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Thornton On-site Waste Water Feasibility Study Page 7 of 9 <br /> Our Project Number: 2017-00010 <br /> December 1,2017 <br /> 5.0 RECOMMENDATIONS AND CONCLUSIONS <br /> There are three main concerns when considering the preliminary on-site waste water <br /> feasibility for the site. First, based on our concurrent NLS, we expect with the estimated <br /> effluent for the system will cause a buildup of nitrate in the groundwater above the <br /> maximum contaminant level of 10 mg/L-N as set forth by the U.S. EPA. The second <br /> concern is, will the 0.55-acre/24,000 square-foot lot located at 8875 W. Thornton Road, <br /> allow for sufficient space for a septic effluent dispersal field plus the required dispersal <br /> field replacement area equal in size? Finally, is the depth to groundwater separation <br /> distance sufficient to allow for a standard leach field or will the site require a mound <br /> system? <br /> To mitigate potential buildup of nitrate in the aquifer, an advanced treatment system <br /> should be installed which is capable of reducing nitrate to 10 mg/L-N. The SJCEHD states <br /> the percolation rate in the disposal field shall be no greater than sixty (60) minutes per <br /> inch or less than one (1) minute per inch and a mitigation by system design or <br /> enhancement is required for parcels with percolation test results not meeting these <br /> criteria. <br /> Our office did not obtain percolation test results during our preliminary septic permit <br /> review. Based on the NLS soil survey date, the permeability of soil of the Sailboat silt <br /> loam (see Table 1) at the site is estimated to be 0.6 — 2.0 inches per hour from the <br /> surface to 8 inches bgs; this equates to approximately 100 minutes to 3 minutes per inch <br /> potential percolation rate. It is possible that the percolation rate from 0 to 8 inches would <br /> have a passing rate. The permeability from 8 inches bgs to 61 inches bgs is reported as <br /> 0.2 to 0.6 inches per hour(Table 1) or approximately 100 minutes per inch to 300 minutes <br /> per inch, which does not pass the standard requirement rate. <br /> Based on the permit number 20246 for the 0.55-acre/24,000 square-foot parcel planned <br /> to accommodate the proposed septic system the depth to water was at 10 feet and the <br /> soil to three feet is a clay loam. Per the OWTS Standards, a method of calculating leach <br /> line requirements for all non-standard OWTS design is to multiply the Base Tank Capacity <br /> (BTC) plus the Average Daily Flow (ADF) by the Soil Factor noted below to determine the <br /> total lineal feet of leach line required. <br /> Table 4. <br /> Soil Factors <br /> SOIL SOIL FACTOR <br /> Clay and/or Peat 0.250 <br /> Silt and/or Sandy Clay Loam 0.225 <br /> Sand and/or Sandy Loam 0.200 <br /> Source:San Joaquin County Environmental Health. Onsite Wastewater Disposal Standards,2017 <br /> paf calrni'+'f n±7•n�orinn,!nr. rsP:=yr%yn::-,rJ:c <br /> 26675 Bruc4h)Rrad,GA,Cu 95632 <br /> e° g <br /> I209I-A00-5729 a£ u <br /> wtvw,pctralogix,com ,; , <br />