01-13-2014 Council Packet - Laserfiche WebLink

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SECTION 3 PROPOSED SA1vITARY SEWER EXTENSION A. ALTERNATE 1 -FORCEMAIN Alternate 1 proposed extension of a 2-inch diameter forcemain from the gravity sewer on Shoreline Drive within Green Trees Road and north of the cul-de-sac to the most northerly lot. Figure 1 in the Appendix shows the proposed plan. This forcemain would allow each lot to pump raw sewage into the municipal sewer system and would allow eliminating the current sepric tanks and c3rain fields. Each lot would need a private grinder pump station to provide the pumping. Grinder pumps cut up the solids to allow raw sewage to be pumped through the 2-inch forcemain. The lots with existing pump stations likely are effluent pumps that pump relatively solids-free effluent from the septic tanks. These effluent pumps would need to be replaced with grinder pumps. The septic tanks would need to be pumped out and abandoned by filling with sand. The forcemain is proposed to be constructed by direction drilling, a trenchless construction method. The drilling would be done from the forcemain angle point in front of House No. 1485 which will require excavation for access. Excavations will also be required at both ends and also for the installation of the forcemain stubs to each lot. The service stubs can be located to facilitate connections to each house and to minimize disruption of surface improvements and landscaping. The forcemain will be 7.5' deep to protect it from freezing. Restoration of all disturbed surface areas is included in the project. The final plat dedicated utility and drainage easements to the City of Orono over the street outlot, plus 10 feet on each side of the outlot and also 5 feet on each side of the property lines. The proposed forcemain is within the street outlot up to the cul-de-sac. A new 20 foot wide permanent easement is required north of the cul-de-sac as shown on Figure 1. The easement is shown along driveways as much as possible. The forcemain curves shown on the plan are the minimum radius curves possible with directional drilling which limits the flexibility in the forcemain route. The extension of sewer service requires analysis to determine if existing facilities have adequate capacity to accommodate the increased flow. The critical component of the existing system is Grinder Station 9. This station has two grinder pumps each with a Page 4