settling velocity was then used to determine the retention time needed to provide adequate sedimentation within the containment basin . Retention time relates directly to the depth of ponded water maintained within the basin . The preliminary design of the containment basin provides a minimum 2 . 0-ft mean ponding depth above the deposition surface . Analysis of the hydraulic characteristics of the proposed containment basin (Gallagher and Company, 1978 ) indicates that a 2 . 0-ft mean ponding depth will provide a maximum retention time of 6 . 19 hours during which the flow over the weir balances the liquid discharge of the dredge . In comparison, the time required for the sediment to settle out of the'2 . 0-ft mean ponding depth is less than 4 . 13 hours based on the projected zone settling velocity of the Station IR-3 -2 material . However, research (Shields, Thackston and Schroeder, 1987) by the WES under the DMRP indicates that the predicted settling time of the dredged material should be multiplied by a correction factor of 2 . 25 to account for field conditions . This yields an adjusted required settling time of 9 . 28 hours , a time which exceeds the maximum retention time of 6 . 19 hrs produced by a 2 . 0- ft mean ponding depth . Increasing the mean ponding depth to 4 . 0 ft provides a maximum retention time 12 . 38 hrs, which exceeds the adjusted settling time required to maintain acceptable effluent 17 ELLIS & ASSC1i. tATES . INC . U . S . STANDARD SIEVE OPENING IN INCHES U . S . STANDARD SIEVE NUMBERS HYDROMETER 300 6 4 3 2 1 . 5 1 . 75 . 5 3/6 3 4 6 810 14 16 20 30 40 50 70 100140200 0 so I T 10 80 20 ~ 70 70 2 2 O H w X so y40 r m In ac LIJ 50 50 N Z ac rr Q O Z 40U 60 W UJ U o` 30 70 w a 20 60 r- 00 — - so yo 0too 500 100 50 ! 0 5 1 0 . 5 0 . 1 0 . 05 0 . 01 0 . 005 0 . 001 GRAIN SIZE MILLIMETERS COBBLES GRAVEL_ _ SAND SILT OR CLAY I_ I COARSE FINE COARSE MEOTUM FINE SAMPLE NO . CLASSIFICATION NAT w% LL PL PI GRADATION CURVES IR-3- 2 Hydrometer and Grain Size Analyses E&A Project No . 95-1497 Figure 2 . 4 716 TAYLOR ENGINEERING INC . Grain Size Distribution , ICWW Sediment , Reach III 9000 CYPRESS GREEN DRIVE , SUITE 200 IR - 14 Dredged Material Management Area JACKSONVILLE . FLORIDA 32256 Indian River County , Florida °"" A rii 1999 2 . 00 s • • = 1 . 50 - ♦♦ E E v 0 a� c� 1 . 00 � N c - 0 � . \ ® • s d) o 3 ♦ � e m 0. 50 • �� --� -o.ezez ♦ e y = 3 . 8921x -- ~— R2 = 0 .4779 0 .00 0 10 20 30 40 50 60 70 80 90 Percentage Finer than #200 Sieve (%<0.074mm) Figure 2.5 Zone Settling Velocity of Intracoastal Waterway Sediments (based on Taylor and McFetridge, 1989) quality by a factor of 1 . 33 , and provides a margin of safety to ensure that the clarified supernatant released from the IR- 14 containment basin will meet state water quality standards . Therefore, the IR- 14 containment basin requires a 4 . 0- ft mean operational ponding depth . However, care must be taken not to increase ponding depth above the 2 .0- ft minimum too quickly . This may lead to dike saturation and promote dike instability. Operational experience has demonstrated that dike permeability typically reduces with time as percolation filters and traps fine sediments . Thus , a sufficiently slow increase in ponding depth will avoid piping, slumping, and other indicators of dike saturation and instability . Restricting the operational ponding depth to 4 ft should also reduce the likelihood of dike instability and provide an appropriate safety factor to ensure adequate solids removal . Consideration of realistic field conditions further reinforce the IR- 14 containment basin ' s conservative design . First, DMRP research indicates that under typical field conditions the actual depth of withdrawal may be significantly less than the WES Selective Withdrawal Model predicts . Solids retention should improve with decreased withdrawal depth . Second , field conditions may reduce dredge discharge rates below the design criterion . The design dredge discharge (3 , 560 cy/hr) reflects a minimum separation between the dredge plant and the placement site and thus a minimum discharge line length . Increasing the discharge line length also increases frictional losses and correspondingly reduces dredge discharge and extends basin retention time . The maximum pumping distance for Site IR- 14 to serve the extreme southern end of Reach III is 4 . 47 miles . Thus, actual dredge discharge rates will likely fall well below the design criterion and further improve basin solids retention . 2. 3. 4 Interior Earthworks The IR- 14 containment basin design specifically excludes secondary interior dikes — e . g. , multiple cells or spur dikes . Multiple cells are typically employed for continual or successive placement projects that cannot provide adequate time for dewatering the previous deposition . The projected dredging frequency for Reach III , once every 5 to 10 years , and the relatively small quantities anticipated with each operation, from 16 ,300 cy to 32,600 cy, do not warrant the use of multiple cells . Spur dikes are typically used in applications where the basin ' s size or configuration cannot provide adequate retention time . However, hydraulic analysis 20 ( Section 2 . 3 .3 ) indicates the IR- 14 containment basin design provides sufficient retention time to allow precipitation of the finest sediments anticipated in Reach III without recourse to spur dikes . 2. 3. 5 Ramps An important goal of the Long- Range Dredged Material Management Program for Florida ' s ICWW is to manage each dredged material management site as a permanent operating facility . This goal carries two operational criteria. First, the material is to be actively worked to accelerate the drying process and thus render the material suitable for removal and reuse as quickly as possible . Second , to restore the basin ' s capacity and thereby extend its service life, material must be removed from the basin at or before the point at which the basin reaches its design capacity. As a result, ramps to provide heavy equipment access to the containment basin interior have been integrated into the design of the containment dike (Figures 2 . 1 and 2 . 5 ) . Thus , the site is designed to function more as a material processing and rehandling station than as a permanent storage facility . Although the design capacity of the IR- 14 containment basin ( 178 , 051 cy, Section 2 . 1 . 2) is adequate to receive the projected 50-year material storage requirement for Reach III , removing the dewatered material off site can effectively expand its capacity. In this manner, the useful service life of the site may extend indefinitely . In addition to providing for material removal , the ramps also allow easy entry for equipment used in the dewatering process . This latter process is discussed in Section 4 . 1 . The ramps will be positioned on the western and southern sides of the containment dike . An on-site access road will connect the ramps to Indian River Boulevard ( Figure 2 . 1 ) . Obliquely traversing the containment dike, the ramps will maintain the same 1 V : 3H side slope as the dike. The road surface of the ramps will be 12 ft wide with an ascending/descending grade of 5 % . 2. 3. 6 Perimeter Ditch Saltwater seepage from the interior of the containment basin into the on- site shallow aquifer is not expected to be a significant problem for several reasons . First, saltwater pumped from the ICWW (Indian River) will remain ponded within the containment basin only during actual dredging operations and for a short period immediately following dredging as the clarified effluent is released back to the ICWW . Such periods are expected to last approximately 8 to 12 weeks, once every 5 to 10 years . Second , during the site ' s 21 first use and each subsequent use, percolation filters and traps fine sediments and thereby continually reduces the permeability of the basin interior. Thus, although some minor seepage should be expected , particularly during the basin ' s first use, the basin floor and dike walls are, within limits, self-sealing . Third , elements of the facility design and its operational guidelines incorporate additional precautions against the off- site migration of saltwater. Operational precautions, most notably the implementation of a groundwater monitoring program , are discussed in Sections 2 .4 , 3 . 5 , and 4 . 5 . Design features to control the off-site migration of basin seepage include a perimeter ditch , discussed below . A perimeter ditch, constructed at a 20-ft setback from the outside toe of the containment dike and surrounding the basin (Figure 2 . 1 ), will serve several purposes . First, as discussed above, the ditch must interdict the lateral spread of saline seepage through the dike ' s side slopes and foundation . To accomplish this purpose , the mean invert of the ditch must fall at or below the mean excavated grade elevation of the basin interior. If inspection of the dike during dredging and decanting identifies excessive basin seepage , its control may require that all water entering the perimeter ditch be continuously pumped back to the basin until all ponded water is released over the weirs. Dike inspection requirements during dredging and decanting arc discussed in Sections 3 . 2 . and 3 . 3 . Additional design measures to control basin seepage (e . g . , underdrains) require site- specific geotechnical information not presently available , and thus must be deferred to the facility ' s final design phase . In addition to intercepting seepage from the basin , the perimeter ditch must serve two other functions . First, the ditch must maintain the drainage and conveyance capacity provided by the east-west ditch that presently bisects the site . Facility construction requires that this ditch be rerouted around the containment basin . As shown in Figure 2 . 1 , the perimeter ditch will connect to the existing ditch on the basin ' s western side, redirect the ditch ' s flow around the basin ' s northern and southern sides, then reconnect to the existing ditch on the basin ' s eastern side before continuing to the Indian River. Thus, the perimeter ditch must match the existing ditch ' s invert elevation at both intersection points . By these criteria, the perimeter ditch ' s preliminary design includes a mean invert elevation of approximately 45 ft NGVD, or 4 . 2 ft below the existing mean grade elevation within the basin ' s footprint, 1 V ; 214 side slopes and a bottom width of 3 ft, to yield a mean top width of 20 ft. The slope of the existing ditch between the prescribed intersection points dictates the mean slope within the perimeter ditch . Second , the perimeter ditch must control stormwater runoff from the exterior face of the containment dike, the perimeter road , and portions of the buffer area . 22 Preliminary analysis indicates that the perimeter ditch will provide adequate conveyance for the 25 -year storm runoff. Control and conveyance of stormwater runoff from within the containment basin is discussed in Section 4 . 2 . 1 . 2. 3. 7 Dike Erosion and Vegetation The stability of the containment dike must also be ensured against erosion from rainfall runoff and wind . Immediately following dike construction , native grasses will be planted on the exterior dike slopes and crest (Figure 2 . 3 ) . While they quickly form soil binding mats , these grasses do not root so deeply as to weaken the dike . An acceptable turf cover may be planted by approved techniques of sprigging, sodding, or seeding (broadcast or hydroseeding), or a combination of these methods, as determined by the contractor. Contract responsibilities shall include the maintenance of the vegetation until adequately established , as certified by the COE or FIND ' s designated representative . Vegetating the dike in this manner will also improve the site ' s appearance. 2. 3. 8 Site Security Site security provided for the project area will restrict access, prevent vandalism and damage to site facilities, and ensure public safety. As stated in Section 2 .2, permanent security fencing will be erected around the site ' s upland perimeter (Figure 2 . 1 ) . Locked gates will control access to this area . The FIND and the Jacksonville District COE will hold the gate keys and distribute them on an as- needed basis to agents of the COE, dredging contractors, and other authorized parties . Site security is most critical during active dredging and dewatering operations . Therefore, a qualified facility operator must remain at the site at all times during active dredging operations and decanting procedures following a dredging event, as well as at any time when significant ponded water remains within the containment basin . Among his other responsibilities , discussed further in Chapters 3 . 0 and 4 . 0 , the site operator will ensure proper operation, adjustment, and maintenance of the weir and will prevent premature release of effluent through unauthorized weir operation . 23 2 .4 Groundwater Monitoring To ensure that the construction and operation of the IR- l4 containment facility does not adversely affect local groundwater, a comprehensive groundwater monitoring program will be a key element of site management. At present, data characterizing soil and groundwater conditions on site are limited . More detailed information characterizing on-site soil conditions — to be obtained through comprehensive subsurface investigation during the final design phase — is required to assess the site ' s potential to impact local groundwater. Additional sediment data will be derived from core borings taken in channel shoals before each scheduled maintenance operation . As discussed in Section 2 . 1 , excavation depth wil l be limited as much as practical . Nevertheless, containment basin construction will still require excavation below the apparent seasonal high water table . Material dredged from the ICWW will be discharged into the IR- 14 containment basin as a slurry containing approximately 20% marine sediments and 80% saline water. Hydrostatic pressure could potentially force saline water from the basin into the local shallow aquifer. However, two factors limit the off-site movement of saline water. First, a system of perimeter ditches (discussed in Section 2 . 3 . 