10200 19TH AVE SE COSTCO FUEL STATION Geotech Report 2022-10-25

GEOTECHNICAL ENGINEERING STUDY Costco Wholesale c/o Barghausen Consulting Engineers E-8556 January 13, 1999 Page 9 The slab-on-grade floors should be underlain by a capillary break consisting of a free draining poorly graded sand or gravel with less than four percent fines (percent passing the #200 sieve, based on the minus 3/4-inch fraction). In areas where slab moisture is undesirable, a vapor barrier such as a 6-mil plastic membrane can be placed beneath the free draining sand or gravel. If no amount of slab moisture can be tolerated, moisture protection measures such as described above should be considered. Site Drainage The site must be graded such that surface water is directed off the site. Water must not be allowed to stand in construction areas. During construction, loose surfaces should be sealed by compacting the surface to reduce the potential for moisture infiltration into the soils. We do not anticipate groundwater seepage will be encountered in the storage tank excavations. However, if seepage is encountered in the excavation, the use of sumps may be necessary to collect and discharge groundwater from the excavations. A perimeter footing drain should be installed around the proposed controller enclosure to help reduce the potential for water infiltration during periods of high groundwater seepage. A typical footing drain detail is provided on Plate 3. Under no circumstances should roof downspout drain lines be connected to the footing drain system. All roof downspouts must be separately tightlined to discharge. Excavations and Slopes The following information is provided solely as a service to our client. Under no circumstances should this information be interpreted to mean that ECI is assuming responsibility for construction site safety or the contractor's activities; such responsibility is not being implied and should not be inferred. In no case should excavation slopes be greater than the limits specified in local, state and Federal safety regulations. Based on the information obtained from our field exploration, the upper deposit of fill would be classified as Type C by OSHA. As such, temporary cuts in the fill soils should be sloped at an inclination no steeper than 1 .5H:1V (Horizontal:Vertical). Below the fill, Type A soils were encountered. Temporary slopes in Type A soils can be inclined at inclinations of 0.75H:1 V. ECI should observe the excavation to verify soil and groundwater conditions, and determine if flatter temporary slope inclinations are necessary. Earth Consultants, Inc.