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1 street right-of-way corridor which exists within the Rockridge service sewer/conventional pumping station alterna- area. The gravity collection tive will be investigated in this report. collection A second alternative is the use of a low-pressure pump This system makes use of the existing septic tanks which would ' system. storage receptacles for sludge on the tank continue to function as the top of the tank. With this system, a pump and bottom and scum on ' pump chamber are suspended from the top of the septic tank and the of the existing septic tank and liquid is drawn from the middle zone pumped into a series of manifolded force mains to a central collection a Each house would have its own pump installed in or discharge point. A requirement of this alternative is that each its own septic tank. ' septic tank be totally water tight or the constant leakage of ground into the septic tank will cause the pumping system to operate water and pump large quantities of ground water into the treat- continuously ment plant. Since all of the septic tanks are quite old and it is ' suspected that they all leak substantially, it would be necessary to with this measure, and replace each of the 375 septic tanks. Even remove table would establish a major realistic source the high ground water ' to whether the new septic tanks would be, and remain, of concern as it was decided not to further water tight. Because of these reasons, ' explore this alternative. The third alternative is the installation of a grinder pump and ' pump chamber for each of the 375 dwelling units with each grinder pump into a small sized manifolded system of force mains. These discharging 6" small force mains would discharge at a point or points along the and 18" existing force mains which run by, or cross through, the Rockridge Construction which would require excavation project service area. of the existing limestone could be avoided by installing each grinder and chamber within the septic tank which is presently in place ' pump for each of the 375 dwelling units. The lid of the existing septic be removed, the contents of the septic tank pumped out and ' tank would the existing septic tank back-filled with sand material. The grinder back-filled sand chamber would be installed within the pump and pump and the existing 4" lateral from the house connected to the ' material A system of small force mains would be constructed grinder pump chamber.