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Site Report: Swanson River Tank Setting 1-33

Site Name: Swanson River Tank Setting 1-33
Address: Mi. 17.5 Swanson River Rd, Sterling, AK 99672
File Number: 2334.38.021
Hazard ID: 443
Status: Active
Staff: Peter Campbell, 9072623412 peter.campbell@alaska.gov
Latitude: 60.746667
Longitude: -150.861111
Horizontal Datum:NAD83

We make every effort to ensure the data presented here is accurate based on the best available information currently on file with DEC. It is therefore subject to change as new information becomes available. We recommend contacting the assigned project staff prior to making decisions based on this information.

Problems/Comments

Numerous spills at this site with contaminated soils present. Impact to human health or total extent of contamination unknown. Groundwater contamination present. Numerous monitoring wells have floating product. Light non-aqueous phase liquid (LNAPL) recovery and annual groundwater monitoring. Plume appears stable and not expanding. Risk to human health and the environment minimal under current conditions. Due to the oil field infrastructure, major contaminated soil excavation and remediation is not feasible until abandonment of the pad.

Action Information

Action Date Action Description DEC Staff
5/23/1990 Update or Other Action (Old R:Base Action Code = SI - Site Investigation). Arco sent in Phase II Investigation Report. All locations investigated except 1-9 have glacial drift which strongly limited the vertical/horizontal migration of hydrocarbons in subsurface soils. At 1-9 tank setting, permeable coarse grained soils have allowed hydrocarbons to migrate substantially in the subsurface soils/groundwater. Former Staff
11/1/1991 Update or Other Action (Old R:Base Action Code = TOTH - Treatment, Other). Results of Bioventing treatability test provided to the Department. Former Staff
7/15/1992 Update or Other Action (Old R:Base Action Code = TAS - Treatment Alternative Study (CS)). ARCO submitted results of evaluation remediation alternatives for SRF. Report identified numerous potential remediation methods for the contaminated soil and groundwater. Report concluded that in-situ bioventing was the optimum alternative for soil remediation, and disposal of contaminated groundwater at class II wells was optimum method for mitigating contaminated groundwater concern. Former Staff
8/24/1992 Update or Other Action (Old R:Base Action Code = RAPR - Remedial Action Plan Review (CS)). ADEC provided conditional approval of bioventing pilot study. Former Staff
3/8/1993 Site Ranked Using the AHRM Initial ranking. Former Staff
9/20/2000 Meeting or Teleconference Held Meeting at the oil field with Unocal, Chevron, USFWS to discuss past sampling results, improvements to sampling this year and approach to addressing problems. Will have meeting after this years monitoring report has been reviewed to discuss approach for the sites. Informed participants that in order to comply with USFWS regulations, Method 2 cleanup levels (Tables B and C) must be met, not 10 times or risk assessment. Donald Seagren
10/9/2000 Update or Other Action Re-reviewed the 1999 GW Monitoring Report. Final decision will wait until fall 2000 sampling event. At minimum, Unocal will have to determine extent of free product migration and begin free product recovery where needed. Donald Seagren
1/24/2001 Site Added to Database Site broken out of Swanson River Field Tank Setting that was formerly inclusive of all Swanson River Field Tank Setting sites. Former Staff
5/14/2001 Update or Other Action Reviewed 2000 monitoring report; discussed free product recovery work plan with John Hammelman. Donald Seagren
9/12/2002 Site Characterization Workplan Approved Review and approve Work Plan for Monitoring Well Installation. Coordinate with USFWS. Donald Seagren
4/23/2003 Meeting or Teleconference Held Annual meeting to discuss 2002 work and 2003 plans. Donald Seagren
4/29/2003 Update or Other Action Reviewed 2002 MW installation report. Donald Seagren
4/30/2004 Update or Other Action File number assigned and entered into the Fileroom DB and CS DB. Alyce Hughey
5/27/2004 Meeting or Teleconference Held Monthly progress meeting. Revised NAPL recovery plan to be submitted by 30 June 04. Donald Seagren
6/18/2004 Cleanup Plan Approved Reviewed and approved NAPL recovery plan Donald Seagren
3/21/2005 Update or Other Action Reviewed the 2004 GW monitoring report. No appreciable change in risk to human health or the environment. Donald Seagren
10/7/2005 GIS Position Updated Using a Swanson River Layout Map from Unocal, in conjunction with TopoZone Pro and the KPB Parcel Lookup, entered the coordinates for this site. Metadata includes No Topo Basemap, TopoZone Pro Street Maps, Black and White Aerial Photo, on a Medium Size Map, View Scale 1:24,000, Coordinate Datum, NAD83. High degree of confidence in accuracy of location. Alyce Hughey
3/9/2006 Update or Other Action reviewed 05 monitoring rpeort. No significant change to risk to human healt or the environment. Annual monitoring & LNAPL recovery to continue Donald Seagren
4/2/2007 Update or Other Action Reviewed 06 monitoring report. No significant change to risk to human health or the environment. Annual monitoring and LNAPL recovery to continue. Donald Seagren
5/7/2007 Exposure Tracking Model Ranking Donald Seagren
6/11/2008 Update or Other Action Site transferred from Don Seagren to Paul Horwath per Linda Nuechterlein. On 6-30-08 transferred from Paul Horwath to Don Fritz per Paul Horwath. Alyce Hughey
