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LOGE 1607: Venice Island Ferry Tender's Residence Page 4 April 13, 2016 The soils above this layer were identified as organic silts/clays and peat. This zone exists from 5 ft to the surface. The surface layer contains a lightly compacted pad of the same material. These soils tested either rapid (<5min/in) or satisfactory (50min/in) in percolation tests (See Plate 3). Based on the soil layering, percolation rates, and the depth of ground water, this site appears to be suitable for a standard SJCEHD filter bed disposal field placed about 3.0 ft into the semi-compacted pad material (new pad). Below the filter bed are highly organic layers with rapid percolation rates to a depth of about 5 ft. Below 5 ft, the soils show low permeability (greater than 60 min/in) and will provide an 8-ft low-permeability barrier to ground water. In addition to the favorable soil layering restricting downward flow of effluent, the carbon soils tend to enhance denitrification of effluent where both aerobic and anaerobic conditions occur. It is our opinion that the organic soils may provide a relatively high amount of natural treatment (denitrification) when compared to sandy soils in the County. Septic system design recommendations are provided next. Recommended Septic System Design Based on the soil conditions and the depth to ground water, a standard septic system using a filter bed design is proposed for the site. The septic system sizing is calculated based on the San Joaquin County Environmental Health Department's On-Site Wastewater Disposal Standards and Residential Onsite Systems Bulletin. • For a 2-bedroom house, a 1 ,200-gallon septic tank is required. o Septic tank is to be placed on stable pad near the mobile home above flood level or anchored if it is below the flood level, per SJCEHD requirements. • 200-lineal feet of leach line is required for clay and/or peat sites; however, a filter bed disposal system will be required for shallow ground water sites, per SJCEHD requirements. • Filter bed: Multiply the length of leach line requirement by a factor of 4 in clay soils. This gives the required square footage of the filter bed, per SJCEHD requirements. 0 200 (lineal ft) x 4 (factor) = 800 sq-ft (filter bed in clay soils) o The disposal area will be determined by the owner and septic bed geometry.