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State of Oregon Department ofEnviromnental Quality Memorandum Date: May 18, 2017 To: Kevin Parrett, Manager Northwest Region Cleanup and Tanks /' From: JenniferSutter, Project Manager PROVER�-./�-;.&./�s:S:::::==::'::_ Northwest Region Cleanup and Tanks Kevin Paqett, Manager J Subject: No Further Action Recommendation ATE f;/t2{1l 7 Shoreline Source Control I I Evraz Oregon Steel Mills ECSI #141 Purpose This memo provides a summary of investigation and remedial action to prevent the transport of contaminated soil from the riverbank and upper beach along the Evraz Oregon Steel (EOS) site (Site) to the Willamette River. The EOS Site is located at 14400 N Rivergate Avenue, Portland, Oregon (see Figure 1). Oregon Steel Mills entered into a Voluntary Agreement with the Oregon Department of Environmental Quality (DEQ) in June 2000 to complete enviromnental work at the upland portion of the Site. EOS acquired OSM in 2007 and has been working under the Voluntary Agreement since that time. Several phases of site investigation and cleanup evaluation have been completed with Cleanup Program oversight. With EPA agreement, DEQ selected the riverbank source control measure for the Site in 2014 (EPA, 2014). The design was approved in 2015 afterreview and input fromEPA (EPA, 2015). A determination that the selected riverbank source control measure has been constructed consistent with the approved design and no further action (NF A), other than long-term monitoring and maintenance, is required for shoreline source control is proposed for the Site which requires the approval of the DEQ Cleanup Manager. A public notice for the proposed determination is attached. Status of Other Source Control Pathways and Uplands A source control decision addressing stormwater run-offfrom the facility was issued by DEQ in December 2010. A primaryelement of the stormwater source control action consists of end-of-pipe treatment, which has been implemented and is currently undergoing final design evaluations, including consideration of additional treatment using sand filters and the addition of a coagulant. A No Further Action proposal for groundwater source control at the facility has been prepared and submitted to United States Enviromnental Protection Agency (EPA) for review as it relates to the Portland Harbor Superfund site. Additional sampling to address concerns raised by EPA is currentlyunder discussion. Memo to: Kevin Parrett 5/18/2017 Page 2 A risk assessment addressing potential upland exposures to contaminants has been approved by DEQ. EOS is preparing a feasibility study to address potential future worker exposures to upland contamination. Background The EOS facility is situated on the eastern bank of the Willamette River in the Rivergate industrial area of Portland, Oregon. The facility covers approximately 145 acres and has a physical address of 14400 N Rivergate Avenue. The facility layout is shown in Figure 2. Gilmore Steel, a predecessor of EOS, purchased the EOS property from the Port of Portland in 1967. Prior to the purchase, the Port authorized Shaver Transportation and others to operate a former oil sump (the Ramsey Lakes Sump Area) on the Port property from approximately 1942 to 1960. The former sump was used for the disposal of ship bilge water and other waste oils and fluids. During the time of Port ownership, the Port filled much of the portion of the property outside the sump area with dredge materials from the Willamette River, currently part of the Portland Harbor Superfund site. Fill material consisting of slag from steel making mixed with soil was also placed on the Site by Oregon Steel Mills periodically during plant expansion and construction activities. This mixed slag-soil fill is present as near surface fill across much of the facility; however, the thickness and character of the fill (e.g., amount of fine-grained soil mixed with the slag) vary somewhat across the facility. The mixed slag-soil fill forms a dense, semi- consolidated unit with a thickness of approximately two to ten feet across much of the facility, thickening at the riverbank to approximately fifteen feet. The berm at the top of the riverbank contains stormwater runoff from the Site (landward of the riverbank) and routes it through the stormwater treatment system, thereby preventing direct runoff of stormwater in contact with the slag-soil fill to the river. No known industrial activities occurred at the Site between the closure of the former oil sump and construction of the steel mill, which was completed in 1969. Since 1969, the facility has been used for steel production and related ancillary operations. The EOS facility includes several large industrial process buildings (e.g., combination rolling mill, cut to length facility, former melt shop (currently used for storage), surface processing pipe mill, and pipe coating mill), a