5901 23RD DR W Geotech Report 2025-07-29

i October 72,2007 Project No.T-5922-1 The capillary break layer wilt not prevent moisture intrusion through the slab caused by water vapor transmission. Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or fine gravel to protect it from damage during construction, and aid in uniform curing of the concrete slab. It should be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will be ineffective in assisting in uniform curing of the slab, and can actually serve as a water supply for moisture transmission through the slab and affecting floor coverings. Therefore, in our opinion, covering the membrane with a layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the layer cannot be effectively drained. We recommend floor designers and contractors refer to the 2003 American Concrete Institute (ACI) Manual of Concrete Practice,Part 2, 302.1R-96, for further information regarding vapor barrier installation below slab-on-grade floors. 5.7 Retaining Walls The magnitude of earth pressure development on retaining walls will depend, in part, on the quality of the wall backfill. We recommend placing and compacting wall backfill as structural fill. Below improved areas,such as pavements or floor slabs, the backfill should be compacted to a minimum of 95 percent of its maximum dry unit weight, as determined by ASTM Test Designation D-698 (Standard Proctor). To guard against hydrostatic pressure development, drainage must be installed behind the wall. A typical wall drainage detail is shown on Figure 3. All drains should be routed to the storm sewer system or other approved point of controlled discharge. Provided wall backfill is placed and compacted as recommended and wall drainage is properly installed, we recommend designing unrestrained walls for an active earth pressure equivalent to a fluid weighing 35 pcf. For restrained walls, an additional uniform lateral pressure of 100 psf should be added. These values assume a horizontal backfill condition and that no other surcharge loading, such as traffic, sloping embankments, or adjacent buildings, will act on the wall. if such conditions will exist, then the imposed loading must be included in the wall design. In this case, we should be contacted for the appropriate design parameters. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.5 of this report. Rockeries As discussed, rockeries are shown facing near-vertical grade transitions adjacent parking lot fills in the northeastern and southeastern portions of the planned development area. It should be noted that rockeries are not engineered structures that are designed to retain earth in a manner similar to structural wall systems. Rocks used to construct the wall will by virtue of their mass enhance stability; however, the soil against which the rockery is constructed must be inherently stable and able to stand unsupported in a near-vertical condition. In our opinion, rockeries can be used to face unreinforced structural fill to a maximum height of four feet, provided the fill is placed and compacted as recommended in Section 5.2 of this report, and the structural fill face is overbuilt, then cut prior to rock placement. For fill heights of greater than four feet and where the rockery will be surcharged by structures or roadway/parking areas, the structural fill immediately behind the rockery facing should be reinforced with geosynthetic reinforcement. A detail for a mechanically stabilized earth (MSE) wall with a rockery facing is presented as Figure 4. Design calculations for the MSE wall are presented in Appendix C. I Page No. 10 I