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M K L E I N F E L D E R Where: Ne = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources and precipitation—mg/l, as N. A = Number of dwelling units per acre on septic tanks (unit/acre) = 0.025 (estimated based on a maximum of 2 residences per parcel divided by 80 acres.) W = Annual wastewater loading per dwelling unit per acre (inches)=2.0 inches (per year per dwelling unit assuming a flow of 150 gal./day/dwelling unit.) Nw = Nitrate concentration of nitrified leachfield effluent (mg/1) = 35 mg/l (Hantzsche and Finnemore (1992)). Percent denitrification selected based on past discussions with Mr. Mike Huggins of SJCEHD. D = Percent dentrification of leachfield effluent = 0.35 percent (0.1 to 0.35 percent typical per Hantzsche and Finnemore (1992). 0.35 selected given the deep depth to groundwater and interbedded strata of low-permeable soils. R = Annual deep percolation of precipitation (inches) = 13.6 inches (representing 80 percent of average annual rainfall of approximately 17 inches in project area. Remaining 20 percent of rainfall is assumed to drain off-site into natural or manmade drainages.) Nb = Background nitrate nitrogen concentration of rainfall recharge at the water table = 0.5 mg/l (per Technical Memorandum, Hydrologic and Soil Investigation for the Chico Urban Area,page 6, Dames and Moore, April 1996) Our calculation is as follows: Ne = 0.025(2)(35)(1 —0.35) + 0.5(13.6) = 1.14+6.8 = 0.6 mg/1 as N 0.025(2) + 13.6 0.05 + 13.6 8. CONCLUSIONS As shown above, we calculate 0.6 mg/l of nitrate-nitrogen (l) in groundwater resulting from the proposed leach fields, a result that is well below the state standard of 10 mg/l. Based on this relatively low level of nitrate-nitrogen, we anticipate that the impact on surrounding wells will be minimal and no remediation will be necessary. Goose Creek and an unnamed reservoir are the nearest natural water bodies to the site and are located about 1/4 to 1/3 mile from the site,but are generally not down gradient. Based on this distance and the relatively low nitrate-nitrogen levels calculated, we anticipate that the impact to water bodies will be minimal and no remediation will be necessary. There also appear to be two unnamed creeks west of the site; however, these appear to be predominantly dry creeks that will carry water only during storm events. 36600.G01/ST03R1537 October 16,2003 ©2003 Kleinfelder,Inc. Page 5 of 7