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1 <br />' <br />The existing disposal field for each home would be abandoned and <br />installed in each basin would intermittently discharge <br />a grinder pump <br />' <br />the wastewater from each house into the manifolded small force <br />main system shown on "Exhibit B " In effect, the grinder pump/small <br />' <br />force main system functions as a water supply system in reverse. <br />Instead of pressurized water being supplied by a main pipeline <br />to each dwelling unit, pressurized wastewater is discharged from <br />' <br />each dweling unit into a common main. <br />Each of the 375 units in the Rockridge project service area <br />' <br />would be furnished with its own basin and grinder pump. When <br />considering the layer of hard limestone and high ground water <br />table factors, the grinder pump/manifolded small force main system <br />results in distinct and profound advantages since construction <br />will be above the ground water table and layer of hard limestone. <br />In addition, the small manifolded PVC force mains have flexibility <br />which allows them to be deflected around trees, shrubs, sheds, <br />' <br />and utility poles located within the existing back yard easement <br />area. <br />' <br />The small 2 and 3 inch diameter PVC force mains will primarily <br />be constructed in a north -south direction and it is proposed that <br />the force mains connect directly into the existing 6" PVC force <br />' <br />main along 16th Street and directly into the 18" existing force <br />main along 18th Street. <br />' <br />The grinder pump system is a proven system with a track record <br />of reliability provided that the system is properly designed and <br />' <br />quality pumping equipment is used in its construction. Once installed, <br />the system should provide trouble-free operation and effectively <br />solve the existing sewage problems in the Rockridge area. <br />A disadvantage of the grinder pump system, when compared <br />to the conventional gravity sewer collection system, is that the <br />grinder pump will cause an increase in the homeowner's electrical <br />bill due to the intermittent operation of its 2 HP, single phase <br />motor. Assuming the average dwelling unit discharges approximately <br />300 GPD of wastewater into the system, it is estimated that the <br />' <br />2 HP, single phase pump motor will cycle approximately 6 times <br />and pump a total of 15 minutes out of every 24 hours. Using an <br />-8- <br />r� <br />