6) surrounding the containment basin will interdict the horizontal migration of basin seepage . Second , ponded saline water should remain in the basin for relatively short periods (about 8 to 12 weeks) only once every 5 to 10 years . Thus, the contamination of off-site groundwater by saline water seepage from the basin appears unlikely . Notwithstanding the above, an on- site groundwater monitoring program will be implemented to detect any changes in local groundwater chemistry due to site operations . The program will begin before facility construction and will remain in place throughout the life of the site . Preconstruction groundwater monitoring activities are discussed below . Implementation of the groundwater monitoring program requires the installation of shallow test wells before site construction activities begin . Initially, three pairs of wells — one pair each on the containment basin ' s north, west, and south sides -- will be sunk within the buffer area . Each pair will consist of one shallow well (to 8 ft below soil surface) and one deeper well (to 30 ft below the soil surface) . Samples from the test wells will be analyzed to document preconstruction groundwater elevations and chloride concentrations . Analysis of the groundwater samples may also include additional chemical constituents if present in the sediment to be dredged . Well monitoring data will be used to establish baseline groundwater 24 conditions before site development and to identify changes in groundwater elevation due to site development or to changes in off- site groundwater demand . Additional wells may be installed if initial test results or specific local concerns require an increased monitoring capability . Prescribed monitoring activities during and between dredging operations are discussed in Sections 3 . 5 and 4 . 5 , respectively . Though little change in groundwater conditions is anticipated before the first dredging operation , groundwater monitoring should continue on a regular schedule . Samples should be taken monthly for the first year after the wells are installed and quarterly thereafter until the containment facility ' s first use . 2.5. Migratory Bird Protection The Jacksonville District Corps of Engineers district-wide migratory bird protection policy (COE, 1993 ) will be followed to ensure that operation and construction of the dredged material disposal area will not adversely impact migratory birds . The purpose of the migratory bird protection policy is to "provide protection to nesting migratory bird species that commonly use the dredged material disposal sites within the Jacksonville District while facilitating disposal of dredged material to meet the Federal standard for navigation channel and harbor maintenance as authorized by Congress" (pg . 1 ) . Issues related to migratory bird protection will be addressed during all phases of site operation . Specific actions taken to protect migratory birds during pre- dredging site preparation are identified below . Should construction activities at Site IR- 14 take place during the migratory bird nesting season4(April 1 through September 1 ) , the site protection plan presented in Appendix I of the Migratory Bird Policy (COE, 1993 ) will be implemented . This plan provides for education of contractor personnel , daily monitoring for nesting activity, steps to deter nesting in the construction area, avoidance of nests and, if necessary to protect nesting birds, cessation of construction activities . Alternatives that may be considered to prevent impacts to nesting birds include creation of undesirable habitat (e . g . , flagging construction area, placement of ground cover, seeding or sodding exposed areas), dissuasion through noise or activity, or creation of alternative nesting sites . A final, undesirable alternative — incidental take --- should only be considered during a documented emergency . 25 2. 6 Cultural Resources Inquiry to the Florida Department of State, Division of Historical Resources, revealed that the Florida Master File records an archeological site ( 8IR835 ) near or within the boundaries of Site I11- 14 ( letter from G . W . Percy, State Historic Preservation Officer, dated January 14, 1998 , Appendix A) . Described as inundated artifact scatter, this site lies east of the mangrove impoundments near the Indian River shoreline . Given this location , facility construction will have no impact on the archeological site . However, the site lies near the proposed pipeline routes (Section 3 . 1 ) and thus pipeline placement and retrieval may impact the site without appropriate protective measures . As recommended by the state Division of Historical Resources , before any land clearing or construction activities, Site IR- 14 will " . . . be subjected to a systematic, professional archeological and historical survey to locate and assess the significance of the recorded sites and any as yet unrecorded historical sites in the project area . . . " The need for additional , more detailed (Phase II ) archeological survey work will be determined by the results of the initial (Phase I ) investigation . 26 3 . 0 OPERATIONAL CONSIDERATIONS DURING DREDGING The primary objectives of site management during dredging operations are to maintain acceptable effluent quality during the decanting process , to maximize the dewatering rate of the deposited material by controlling the pattern of deposition , and to minimize the impact of the site on adjacent properties . To this end, six elements of site management are discussed : ( 1 ) placement and handling of the dredge discharge and return water pipelines, (2) operation and monitoring of the dredged slurry inlet, (3 ) operation and adjustment of the weirs , (4) monitoring of the released effluent, ( 5 ) continued monitoring of local groundwater conditions, and (6) compliance with the Jacksonville District ' s Migratory Bird Policy . 3. 1 Pipeline Placement The dredge (with additional boosters as necessary) will pump the dredged material as a slurry from the dredging site to the containment basin via pipeline . Thus, each dredging operation over the design life of Site IR- 14 will involve placing and retrieving both dredge discharge and return water pipelines . To minimize impacts to the mangrove wetlands, the dredge discharge pipeline will follow an existing graded road from near the Indian River shoreline to the road ' s intersection with the dike ' s eastern side (Figure 2 . 1 ) . The pipeline will then follow the dike ' s outside toe south and west to the basin ' s southwest corner and enter the basin by passing over the dike crest. This route will temporarily impact only a narrow fringe of mangroves at the Indian River shoreline . The return water pipeline will exit the basin near its northeastern corner and follow the same graded road to the Indian River shoreline . The return water pipeline outfall will be placed at or beyond the Indian River shoreline as necessary to minimize possible impacts to local seagrass beds . The pipelines will be placed immediately before dredging begins as part of the dredging contractor' s mobilization procedures . The dredge discharge pipeline will remain in place only during active dredging operations . The time required to complete this phase of operations Will depend on the quantity and distribution of the dredged material . As discussed previously, a 10- year dredging cycle is likely to produce a bulked volume of approximately 32 ,600 cy of material . This volume corresponds to an in situ volume of approximately 16 ,300 cy . Dredging this volume of material and transporting it to the containment basin, combined with reasonable delays associated with dredging projects of this complexity, yields an estimated 27 four to six weeks to complete each dredging operation . Immediately upon completion ofdredging, the dredge discharge pipeline will be removed. The return pipeline will remain in place to transport water decanted from the containment basin or released by initial trenching procedures (Section 4 . 1 ). After completion of this procedure, approximately four to six weeks beyond the completion of dredging, the return pipeline will also be removed . Ponded stormwater collected in the containment area will be subsequently removed via the weir system so that any suspended sediment will be retained in the containment basin . However, unlike the clarified effluent removed during dredging operations , stormwater will be routed to the on -site mangrove impoundment via the perimeter ditch . The removal of runoff is discussed further in Section 4 . 2 . 1 . 3 . 2 Inlet Operation The quality of the dredged sediment; specifically, the settling characteristics of the different grain - size fractions, will primarily determine the operation of the inlet pipe. The coarsest fraction of the material will settle out of suspension very rapidly and form a mound near the inlet. Successively finer fractions, characterized by lower settling velocities, will be deposited closer to the outlet weir. Thus, absent an inlet operation strategy, the dominant grain-size fraction will determine the distribution of sediment within the basin . For example, if fine-grained sediments dominate, a relatively large volume of material may be concentrated nearest the weirs . An extensive concentration of fine-grained sediment may require specialized dewatering procedures to speed drying. As discussed in Section 2 . 3 . 3 , analysis of samples taken at three locations within Reach III suggests that channel sediments in this reach contain significant fine-grained material . Mean grain diameters of individual samples ranged between 0 . 104 mm (Station I11- 3 -3 , categorized as fine sand) and 0 . 031 mm (Station IR-3 -2, categorized as silt). The silt-sized fraction ( i . e . , particles <0 . 074 mm diameter) comprised between 19 and 80% of the total . The one sample subjected to chemical analysis (Station IR- 1 - l ) yielded an organic matter content of 3 % . Additional data characterizing specific channel shoal sediments will be obtained before future dredging operations . These data will include, at a minimum, core boring logs containing a qualitative categorization of each sediment strata ; laboratory data, including sediment size 28 distribution curves and/or Atterberg limits ; and suspended sediment- settling time curves representing the finest-grained sample from each boring location . The recommended inlet operation strategy, based on the sediment data presented above, reflects a poorly graded mix of fine sand and silt-sized particles . This strategy makes no attempt to segregate material grain - size fractions by inlet manipulation , although some segregation will occur naturally as a result of differential settling behavior as described above . Tom inimize the mounding ofthe coarsest sediment fraction and to distribute the deposited material more uniformly, the inlet pipeline should be repositioned during dredging operations . This will require extending the pipeline and resting each extension on the sediment mound formed at the previous position . A minimum distance of 100 ft must be maintained between the inlet and the inside toe of the dike to preclude erosion or undercutting the interior dike slope . This strategy will also reduce the concentration of the finest sediment nearest the weirs as each deposition mound captures a portion of the silt- sized particles . ( With a fixed discharge position , these particles would continually wash from the mound . ) The resulting deposition pattern should maintain a consistent slope from inlet to weir, should minimize dead zones and channelization, and should reduce the requirement for grading the deposited material to reestablish the desired 0 . 2% slope between successive dredging operations . 3. 2. 1 Monitoring Related to Inlet Operation During active dredging operations, several monitoring procedures related to inlet operations will be required . Ponding depth , as previously mentioned , is a critical parameter for maintaining acceptable containment basin performance. Increased ponding depth improves the basin ' s solids retention performance by increasing retention time. However, under saturated foundation conditions, unbalanced hydrostatic forces resulting from too great a ponding depth can lead to slope instability, slumping, and the potential for dike failure. Indications of impending dike instability" include evidence of seepage related to piping and foundation saturation at the outer dike toe and small-scale slumping . Obviously, such conditions must be avoided . Therefore, ponding depth should be increased above the 2- ft minimum mean depth only under close monitoring by visual inspection of dike integrity. As discussed in Section 2 . 2 .2 , a 2-ft mean ponding depth corresponds to a 2 . 8-ft depth at the weirs as a result of the initial slope of the basin interior. If no effluent is released at the weir, the output of an 18 - in . dredge ( i . e . , 3 , 560 cy/hr slurry at a 20/80 solids/liquid mix, or 2, 848 cy/hr liquid) will produce an increase in ponding depth of about 2 . 1 in ./hr and a rise in the water 29 surface (i . e . , deposition layer plus ponding) of less than 2 . 6 in ./hr. These rates are slow enough to allow close continual monitoring of the entire dike perimeter. However, ponding depth should not be permitted to increase beyond a maximum of 5 ft (5 . 8 ft at the weir) . Dike stability should be monitored continuously during periods when ponding depth is maintained above the 2-ft minimum . Optimal operating efficiency requires that flow through the containment basin approachs plug flow to the greatest degree possible. Uneven flow distribution — evidenced by irregular sediment deposition , channelization , and short-circuiting — increases flow velocities, reduces retention time, and promotes sediment resuspension . If inspection reveals an irregular deposition pattern , the inlet pipe should be repositioned to produce a more uniform depositional surface . Last, the incoming slurry should be periodically monitored at the containment basin inlet to confirm or refine dredge output specifications , including volumetric output and slurry solids content . These parameters , in combination with the actual duration of dredging, can be used as an independent measure of deposition volume to determine remaining site capacity. Additionally, the computed deposition volume can be used with pre - and post- dredging bathymetric surveys of the channel and , following placement and dewatering of the deposition layer, topographic surveys within the containment basin to refine the bulking factor employed to translate in situ dredging volume to required storage volume . Also, within the same monitoring program , the quality of dredged sediment should be established by laboratory analysis of grain size distributions, settling velocities, specific gravity, and Atterberg limits . 3 .3 Weir Operation Weir operation — that is, controlling the ponding depth and flow rate over the weir by adjusting the weir crest elevation — is the procedure most critical to maintaining effluent quality during dredging and decanting operations . Operational requirements extend to the period during and immediately after containment basin construction . Initially, the weir crest elevation should be set as high as necessary to prevent unwanted release of stormwater and groundwater seepage . Before the site ' s initial use, the site operator will periodically release ponded stormwater and groundwater seepage during regularly scheduled inspections. 30 Immediately before the first placement operation at Site IR- 14, the weir crest should be set to an initial weir crest elevation of +3 . 6 ft NGVD to provide the recommended mean operational ponding depth of 4 . 