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Mike Huggins of EHD requested that the agrichemicals DBCP/EDB not be analyzed c;nrP ;t w ,s n_ot used in this locale in the 1970s. The sample was drawn after the well pump had run for ten minutes to ensure aquifer formation water was obtained. The samples were placed in a cooled ice chest and transported to A&L Labs of Modesto, under the attached Chain of Custody. Testing of the well water sample reveals a nitrate concentration of 17 ppm NO,. The Maximum Contaminant Level(MCL) for nitrate (as NO3) is 45 ppm. As referenced, the nitrate-nitrogen loading originating from the septic system effluent is contingent upon the environmental factors required for nitrification to occur. These environmental conditions include soil pore-space oxygen content, soil temperature,pH, electrical conductivity, organic matter, cation exchange capacity, and alkalinity. Alkalinity in wastewater effluent is derived from the domestic water supply and the introduction of wastes to the wastewater. Nitrification consumes approximately 7.1 mg of alkalinity for every milligram of ammonia-nitrogen (NH4-N) oxidized. Water chemistry results for the on-site domestic well indicate a Total Alkalinity of 212 mg/L. Assuming complete nitrification of ammonium from an assumed Total Nitrogen(TN) concentration of 90 mg/L and considering that ammonium typically composes 70-90% of the total nitrogen in septic tank effluent,we find that: 90 mg N/L x 80% =72 mg NH4 N/L x 7.1 mg CaCO3 = 511 mg/L alkalinity required. However, only 212 mg/L of alkalinity exists in the well water. Therefore the alkalinity in the domestic water supply may be deficient for nitrification if the TN will be approximately 90 mg/L. The remaining alkalinity requirement for nitrification to occur will therefore have to originate from the septic effluent. E. SURFACE WATER INFORMATION Surface water congigtg of all other water sources originating on the surface of the project, other than septic system effluent. These sources include rainfall, surface runoff, domestic irrigation and on-site stormwater retention. The stormwater retention basin is proposed to be in the "back"or at the east end of the property,with all stormwater pipelined to this basin. Consequently, there should be no impact to surface waters from the on-site septic system effluent. -4- 0 F. ON-SITE SEPTIC SYSTEM PARAMETERS As stated in the Introduction, a new septic effluent disposal area must be constructed for this proposed industrial complex. Denoted on the applicable portion of the Site Plan, are the primary disposal and 100%replacement areas. The following septic system installation parameters were derived from the San Joaquin County Sewage Standards in determining the required lineal feet of leachline and the number of seepage pits: Maximum number of on-site employees per day=6 Anticipated number of customers per day=6 12 people x 15 gallons/person= 180 gals/day (Note:There will be only one toilet in the office for this Phase I project. One toilet is equivalent to 150 gals/day in wastewater flow. A new low flow toilet at 1.5 gallons/flush is to be installed;therefore,the toilet would have to be flushed 100 times to equal 150 gals/day.) 6 Chesney Consulting