3000 ROCKEFELLER AVE PARKING GARAGE 2018-01-02 MF Import

�; ;Gt:!;,...��\ G,f1�ILS�i':. Ii'�C. cncountcrcd, wc rccommcnd that cut slopcs bc no stccper than LSH:1V. Flattcr cut slopes may bc rcquircd whcrc loosc soils or sccpagc zoncs arc cncountcred during excavation. Exposcd cut slopes may necd to bc protcctcd �aith a ��atcrproof covcring dming periods of wet wcather to rcducc sloughing and crosion. � The abovc rccommcndations are for temporary cut slopes in dry conditions. If wet conditions or uncontrolled groundwater flow is encountercd, ilattcr slopes may be required. Based on our experiencc, in addition to the anticipatcd groundwater table, sceps and springs may be � encountered, even in ��cry dense, glacial till cut slopes. Care should be taken near the existing buildin� footings to make sure that the open cut docs not undennine the bearing capacity of the footing suboradc soils. Also, all Iraffic ancUor construction equipment loads should be set back from the edgc of the cut slopcs by a minimum of 2 fcet. Cxcavatcd matcrial, slockpilcs of construction matcrials, and equipmcnt should not be placed closcr to tiie cdge of any excavation than the dcpth of the escavation, unless thc excavation is shored .md such matcri:ils are accountcd for as a surchargc IoaJ on Qic shoring system. � 1U.10 Gxcavalion of Polentially Contaminalcd Soil Soil and groundwatcr contamination are present in approximatcly thc no�th half of thc sitc (thc Administration Garagc). More spceifically, past operations in thc area of borings B-10, B-12, B- 13, B-Id, B-1G, and [3-15 (sec Pigure Z) have apparcntly resulted in thc rcleasc of hydrocarbons to thc soil and �mund��atcr. Our asscssmcnt oC thc arca's conditions is ongoing. Somc of thc soil and groundwater encountered in the proposed e�cavation �vill be affected hy Ihe contamination and will nccd to bc h:mdlcd :md disposed of properly. Based on our ezperience with �Vashington State Department of Hcology (L"cology), sourcc remo��al and proper disposal of contaminatcd soil ��ithin the limits of the proposed excavation will likely bc an appropriate soil cicanup action. �Vc have discussed this potential action �aith thc County and L'cology, but bccausc wc have yct to idcntify thc sourec location, actual soil cicanup actions are still under consideration. Oncc a cicanup action is selected, we recommend that a Clcnnup Action Plan summanzing proposed remedial actions be prepared for and suhmittcd to L-'colo��y, or th:u a mceting �vith C-coloey takc placc to discuss proposcd actions. In !1.1.119411-IFlig1��•11d �7 21- I -096�4�-005