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File No. CO-9018-SO1 June 11, 1991 Walnut Street and Almond Street. There are approximately 14 single-family residences on the 2 streets. These residences are currently on individual septic systems. Environmental Health Division records of permits associated with septic systems on these 2 streets were examined to assist in defining past septic usage. A total of 6 permits associated with addresses adjacent to the project were found in these records. The permit information obtained from these records is summarized below. Street Address Permit Date Work Performed 1. 18446 Walnut 01 /09/80 Install leach field and sump 03/87 Add seepage pit, 15' X 2' X 18' 2. 18490 Walnut 06/04/74 Add 50' of leach line and 25' X 33" pit 3. 18418 Almond 06/03/85 Add 40' of leach line and 2' X 10' X 12' pit 4. 18465 Almond 05/19/75 Add 40' of leach line and 25' X 33" pit 5. 18470 Almond 06/06/73 Add 100' of leach line 6. Almond & Athearon 06/17/60 Add three leach lines, 1 @ 100', 2 @ 40' It can be seen from the above records that the existing single-family residences adjacent to the proposed project utilize septic systems with either leach lines and/or seepage pits. The San Joaquin County, Semi-Annual Groundwater Report (Spring, 1990) indicates that the depth the groundwater in the project area is approximately 130 to 140 feet. Soil Survey Maps by the U.S. Soil Conservation Service were examined and identified 3 soil types within the project boundaries: (i) (HH) - Tokay fine sandy loam, (ii) (MHC) - Ramoth sandy loam, and (iii) (MAA) - Madera-Alamo complex. Soil descriptions of these soil types indicated the possibility of cemented or hardpan layers with permeabilities varying from moderately rapid to very slow. It was also indicated that permeability limitations for septic tank absorption fields can be overcome by increasing the size of the absorption fields. Summary of Percolation Tests The percolation tests were performed by drilling and 8-inch diameter hole to a depth of 36 inches at all locations. The sides of the holes were scored and loose materials removed from the base of the hole. The bottom of the hole was filled with a 2-inch layer of gravel and a perforated 4-inch diameter PVC pipe installed. The annular space between the pipe and hole sides was backfilled with gravel for some distance above the base of the hole to sturdy the PVC pipe. A 2