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Soil Suitability/ Nitrate Loading Study 1rerracon ' Eagle's Nest Motorcycle School Stockton, California July 27, 2021 Terracon Project No. NA217040 1.6.2 Number of Percolation Tests Three percolation tests were performed. 1.6.3 Boring Preparation and Presaturation The percolation test borings were excavated on July 6, 2021. Approximately two inches of "pea gravel" was placed in the bottom of the open borings. A 2.0 -inch diameter PVC pipe with perforations towards the bottom was installed on top of the gravel and the annular space was backfilled with "pea gravel". Presaturation of the percolation test holes occurred the same day approximately 24 hours prior to the day of testing. The depth of water used to pre-soak the shallow boring was approximately 1.0 foot above the top of the gravel. 1.6.4 Condition of Borings after Presaturation Borings P4 (25 feet) and P5 (16 feet) were dry and intact after the 24-hour pre-soak period. Boring P6 (3.5 feet) contained water after the 24-hour pre-soak period and failed to percolate on the day of testing. 1.6.5 Percolation Test Procedure Percolation tests were conducted for the two deep borings (P4 and P6) on April 7, 2021 in accordance with the requirements of the San Joaquin County EHD. Each percolation test had a duration of four hours. The last half an hour of the test was observed by a representative from the EHD. Measurement of the water level during the percolation tests was from a fixed reference point on the PVC casing using a calibrated Solinst electric water level detector with a depth accuracy of 0.01 feet. All tabulated values on the field data sheet (Appendix E) are in decimal feet. After water drop was observed, the holes were checked for refill. The holes were refilled as necessary to maintain approximately 0.5 feet (6 inches) of water above the bottom level of the percolation test holes. The readings were taken every 30 minutes for a period of four (4) hours." 1.6.6 Percolation Test Forms and Results A shallow percolation test is defined by the EHD as being between 36 and 42 inches in depth. While a deep percolation test is defined by the EHD as being between 42 inches and 25 feet in depth. The shallow percolation test must demonstrate a satisfactory percolation rate of less than or equal to 60 minutes per inch drop in water level within the existing septic system disposal field of a parcel to utilize a standard septic system and 30 minutes per inch or less for septic pits. Details of the percolation tests are summarized in the table below. responsive ■ Resourceful ■ Reliable 11