0 ft . Thus, the initial maximum ponded water elevation at the facility ' s first use lies at or below the existing mean elevation within the basin footprint . Given the initial 0 .2% bottom slope within the basin , a 4 . 0 - ft mean ponding depth corresponds to a 4 . 8- ft depth at the weirs . The initial weir setting prevents the release of effluent until the ponded water reaches its recommended operational depth . During this initial operational phase, the design dredge discharge (3 , 560 cy/hr) will increase the ponding depth at a rate of approximately 2 . 1 in ./hr and increase the ponded water surface elevation ( ponding depth plus deposition layer) at a rate of approximately 2 . 6 in ./hr. This relatively slow rise should allow for close continual monitoring of the entire dike perimeter for indications of slope instability . Inspection is most critical during periods when the ponded water surface elevation is allowed to rise above its previous maximum . Experience has shown that as the ponded water percolates into the interior dike slope, the coarser dike material filters the fine suspended sediment . This filtering reduces the dike permeability and thus decreases the dike ' s susceptibility to piping and saturation . As stated above , no effluent should be released until the surface of the ponded water approaches the weir crests ' initial setting of +3 . 6 ft NGVD . Notably, a flow control structure such as a weir cannot improve effluent quality beyond that of the surface water immediately upstream . Thus , the decision to release effluent over the weirs should be based on the analysis of water samples taken immediately upstream of the weir at the maximum depth of withdrawal . For Site IR- 14, recommended WES procedures (Section 2 . 3 . 2 ) determined this depth to be 2 . 0 ft, based on the design dredge discharge of 3 , 560 cy/hr and a design weir loading of 0 . 89 ft'/ft- sec . If testing shows that the turbidity of the interior surface waters remains unacceptably high, the release of effluent must be delayed by one of two methods : ( 1 ) raising the weir crests by adding flashboards or (2) shutting down the dredge plant. Additional alternative measures may include installing turbidity screens surrounding the weirs . _ Once the weir has begun to release effluent that meets established performance criteria ( Section 2 .3 ), the outflow over the weir must not exceed the design dredge discharge, or 0 . 89 ft'/ft- sec . As discussed below, static head over the weir then becomes the most practical criterion to ensure that the flow over the weir, and thereby the effluent quality, remains within the design limits . 31 Static head represents the maximum elevation of the water surface above the elevation of the weir crest as measured upstream of the weir at a point where velocities are low ( 1 to 2 % of the velocity at the weir crest) . The static head can be measured directly by a stage gauge located at least 40 to 50 ft upstream of the weir. The water surface elevation can be read directly from the gauge, with the difference between the gauge elevation and the weir crest elevation indicating the static head . An empirical relationship applicable to narrow- crested weirs (Walski and Schroeder, 1978) indicates that a design weir loading of 0 . 89 ft /ft-sec corresponds to a static head 0. 41 ft (4. 9 in . ). Alternatively, the static head can be determined indirectly by measuring the depth of flow over the weir. The ratio of depth of flow over the weir to static head , estimated as 0 . 85 for narrow-crested weirs, yields a design flow depth for the IR- 14 facility of 0 .35 ft or 4 . 2 in . If the head over the weir, as measured by either method, falls below these design values as a result of unsteady dredge output or intermittent operation , effluent quality should increase. However, if the head exceeds these values, the ponding depth should be increased by adding flashboards until the mean ponding depth reaches its 5- ft recommended maximum . To safeguard dike stability, dredging should be temporarily halted rather than allow the mean ponding depth to exceed the recommended 5 - ft maximum . At all times , each of the three weir sections must be maintained at the same elevation to prevent flow concentration and a decrease in effluent quality related to an increase in weir loading . Preventing floating debris from collecting in front of the weir sections is also important . An accumulation of debris at the weir will reduce the effective weir crest length and thereby increase the withdrawal depth . This, in turn, may increase the effluent suspended solids concentration . To maintain the recommended 4 . 0-ft mean ponding depth throughout the dredging operation , the weir crest should be raised at approximately the same rate as the rise of the deposition layer. Based on the projected bulked volume produced by the typical dredging operation within Reach III — 16, 300 to 32,600 cy per event based on a 5 - to 10-year maintenance interval — the average depth of deposition per event will range from 1 . 0 ft to 2 . 0 ft. Thus , the typical maintenance operation will result in a final weir crest elevation ranging from +4 . 6 ft to +5 . 6 ft NGVD at completion of the first dredging operation . After dredging has been completed, the ponded water that remains within the basin must be slowly released by gradually removing flashboards — a process known as decanting. Flow over the weir should drop essentially to zero before the next flashboard is removed . Effluent monitoring must continue during the 32 decanting process. If at any time during this process effluent turbidity violates water quality standards , the effluent must be retained until analysis of the interior surface waters shows the suspended solids concentration to be within acceptable limits . Decanting then continues in this manner until all ponded water is released over the weir . Subsequent dewatering techniques are discussed in Chapter 4 . 0 . 3A Effluent Monitoring As discussed in the preceding section , effluent monitoring will be an integral part of facility operation . The IR- 14 containment basin has been designed to produce effluent which meets water quality standards for Class III waters as set forth in Chapter 62-302 of the Florida Administrative Code . These rules require a comprehensive monitoring program to document permit compliance . The monitoring program should therefore continue throughout active dredging and decanting operations . Effluent samples should be taken and analyzed as often as practical . The minimum recommended sampling frequency is two times per eight hour shift. Although effluent turbidity is only 1 of 29 parameters addressed in Florida ' s state water quality standards, compliance with these standards has been historically based on turbidity alone for several reasons . First, turbidity is reliably measured in the field and is the only water quality parameter over which the site operator may exercise direct control . Second, turbidity is a strong indicator of general effluent quality since many contaminants, most notably metals, exhibit a strong amity for fine particles . Thus, reducing turbidity should result in an overall improvement in effluent quality . However, the disturbance of contaminated sediments may result in the release of other pollutants (predominantly nutrients and hydrocarbons) which do not necessarily associate with fine particles . If the in situ sediments contain elevated levels of these contaminants, turbidity may be an inadequate indicator of effluent quality . Shoal sediments should undergo comprehensive elutriate and dry analysis to determine the presence of these contaminants . Additional testing under the effluent monitoring program , if required , should then focus on those contaminants documented by pre-dredging sediment analysis . Because effluent turbidity is a primary water quality parameter for site operation, compliance with turbidity standards will largely control both the dredge plant output and the release of effluent . However, the 33 prediction and interpretation of basin performance and effluent quality in terms of these standards can be problematic . This situation arises from the incompatibility of established design and compliance criteria. State standards for effluent turbidity are expressed in terms of optical clarity relative to ambient conditions of the receiving waters. By comparison, containment area design guidelines published by the U . S . Army Corps of Engineers Waterways Experiment Station (WES) under the Dredged Material Research Program (DMRP) relate containment area performance to the suspended solids concentration ofthe effluent. The level of turbidity produced by a specific suspended solids concentration depends highly on the physical characteristics of the suspended material . Previous investigation (e .g. , Walski and Schroeder, 1978) could not establish a method to effectively translate suspended solids concentration to optical clarity even for sediments with well -defined - physical characteristics. The design and operation of this and other similar sites would greatly benefit from such a predictive relationship . A primary objective of the effluent monitoring program should be to relate suspended solids concentration to the state performance criterion based on turbidity for sediments typically encountered in the ICWW. 3 . 5 Groundwater Monitoring As discussed in Section 2 . 4, groundwater monitoring forms a key element of Site IR- 14 ' s long-term management. Sampling and analysis of groundwater throughout the dredging and decanting operation comprises an essential component of the monitoring program . The duration of this program component should extend from the start of dredging to the completion of decanting, a period projected to last about 8 to 12 weeks . The site ' s first use as a containment facility will likely be the most crucial period for monitoring the potential seepage of saline water through the dike ' s side slopes and foundation . During this time, soils forming the dike will be most porous due to their disturbance during site construction . Thus, the initial period of each dredging operation requires frequent sampling and analysis of groundwater. During the site ' s initial use, groundwater samples should be taken twice every 24 hours . This sampling regimen should begin at the start of dredging and continue for a period equivalent to the theoretical transit time of saline water from the basin to the furthermost sampling well . Maximum transit time should be estimated during the final site design process, given adequate data to define soil permeability, stratification , and the governing groundwater flow gradient . Such data should be obtained from core borings taken in association with monitoring well 34 installation . Following the estimated maximum transit time through the remainder of the decanting process, sampling should occur a minimum of once every 24 hours . If at any time elevated chloride levels are detected in the monitoring wells , pumping will be stopped and ponding depth will be reduced until additional corrective measures can be taken . These may include the installation of a system of well points around the dike to reverse groundwater flow. Operational experience has shown that dike permeability decreases as the dike material filters and traps the finer fraction of dredged sediments . Thus , saline seepage from the containment basin should become increasingly limited with each successive dredging operation . 3 . 6 Migratory Bird Protection Should dredging be necessary during the migratory bird nesting season (April I through September 1 ), procedures presented in Appendix I of the Migratory Bird Policy (COE, 1993 ) will be implemented . These procedures include a variety of measures, summarized in Section 2 . 5 , to ensure avoidance of impacts to migratory birds during periods of active dredging operations . 35 4 . 0 POST-DREDGING SITE MANAGEMENT The post- dredging phase of site operation begins following the completion of decanting and continues until the start of the next planned dredging event. Post-dredging site management will be accomplished through the joint efforts of the FIND and the Jacksonville District, COE, and will include, at a minimum , quarterly site inspections . Additional post- dredging site management tasks are discussed in the following section . During the post- dredging phase, dredged material deposited within the containment basin is actively managed to reduce its moisture content. Through this process, the material is made suitable for handling and removal , should market conditions prove favorable . However, Site IR- 14 ' s intended use as a permanent facility requires other management procedures between successive dredging operations . These include a comprehensive monitoring and data collection effort, mosquito control , and site security. Each element of post-dredging site management is discussed below . 4. 1 Dewatering Operations Dewatering techniques to be used at Site IR- 14 depend on the physical characteristics of the dredged material . As discussed in Section 2 . 3 . 3 , preliminary data indicate that the material to be placed in the IR- 14 containment basin may contain up to 80% silts .and clays ( i .e . , particles <0 . 074 mm in diameter), with organics comprising up to 3 % . This fine-grained fraction will be the most resistant to drying . The relatively thin deposition layer resulting from a typical dredging operation ( <2 . 0 ft, Section 3 . 