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. k� K L E I N F E L D E R Water Quality Control Board criteria (equation 4 on }gage 43, October 1986) for example, assuming an environmental attenuation factor (EAF) of 100, the nitrate concentration of nitrified leach field effluent (N,N) would need to be 1,000 mg/l or greater to effectively increase the nitrate N of the groundwater above 10 mg/l. The EAF represents an average disposal situation like a landfill in the alluvium of the Central Valley with a significant depth (i.e., 15 to 50 feet) of soil containing appreciable and continuous clay or silty-clay strata between the base of the landfill and groundwater. In summary, the Hantzsche equation without applying an EAF indicates that only one home can be placed on each lot in order to maintain the nitrate levels in groundwater below the state I drinking water standard. If the EAF is applied, two homes could be placed on each lot without raising the nitrate level in groundwater above state levels. if the SJCPHS does not allow application of the EAF, a deed restriction limiting the number of homes on each lot to one will need to be applied to the development or an engineered system to increase denitrification will need to be specified. Although the final system design will be provided by others, we recommend that all seepage pits extend at least 25 feet, because of the variability of the more permeable sand lenses on which our percolation tests were generally performed. During our recent services, a sample of groundwater was obtained from an on-site well using clean procedures to evaluate EDB and DBCP in accordance with EPA method 504.1. The results of the tests indicated a non-detectable concentration of either constituent. Results of our tests are attached. LIMITATIONS The conclusions of this report are based on the infonnation provided regarding the existing and proposed development and on the site conditions. It was assumed that the percolation test result is representative of the subsurface conditions in the general area. i This completes the scope of work requested. Our work was.-performed in general accordance with the standard of care that exists in San Joaquin County. No other guarantee or warranty, expressed or implied is made. Respectfully submitted, KLEINF PRO- LDER, l ., G�� f,y fi m - Ron Heinzen, G.E. `�o �3rAa Regional Manager/Principal -MICM- \r4V F 0?' RH:Ir 20-4476-0 I.G02/201 1 R 1242 Page 6 of 6 O 2001 Kleinfelder, Inc. October 11,2001