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4 7Thecolation tests exhibited rapid rates among the three borings. Although the soil in the shallow boring was very wet from the recent, heavy rainfall, a relatively rapid perc rate was obtained. The medium depth perc test also exhibited rapid percolation. This boring was set on top of the encountered sand stratum. The deep perc test was set in this sand stratum, and therefore exhibited a rate that is too fast to be acceptable. The following Table summarizes and illustrates the perc test results and the applicable information, including potential septic system structures based on depth of passing rates, proposed acreage, post soak period status and test results for the respective perc test depths: TABLE 2 SUMMARY OF PERCOLATION TEST RESULTS PROPOSED PARCEL PROPOSED PERC POST SOAK PERC TEST AND POTENTIAL ACREAGE TEST PERIOD RESULTS SEPTIC SYSTEM STATUS STRUCTURE DEPTHS Parcel 4 1.03 Acres Shallow-42 Inches FNoanding Water 20.8 minlin wet before pre-sat. Shallow Leachlinesand Potentially Medium-9 Feet anding Water 6.6 min/in Shallow Sumps Deep-.25 Feet No Standing Water 2.1 min/in ///B. SURFACE WATER INFORMATION Surface water consists 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 stormwater retention. The San Joaquin County of Public Works- Isohyetal Map indicate 17 inches of rainfall to be the Mean Annual Precipitation in the area of the project. After project development, a percentage of the land surface will be impermeably covered with structures, concrete and asphalt. This will have a minor attenuating effect on the downward migration of nitrate molecules currently"in-transit" and on nitrate yet to be formed. From the soil test results of each tested depth illustrated on Table 2, it is noted that nitrate-nitrogen concentrations exists primarily in the finer-grained soils. The impermeable surfaces will be traded for potential point sources of nitrate: on-site septic systems, lawns, landscaping and the retention basin. Domestic irrigation use from upscale residences on large lots can account for 1,000 to 3,000 gallons of water/day/residence during the spring and summer months (approx. 6 mos. out of the yr). As referenced exces ' d landscape watering can lead to nitrogen_leachin , and runoff to pgna e � ItualLy o-the on-site stormwater retention basin. However, during the winter months rainfall runoff into the proposed stormwater retention basin at the north end of the project ma contribute a dilution effect to ercolat ng effluent. Page-6- Chesney Consulting