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File: 218267 November 30, 2018 The footing drain system should consist of a 12 inch wide gravel-filled trench, dug at least 12 inches below the elevation of the adjacent crawlspace. The trench should be lined with a layer of filter fabric (Mirafi 140N or equivalent)to prevent migration of silts and clays into the gravel,but still permit the flow of water. Then I to 2 inches of drain rock (clean crushed rock or pea gravel) should be placed in the base of the lined trench. Next a perforated pipe (minimum 3 inch diameter) should be placed on top of the thin rock layer. The perforations in the pipe should be face down. The trench should then be backfilled with more rock to within 6 inches of finished grade. The filter fabric should be wrapped over the top of the rock. Above the filter fabric 6 inches of native soils should be used to cap the drain. If concrete slabs are to directly overlay the drain, then the gravel should continue to the base of the slab, without the 6 inch soil cap. This drain should not be connected to any surface drainage system, but may tie to the basement subdrain system. Drainage Discharge-The surface drain lines should discharge at least 15 feet away from the house, preferably at the street or at a location approved by our office. The discharge location(s) may need to be protected by energy dissipaters to reduce the potential for erosion. Care should be taken not to direct concentrated flows of water towards neighboring properties. This may require the use of multiple discharge points. The footing drain and basement wall drain lines should discharge independently from the surface drainage system. A sump pump may be required for the footingibasement drain discharge system. The surface and subsurface drain systems should not be connected to one another,except as discussed above for the basement light and stairwells. Drainage Materials - Drain lines should consist of hard-walled pipes (e.g. SDR 35 or Schedule 40 PVC). In areas where vehicle loading is not a possibility, SDR 38 or HDPE pipes may be used. Corrugated, flexible pipes may not be used in any drain system installed at the property. Surface drain lines (e.g. downspouts, area drains, etc.) should be laid with a minimum 2 percent gradient (a/4 inch of fall per foot of pipe). Any subsurface drain systems (e.g. footing drains) should be laid with a minimum 1 percent gradient(1/8 inch of fall per foot of pipe). Utility Lines Unless they pass through the perimeter footing drain system, all utility trenches should be backfilled with compacted native clay-rich materials within 5 feet of any buildings. This will help to prevent migration of surface water into trenches and then underneath the structures' perimeter. The rest of the trenches may be compacted with other native soils or clean imported fill. Only mechanical means of compaction of trench backfill will be allowed. Jetting of sands is not acceptable. Trench backfill should be compacted to at least 90 percent of its MDD. However,, under pavements, concrete flatwork,and footings the upper 12 inches of trench backfill must be compacted to at least 95 percent of its MDD. 13