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Soil Suitability /Nitrate Loading Study Irerracon <br />JPM a Lathrop, Califomia <br />May 24, 2022 n Terracon Project No. NA227026 <br />1.5.4 Discussion of Soil Lithology <br />The soils encountered in the percolation test borings consisted generally of silty sand or sand with <br />silt. Terracon met refusal at 6.5 feet bgs at boring 131 located near proposed Septic System 1, <br />north of the pond. Refer to Section 1.5.3 for a more detailed lithology. Generally, coarse-grained <br />soil has a greater potential for percolation than fine-grained or cemented soil. <br />1.6 Percolation Test Information <br />1.6.1 Percolation Test Locations <br />Refer to Section 1.5.1 and Appendix A, Exhibit 2. <br />1.6.2 Number of Percolation Tests <br />A total of three percolation tests were conducted on the site. The percolation tests (131 at 6.5 feet <br />bgs, 133 at 3.5 feet bgs, and 136 at 3.0 feet bgs) were conducted and witnessed by Ms. Aldara <br />Salinas, EHD representative. <br />1.6.3 Boring Preparation and Presaturation <br />The percolation test borings were excavated on April 5, 2022. Approximately two inches of "pea <br />gravel" was placed in the bottom of the borings. A 2.0 -inch diameter PVC pipe with perforations <br />towards the bottom was installed on top of the gravel and the annular space was backfilled with <br />"pea gravel'. Presaturation of the percolation test holes occurred on April 11, 2022 approximately <br />24 hours prior to the day of testing. The depth of water used to pre-soak the shallow borings was <br />approximately 1.0 foot above the top of the gravel and 0.5 feet above the top of gravel for the <br />deep boring. <br />1.6.4 Condition of Borings after Presaturation <br />All borings were dry and intact after the 24-hour pre-soak period. <br />1.6.5 Percolation Test Procedure <br />Percolation tests were conducted for the borings on April 12, 2022 in accordance with the <br />requirements of the San Joaquin County EHD. The tests were observed by Ms. Salinas from the <br />EHD. Measurement of the water level during the percolation tests was from a fixed reference <br />point on the PVC casing using a calibrated Solinst electric water level detector with a depth <br />accuracy of 0.01 feet. All tabulated values on the field data sheet (Appendix E) are in decimal <br />feet. After water drop was observed, the holes were checked and refilled as necessary to maintain <br />approximately 0.5 feet (6 inches) of water above the top of gravel. The readings were recorded <br />every 10 minutes for a period of approximately 1 to 2 hours or until the EHD representative arrived <br />Responsive ■ Resourceful ■ Reliable 12 <br />