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Soil Suitability I Nitrate Loading Study Irerracon Proposed Commercial Truck Yard ■ Stockton, CA August 16, 2019 ■ Terracon Project No. NA197053 occurred approximately 24 hours prior to the day of testing. The depth of water used to pre-soak the shallow borings was approximately 1.0 foot above the top of the gravel. 1.6.4 Condition of Borings after Presaturation Boring B1 was dry and intact after the 24-hour pre-soak period. 1.6.5 Percolation Test Procedure On July 31, 2019, the percolation tests were conducted in accordance with the requirements of the San Joaquin County Percolation Test Procedure (Form: EHD 42-01-002 Revised 08-23- 2011). There was no water remaining in the test holes; therefore, Terracon conducted the percolation tests by following Procedure #2. Terracon added clear water approximately 0.5 feet above the top of the gravel and recorded the drop in water level at thirty minute intervals over a four hour period. Measurement of the water level during the percolation test 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 are in decimal feet. The percolation tests were observed by Ms. Daria Afonskaia, EHD representative. 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 test are summarized in the table below. Table 7. Summary of Percolation Tests. Percolation Percolation Test No. Comments Date Tested Test Rate Test Duration (see notes) Depth (feet) (minutes/inch) 131 Satisfactory Percolation 07/31/2019 3.5 9.62 4 hours Rate Note: A satisfactory percolation rate is 60 minutes per inch or less for shallow leach lines and 30 minutes per inch or less for septic pits per SJEHD,Onsite Wastewater Disposal Standards,October 2003. The completed percolation test form with Ms. Afonskaia's verification signature is included in Appendix E of this report. Responsive■ Resourceful ■ Reliable 11