3 ) suggests that the coarser sediment fraction will likely dry through natural evaporation and percolation alone . However, effectively lowering the moisture content of the fine-grained fraction will likely still require supplementary dewatering techniques . The most appropriate dewatering techniques for this purpose include surface water removal , progressive trenching to promote continued drainage, and progressive reworking or removal of the dried surface layer. Each procedure and its specific application to the present situation are discussed below . Decanting all ponded surface water is necessary before significant evaporative drying of the fine- grained material can occur . Simply continuing to lower the weir crest will remove most of the ponded water following the completion of dredging operations . However, the anticipated topography of the deposition 36 layer makes draining off all ponded water in this manner unlikely . As discussed , differential settling of the various size fractions of the sediment results in partial segregation of the dredged material within the containment basin . Coarser sand- and gravel - sized particles settle nearer the inlet, while finer particles concentrate nearer the weir . The sand-sized fraction , concentrated nearer the inlet , should experience relatively little consolidation because of its low initial water content. However, the fine material ' s greater consolidation will likely form one or more depressions nearer the weirs . To remove the ponded water that remains in these areas, a drainage trench must connect each depression to a sump excavated adjacent to one or more weirs. During this phase of operations , the weir crest must be raised to prevent the premature release of the ponded water which , as a result of the excavation , will likely contain a high concentration of suspended solids . Clarified water can then be released over the weir as soon as effluent turbidity standards are met. Following the removal of all remaining ponded water, evaporative drying will eventually form a crust over the layer of fine-grained material nearer the weir. This crust will trap water beneath its surface and retard continued evaporation . In addition , the desiccation cracks which quickly form in the crust will hold rainwater and limit further drying . Therefore, complete drying will require additional trenching . Initially, a perimeter trench can be excavated by dragline or clamshell operating from the crest of the containment dike . More intensive trenching must wait until a crust of significant thickness (greater than 5 to 6 in . ) has developed on the deposition surface . The crusted surface will allow the use of conventional low ground pressure equipment . A network of radial or parallel trenches should then be constructed throughout the area of fine sediment deposition . The depth of each trenching operation will be dictated by the slumping resistance of the semiliquid layer beneath the crust . Based on the projected mean thickness of the deposition to be placed in the IR- 14 containment basin (<2 . 0 ft, Section 3 . 3 ), adequate drying should require no more than two successive trenching operations . As an alternative to intensive trenching, the dried surface crust can be transferred to a more well-drained area of coarser material nearer the inlet . This would expose the wetter under layers and restore a relatively high rate of evaporative drying . The dewatering process will continue until the crust extends over the entire depth of the deposition layer. The time required to complete this phase of site operation will depend on the physical characteristics of the sediment, as well as climatic conditions (e . g . , rainfall , relative humidity, season , etc . ) . During the entire dewatering phase of the site operation, the weir must be operated to control the release of residual 37 water and impounded stormwater. The clarified effluent will be routed to the perimeter ditch and drained off site . 4 .2 Grading the Deposition Material Following the completion of dewatering, the dried sediment must be graded to prepare for the next dredging operation . Grading — that is, distributing the mounded sand , shell , and gravel over the remainder of the containment area — serves a number of necessary functions . These include reestablishing the initial uniform 0 . 2 % slope from the inlet down to the weirs, restoring the effective plan area of the containment basin , and improving subsequent dewatering ofthe fine-grained material by separating successive deposition layers with a free-draining substrate . As discussed in the next section , grading also provides for stormwater runoff control . Finally, a series of post-grading topographic surveys will assess material consolidation and refine estimates of remaining storage capacity . 4. 2. 1 Control of Stormwater Runoff As stated , grading the dewatered deposition layer provides the additional benefit of allowing the control and release of stormwater that drains from the interior slopes of the containment dike as well as the dewatered sediment. A shallow, uniform slope (0 . 2%f, Section 2 . 1 . 2 ) toward the weirs ensures adequate drainage, eliminates ponding of runoff in irregular depressions, and minimizes flow velocities and the risk of channelization and erosion . In compliance with regulatory policy, a sump or retention area of adequate capacity should be constructed adjacent to the weirs (with the weir flashboards in place) to retain the runoff from the first 1 in . of rainfall . For the IR. 14 containment basin interior area of 12 . 87 acres (from the dike crest centerline inward), a circular basin with a radius of 86 ft and an average depth of 2 ft will provide a retention pond with the required minimum capacity- of approximately 46 ,700 W . A site operator would then be responsible for the gradual release of the ponded runoff at intervals determined by local weather conditions . Providing shallow trenches or swales from the center of the retention basin to one or more weir sections may also be necessary to facilitate the rapid removal of runoff. As discussed in Section 3 . 1 , the clarified runoff will be routed from the containment basin to the perimeter ditch via the weir discharge culvert . The perimeter ditch, in turn , will drain to the on-site mangrove 38 impoundment through the existing drainage network and ultimately will discharge to the Indian River. Ditch construction details such as required slope and stabilization will be deferred to the final design phase of site development. 4. 2. 2 Topographic Surveys Monitoring the containment area between successive dredging events will include two topographic surveys of the deposition surface. Results from a post-dredging survey, performed as soon as possible after grading of the dewatered material , will provide an independent check of the dredging pay volume derived from pre- and post dredging bathymetric comparison . A second topographic survey should be performed immediately before the start of the next dredging operation . Used in combination with the earlier post- grading survey, this second survey will assess the degree of material consolidation and determine the remaining site capacity . 4 .3 Material Rehandling/Reuse As discussed in Section 1 . 0 , Site IR- 14 is one of three dredged material management areas being developed to serve the long-term maintenance requirements of the ICW W within Indian River County. This report, as well as the accompanying permit documentation , has emphasized that although each site has been designed fora specific service life , each is also to be operated as a permanent facility for the intermediate storage and rehandling of dredged material . To fulfill this intended use, at some point the dewatered material must be removed off site . The ultimate use of this material is discussed in the following paragraphs . Based on a comprehensive analysis of dredging records and survey data, the bulked material volume projected for placement and temporary storage over the 50-year design service life of the three Indian River County facilities exceeds 600,000 cy . Although relatively minor by the standards of some dredging operations , this volume still represents a significant quantity of potentially valuable material . Even if the possible return on the sale of this material were disregarded, the cost saving of permanent storage alone would justify an effort to determine, through a formal market analysis, the potential demand for dewatered dredged material . 39 If such a determination reveals that material resale and/or reuse is practical, the properties of the dredged material must then be demonstrated to satisfy the requirements of commercial interests . The coarsest fraction of material (sand and gravel), having been partially segregated through differential settling, can likely be used as is . However, the feasibility of compartmentalized segregation of material during dredging or mechanical separation following dewatering should be explored if market conditions dictate. Portions of the material determined to be unsuitable for fill or other construction purposes because of organic silt or clay content might be used for landfill capping or agricultural purposes . A determination that resale or reuse is unfeasible will dictate locating and developing a centralized permanent storage facility. The appropriate location for such a facility would appear to be inland where lower real estate values and development potential make permanent storage more economically feasible . The optimal distance from the initial containment area to the permanent storage site would represent a compromise between lower land costs and higher transportation costs . 4. 4 Additional Environmental Considerations 4. 4. 1 Biological Monitoring A primary consideration in the design and operational guidelines for Site IR- 14 is the intent to limit adverse impacts to those directly related to construction of the dredged material management facility . Notwithstanding the above, additional biological monitoring will be required within the buffer zone which lies outside the containment area. A biological monitoring program , which may be extended to the proposed pipeline route as well as the immediate vicinity of the site , may include the following elements . If required to update existing information, an environmental survey of these areas will be performed before site construction to establish current baseline habitat conditions and population densities . Periodic resurveys should then continue throughout the service life of the site. Impacts to local habitat resulting from site construction oroperation should be noted, corrective actions taken , and guidelines developed to avoid similar consequences . Similarly, beneficial aspects of site management should be recognized and encouraged, and the lessons learned should be applied to the future operation of this and other comparable dredged material management areas . 40 4. 4. 2 Migratory Bird Protection As discussed in Section 2 .4 , migratory birds may nest on the sandy substrate left in the containment basin following dewatering and grading. Should post- dredging site management activities be required during the April 1 through September 1 nesting season , they will be carried out in accordance with the site protection plan (COE, 1993 ) summarized in Section 2 . 4 . 4. 4. 3 Groundwater Monitoring As discussed in Sections 2 . 4 and 3 . 5 , a groundwater monitoring program will be implemented at Site IR- 14 to detect possible saline water migration from the containment basin into local groundwater. Between dredging events , sample collection and analysis will continue as part of the site operator' s regular inspection routine . After the release of all ponded water remaining from the previous dredging operation, a period of post- dredging sample collection will begin . During this period , groundwater samples will be collected and analyzed monthly for the first year following the completion of decanting and quarterly thereafter unless otherwise needed . More frequent sampling intervals may be required should conditions warrant. Should elevated chloride levels be detected at any time, the source will be determined . If the containment basin is the source, corrective actions will be taken . As discussed in Section 3 . 5 , these may include the installation of a system of well points around the dike to reverse groundwater flow . If chlorides originate from a source external to the IR- 14 facility ( Le. , intrusion caused by off-site groundwater demand), the proper authorities will be notified. 4. 4. 4 Mosquito Control The basic approach of the mosquito control program for Site IR- 14 will emphasize physical rather than chemical control . The time during which standing water remains in-side the containment area will be kept to a minimum to reduce the potential for mosquito breeding . The operational phase most favorable for mosquito breeding follows the completion of decanting when desiccation cracks form in the crust. Trenching procedures ( Section 4 . 1 ) will accelerate the dewatering process by allowing much of the moisture within the 41 cracks to drain to the weirs . However, adverse climatic conditions could delay the dewatering phase long enough to result in successful breeding within the desiccation cracks . This would require a short- term spray program coordinated through the Indian River County Mosquito Control District, 4. 5 Site Security Providing adequate site security will remain a key element in the proper management of IR- 14 . Unsecured dredged material containment areas typically host a variety of unauthorized activities including illegal dumping, vandalism , hunting, and dike destruction through the use of off-road vehicles. As discussed in Section 2 . 3 . 8 , security fencing installed around the site ' s upland perimeter should preclude such activities within the IR- 14 containment facility. Access to the area within the fence will be limited to agents and representatives of the FIND and the Jacksonville District Corps of Engineers, and authorized contractor personnel . Access gates will remain locked at all times except during dredging and maintenance operations . The presence of an on- site operator duing such operations should further discourage unauthorized entry to the site and the occurrence of unsanctioned activities . Between dredging operations the site operator will be responsible for carrying out regularly scheduled inspections . The primary purpose of these inspections will be to perform routine operational functions and to ensure that facility security is maintained . Breaches in site security will be identified and appropriate actions will be taken as quickly as possible to restore the site to a fully operational standby condition . Other responsibilities of the operator during these visits will include weir operation and stormwater release, groundwater monitoring, and routine inspection of dike integrity and buffer area conditions . 42 REFERENCES Gallagher (Brian J.) and Company. 1978 . Investigation of Containment Area Design to Maximize Hydraulic Efficiency. Technical Report D- 78- 12 . U . S . Army Engineer Waterways Experiment Station , Vicksburg, MS . Palermo, M . R . , Montgomery, R. L . , and Poindexter, M . E. 1978 . Guidelines for Designing, Operating, and Managing Dredged Material Containment Areas. Technical Report DS-78 - 10 . U . S . Army Corps of Engineers Waterways Experiment Station , Vicksburg, MS . Shields , F . D . , Jr. , Thackston , E . L . , and Schroeder, P . R. 1987 . Design and Management of Dredged Material Containment Areas to Improve Hydraulic Performance. Technical Report D- 87 -2 . U . S . Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS . Taylor, R. B . and McFetridge, W . F . 1989 . Engineering Evaluation of Proposed Dredged Material Transfer and Handling Operation . Taylor Engineering, Inc . , Jacksonville, FL . Taylor, R. B . , McFetridge , W. F . , and Schropp, S . J . 1997 , Long-Range Dredged Material Management Plan for the Intracoastal Waterway in Indian River . County, Florida. Taylor Engineering, Inc . , Jacksonville, FL , U . S . Army Corps of Engineers (COE) . 1993 . Draft Final Migratory Bird Protection Policy. U . S . Army Corps of Engineers, Jacksonville District, Jacksonville , FL , Walski, T. M . , and Schroeder, P . R. 1978. Weir Design to Maintain Effluent Qualityfrom Dredged Material Containment Areas . Technical Report D-78 - 18 . U . S . Army Engineer Waterways Experiment Station , Vicksburg, MS . Wettstein , C . A . , Noble, C . V . , and Stabaugh , J. D . 