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Mr. Himanshu H. Mehta, P.E. 3 August 2021 Page 3 establishing background water quality for seven (7) additional surface water sampling sites (LC4-SW to LC10-SW) along the Lateral C Canal. SWDD sampled and analyzed water -quality for these surface water sites in the January and April 2020 quarterly water -quality assessment events. Following, the April 2020 quarterly sampling event, FDEP approved (via e-mail on 17 July 2020) SWDD's request to limit the monitoring of the surface water sites to SW -LCI, SW- LC2, S W-LC3 and S W-LC4. Results of the quarterly sampling downgradient of the C&D debris disposal facility have indicated persistent. detections of ammonia, arsenic, sodium, iron, total dissolved solids (TDS), total nitrogen (TN) and total phosphorus (TP) in groundwater and persistent detections of ammonia, sodium, iron, TDS, TN and TP in surface water sampling locations in the Lateral C Canal adjacent to the evaluation groundwater monitoring locations. Geosyntec completed a site visit on 21 July 2020 and prepared a 10 August 2020 memorandum to SWDD. One of the objectives of the site visit was to visually observe the Site conditions on the east side of the C&D debris disposal facility and the Residuals Dewatering Facility (RDF) relative to the current monitoring wells and surface water monitoring locations. A stormwater management ditch located between the C&D debris disposal facility and the RDF is suspected to be a potential source area for the persistent detections. A supplemental groundwater assessment was completed in this area in late 2020 to identify.the lateral and vertical extent of the groundwater impacts. Results of the assessment, as indicated in the "Draft Supplemental Groundwater Assessment Report, C&D Debris Disposal Facility" (hereafter referred to as Draft Supplemental Report) dated July 2021, indicated groundwater impacts downgradient of the C&D debris disposal facility and the RDF. The Draft Supplemental Report recommended additional assessment of the RDF area including historical compliance document review, stormwater system as -built documents review, groundwater sampling and sediment sampling. The remainder of this proposal provides additional detail on the proposed assessment activities. PROPOSED SCOPE OF SERVICES The proposed scope of services includes activities to be performed on behalf of SWDD for the additional assessment at the RDF and C&D Facility. For the purpose of budgeting, the scope of work has been divided into the following four (4) main phases: • Phase 1 — General Consulting/Meeting Support/Project Management; • Phase 2 — Historical and As -Built Documents Review; • Phase 3 — RDF and C&D Debris Disposal Facility Additional Assessment; and NCP2020-3158/JL21057 GW Compliance Technical Support Services.doc