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N.New Hope Road (27300)-Septic Feasibilty and Design Project No.E09041.000 Page 3 14July 2009 Leach Trench Sidewall &Lineal Footage The leach trench design requires that the trench be a maximum of 3.5 feet in depth and a minimum 2 feet in width.Therefore,if the trenches are constructed to a depth of 3.5 feet,there would be 6 square feet of trench sidewall for effluent application for every lineal foot of trench, with the minimum 6 inches soil cover over the leach line.A minimum of 320 lineal feet is given in the design manual and a minimum 6,000 square feet of disposal area required.Based upon County minimum requirements,the leach field can be divided into four lines 80 feet in length and spaced 10-feet apart.San Joaquin County requires that all residential disposal systems be installed with a 100 percent replacement at the time of installation,so we recommend that a minimum of 640 lineal feet of leach trench,3.5 feet deep and 2.0 feet wide be installed,(See Figure 2 -Site Plan). Trench Design All the trench bottoms should be excavated level to within 0.5%.Youngdahl Consulting Group, Inc.recommends using a laser leveling device to ensure that the trench bottoms are level. Following excavation of the trenches,we recommend that the trench sidewalls be scarified with a long-handled metal rake prior to backfill with drain rock.The drain rock should be crushed rock,clean and :x to 1Y:z inches in diameter.We recommend that the contractor install the gravity feed leach lines level approximately 2 inches below the top of the gravel layer.These lines should be constructed of Schedule 40 or SDR-35 4-inch rigid wall perforated pipe with the holes turned downwards forming a low trough between parallel sets of holes (See Figure 2).We also recommend that a section of 3 to 4 inch diameter,perforated,rigid-wall pipe be installed vertically at the end of each trench.The bottom of the vertical pipe should be on the trench bottom,and the top of the vertical pipe should be one foot below ground,enclosed within a valve or sprinkler box.The end of the vertical pipe should be capped with a gas-tight end cap that can be removed to allow the measurement of effluent levels within the trench.The crushed drain rock envelope of the trench should be covered by building paper,or equivalent,before backfilling,(See Figure 2 -Site Plan).A reasonable attempt should be made to keep trenches at least 5 feet from existing trees on the property. Setbacks The following setbacks for the system features should be maintained: T bl 1 R .d L h L·S tb kae-equrre eac me e ac s Feature Requiring Set Back Distance (feet) Structures ..10 Water Wells 100 Flowing Stream*100 Drainage Course or Ephemeral Stream *100 Property Llne 5 Lake or Reservoir **200 Side Walls of Adjoining Leach Lines 10 Water Lines 5 *As measured from the edge of the channel. **As measured from the high water line.