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Oa/05/99 14: 37 $503 588 523 i 112ARION C0. COhf. ~lcven soi~ samPles were coli~cted frotn the non-impacted overburden, which was managed as described ia Section 4,1_ 5,1,Z Dewatering [~j 002/003 Groundwater wos initiaily encountcrcd within the excavation at agproximately 15 feet bgs. Free product was not observed on the water swrface_ Approximately 4b,400 gallans of groundwazcr wes pumped fram the exeavation and tran9ported off-site for recycling during thc inidal excavation activities. Wlun on-site ~~ater treatment was established, an additiona140,000 gallons af water was ptunped from the ezcavation and treatod on site during soil excavation. Discharge samples I3Ti-3, BT2- 2, and BT1-5 were collected from the ~reated water on Novembar 7 and 2a, a.~d T)ecember !0, 1997~ respecti~ely, to satisfy NPDES permit requirements. ~2~ " '~- `r r Wesi collected Afrer swccessively dewatering the e~.cavation to con inue soil removal, Century gtc-undwater samples fmm the excavation following overnight g~oundwater recharge. F.arthen dams were constructed to limit groundwatet recharge from previottgly dewatered az~S into newly dewatered portions of the excavation. Thereforc, groundwater qualiry was evaluated in d,iffetrat regio~s of the excavation A totsl of five goundwater samples idcntificd as 6-1-GW thtough 6-5-GW were collected from various regions of the excavation pit to investigate potentiat pe~roleum hydrocarbon impacts to groundwater (Figure 3). To creau stable excavation wall slopes after ze~m~.dial excsvation was completed (Seetion 4.1), the entire excavation was dewatered to provide equigment access to the south and east excavation wa11s. A minzmum of 200,000 gallons ot water ~was pumped from Yhe Site 6 excavatioa on December 19, 1997 and dischsrged direcdy to two slorm sewers after 9edimtnt filtration. Direct dischazge to Lhb stonn sewess was acceptable due to the low conta~minaat lerreis detecud in gxoundwater samples pieviously collected from the excavation. Water dischazge sample SE-1 was collected to satisfy NPDES permit requiremenrs_ ~~ g.1.3 Analytical So' Analytical results aze presented in Tablo 1. Nine soil confirniation samples exceed the DEQ level2 cleanup concentrativn of 80 mg/kg for TPH-G, However, soil at locations 6-i 1, 6-24, b-. 2'7, and 6-31 w~s further excavated about two to four feet beyoad the initial confirraatien samPle elevation, as indicated by a-djacent confirmation samples collected at lower depths. For example, soil with elevated TPH-G indicated at sample location 6-11-15.0' was subsequently excavated to accc3ptable cancenerations down to apprvximately 1 S.5 feet bgs as shown by analytical results frou't samples b-18-18_5' snd 6-22-18.0'. Therefore, only five of the nine soil confirmation sarnples that e~ce.ed the DEQ level2 cleanup concentration, 6-33-15.0', 6-45-15.5', 6-4b-15.5', 6- ~ Corrective Aetion Pl~ Che~+ron Parcel - Coutthousc Sguare ~oizo ~a 559~[8S£09 'ON Xd~ -9- ~~ 1 H~~d ~ i sso~ ~zx~na~~ 40806-001-19 Apri123, 1998 Z~ ~ Zt I~~ 66-50-~d41