1987 , Soil Survey oflndian River County, Florida. Soil Conservation Service, U . S . Department of Agriculture, Washington , D . C . 43 APPENDIX A T H Y L O R N G l N E E r January 21 , 1998 Mr, David K. Roach Assistant Executive Director Florida Inland Navigation District 1314 Marcinski Road Jupiter, FL 33477 Re: Response from the Department of State, Division ofHistorical Resources , Concerning Proposed FIND Sites in Indian River and St. Lucie Counties Dear Mr. Roach: Enclosed please find a copy of the letter we received from the Florida Department of State, Division o£I3istoric Resources, Bureau of Historic Preservation, in response to our December 3 , 1997 , letter of inquiry concerning the proposed FIND sites in Indian River and St. Lucie Counties . Also please find a faxed copy of maps showing the recorded locations of the cultural resource sites . Please note that the two cultural resource sites identified within the proposed FIND sites — archeological site 81R849 in Site IR-2 and archeological site 8IR935 in Site MrM — lie along the Indian River shoreline, east of the mosquito impoundment, and would not be impacted by site construction. If you have any questions or comments, please do not hesitate to call. Sincerely William . McF e Senior nginee enclosures 4nRA C' YPRFCC GREEN OR I ArKCnNV111 F F I 122 56 TEL 904 711 7 n 4 n F AX Qn4 7i 1 4H4 PWRMA DEPARTMwT OF BTATI offimumtw 063Mof ho mationd 1dB, um OF THE FLORIDA Cal.wIT oAfioe of iatrrnsaotul Rel�dota ! DivU4n of mm61vmve s4Nicb of libr u, k motion Serres Difta ojcorporjta u 0*00 of &Orw Rwtxo ate„ dCo1hv11 utw, kn0qMWft *rArt of tom„ • Comon ora�oN FLORIDA 0EPARu TMENT Op STATE Sftndra B - Mortham 5&7etiry of State DY MON w HI9WRICAL RESOURCIZ BUREAU OF HISTORIC PRESERVATION FACSIMILE TRANSMITTAL SHEET TO FAX NrUNMER L3 � COMPANY: DATE • NUMBER OF PAGES (Including transmittal sheet) : From Phone ( 950) 487. 333 Suncom 277.2333 Fax (850). 922&0496 RA Gray Building 600South &onouDM T R'S 0MCZ FAX* Sh TAUAheaa�, FIorfda 32999-0250 (8S0}d88-1480 O ARCHASOLOQICAL RESEEAIZC4 �3 C3 HISTORICR$SERVA WWWAddzem O•Q08• r3 HISTORICAL MUSEUMS (838) 487-2249 • FAX: 4142207 (830) 487.1733 • FAX: 922.0496 (830) 4f18-I484 6 pAX; 921 .2503 MEMBER OF THE FLORIDA CABINET FLORIDA DEPARTMENT OF STATE Division of Library & Information Services Office of the Secretary Division of Historical Resources Office of Intemational Relations Ringling Museum of Art Division of Administrative services Division of licensing Division of Corporations Division of Elections Division of Cultural Affairs 4W FLORIDA DEPARTMENT OF STATE Sandra B . Mortham Secretary of State DIVISION OF HISTORICAL. RESOURCES January 14, 1998 Mr , William F . McFetridge In Reply Refer To : Taylor Engineering, Inc . Frank J . Keel 9086 Cypress Green Drive Historic Preservation Planner Jacksonville, Florida 32256 Project File No . 976476 RE : Cultural Resource Assessment Request Florida Inland Navigation District Long-Range Dredged Material Management Plan for the Intracoastal Waterway Indian River and St . Lucie Counties, Florida Dear Mr. McFetridge : In accordance with the provisions contained in Chapter 267 . 061 , Florida Statutes, we have reviewed the above referenced project(s) for possible impact to archaeological and historical sites or properties listed , or eligible for listing, in the National Register of Historic Places, or otherwise of historical or archaeological value . A review of the Florida Site File indicates that two archaeological sites, 8IR849 and IR835 are recorded within the IR-2 and IR- 14 project areas, respectively . No formal assessment of significance has been complete for either site. Archaeological site 818849 is recorded as a disturbed artifact scatter. Archaeological site 8IR835 is recorded as a partially inundated artifact scatter. Both sites were recorded based only on surface inspection . It is, therefore, the recommendation of this office that, prior to Initiating any project related land clearing or ground disturbing activities within the IR-2 and IR- 14 project areas, they should be subjected to a systematic, professional archaeological and historical survey to located and assess the significance of the recorded sites and any as yet unrecorded historic sites in the project areas . It is also our recommendation that the IR- 12B , and M-8 project areas be subjected to a systematic, professional survey. The purpose of these surveys will be to locate and assess the significance of historic properties present. The results of the investigations will determine if significant historic properties would be disturbed by this project . In addition, if significant remains are located, the data described in the report and the archaeologist' s conclusions will assist this office in determining measures that must be taken to avoid, minimize, or mitigate adverse impacts to significant historic properties. DIRECTOR'S OFFICE R. A. Gray Building • 500 South Bronough Street • Tallahassee, Florida 32399-0250 (850) 488-1480 FAX: (850) 488-3353 * Address httpJ/www .dos. state .fl .us O ARCHAEOLOGICAL RESEARCH rWHIWSTORIC PRESERVATION O HISTORICAL MUSEUMS (850) 487-2299 • FAX : 414-2207 (850) 487-2333 • FAX: 922-0496 (850) 488-1484 • FAX: 921 -2503 Mr. McFetridge January 14, I998 Page 2 Finally, a review of the Florida Site File indicates that no significant archaeological or historical sites are recorded for or likely to be present within the proposed SL-2 and SL-26 project areas . Therefore, it is the opinion of this office that these projects will have no effect on significant historic properties . Because this letter and its contents are a matter of public record, the applicant may be contacted by consultants who have knowledge of our recommendations . This should in no way be interpreted as an endorsement by this agency. The Society of Professional Archaeologists (SOPA) is the national certifying organization for archaeologists. Upon request, our office can supply a listing of archaeologists who are SOPA members living or working in Florida. In addition, we can provide information on ordering their Directory of Certified Professional Archaeologists from them . If you have any questions concerning our comments, please do not hesitate to contact us . Your interest in protecting Florida's historic properties is appreciated . Sincerely, George W. Percy, Director Division of Historical Resources and State Historic Preservation Officer GWP/Kfk xc : C . L. 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J x0 1 , - ENNIS • .. ./' 0 Q p � + Q , U 14 Cr y ' fes, ; , 1 bra II . : .W Q I �� . , I �? i :'f ; - ' . n " _ !�(��/i � " ' 1 ' f1 ' � !•t,' 1 �/ � n � � • 1 1a^— ; Q� � it t � : y SSS ''��KK ' + •ate '/`� t..� �'.s� 1l� ell d f) ON} 0 Cv `yb TECHNICAL ADDENDUM Weir Design Modifications and Operational Guidelines Site IR- 14 Indian River County Prepared for FLORIDA INLAND NAVIGATION DISTRICT by R . Bruce Taylor, Ph . D. , P .E . William F . McFetridge Taylor Engineering, Inc . 10151 Deerwood Park Blvd . 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U21sa ata Q M luuurutopaa(iaz{ljo sauauYala I ' Z SNOISIA3H N91M UlaM, 0' Z [ . .. ... . .... ... . .. . . . .. . .. . . . . . .. . ... . .. . ... ....... ..... . . .. .. . . . . . . . . ... pas . . . . . . . . . . .. . . . . ... . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. Noll:) fla0lcm 0' 1 SILN31LNOD 3o 3 19viL 1 . 0 INTRODUCTION This Technical Addendum to the existing Management Plan for the IR- 14 Dredged Material Management Area (Taylor et al , May 1999) presents preliminary design revisions and operational guidelines for the proposed weir system at FIND Site IR- 14 in Indian River County . It also presents additional operational requirements contained in recently adopted Draft Environmental Resource Permit (ERP) review criteria for dredged material containment facilities first proposed by the Florida Department of Environmental Protection (FDEP) . The Florida Inland Navigation District (FIND) , local sponsor of the Intracoastal Waterway (ICWW) and owner of Site IR- 14 , contracted Taylor Engineering to develop this addendum to improve weir performance and establish operational constraints on the dredging contractors ' use of all FIND dredged material placement sites . No schedule has been set for the final design and construction of the IR- 14 facility. The design revisions and operational guidelines this addendum presents assume that the IR- 14 facility ' s final design and construction — in particular, the final design and construction of its weir structure — remains consistent with its preliminary design first presented in the site ' s Management Plan. The FIND intends that both the site ' s earlier Management Plan and the present addendum to that plan be included as part of the bid package for the next dredging contract for maintenance of the ICWW, Indian River County Reach III, not yet scheduled . The FIND also intends that both documents form attachments to the contract for these dredging services . In all cases where the present Technical Addendum conflicts with the earlier Management Plan , the Technical Addendum shall take precedence. All design elements presented in these documents , including the weir design modifications described in Chapter 2 .0 of the present addendum, represent conceptual preliminary designs only. During the project ' s Final Design Phase, it will remain the responsibility of the project ' s Engineer of Record to fully design and specify each of these conceptual designs elements for inclusion in the project ' s Final Design and Construction Drawings and Technical Specifications . Throughout, this Technical Appendix references the need for the Project Engineer to review and approve contractor submittals . In each case, the Project Engineer refers to an authorized representative of the contracting entity (USACE or the FIND) that assumes overall project responsibility for the dredging project by authorizing and/or approving the project ' s final design, advertising the project for bid , selecting the contractor, awarding the contract , administering the contract, and providing construction observation and/or inspection services, as required . Responsibility for the initial placement operation at Site IR- 14 remains to be determined . The Addendum is organized as follows . Chapter 2 . 0 first outlines basic elements of the IR- 14 weir design as described in the site ' s original Management Plan, then presents prelirunary minor revisions to the IR- 14 weir system that are intended to improve performance without requiring significant alteration of the weirs ' basic structure. Chapter 3 .0 presents guidelines for operating the modified weir system that the selected contractor must follow before, during, and immediately after dredging . Chapter 4 . 0 presents inspection criteria designed to ensure the stability and safety of the site ' s containment dikes . Chapter 5 . 0 presents additional criteria for maintaining a vegetative cover on the containment dikes to facilitate the required inspections . 2 . 0 WEIR DESIGN REVISIONS 2 . 1 Elements of the Predominant Weir Design This section presents the basic elements of the preliminary design for the IR- 14 weir structure. As described in the site ' s original Management Plan, the preliminary design for the IR- 14 weir structure follows the predominant weir design now in use within the Jacksonville District, as well as the design installed at almost all FIND containment facilities built since 1991 . This design features a .parallel arrangement of three to four pile-supported weir stacks, each stack formed by a corrugated metal half. pipe. Removable flashboards key loosely into vertical I-beam channels to form a vertical barrier across the otherwise open side of each half-pipe. This face acts as a dam to retain water within the basin. Under ideal conditions (that is, no leakage between the boards or around the boards ' ends), water may only exit the basin by passing over the weir ' s crest, that is, the top board in the stack. Adding or removing weir boards allows the operator to maintain the crest elevation to just below the ponded water surface elevation. In this manner, the weir maintains effluent quality by discharging only the clarified surface layer from which almost all suspended sediment has already settled. The total weir crest length (that is, the combined length of the weir crests of each weir stack) reflects the length needed to maintain the withdrawal depth less than the minimum 2 . 0-ft ponding depth (Section 3 . 3 . 1 ) . Withdrawal depth refers to the theoretical depth of the surface layer of water selectively withdrawn over the weir crest . For the weir to function as intended and maintain effluent turbidity within acceptable standards, the basin must provide sufficient retention to allow the finest sediment component to settle from the weirs ' design withdrawal depth . Given that the suspended sediment concentration within the ponded water increases with depth, - 2 . decreasing the withdrawal depth should improve the basin ' s solids retention performance and improve effluent quality. Under most circumstances , maintaining the withdrawal depth less than the minimum ponding depth should help ensure that the weirs release only the clarified surface layer that contains relatively low concentrations of suspended sediment . The specified total weir crest length — 36 ft for the four weir stack design and 24 ft for the three weir stack option — derives from nomographs developed under the USACE ' s Waterways Experiment Station (WES) Dredged Material Research Program (e . g . , Walski and Schoeder, 1978) . Based on the discharge of the design dredge plant , the 36 -ft total length assumes the output characteristics of a 24 - in . dredge, while the 24 -ft length assumes an 18 -in. dredge. The preliminary design for the IR- 14 weir structure recommends the three weir stack option. This remainder of this chapter presents recommendations for minor design revisions to the weir system proposed for installation at the IR- 14 containment facility . As discussed above, the basic installation follows the predominant weir design now in use within the Jacksonville District, as well as the design installed at almost all FIND containment facilities . The proposed revisions do not require significant alteration of the weirs ' basic structure and can be installed as part of the dredging contractor' s site preparation responsibilities . 2 . 