1987-055 - Laserfiche WebLink

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1 ' The ground water table rests immediately below the layer of limestone and the presence of both the limestone layer and shallow ground water table make the construction of a conventional gravity sewage collection ' system very difficult. The Rockridge area consists of approximately 375 existing dwelling ' units, each built on lots generally 57' wide by 97' deep. The area is furnished with a water supply system by Indian River County. The ' water supply piping is constructed on top of the existing limestone layer and within back yard easements. Two alternatives were considered and schematic designs of each included in this report. One sewage collection alternative was the construction of a conventional gravity sewer collection system with ' conventional pumping stations. The total construction cost estimate of this alternative, including 15% contingencies and the engineering ' design fee, is $2,084,593.00. The construction of the conventional gravity collection system would also involve the total destruction of the existing roadway street within Rockridge and the need to completely 1 restore the street system. Also, a substantial amount of vibration and noise would be experienced during construction due to the break - up and removal of the existing hard limestone layer. The second alternative involves the installation of an individual ' grinder pump and basin for each of the 375 dwelling units and the con- struction of a network of small manifolded PVC force mains within the ' back yard easement areas. The estimated construction cost for this alternative, including 15% contingencies and the engineering design fee, is $1,108,195.00. The grinder pump/small force main alternative ' would enable construction by the use of small equipment and it is antici- pated that the entire construction of the project could occur without ' the need to remove rock. The anticipated operation of the 2 HP, single phase grinder pump would result in additional electrical expense to ' each homeowner, which is estimated in the range of $1 to $2 per month. It is our recommendation that the alternative using a conventional gravity collection system be rejected and the alternative utilizing the individual grinder pump/small network force main system be accepted as the best means of providing sewage service to the Rockridge area