04-22-1985 Council Packet - Laserfiche WebLink

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the MPCA suggest that a community septic-tank/drainfield system should generally not be used for more than 10 homes. Greater amounts of effluent discharged into a concentrated location in the soil will either not be accepted hydraulically or will create nutrient or ni- trate problems as the liquid percolates downwards. Aside from these potential hydraulic/pollution problems, the estimated costs of a collection system and community drainfield for the Crystal Bay area rival the costs of a collection system dis- charging to the MWCC interceptor. System design and estimated costs. The collector system would include individual septic tanks and effluent pumps discharging to a pressure sewer line which would extend to the community drainfield location. Installation of the pressure collection system, including new septic tanks, pump chambers, pumps and controls and the pressure collection lines, (which need only be 8' deep, and require minimal restoration) is estimated at about $500,000 or about $6,000 per unit for Crystal Bay. The treatment portion of the system would include a stilling tank discharging to a large drainfield. Drainfield sizing would be based on an average f low rate of 274 gpd/unit x 83 units or about 22,750 gpd. Two possible locations for this drainfield were considered in the Crystal Bay area. Site A is P.I.D. #10-117-23 21 0007, an undeveloped parcel of approximately 9 dry acres lying immediately adjacent to Crystal Bay on the north side of Willow Drive. Based on the Hennepin County Soil Survny, an estimate of the percolation rate of the soils at this site would be 15-30 minutes per inch, requiring 2 square feet of drainfield area per gallon of waste per day, or a drainfield of 45,500 square feet of trench bottom area, using approximately 3 acres of land area after proper trench spacing. An equivalent additional acreage would be prudently required to ensure that replacement of this system could be installed should the original system fail. This site potentially could be divided to create 4 attractive residential 2-acre building sites, with an estimated raw land value for the entire 9-acre parcel of $125,000. The cost of trench drainfield is estimated at $2.50/square foot. Hence, the drainfield system is estimated at $91,000 plus approximately $30,000 in additional site work (stilling tank, fencing, seeding, etc.). The total cost then is estimated at: $500,000 pressure collections system 125,000 land acquisition 91,000 drainfield construction 30,000 site work $746,000 190,000 plus 25% legal, administrative, engineering $936,000 T 83 s $11,275/unit. Site R, P.I.D. #10-117-23 33 0002, is a parcel of about 40 dry acres, about 2/3 wooded, on the south side of Country Road 51 across 12