2 Deficiencies of the Predominant Weir Design As part of our investigations into possible deficiencies in the predominant weir design currently installed at existing FIND containment facilities , Taylor Engineering staff solicited information from two groups : ( 1 ) USACE personnel presently or recently engaged in planning, designing, contracting, or inspecting dredging/dredged material management operations at FIND dredged material containment facilities and (2) dredging contractors that have recently used or are familiar with existing FIND facilities . In addition to establishing typical weir operating procedures , these inquiries were intended to investigate perceived deficiencies in the design and construction of the weir systems presently installed in FIND dredged material containment facilities . The discussions with representatives of both the USACE and private dredging contractors focused on three basic concerns regarding present weir design : ( 1 ) the design ' s failure to adequately control leakage around the ends of the weir boards , where the boards key loosely into the vertical 1-beam channels; (2) its failure to adequately control leakage between the weir boards ; and (3 ) its failure to adequately provide a means to safely access the weirs as required to add or remove weir boards and to secure the boards in position. The discussions confirmed Taylor Engineering ' s own observations that - 3 - contractors typically use a combination of plastic sheeting, plywood , and roofing tar to address the first two concerns — leakage around and between the weir boards — with varying degrees of success . The discussions also confirmed that the third concern — the difficulty of accessing the weirs and adjusting and securing the weir boards — has forced contractors to resort to a variety of means, none of which promote safe and efficient weir operations . Contractors typically use the limited access provided by the existing fixed ladders to install or remove weir boards from above, and use a johnboat or similar small vessel positioned directly in the discharge flow to install or remove weir boards from below . From these precarious positions , the contractors then typically secure the boards by pounding in wooden wedges or shims . The remainder of this section specifically addresses these three issues by presenting a conceptual design for minor modifications to the weir system proposed for installation at the planned IR- 14 containment facility. All site-specific elements of the proposed modifications (e. g., elevations) refer to the preliminary weir design as presented in the site ' s Management Plan (Taylor et al . , May 1999) . 2 . 3 Conceptual Weir Modifications Figure 2 . 1 presents the basic elements of the proposed weir modifications . Notably, these revisions require no dismantling, and only minor modification , of the weir system ' s basic structure. Each of the proposed modifications is presented here as a preliminary conceptual design only. The Project Engineer remains responsible to fully design, specify, and incorporate the proposed modifications into the bid package for the site ' s first use. The selected contractor must then complete the proposed weir modifications before the initiation of dredging as part of required site preparation activities . As shown , the proposed modifications include three basic elements . First, to address the issue of leakage around the ends of the weir boards , the modifications include wooden extensions, fabricated from dimensional pressure-treated (PT) lumber, installed vertically against the inside (downstream) flange of each vertical I-beam channel that holds the weir boards . These flange extensions will provide a smooth, wide surface against which the downstream face of the weir boards will seat. Although providing an imperfect seal, the width of these mating surfaces will greatly reduce the likelihood of leakage around the ends of the weir boards. Equally important, the flange extensions will also provide a means to secure each weir board in position without the use of wedges that can become dislodged by changes in water level . Second, to address the issue of leakage between boards , the modifications also extend to the weir boards themselves . The contractor must still supply all required weir boards, but with the boards modified - 4 - BAR C 15 X 33 .9 5116" X 3" S .S . BOLT C MF GALVANIZED SPACER 1 , 3" LAG SCREW FLANGE EXTENSION ST EA 6 (TYP . ) 2x8 PT ( NOMINAL) FLANGE EXTENSION 2 x 8 PT (NOMINAL) 1 i _ I I WSX18 STL . BEAM i 1 'I WEIR BOARD 0 .33" 023.. 1 1 . 5., \ ` ` //r. I I (NOMINAL) ok1 0.25" I i 3 .4" i j 1 .5" 1 . 0 lw WEIR BOARD 8 . 14' 4 X 6 PT GASKET z" i I (NOMINAL ) (NEOPRENE ! ROOFING FELT) Ii I � ' II i ; WEIR BOARD 6X6PT NOMINAL;r r ( ) r . %% ' ':`. ' F.' 1, i !' ' � •''.Ii `• r " I 5 .25" - i 3" LAG SCREW P WEIR BOARD _ `• l' I I SPLINE 6 X 6 PT (NOMINAL ),TYPICAL �1� X X lIdk ALUMINUM (TYP. ) 2 . 1A - PLAN 2. 18 - SECTION TAYLOR ENGINEERING INC . FIGURE 2. 1 pOJeCT C200' -015 ov.w" n. 10151 DEERWOOD PARK BLVD . PRELIMINARY DESIGN, PROPOSED WEIR MODIFICATION AL BLDG . 300, SUITE 300 SHEET 1 of 1 JACKSONVILLE, FL 32256 axTc o+lc ` CERTIPICATE OF AUTHORIZATION s191S JUNE2008 Ma PRELIMINARY DRAWINGS : THESE DRAWINGS ARE NOT IN FINAL FORM. BUT ARE BEING TRANSMITTED FOR REVIEW. to accept a spline that ties each board to the adjoining boards above and below . The splines, constructed from % -in . aluminum, %z -in. marine plywood, or other appropriate material and supplemented by appropriate sealants or lubricants (e. g. , beeswax or non-toxic grease) , will largely eliminate between- board leakage while they also significantly strengthen each individual board by transferring to the adjacent boards a portion of the bending moment produced by hydrostatic pressure. Third , to address the issues of adjustability, the modifications include installing steel or wooden cantilevered -beam hangers above each weir from which the contractor will hang commercially-available, adjustable scaffolding similar to that used in commercial painting or window washing . The scaffolding will provide the contractor ' s designated weir operators a safe means to lower the weir boards from the weir walkway to the correct level for installation . The scaffolding will also provide an adjustable work platform , safely suspended above the discharge flow, from which the weir operators can efficiently place and fasten the weir boards to the flange extensions . The remainder of this section discusses the concept of the required modifications in more detail . 2. 3. 1 I-Beam Channel Flange Extensions As stated above, the I-beam channel flange extensions will serve two functions. First, they will provide a wide and smooth surface against which the back (downstream) face of the weir boards will seat to form an effective, although imperfect, sea( . Although not completely water-tight, this seal will greatly reduce the likelihood of significant leakage around the ends of the boards . Second, they will also provide a means to connect and secure each weir board in position without resorting to wedges that may be dislodged by changes in water level or pressure . The contractor will fabricate the flange extensions from nominal 2x8 PT lumber (finished dimensions — 1 %Z in. x 7 % in . ) and install the wooden extensions vertically against the inside face of the downstream flange of each W8xl8 I-beam channel that holds the ends of the weir boards. Adjacent vertical members restrict access and prevent bolting the flange extensions through the I-beam flange itself. As a result , the flange extensions must be bolted through the flange of the adjacent C1503 . 9 channel , with a metal spacer or rubber bushing inserted between the outside face of the C-channel flange and the wooden flange extension (Figure 2 . 1a) . This length of the spacer or the compression applied to the bushing must be adjusted to insure that the flange extension remains parallel to the I-beam flange against which the flange extension must seat . - 6 - The weir system proposed for installation at Site IR- 14 consists of three weir stacks with each stack containing two single side channels and one double center channel for a total of four channels per stack . As a result , the IR- 14 installation will require 12 separate 2x8 flange extensions . Each 2x8 flange extension must be fabricated from a single board to extend the full 13 . 9- ft range of adjustability required by the IR- 14 facility, from - 1 . 2 ft NGVD to at least + 12 . 7 ft NGVD . The first elevation corresponds to the height of the base plate or sill of each weir stack. The second elevation corresponds to the maximum allowable water level in the IR- 14 basin to maintain the required 2 ft freeboard below the + 14 . 7- ft elevation of the dike crest . The contractor will permanently attach each 2x8 flange extension to the I-beam flange as follows : 1 . Drill a series of holes , 2-ft on center and arranged vertically , through the center of the C-channel flange (that is , 1 % in . from the flange ' s edge) to accept 5/ 16-in . x 3 -in . stainless steel bolts . 2 . Chamfer one corner of each 2x8 flange extension to clear the filet of the I-beam channel and thereby allow one edge of the 2x8 to seat against the I-beam' s web (Figure 2 . 1a) . 3 . If necessary, plane one face of the 2x8 flange extension to match, as closely as possible, the taper of the I-beam flange . 4 . With the 13 . 9-ft+ base of the flange extension firmly seated on the weir base plate and the edge of the flange extension firmly seated on the I-beam web, mark then drill matching holes in the extension. 5 . On the upstream face of the flange extension , counter-sink the holes 3/ in. to accept a nut and washer. 6 . Begin installation of the flange extensions by placing a bed of roofing asphalt on the weir base plate to receive and seal the bottom of the flange extension. 7 . To improve the seal between the flange extension and the I-beam channel ' s bituminous coating, wrap the mating surfaces (edge and face) of the flange extension with a continuous gasket fabricated from rubber, neoprene, heavy roofing felt, or other approved materials . 8 . Firmly seat the extensions against the weir base plate and the inner face and web of the I-beam channels . 9 . Align the holes with the pre-drilled holes in the C-channel flange . . 7 - 10 . Insert the 5/ 16 - in . x 3 -in. stainless steel bolts through the C-channel flange, the spacer or bushing, and the flange extension and securely tighten into position with matching washer and nut. 11 . Following installation , ensure that the bolt does not project beyond the upstream face of the flange extension and prevent the weir boards from seating firmly against the face of the extension. 12 . Confirm that the face of the extension remains parallel to the axis of the weir crest to maximize the mating surfaces and provide the optimal seal . 2. 3 . 2 Weir Boards and Splines The contractor will be responsible for providing and fabricating — from standard (PT) dimensional lumber — all weir boards required for the minimum 13 . 9 -ft range of weir adjustment for each of the three weir stacks . To adequately resist the greater hydrostatic forces near the bottom of the weir stack, the contractor must use (nominal) 6x6 boards (finished dimensions – 5 '/� in . x 5 '/� in.) within the lowermost 4 ft of the weir stack (that is , below +2 . 8 ft NGVD) with (nominal ) 4x6 boards (finished dimensions – 3 %x in . x 5 % in . ) for only the upper 10 ft of the weir stack (that is, above +2 , 8 ft NGVD) . In addition to reducing cost and weight, using 4x6 weir boards (3 '/z in . finished vertical dimension) above +2 . 8 ft will improve the accuracy and resolution of the weir height adjustments . To further reduce cost and weight the contractor may use (nominal) 4x4 weir boards (finished dimensions – 3 . 5 in . x 3 . 5 in .) , but only within the uppermost 3 ft of the weir stack (that is , above + 9 . 7 ft NGVD) (Figure 2 . 1 b) . To maximize the mating surface between the flange extension and the weir boards, each weir board must be of sufficient length to extend to within 1 in . of the web of both opposing I -beam channels . No weir boards can be used that when fully saturated would bind within the channels . For the Site IR- 14 installation , a weir board length of 52 in . should meet this requirement based on a 53 . 5 -in. design separation between opposing webs . However, the FIND cannot guarantee that the I-beam channels remain plumb and parallel throughout their length . The contractor remains responsible to verify the actual field dimensions and provide weir boards that will fall within the required tolerance throughout the full height of the weir stack. As stated earlier, to prevent between board leakage and to strengthen the weir stack, a spline will tie each weir board to the adjacent members above and below . To provide a keyway for the spline, the contractor must mill a matching dado or slot on opposite faces of each weir board, each slot set back 1 '/� - 8 - in . from the common, downstream face (Figure 2 . 1b) . For the spline itself, '/ -in . aluminum is the recommended first-choice option , with ''/z -in. 5 -ply , marine-grade plywood ( actual thickness — 12mm, or 15/32 in. ) the lower-cost, second-choice alternative. Other materials , such as plastics or composites may be acceptable , but must be submitted to the Project Engineer for review and approval . Each spline shall be fabricated from the approved material, 2 -in . wide and of an equal length as the weir boards into which each will be inserted . Despite its greater cost compared to marine plywood, aluminum remains the preferred alternative. Unlike marine plywood or other wood-based materials (e . g., wood/plastic composites) , aluminum will not adsorb water, expand , and potentially lock the spline into the slot . As a result , the slot to accept the spline can be milled to a closer tolerance . The addition of an approved , non-toxic lubricant will improve the effectiveness of the sea] , limit corrosion, and insure that the spline will not lock in place . Other non-wood materials (e. g. , plastics) may also prove acceptable, but would likely require a thickness greater than '/ in. to provide sufficient shear strength . Marine plywood remains the second-choice alternative. Its primary advantage, in addition to its relatively low cost, is that additional splines can be easily fabricated on-site as needed . Milling the slot with sufficient tolerance to allow for the plywood ' s inevitable expansion will reduce the likelihood that the spline will lock into position . The addition of a non-toxic lubricant such as a heavy coating of beeswax will reduce the plywood ' s tendency to swell and lock itself into the slot. 2 . 3 . 2 . 1 Weir Board Installation During dredging, each weir board will be added to the stack as follows . Because water typically will flow over the weir crest , the weir operator must first divert the flow to the two remaining weir stacks by driving a section of 1/2 -in. marine-grade plywood between inner face of the upstream I-beam flange and the weir boards . To adequately divert the flow , this section of plywood must span the full distance between the webs of the opposing I-beam channels into which the weir board will be placed, and extend sufficiently above the weir crest such that little or no flow continues over the weir. If necessary to prevent hydrostatic pressure from bending the plywood , the operator may reinforce the plywood ' s upper edge by securing a metal channel to its downstream face . The weir operator must then clear excess water from the slot in the upper surface of the top board in the stack . [Note: the above procedure applies only during active dredging as water flows over the weir crest. Obviously, diverting the flow will not be required when the contractor prepares to start dredging and the weir operator initially installs weir boards to set the initial ponding depth (Section 3. 