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VALLEY AG R E S E A R C H October 28, 1999 VAR Job No: NLS-01.99A FOR: Mr. Bruce Perrson California Paving Company P.O. Box 1393 Oakhurst, CA 93644 PROJECT: T.G.S. Trucking Facility (Timothy G. Schneider) U.P. No: SA-98-72 10720 South Harlan Road Lathrop, CA SUBJECT: Nitrate Loading Study/Soil Suitability Study (NLS/SSS) Addendum Reference is made to our NLS/SSS report dated April 9,1999. The San Joaquin County Environmental Health Department has requested additional information regarding the existing septic system which serves the office for the above-referenced facility. At the time our report was compiled, the permit application to install new septic systems for the south structure (which serves as the T.G.S. Trucking office) and the north structure (which is now not part of this project)were not on file at the Environmental Health Department. These two documents were subsequently obtained by Mr. Penson from the septic contractor and illustrate the as-built orientation of the septic systems currently in place. It was, and is our understanding that there are only two or three people in the T.G.S. office during business hours. However, the Environmental Health Department requires that nitrate loading and septic system sizing calculations be based on the number of parking stalls. Consequently, the calculations demonstrate a larger sized system than what may be realistically needed. Currently, the system consists of a 1200 gallon tank, 40 feet of leachline and a 2' x 8'x 10' sump, for an equivalent length of 100 feet of leachline. The first concern of the Environmental Health Department is with regard to nitrate impact from the current system. It is our opinion that the severe nitrate impact is localized to the south of the T.G.S. Facility. This opinion is based on the nitrate and chloride levels measured from the T.G.S. on-site domestic well. Although it is unknown as to when this well was drilled, it can be reasonably assured that it was more than thirty years ago. The test results reveal an upper- medium level of nitrate concentration at 29 ppm and a comparatively low level of chloride concentration at 92 ppm. These concentrations would in all probability be higher if the nitrate problem to the south was regional instead of localized. The primary issue is that only two to three people will be using the system during business hours, Monday through Friday. This is considerably less loading than what would be expected from a typical domestic residence, or from agricultural operations. We are recommending that the domestic well which serves the T.G.S. Facility be tested for nitrate on a yearly basis to monitor for a potential increase in nitrate concentration. P.O. Box 3794 a Turlock,California 95381 1 (209)668-1403 a Fax (209)668-2598