SR0081407 SSNL - Laserfiche WebLink

Home Browse Search

Soil Suitability/Nitrate Loading Study Irerracon Gribaudo Property ■Acampo, CA November 12, 2019 ■ Terracon Project No. NA197081 2.4.2 Methods of Mitigation Based on the groundwater analytical results(Section 1.4.3)and anticipated depth to groundwater (120+feet bgs), nitrate impacts to groundwater are not anticipated;therefore, mitigation measures appear unwarranted. 3.0 CONCLUSIONS AND RECOMMENDATIONS The site consists of an approximately 37.81-acre tract of land located at 10516 E. Peltier Road, Acampo, California, San Joaquin County, California, Assessor Parcel Number (APN) 017-260-30 and 017-260-31. The site boundaries are proposed to be re-aligned into a 2.0-acre home site (Parcel 1 — APN 017-260-31) and 36.62-acre agricultural land (Parcel 2 — APN 017-260-30). There are currently no future developments planned. One septic system is located on the 2.0 acre parcel west of the residence (APN 017-260-31). No septic permits were found for the site address on the EHD website; therefore, the details of the septic system are not currently known. The septic systems in the area appear to utilize 40 to 100 foot leach lines with 25 foot deep seepage pits at the end of each leach line. Septic repair permits appear to be for the addition or replacement of leach lines with seepage pits. Depth to groundwater is anticipated to be greater than 120 feet bgs. Two groundwater samples collected from the onsite domestic well (6.0 mg/L-N) and agricultural well (5.3 mg/L-N) reported below the MCL of 10 mg/L-N. DBCP was reported at 0.18 ug/L in the domestic well and at 0.12 ug/L in the agricultural well below the MCL of 0.20 ug/L. The soils encountered on the site generally consisted of sandy silt with cementation at depth. A satisfactory percolation rate of 5.31 min/inch at 3.25 feet was obtained near the existing leachfield located on the 2.0 acre parcel (APN 017-260-31). APN 017-260-30 also demonstrated a satisfactory percolation rate of 8.62 minutes per inch at 3.25 feet bgs. Based on the favorable percolation results, the site soils appear suitable for a standard septic system. The nitrate loading balance (11.9 mg/L N) indicates that the existing residential use on the 2.0 acre parcel (APN 017-260-31) may cause a buildup of nitrates in the aquifer slightly above the MCL of 10 mg/L-N. The proposed 36.62 acre parcel (APN 017-260-30) can theoretically be developed with a residential use septic system up to 5,500-gallons per day resulting in a nitrate loading balance of 9.8 mg/L-N and remain below the MCL of 10.0 mg/L-N. Based on the groundwater analytical results and anticipated depth to groundwater, nitrate impacts to groundwater are not anticipated; therefore, mitigation measures appear unwarranted. In summary, the parcels are suitable for use of a standard septic system. The septic system design should accommodate the peak flows and follow the San Joaquin County OWTS standards where applicable. Responsive■ Resourceful ■ Reliable 18