2), or after the completion of decanting as he closes off the weirs as part of his demobilization procedures (Section 3. 4). ] Next , the operator must apply a thick coating of the - 9 - approved lubricant/sealant to the entire length of the spline and insert a spline into the slot . If necessary to firmly seat the spline against the bottom of the slot, the weir operator may drive it into position by placing a short length of 4x4 with a matching mortise over the spline and striking the 4x4 with a hammer until lubricant extrudes from the joint on both sides of the spline. To prevent deformation of the spline, the operator should not directly strike the spline under any circumstance. The operator then must align the slot of the board to be added with the spline just inserted, and apply pressure to the added board until its bottom face seats firmly against the upper face of the board below . Again, to preserve a smooth mating surface, the operator must not strike the weir board directly with the hammer, but rather must first place the short section of 4x4 on the board being added and then strike that section. With the added weir board seated firmly against the board below, the final step in adding each weir board requires that the weir operator secure the board in position as follows : 1 . If necessary to force the downstream face of the added board firmly against the flange extension, temporarily drive a wooden shim between the inner surface of the upstream I- beam channel flange and the plywood that temporarily diverts the flow . 2 . Working from the downstream (inner) side of the flange, drill a pilot hole through the flange into the added board . The holes through the extension should then be enlarged such that the lag screw that will attach the weir boards to the flange extension will not bind in the hole . 3 . Insert a minimum 3 -in . lag screw through the extension hole, and drive it fully into the pilot hole in the weir board until the screw head seats against the extension and draws the downstream face of the weir board tightly against the flange extension. 4 . After ensuring the added board remains firmly in position, remove the temporary plywood that had been blocking the flow (and , if used, the additional shims) , 5 . Proceed to the next weir stack, continuing the process until all three weir stacks are set at the same, higher elevation. 2 . 3 . 2 . 2 Weir Board Removal Following the completion of dredging, the contractor must begin decanting the ponded water within the basin by gradually removing the weir boards . Section 3 .4 describes the decanting process . However, in removing the individual boards , the contractor must follow the procedures outlined below . - 10 - With the work platform of the scaffolding lowered into position near the weir crest , the weir operator will remove the lag screws that have connected each board to the flange extension and remove the top board with a pry bar. Through this process , the weir operator must take care to minimize damage to the board and spline. All boards and splines removed intact and with minimal damage should then be stacked neatly on a level surface with spacers separating each level to promote air-drying . The contractor should use these boards and splines removed intact to close off the weirs following the completion of decanting. However, if swelling of the board or spline prevents the operator from prying the top board from the one beneath intact, the operator may remove the top board by cutting it into several sections with a chain saw or cordless electric saw and knocking the sections loose with a sledge . All boards and splines removed in such a manner must be discarded offsite in an approved manner. 2. 3. 3 Seaffolding/Ladders To provide safe access to the weir boards and a secure working platform from which to perform the now more complex weir board installation procedure, the contractor must provide an approved, OSHA -compliant , moveable scaffolding system, similar to those in wide commercial use for painting or window-washing. The scaffolding must be suspended by ropes or cables from contractor-installed, wooden or steel cantilevered beams permanently fastened to the 3 " x 12 " bridging that supports the walkway deck stringers, or to the wooden support piles themselves . The specific strength requirements and fittings for the beams will depend on the requirements of the specific scaffolding system employed . The scaffolding must provide access to the full span of the three stack weir system, either through the use of a single scaffolding platform that may be moved from one stack to another or multiple platforms that can provide access to all three stacks simultaneously . The contractor must use the scaffolding to lower the weir boards to be installed from the weir walkway to a position near the weir crest from which the weir operator may safely install additional weir boards . Installation of the scaffolding will require removal of the existing ladder system that presently extends from the walkway down the upstream face of each weir stack. This must be replaced with a ladder system, either fixed or movable, on the inside of each weir stack that will allow the operator to access the back (downstream) side of the weir boards, if necessary to install the weir boards and attach each board to the flange extension. - 1t - 2. 3. 4 Weir-Mounted Stage Gauge Finally, to improve the contractor ' s ability to monitor water Ievels and ponding depths within the basin , the contractor must install a stage gauge, or staff, constructed of UV-resistant PVC or fiberglass, to the front face of the weirs . Clearly marked in feet and tenths (as for a surveyor ' s stadia rod) and leveled to NGVD, this gauge will provide a means for the contractor (as well as inspectors, site operators , or other personnel authorized to enter the IR- 14 facility) to directly read the water level within the basin from any position around the basin ' s perimeter. 3 . 0 WEIR OPERATIONAL GUIDELINES 3 . 1 Introduction This section presents guidelines for operating the discharge weirs at FIND Site IR- 14 during all phases of operations for which the selected dredging contractor will be responsible as part of his contracted services . These guidelines are intended to supplement the guidelines contained in the site ' s Management Plan (Taylor et al . , April 1992) . In those cases where the guidelines presented here conflict with the guidelines presented in the Management Plan, the present guidelines supersede the guidelines contained in the earlier plan document . The remaining sections of this chapter are organized as follows . Section 3 . 2 outlines requirements for installing the required shut-off valve on the weir outflow pipe and modifying the existing weir system consistent with the preliminary design modifications presented in Chapter 2 . 0 . Section 3 . 3 presents guidelines for setting the initial weir elevation before the start of dredging operations and for operating the weir system during dredging operations as required to control water level and ponding depths within the basin and to maintain effluent quality consistent with permit requirements. Section 3 . 3 also presents dike inspection requirements that may be triggered by excessive ponding depths within the basin . Section 3 . 4 presents guidelines for operating the weir system through the completion of decanting procedures , for securing the weir system to prevent unauthorized discharges following the completion of decanting, and for demobilizing from the site at the completion of contracted services. - 12 - 3 . 2 Site Preparation and Pre-Dredging Operations 3. 2. 1 Installation of Shut- Off Valve To ensure the ability to prevent any possible uncontrolled discharge from the weir system, the contractor must install an approved shut-off valve on the discharge pipeline attached to the weir system . The contractor must submit valve specifications for review and approval by the Project Engineer as an element of his preconstruction submittals . The installation recently completed at FRED Site SJ - 14 suggests that the installation at Site IR- 14 may require a ductile iron resilient wedge gate valve; however, the contractor may submit other valve designs for review and approval by the Project Engineer. Installation must conform to the valve manufacturer ' s specifications , and must be completed before performing the required system leak test . Closure of the shut-off valve at any time that water flows through the valve must follow the valve manufacturer' s recommendations for the pressures and flow velocities at the time of the closure . 3 . 2. 2 Installation of Effluent Discharge Pipeline With the shut-off valve installed and fully closed, the contractor may begin to install the weir discharge pipeline that will extend from the shut-off valve 850 ft} to the shoreline of the Indian River (ICWW) . This pipeline will remain in place following the contractor ' s demobilization from the site as required to discharge stormwater and drainage from the basin. As a permanent installation, the pipeline ' s construction details (e. g. , buried vs . at grade, allowable slopes , etc .) must be addressed during the project ' s final design phase to reflect a topographic survey of the pipeline route . Section 3 . 4 . 2 discusses the periodic release of stormwater following the contractor ' s demobilization . 3. 2. 3 Installation of Required Weir Modifications Simultaneous with or immediately following the installation of the shut-off valve, the contractor must complete all required weir modifications including installation of the I-beam channel flange extensions (Section 2 . 3 . 1 ) , fabrication of all required weir boards ( Section 2 . 3 . 2), and installation of the weir scaffolding and ladder system as required to access and install the weir boards (Section 2 . 3 . 3 ) . - 13 - 3 . 3 Weir Operating Procedures During Dredging Once dredging begins and continuing though the completion of placement operations , the contractor remains responsible for operating the weir system as required to maintain effluent turbidity standards without compromising dike stability. The contractor achieves these objectives by adding weir boards and raising the weir crest elevation as required to control water level and ponding depth, and thereby retention time, within the basin . However, as described in Section 3 . 3 .2 , the contractor must not allow the water level within the basin to increase too quickly or the ponding depth to increase beyond the recommended maximum . Either condition could potentially lead to excessive seepage through the dikes, slope instability and , under extreme conditions , dike failure. Obviously, avoiding these conditions remains the one of the contractor ' s primary responsibilities . The remainder of this section presents guidelines that the contractor must follow to complete the required dredging and maintain effluent quality without compromising the integrity of the dike or the weirs . The following basic principles of operation provide a necessary preface to that discussion : • Throughout all phases of dredging operations, the contractor must maintain a qualified operator at the containment facility. As part of the required pre-construction submittals, the contractor must submit the specific qualifications of the designated operator(s ) to the Project Engineer for review and approval . Each operator shall remain in constant radio contact with the dredge plant and shall possess the direct authority to shut down the dredge if required . Each operator shall retain primary responsibility, either through his direct action or through actions of others under his direct supervision, for adjusting the weirs to maintain effluent quality and ensure dike integrity ( Section 3 . 3 . 1 ), for perfornung all inspections related to dike integrity, for documenting the results of those inspections ( Section 3 . 3 . 2), and for ensuring the security of the containment facility and the safety . of all contractor personnel under his or her direct supervision. • Throughout all phases of dredging operations, the contractor must ensure that all three weir stacks remain fully operational . Closing off one or more weir stacks or weir discharge pipelines by inserting bladders or other blockages is specifically prohibited. • Throughout all phases of dredging operations except during short intervals while weir boards are being added or removed from individual weir stacks , the contractor must - 14 - ensure that all three weir crests remain at equal elevations, and that flow over all three weirs (as measured by the depth of flow over the weir crests) remains essentially equal , within the limits of adjustment provided by the weir boards . 3. 3. 1 Operational Ponding Depths Before dredging begins, the contractor must set the initial elevation of the weir crest . This initial weir crest elevation corresponds to the minimum ponding depth at the weirs that must be reached before the contractor releases any water from the basin. The minimum ponding depth reflects considerations of the basin ' s retention performance with respect to the settling characteristics of the dredged sediment . The retention analysis presented in the IR - 14 Management Plan (Taylor et al . , March 1999) recommended a minimum 4 . 0 -ft ponding depth based on a retention analysis that reflected available sediment data and the performance characteristics of an 18 - in . dredge . The analysis determined that for the 10 . 18 -acre interior plan area of the fR- 14 containment basin , a 2 . 0-ft ponding depth provided a maximum retention time of 6 . 2 hours . This time exceeds the 4 . 1 hours required for the finest fraction of sediment anticipated for placement in the IR- 14 basin to settle out of the 2 . 0-ft withdrawal depth, based on the projected settling characteristics of the sediment to be dredged . However, consideration of actual field conditions suggests that additional retention time may be required to provide adequate settling and further reduce effluent turbidity levels . Given that retention time is directly related to ponding depth, increasing ponding depth to 4 . 0 ft also increases the maximum retention time to 12 .4 hours, or over three times the required settling time . Experience with other similar FIND dredged material containment facilities has shown that increasing the ponding depth to 4 .0 ft should not compromise dike stability . As a result, to ensure that the DU - 8 facility produces acceptable effluent under all foreseeable conditions , the recommended mean operational ponding depth is set at 4 .0 ft, with 5 . 