2320 106TH ST SW Geotech Report 2022-10-25

October 14,2015 Project No.T-6116-2 it is not possible to discharge collected water at the footing invert elevation, the invert elevation of the wall drainpipe could be set equivalent to the outfall invert. For any portion of the wall that falls below the invert elevation of the wall drain, an earth pressure equivalent to a fluid weighing 85 pcf should be used. We would note that the vault is located relatively close to the south property line. If easements allowing temporary sloped sidewall excavations to extend beyond the property line cannot be obtained, temporary shoring to support the excavation sidewalls will need to be constructed. 5.7 Site Retaining Walls As noted above, a retaining wall will be constructed along the west property line. The wall height ranges from four to eight feet. The wall type has not been selected at the time of this report. Based on the soil conditions observed, wall types to be considered would include a cast-in-place concrete wall, rockery, or gravity block wall. Cast-in-place concrete walls should be designed as below-grade walls using the parameters outlined in Section 5.6 of this report. Rockeries A rockery is not intended to function as an engineered structure to resist lateral earth pressure as a retaining wall is. The primary function of a rockery is to cover the exposed soil face to reduce the potential for erosion. All rockery construction should conform to the Associated Rockery Contractors (ARC) Standard Rock Wall Construction Guidelines. 7e recommend limiting cut rockeries to a height of ten feet when facing undisturbed dense native soils, and four I et where placed against unreinforced structural fill. Where buildings will be constructed above and adjacent to rockery construction,the foundations should be lowered to prevent surcharge loading on the rockery. Foundation depths should provide for a theoretical 1:1 influence line extending from the footing edge to pass beneath the rockery base. Where rockeries of four feet or less will be constructed against structural fill,the structural fill should be overbuilt and then cut back prior to constructing the rockery. This will provide a more competent and stable soil face behind the rockery. If rockeries placed against fill will be surcharged, and in those locations where rockeries against fill will be greater than four feet,the fill should be reinforced using a geogrid or geotextile material. We can provide design details if requested. A typical cut rockery detail is attached as Figure 5. Gravity Block Walls Gravity block retaining walls may be constructed in addition to or in lieu of rockeries. We can provide design details, if requested. 5.8 Drainage Surface Final exterior grades should promote free and positive drainage away from the building sites at all times. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building areas. We commend providing a positive gradient away from the building perimeters. If this gradient cannot be provided, dace water should be collected adjacent to the structures and disposed to appropriate storm facilities. Page No. 10