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File: 218267 November 30, 2018 with an inclination of 2:1 (H:V). Where retained slopes are greater than 4:1,though less than 2:1,the designer should linearly interpolate between 45 and 60 pcf EFW. If the walls are considered to be restrained,they should be designed for an additional uniform pressure of 8H psf, where H is the height of the wall in feet. We leave it to the design professional's judgment in determining whether a wall is restrained or not. It is our opinion that a supplemental seismic loading for a basement wall is not necessary. However, if desired, the designer may also apply a uniform seismic force of 10H psf to the retaining wall in addition to the normal active pressures. The walls should also be designed to resist a point load applied at the midpoint of the wall, equal to % of the maximum applied surcharge (if any). Wall Drainage - The above values have been provided assuming that a back-of-wall drain system will be installed to prevent build-up of hydrostatic pressures. This drainage system may consist of a prefabricated drainage panel (i.e. Miradrain) or a gravel and filter fabric type system. The walls should be waterproofed to prevent the transmission of efflorescence through the walls. The waterproofing should be specified by the designer, though we recommend the use of Bituthene, Miradri, or other similar waterproofing membrane. Either drainage system should be installed with a minimum 3 inch diameter perforated pipe incorporated into the subslab granular section. Ideally the base of the pipe should be placed atop 1 to 2 inches of gravel,with its top even with the elevation of the basement subgrade(i.e. under the gravel. Perforations should be placed face-down(at 5 and 7 o'clock). Preferably,the exterior basement walls should be aligned with the exterior face of the slab to provide a planar surface for waterproofing installation across the cold joint. If used, the gravel system should consist of a minimum 12 inch wide column of drain rock (3/4 inch rock or 318 inch pea gravel) extending the full width of the wall. The rock should continue to within 6 inches of finished grade. Prior to backfilling with the drain rock, a layer of filter fabric (Mirafi 140N or approved equivalent) should be placed against all soil surfaces to separate the rock and soil. The filter fabric should wrap over the top of the gravel and then a 6 inch thick cap of native soils should be placed at the top of the drain. If concrete flatwork is to directly overlay the back-of-wall drain, then the drain rock should continue to the base of the concrete. Additionally, where the drain will be located within crawlspace area, the gravel should continue to the crawlspace ground surface without the soil cap. If prefabricated drainage panels are used, these panels should dead-end into the subslab gravel for collection under the slab. The tops of the panels should be sealed and secured in accordance with the manufacturer's specifications. The base of the drainage panels should extend down below the top of the filter fabric-wrapped drain rock. Floor- The basement floor should consist of a mat slab designed for a modulus of subgrade reaction of 50 pci. The entire slab should be underlain by at least 4 inches of clean, crushed drain rock. The drain rock should be covered by a moisture barrier which conforms to ASTM El 745-97 (e.g. Stego Wrap or an approved equivalent). The moisture barrier should wrap up the edges of the mat slab to 9