0 ft the recommended maximum ponding depth . Section 3 . 3 . 2 further discusses maximum ponding depth and related dike inspection requirements . Based on a recommended 4 . 0-ft mean operational ponding depth, the contractor should set the weir crest to an initial elevation of 4 . 0 ft above the -0 .4 ft NGVD mean elevation of the basin floor, or +3 . 6 ft NGVD . Given the slope of the basin floor, this initial weir crest elevation also corresponds to 4 . 8 ft above the - 1 . 2 ft NGVD elevation of the weir base or sill . Lacking a bottom slot and spline to tie it to the weir base plate, the bottom weir board should be set in a thick layer of roofing asphalt or other approved sealant to minimize the potential for water to leak below the bottom board . Because the water nearest the basin floor contains the highest concentration of suspended sediment , the contractor must take particular care to seal the bottom weir board to the weir base plate as well as to the flange extension. All - 15 - remaining weir boards must be set according to the installation guidelines presented in Section 2 . 3 . 2 . In addition, as also discussed in Section 2 . 3 . 2 , the contractor must use weir boards fabricated from nominal 6x6 timbers ( 5 . 5 in. x 5 . 5 in. finished dimensions) for the lowermost 4 ft of each weir stack. As dredging progresses and the level of ponded water approaches the initial weir crest elevation, the contractor must determine whether to begin the release of effluent . This decision must reflect the results of turbidity testing of the upper 2 ft of the ponded water immediately upstream of the weirs . A depth of 2 ft represents the estimated maximum depth of withdrawal , that is, the depth of the surface layer released over the weirs . 3. 3. 2 Maximum Ponding Depths and Required Inspections If testing determines that the ponded surface water at the weirs fails to meet permit requirements , the contractor must provide additional retention time, either by raising the weir crest elevation or shutting down the dredge until sufficient settling has occurred . If the contractor chooses to raise the weir crest by adding additional weir boards, he must proceed with caution. Experience has shown that increasing the water level too quickly or maintaining an excessive ponding depth can lead to excessive seepage through the dike, a condition that increases the potential for slope instability and, under extreme circumstances, dike failure . Considerations of dike safety require that mean ponding depths at the IR - 14 containment facility must not exceed 5 ft without notification and approval of the Project Engineer. Even with all required approvals, the contractor must not exceed the 5 -ft maximum, even to meet required effluent standards, without instituting a significantly more rigorous program of dike inspection. Chapter 4 . 0 outlines the basic requirements for the dike inspection program as well as the critical conditions that would trigger more intensive inspections. Inspections , conducted at least once a week under normal conditions, must increase to at least once a day immediately upon discovery of a critical condition. However, increasing the ponding depth (as measured at the weirs) beyond the recommended 5- ft operational maximum requires that the contractor further increase the inspection frequency and provide close, continual inspection of the entire dike perimeter at all times while ponding depths remain greater than the recommended 5 -ft maximum. All dike inspections must be performed by a qualified geotechnical engineer or engineering technician experienced in the inspection of earthen dams , reservoirs , or dredged material containment facilities . As part of the required preconstruction submittals, the contractor must provide the qualifications of all designated inspectors to the Project Engineer for review and approval . - 16 - Once the basin produces effluent that meets the required turbidity standards , the contractor should then maintain the necessary ponding depth by increasing the weir crest elevation at about the same rate as sediment builds within the basin . The contractor should install additional weir boards at the point the depth of flow over the weir crest approaches the width of the boards to be added . As the basin nears its design capacity, the contractor must reduce his operational ponding depth to ensure that the elevation of the ponded water remains a minimum of 2 ft below the elevation of the dike crest, the minimum allowable freeboard for the IR- 14 containment facility. Continuing to meet effluent standards may require that the contractor reduce the dredge output or operate the dredge intermittently to provide the required retention time . During periods when the dredge remains idle, the contractor may also find it necessary to grade and distribute the mounds of coarser material deposited nearer the dredge discharge outlet to increase the plan area of the ponded water and thereby improve the basin ' s retention performance and effluent quality. Under no circumstances shall the contractor allow the dredged material to mound above the elevation of the dike crest . 3 . 4 Weir Operations During Decanting Following the completion of dredging operations , the contractor must continue to operate the weir system and slowly release the clarified surface water that remains ponded within the basin over the weir crest by incrementally removing weir boards . The process , known as decanting, continues until all residual ponded water within the basin at the completion of dredging is released over the weirs . To maintain effluent quality throughout the decanting process, the contractor should allow the flow over the weirs to drop essentially to zero before removing another set of weir boards . The contractor may be required to grade the deposited dredged material to drain isolated pockets of water so that this water may also be released over the weirs. If at any time during the decanting process monitoring shows effluent turbidity to exceed permitted standards, the contractor must again add weir boards until testing of the ponded water that remains within the basin confirms that turbidity has returned to acceptable limits . While decanting proceeds , the contractor may begin to dismantle and remove the dredge pipeline. Working from the site back toward the ICWW, the contractor must plan the operation to ensure that all residual water contained within the pipeline drains to the ICWW . 17 - 3. 4. 1 Project Close-out and Demobilization Procedures Following the completion of decanting and the removal of all residual ponded water from the basin via the weir discharge pipeline, the contractor must re-install the weir boards to a height sufficient to ensure that no stormwater discharges over the weir crest . Stormwater thus retained must remain within the basin until the FIND ' s designated site operator returns to perform a controlled release (Section 3 . 4 . 2) . To this end, before the contractor demobilizes from the site, the Project Engineer will determine the weir crest height required to ensure that no uncontrolled release of stormwater occurs following project close- out . This determination will reflect information specific to each placement operation at the IR- 14 facility including the bulked volume of the dredged material , the geometry of the deposition, and specific permit requirements that may be imposed to govern the control and release of stormwater from the IR- 14 facility . The contractor must then re-install the weir boards consistent with the procedures outlined in Section 2 . 3 . 2 . 1 and set all weir stacks at or above this elevation. The earlier removal of weir boards to decant the site may have resulted in some boards being destroyed (that is, cut out into sections or damaged such that they cannot provide an adequate seal when re-installed consistent with the procedures outlined in Section 2 . 3 . 2 . 1 ) . The contractor should then fabricate additional weir boards sufficient to reach the required elevation , plus additional boards to replace those that may become damaged during future stormwater releases . The contractor must then close the facility ' s weir discharge shut-off valve (Section 3 . 2 . 2), and verify and certify to the FIND that the valve remains fully closed and free from leaks. To facilitate the future release of stormwater from the basin, the contractor' s final task is to excavate a small sump immediately adjacent to one or more weir stacks . This sump will promote stormwater drainage within the basin to the weirs so that removal of one or more weir boards will allow the water to pass over the weir crest and continue to the ICWW, by gravity flow, through the permanent weir discharge pipeline as discussed below . 3. 4. 2 Stormwater Control following the Contractor 's Demobilization After the contractor completes his demobilization from the IR- 14 facility, responsibility for continued management of stormwater within the basin, as well as all other continuing site maintenance activities between successive dredging operations, resides with the FIND . To this end , the FIND ' s designated site operator will periodically return to the site to release stormwater as well as the accumulated drainage from the dredged material as it continues to consolidate under its own weight . - 18 - To release this water, the site operator will first open the shut-off valve , then remove one or more weir boards from a single stack as necessary to release the surface layer of the ponded water adjacent to the weirs . To minimize the work required, the operator need only open one-half of a single weir stack (that is , one column of boards) and only to the level to start water flowing over the lowered weir crest. Removal of the weir boards should follow the procedures outlined in Section 2 . 3 . 2 .2 . Only when the flow over the lowered weir crest approaches zero should the operator remove another board . This process should continue one board at a time, until all ponded water drains from the site . The operator should then replace the weir boards following the procedure outlined in Section 2 . 3 .2 . 1 , and close the weir discharge shut-off valve. 4. 0 DIKE INSPECTION REQUIREMENTS As discussed in Chapter 3 .0, to comply with likely requirements of the Environmental Resource Permit (ERP) for the operation of the IR- 14 facility, throughout all phases of dredging and dewatering the contractor shall be responsible for additional inspections of the containment facility related to ensuring the integrity and stability of the containment dikes . The remainder of this chapter details specific inspection requirements . 4 . 1 Critical Inspections The contractor shall perform periodic inspections of the containment dikes to check for certain critical conditions that may require the .implementation of remedial measures . As discussed in Chapter 3 . 0 , all inspections shall be conducted by a qualified geotechnical engineer or engineering technician with specific training and experience in performing inspections of earthen dams , earthen reservoirs, or earthen dredged material containment facilities . As part of his required preconstruction submittals , the contractor must submit the qualifications of the designated dike inspector for review and approval of the FIND or its authorized representative. The contractor shall conduct inspections for the items listed below every week. Any of these conditions shall be considered as indicating a critical condition that requires immediate investigation and may require emergency remedial action . Immediately upon confirming the existence of a critical condition, the contractor must inform the Project Engineer and increase the inspection frequency to a minimum of once daily. The Project Engineer will then immediately notify the Florida Department of Environmental Protection (FDEP) . Within 24 hours of confirming a critical condition, the contractor must submit to the Project Engineer documentation of the inspections and implemented remedial actions . The - 19 - Project Engineer will then submit to the FDEP a written report detailing the condition and the implemented remedial actions within seven (7) days of the confirmation of the critical condition . The following items shall be considered as indicating a critical condition : 1 ) Seepage with boils , sand cones, or deltas on outer face of the dike or downstream from the dike' s outer toe; 2) Silt accumulations, boils, deltas , or cones in the drainage ditches at the dike ' s base ; 3) Cracking of soil surface on the dike ' s crest or on either face of the dike; 4) Bulging of the downstream face of the dike; 5 ) Seepage, damp area , or boils in vicinity of or erosion around a conduit through the dike; and 6) Any subsidence of the crest or faces . 4 . 2 Supplemental Inspections During the critical inspections described above, the items listed below shall be considered indicators of potential areas of concern that the contractor must then continue to monitor closely during subsequent inspections and to perform repairs as necessary . Within 24 hours of confirming the presence of an indicator of a potential area of concern, the contractor must also inform the Project Engineer of the item and any required repairs undertaken. Indicators of potential areas of concern include the following: 1 ) Overgrowth patches of vegetation on the downstream face or close area downstream from the toe; 2) Surface erosion, gullying, or wave erosion of the upstream face of the dike; 3 ) Surface erosion, gullying, or damp areas on the downstream face of the dike, including the berm and the area downstream from the outside toe; 4) Erosion below any conduit exiting the dike; and 5) Wet areas or soggy soil in the downstream face of the dike or in the natural soil below dike. - 20 - 5 .0 ESTABLISHMENT AND MAINTENANCE OF VEGETATIVE COVER Following construction of the contairunent facility , and again following each use of the facility to receive and dewater dredged material, the FIND will remain responsible for establishing and maintaining a vegetative cover on all exposed surfaces of the dike . To prevent the establishment of shrubs, trees , or other woody vegetation, the dike ' s slopes and crest will be regularly mowed, and maintained sufficiently short to allow visual inspection of the soil surfaces in critical areas such as 1 ) The condition of vegetation on the dike and in areas for 50 ft downstream from the outside toe; 2) The condition of soil surfaces on the top and slopes of the dike and in areas for 50 ft downstream from the outside toe; 3) The condition of drainage ditches in the area of the base of the dike; 4) The liquid surface elevation and amount of freeboard; and 5 ) The condition of spillways and water level control structures , including all conduits exiting the dikes . . 21 -