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Fcontributed e subject property was under agricultural productionfor several dec77toactivity five years ago. This land use, and upgradient agriculturalldverse constituents to the underlying groundwater,particularly nitrats were found in the water table underlying the property in the investirt. There is no record of any type of residential or commercial struc on the property, which may have contributed nitrate from an on-site septic system(s). SSS2,3.3,3.4,3.5,3.6. Applications on microfiche file with the EHD reveal that there have be five ermits issued for repairs/additions to existing systems within a one-half mile Burro g the project site. As referenced,there apparently has never been a septic system permitted for the property. Permits in this specific area of Tracy would assumed to be a medium number since surrounding county land to the northeast, east and south of the site is low density development. The project site has relatively level terrain, although there is a fall of 12 feet from the southwest comer of the property to the northeast corner(119 MSL to 107 MSL). This is a land surface declination of 12 ft_ 1350 ft= -0.0088 ft/ft or-0.8%. Consequently, there will be no need to , incorporate design considerations for slopes within the filter bed area. Nor are there dramatic elevational differences between the lift stations and the septic tanks which would cause an increase in total dynamic pump head. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS rNLS§ .1. The National Resources Conservation Service(NRCS) - Soil Conservation Service lus tes the soil in the wastewater disposal area to be just inside the Stomar clay loam(#252) series. Stomar soil is referenced has having a slow permeability,which was evidenced in two of the eight perc tests conducted. The soil has an average available water holding capacity of 0.16 to 0.18 inch/inch throughout the top five feet of soil (10.2 total inches of water, on average). Over the proposed disposal area of approximately 3,300 ft(discussed on Page 13), the top five feet of soil can theoretically hold: 0.11 acres x 27,154 gals/ac-in x 10.2 inches=30,500 gallons of water at any given point in time. Over time, obviously water is flowing downward under gravitational pull; horizontally and upward by capillary action. SSSS. 5. NL 1.2. To investigate the soil characteristics underlying the filter bed area, two baekhoe tit pits rexcavated directly adjacent to the east and west ends of the anticipated filter bed area. The test pits were not dug in the actual filter bed soil so as to not create potential saturated flow conditions within the disturbed soil, and secondly to not cause the soil structure within the backfill pits to potentially collapse, rendering impermeability; and thirdly, to not disturb the beneficikl nitrate mitigating properties of the underlying soil. Photographic plates found in (Appendix G illustrates the surface and subsurface soil conditions. Representative soil samples �Vere_obtained from the referenced depths for chemical analyses and particle size analysis, as discussed below. The encountered soil structures are relatively discernable soil horizons consisting mostly of clay and silt, as noted on the particle size analyses for sand, silt and clay percentages illustrated in Table 1. With increasing depth, there is a noticeable increase in gravel/cobble content. At eight feet below grade, the gravel/cobble content increases substantially. Page -3- Chesney Consulting