SR0081147_SSNL - Laserfiche WebLink

Home Browse Search

PRA131 November 20, 2019 FOR: San Joaquin County Environmental Health Department Mr. Michael Kith, Program Manager 1868 Hazelton Ave. Stockton, CA 95205 PROJECT: Navu Farms, Inc. 7300 West Delta Avenue Tracy, California 95304 APN: 213-020-41, SR0081147, PA1800316 SUBJECT: Response to Soil Suitability/Nitrate Loading Studies/OWTS Design Report I submitted the above -referenced Studies/Report/Design Plans pertaining to this project to EHD on September 11, 2019. The following is my response to the comments of EHD's outside consultant, Questa Engineering Corporation, received on November 19, 2019. The main issue with the OWTS Design is the separation distance between the floor of the leachline trenches and the observed depth to the water table, which was directly measured to be 5.7 feet below grade. Separation distances are to be based upon the percolation test rate obtained. This regulation was actually promulgated by the State Water Resources Control Board OWTS Policy: Quality Control Policy for Siting, Design, Operation, and Maintenance of Onsite Wastewater Treatment Systems. My design incorporated a five-foot separation distance, instead of an eight -foot separation distance. This eight -foot separation distance is based on the obtained perc rate of 20.8 min/in. While I was aware of this EHD regulation, I present the following response: 1. This regulation is absurd simply due to the fact that every project is site-specific in terms of the on-site soils and project wastewater flow volumes. This is why a civil engineer for a project should make these site-specific determinations of the soils and project wastewater flows. The onsite soils at proposed leachline trench depth for this project were determined to be a clay loam, with 29% clay, 48% silt and 23% sand contents. This soil structure has three primary benefits: First, this soil structure mitigates saturated flow conditions; one of the biggest concerns of the Water Board. Taking the project wastewater flows into account, the flow volumes will be extraordinarily low, as low as 5-10 gpd, giving the receiving soils ample time and space to process the incoming effluent. Second, the clay content of the native soils is biologically active and consequently, beneficial for the destruction of bacteria and viruses. Thirdly, the clay content is very favorable for the mitigation of nitrate loading by impeding nitrification and promoting denitrification, as stated in my report. Page 1 of 3 -9.0.53ax 3794 t Jut&&, ea 95381 t (20) 402-9652 t ddc&,6nqAdwd&i net