9/29/2011 Document, Report, or Work plan Review - other Reviewed the 2010 Groundwater Monitoring Report Swanson River Tank Setting and Flare Pit report, dated July 2011, from OilRisk Consultants. During the 2010 groundwater sampling event conducted at Tank Setting 1-33 in November through December, ten of the twelve monitoring wells were sampled for BTEX. Well TS1-33Q was not sampled because it was dry and well TS1-33U was not sampled because it was damaged. Analytical results detected Benzene in seven of the monitoring wells above the groundwater cleanup levels at concentrations of 0.00947 to 0.952 mg/L. Alyce Hughey
11/16/2011 Update or Other Action Site transferred from Don Fritz to Peter Campbell per Paul Horwath. Alyce Hughey
8/12/2014 Site Visit Require that Hilcorp submit work plan for thee management of monitoring wells associated with Pad expansion. Peter Campbell
10/21/2014 Document, Report, or Work plan Review - other Approve work plan for contaminated soil management for flow line installations to tank setting 1-33. A flow line is being constructed that will cross over an area of contaminated soils associated with a flare pit. The previously identified contaminated soils associated with a flare pit should be deeper than the proposed five foot deep pipeline installation. Peter Campbell
5/20/2015 Update or Other Action Update from Hilcorp on a line abandonment through an area of historically impacted soil. Peter Campbell
5/26/2015 Update or Other Action Approval to transport contaminated soil for disposal at the gas field grind and inject facility. The soils (<2 cubic yards) were generated from the installation of a pipeline through an area that has historical contamination. Peter Campbell
7/31/2015 Update or Other Action Approval to transport contaminated soil for disposal at the Kenai gas field grind and inject facility. The soils (<1 cubic yards) were generated from the installation of a pipeline through an area that has historical contamination Peter Campbell
9/24/2015 Meeting or Teleconference Held Meeting held to discuss long term sampling strategy and the installation of one new well to address data gaps. Hilcorp proposes to sample the majority of the wells every two years. Peter Campbell
9/19/2017 Document, Report, or Work plan Review - other SRF Tank Setting 1-33 groundwater wells are monitored on a biennial and a four-year schedule. All viable wells are gauged during each sampling event. 2017 field activities include: Decommission and replace wells FS1-33R and TS1-33U. FS1-33R is damaged and cannot be sampled, but has historically been contaminated. TS1-33U has an obstruction; however, LNAPL is observed above the obstruction. Sample seven wells for 8260C and PAH: TS1-33Q, TS1-33UR, TS1-33O2, TS1-33N (to be installed upgradient of TS1-33O2), FS1-33F, FS1-33R2 (replacement well for FS1-33R), and FS1-33S. TS1-33JJ is sampled for 8260C every four years and will be sampled next in 2019. Remove LNAPL from FS1-33H and replace LNAPL-absorbent sock. If LNAPL is not present, sample well for 8260C and PAH. A new well will be installed upgradient (north) of contaminated well TS1-33O2 to confirm the gradient is toward the southeast and not impacting groundwater to the north. See 2017 Kenai Groundwater Monitoring Program Work Plan. Peter Campbell
4/16/2019 Update or Other Action Review Tank Setting 1-33 Soil Sampling Results dated Nov. 14, 2018 that discussed stockpile sampling and open trench excavation work for a produced water flow line. Contaminated soils were removed from the excavation. Trench sidewalls showed that the west end of the trench had evident staining at 1.5 to 2 feet below ground surface for the western most 10 to 20 feet of trench. This is consistent with known soil impacts previously identified. Peter Campbell
11/7/2019 Document, Report, or Work plan Review - other Reviewed the 2017 Groundwater Monitoring Program Report. Monitoring well TS1-33U was decommissioned. Well FS1-33S is mapped as the down gradient well, but FS1-33H is showing the impacts. Down gradient should be further north. Well W was misplaced, should be further north. Peter Campbell
3/25/2020 Document, Report, or Work plan Review - other Review the 2019 Groundwater Monitoring Report. ADEC commented on the representation of groundwater contours on the site maps and requested that future maps honor all groundwater data points to more accurately represent conditions. Peter Campbell
5/27/2021 Site Characterization Workplan Approved Review the Contaminated Soil and Water Management Plan for 2021 Flowline Installation and Inspection. Plan approved. Peter Campbell
7/21/2021 Document, Report, or Work plan Review - other 2021 Groundwater Monitoring Program Work Plan ADEC Approval Letter Peter Campbell
8/1/2022 Document, Report, or Work plan Review - other 2021 Groundwater Monitoring Program Report ADEC Report Plan Approval Peter Campbell
6/1/2023 Long Term Monitoring Workplan or Report Review Review and approve 2023 Groundwater Monitoring Program Work Plan Addendum. Peter Campbell
10/20/2023 Update or Other Action Spill reported to Spill Response at 32A-33, approximately 800 feet south of the 2-15 Pad. Two barrels of produced fluids were reportable released to the ground outside of containment. Peter Campbell
5/17/2024 Update or Other Action Hilcorp is trenching at SRU 1-33 near the wastewater building. A 2’6” foot deep trench, approximately 18” wide and 70 feet in length will be excavated for new high voltage electrical cable in conduits from the pole base to the electrical transformer. Peter Campbell

Contaminant Information

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State of Alaska Department of Environmental Conservation

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Juneau, AK 99811-1800
Phone: 907-465-5066
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