7800 EVERGREEN WAY HYUNDAI Geotech Report 2025-04-28

4.2.3.Construction Considerations Immediately prior to placing concrete,all debris and loose soils that accumulated in the footing excavations during forming and steel placement must be removed. Debris or loose soils not removed from the footing excavations will result in increased settlement. If wet weather construction is planned,we recommend that all footing subgrades be protected using a lean concrete mud mat. The mud mat should be placed the same day that the footing subgrade is excavated and approved for foundation support. We recommend that all completed footing excavations be observed by<a representative of our firm prior to placing mud mat, reinforcing steel,and structural concrete.Our representative will confirm that the bearing surface has been prepared in a manner consistent with our (:;commendations and that the subsurface conditions are as expected. 4.3. Floor Slab Conventional slabs may be supported on-grade on undisturbed native glacial s or on at least 12 inches of recompacted existing fill soils provided the subgr 1 ie is prepared as recornn rlded in Section 4.7. The prepared subgrade should be evaluated by probelv ;rind p ,r(oi ning a proof reIH-1 as described in Section 4.7.2. We recommend that concrete slabs-on-grad be r(di( eructed on q inch-thick layer of clean crushed rock to provide uniform support and to act as a co(((Mary brew,. The 4-inch gushed rock layer should be placed on recompacted suitable fi!! ur approved native !acial soils. The capillary break layer consi4 of at least inchk„s of clean crushed rock with a maximum particle size of 1 inch and negligi>,ft sand and =ilt, in accorlirnce with Section 9-03.1(4)C, grading No. 67 of the 2020 Washington State D,,o.1rtment of Transportauic,n (WSDOT) Standard Specifications. For slabs designed as a beam on an ela c i ; foundation, a moduli'; of subgrade reaction of 75 pounds per cubic inch (pci) may be used for subgrade ils prepare,' I' :-ecummended above. If water vai('n migration throut,l l I.he slab:, ;objectionable, the capillary break material should be covered with a heavy dI ,;tic sheet, such cis a minimum of 10-mil plastic sheeting, to act as a vapor retarder. We recommend j the vapor bay ricr be constructed in accordance with the American Concrete Institute (ACI 302.1R) and tfril (he plastic sd,,,)t be placed over the capillary break layer. The contractor should be made responsible for n kin staining t integrity of the vapor barrier during construction. 4.4. Foundation Drainage We recommend that perimeter footing drains be installed around the planned building addition and the perimeter drains should be installed at the base of the exterior footings(see Figure 3).The perimeter footing drains should be provided with cleanouts and should consist of at least 4-inch-diameter perforated pipe placed on a 2-inch bed of, and surrounded by, 6 inches of drainage material enclosed in a nonwoven geotextile such as TenCate Mirafi 140N (or approved equivalent) to prevent fine soil from migrating into the drain material. We recommend that the drain pipe consist of either heavy-wall solid pipe(SDR-35 PVC, or equal)or rigid corrugated smooth interior polyethylene pipe(ADS N-12,or equal).We recommend against using flexible tubing for footing drain pipes. GEoENGINEERS� December6,2021 Pages File No.24459-003-00