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C) 0 7 Two Well Drillers' Logs were found for nearby domestic wells. Underground lithology specific to the subject property cannot be discerned from these logs; however, they do show intervening strata of various clay types, sand and gravel. The property is not subject to 100-year flooding. Surface water will be managed by on-site retention basins. "/(§4.3 nc�� A domestic well that serves the Andrews' residence was sampled from the hose Bibb next to the well after it ran for 15 minutes to ensure the sampling of aquifer formation water. �/( 4. A plastic bottle was used for the nitrate sample and two amber VOC bottles were used for r t�CP/EDB samples. The samples were placed in a cooled ice chest and transported under the attached Chain of Custody to A& L Labs in Modesto, California to be analyzed for nitrate, and Dibromochloropropane (DBCP), and Ethylene Dibromide (EDB). /,�r. an4 Water analysis reveals a low nitrate (as nitrate -NO3) concentration of 11 ppm for the domestic well. DBCF and E B were foun Below DtirclihIc Limits (BDJ-). The Maximum Contaminant Level MCL for nitrate in drinkin water is 45 m. This II ppm nitrate concentrations may be considered a background concentration that has accumulated over eons. Since 1. The groundwater is dee 2. There are high clay content intervening soil strata 3. Low septic sstem density surrounds the proerty, and 4. Agtcultural 12roductiola.land de lso low nitrate im act ma be attenuated over time. '"o 7.0) CONCLUSIONS P/The perc test results for proposed Parcel 1 and the Designated Remainder show acceptable percolation for the management of septic system effluent flows. For these two Parcels, effluent management will occur at the deeper depths representative of sumps, or limited depth seepage pits. For Parcel 1 effluent management will occur mostly at a sum depth of .5 feet. For the Designated Remainder,percolation of effluent will occur at a depth of 19 feet. It will be the determination of EHD to install a dee sum to be excavated with an"extgrid-a-lige" he test location, or to drill se age ILits to this depth. As noted for the shallow tests on the two Parcels,there will be very little effluent percolation at leachline depth. When the soil becomes saturated, percolation will cease and the sumps and/or seepage pits will manage the effluent flows. e considered for installation, instead of typical leachlines. Chambers may allow for greater 9 A new law that is to be enforced may restrict the installation of seepage pits (Assembly Bill 885). Before this law is implemented, EHD may require the installation of seepage pits on both Parcels of this project for the following reasons: 1.) They are the typical and principle effluent management structure installed in this area, 2.) There is a significant distance of approximately 85 feet between the bottom of a seepage pit at 25 feet b.g.s. and the current groundwater depth of 110 feet, 3.) Seepage pits allow head pressure buildup to force effluent into the underlying anaerobic clay soils, 4.) If effluent levels rise 6 feet above the bottom of the seepage pit, the effluent could then be managed by the more permeable silty sand strata encountered at the higher elevational depths found under the Designated Remainder. An effluent rise of 16 feet would have to occur under Parcel 1 for effluent management to occur in permeable soils. V�_ Page -4- Chesney Consulting