maintenance building, water treatment facilities, office buildings, parking lots, and materials processing and staging areas. The facility is primarily fenced with the exception of the western property boundary along the steep riverbank. The EOS facility property lies adjacent to the Portland Harbor Superfund site, which covers an approximate ten mile stretch of the lower Willamette River from River Mile 1.9 to 11.8. The property is surrounded by other industrial manufacturing and transfer facilities to the north, east, and south. The Willamette River forms the western property boundary. Memo to: Kevin Parrett 5/18/2017 Page 3 Geology/Hydrogeology The area now occupied by the EOS facility is a historic floodplain between the Willamette and Columbia Rivers and is located approximately two miles upstream of the confluence of these rivers (i.e., River Mile 2). The native deposits at the Site consist of sands, silty sands and silts generally characteristic of river floodplains. The native deposits are overlain by various types of fill including dredge fill (which is similar to the native soil), slag-soil fill, and other localized fill units ranging in composition from silty sand to slag aggregate fill. The dominant fill units at the EOS shoreline are as follows (starting from the most recent (uppermost) fill and working downward) (See Figure 3): • Berm Fill – brown to yellow-brown, silty fine sand and fine grained sandy soils with some gravel. The fill soil was used to construct the berm along the western edge of the property for storm water control and aesthetic enhancement in 1995. Fill material used for the berm was generated onsite during excavation of the combination mill. Berm thickness ranges from five to ten feet. The berm is nearly continuous along the developed portion of the property with interruptions in two locations: at the northern end of the property providing access to the riverbank from the uplands, and in the central portion of the property where the dock extends from the uplands. • Mixed Slag-Soil Fill – gray, gravel and silty to sandy gravel mixed with slag in many portions of the facility at a thickness of ten feet or less. The mixed slag-soil fill forms a dense, semi-consolidated unit. Along the riverbank area, the mixed slag-soil fill unit is wedge-shaped, thicker towards the river and has a maximum thickness of approximately fifteen feet, forming the near vertical portion of the bank. The slag-soil fill unit along the riverbank generally contains more fine- grained soil than the slag-soil unit across the rest of the property. The slag-soil fill was placed in the late 1960’s to early 1970’s. • Dredge Fill – brown to gray, silty fine-grained sand used to fill the EOS property and the surrounding Rivergate Area from 1942 up to 1967. The dredge fill is exposed at the surface at the northern end of the riverbank. The dredge fill exposed at the north end of the property merges with slag-soil fill to the south. In many cases, the dredge fill unit is indistinguishable from the underlying alluvium unit based on similar texture and hydrology. The fill unit extends to depths of approximately 20 to 30 feet below ground surface (bgs) in the central and southern upland areas. The upper groundwater bearing unit is a silty, fine sand encountered at a depth of 4 to 20 feet bgs (30 to 14 feet National Geodetic Vertical Datum 1929 (NGVD29)) and extending to the underlying aquitard at depths of 20 to 35 feet bgs (10 to -5 feet NGVD29). The sandy silt to silty clay aquitard is continuous beneath the Site and ranges in thickness from approximately 30 to 70 feet; vertical permeabilities are low (2.6 x 10-6 to 6.7 x 10-8 cm/sec). Memo to: Kevin Parrett 5/18/2017 Page 4 Shallow groundwater elevations measured in EOS upland groundwater monitoring wells range from approximately 26 feet NGVD29 in the eastern portion of the EOS facility to approximately 7 feet immediately upland of the berm. Groundwater elevation at the berm ranges from 7 to 10 feet NGVD29. In beach wells, the groundwater elevation is approximately 4 to 8 feet NGVD29. The groundwater levels fluctuate seasonally by 1.5 to 6 feet across the property, with the greatest fluctuations measured on the eastern side. Groundwater flows generally toward the west- southwest across the property (i.e., toward the Willamette River). Groundwater gradients range from approximately 0.002 to 0.003 feet/feet in the upland areas of the facility to approximately 0.03 to 0.06 feet/feet adjacent to the shoreline. Groundwater monitoring conducted from 2002 to 2005 indicates groundwater gradients and flow directions are seasonally consistent. Willamette River levels along the shoreline range from a mean low water level of 4.1 to a mean high water level of 9.6 feet NGVD29. The ordinary high water (OHW) level is 16.6 feet and the 100-year flood level is 27.5 feet NGVD29.

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