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i <br /> `►✓ \./ <br /> January 17,2006 <br /> NOA Project Number:E05089A <br /> Practice indicates that septic system leach field can be developed using a rates between 1 to 60 minutes per <br /> inch for a shallow percolation test. <br /> Regarding the ground water depth(10 feet): <br /> In the report(Section 4.1),the groundwater depth was estimated to be deeper than eight feet based on a <br /> "dry"soil boring. The fluctuation of the ground water surface cannot be determined based on one boring <br /> however,it is our experience that the shallowest levels occur in the summer months during alfalfa irrigation <br /> in the area. The boring was excavated on June 24,2006. With at least five feet of separation to ground <br /> water,a standard(three foot deep) septic system could be constructed as recommended in Section 6.8. <br /> Regarding an Alternate System: <br /> In further review,it still does not appear that a raised system is warranted based on the information <br /> presented in the report. However,some simple steps may be taken in order to reduce the nitrate impacts to <br /> the ground water. The following steps are proposed to reduce the concentrations nitrates in percolating <br /> septic system effluent: <br /> • Utilize standard filter bed system design with the following exceptions. <br /> • Minimum Septic Tank Sizes <br /> 2 bedroom—1600 <br /> 3 bedroom—2000 <br /> 4 bedroom—2000 <br /> 5 bedroom—2400 <br /> 6 bedroom—3200 <br /> 7 bedrooms and above will require consultation from our office or EHD input. <br /> • Apply four inches of loose compost or peat in the bottom of the filter bed. Utilize gravel <br /> drain systems to improve denitrification. The addition of compose or peat will provide a <br /> supplemental carbon source with may help improve denitrification while reducing the <br /> percolation rate of the soil. <br /> • Since these steps are fairly straight forward,the contractor with supervision of EHD staff, <br /> can install these modifications without detailed drawings or inspections from our office. <br /> If you have any questions or comments,please do not hesitate to call. <br /> Best Regards, <br /> ERSON&ASSOCIATES,INC. ��PEG GEOZ <br /> � <br /> ,�� 3. WFC 0 <br /> C <br /> rinctpal Geo o ' p� No. 2151 y N1 <br /> P <br /> IED <br /> CEG-2151 CHG-653,GP-1049 GERTIERI <br /> > ENGINEERING <br /> tr GEOLOGIST \� <br /> PC <br /> CC: Rodney Estrada,EHD <br /> attachment: December 12,2005 EHD Letter <br />