1987-055 - Laserfiche WebLink

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' were paved and houses constructed in Fairlane Harbor. For the purposes of this study and report, it is assumed that once the wastewater has been collected from the Rockridge project service a it will be possible to pump the collected wastewater into the are , existing 18" and 6" force mains for the continued conveyance of the ' wastewater to the Vero Beach wastewater treatment facility. It should be recognized that future refinements of the selected collection system ralternative, together with subsequent negotiations with the City of Vero Beach, may alter this assumption. Viable Alternatives 'L� �I There is no question that the existing 375 dwelling units within the Rockridge service area would have had sewer service long before now were it not for the soil conditions which exist within the project site. As indicated before, the soil boring study and report, which is contained in the appendix of this report, shows that the entire project service area rests on a 1 to 2 foot thick layer of hard limestone which is, generally, 1 to 3 feet beneath the ground surface. Under the hard limestone is a high ground water table which is within 3 feet of the ground surface. There is no question why the existing water distribution system is constructed with the small pipes resting on top of the hard limestone layer. The first alternative to consider is to construct a conventional gravity collection system consisting of manholes and 8" gravity sewer along with a system of conventional sewage pumping stations. The con- struction of the gravity sewers will involve the break-up and removal of the layer of hard limestone in the sewer line's path as well as the installation of well point dewatering systems as the sewer system is constructed. It is anticipated that at least a 20' wide swath of hard limestone would have to be removed in order that proper dewatering can be done and to prevent undermining of the existing sand from beneath the layer of limestone remaining on each side of the trench. The need for the wide trench area, plus additional space requirements to store the excavated material and provide for equipment maneuvering, requires that the gravity collection system be installed within the 70' wide -3-