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IQ fFNb 03 mg N/L,Page 8 ssume 15% due to fine-grained soil located at the 15-ft depth. ! 5 in/yr. ssumed to be 0.1 ppm NO,N j�aL ��5c/ d4e*L. .w ir/ ��s�n+rrne ✓ v,ey�j a 7.rn^ ; !,5't Tidy /k'tG1C 1.86 in/yr(103 me N/L) (I -0.15)+(15 in/yr x 0.1 me/L) 14Y.3.9 Nr = (1.86 in/yr+ 15 in/yr) 3.e Nr 9.8 pp nitrate-nitrogen(NO,-N)or 45 ppm as nitrate(NO,) Area constraints caused by building footprints, stormwater retention,parking,well site location, septic system location and 100%replacement area may decrease the number of on-site people allowed within the nitrate loading criteria. IV. CONCLUSIONS AND RECOMMENDATIONS SSS§ 5.4,6.8. The soils underlying the subject property show unacceptable permeability at the shallow depths representative of filter beds and leachline depths. Acceptable permeability exists at . depths representative of sumps and seepage pits. It can be anticipated that for long-term effluent acceptance rates, the permeability of these deeper soils will no doubt slow based on the factors described in this report. This includes historical evidence based on repairs/replacements/additions permits within the study area along the Highway 99 corridor. From the soil chemistry test results, it appears that there is some denitrification potential from the soils, but not as significant as has been observed in other locations of San Joaquin County. The soil analytical test results show low concentrations of subsurface soil nitrate-nitrogen, even though the subject property was under agricultural production for at least the past four decades. The amount of nitrogen applications in the past are unknown, although decomposing organic matter from residual crop decomposition may supply subsurface nitrate-nitrogen higher than those concentrations observed, again indicating some denitrification potential. Jenssen and Siegrist (1990) found the factors that favor denitrification are fine-grained soils such as clays and silts layered with soils consisting of alternating fine-grained and coarser grained soils with distinct boundaries between the texturally different strata. This was observed in the exploratory 5• boring. Percolating water encountering coarser soil strata will accumulate on top of this stratum until sufficient soil moisture builds up for the soil water to travel into this stratum. NLS§4.2, SSS§ 6.7. Due to the referenced problems that have occurred along Highway 99 with conventional septic systems, it is the opinion of EHD that the upcoming new General Plan will require commercial facilities along Highway 99 and Interstate 5 that must operate with decentralized y Z systems to treat their wastewater to a high degree(tertiary, or full treatment standards)by a Package Treatment Plant. The`lead agency"to oversee this treatment will be the Central Valley Regional �) Water Quality Control Board in Sacramento. The Regional Board will also have jurisdiction with regard to wastewater reuse,whether it is: 1.) Subsurface soil discharge and groundwater recharge, which these Studies focused upon, 2.) Re-use for domestic on-site landscaping, 3.)Re-use for irrigation on adjacent agricultural production land, or 4.) Discharge into the adjacent Bear Creek. 10 Chesney Consulting