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Site Report: Alyeska PS 01 Former Gas Tank Area


Site Name: Alyeska PS 01 Former Gas Tank Area
Address: Spine Road, Pipeline Mile 0, Deadhorse, AK 99734
File Number: 330.38.019
Hazard ID: 1741
Status: Active
Staff: Grant Lidren, 9072698685 grant.lidren@alaska.gov
Latitude: 70.258467
Longitude: -148.619892
Horizontal Datum:WGS84

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

An aboveground storage tank (AST) leaked approximately 112 gallons of gasoline in December 1992. Subsequent soil samples collected in spring 2013 indicated gas range hydrocarbon contamination in soil and water. Contaminated soil excavation, Soil Vapor Extraction (SVE), and Air Sparging (AS) remediation have occurred. Several prior, small spills occurred in the area. In 1991, there was a release at the fuel island located adjacent to the former gas tanks and a release investigation and closure report was submitted. Confirmation results showed concentrations up to 5,200 mg/kg volatile petroleum hydrocarbons (VPH) (gas), 11,000 mg/kg extractable petroleum hydrocarbons (EPH) (diesel), 13,000 mg/kg total recoverable petroleum hydrocarbons (TRPH) (residual) and 1.1 mg/kg benzene. Subsequent investigations in the area sometimes included both the former gas tank area and adjacent fuel island.

Action Information

Action Date Action Description DEC Staff
8/15/1993 Preliminary Assessment Approved (Old R:Base Action Code = SA1R - Phase I SA Review (CS/LUST)). Preliminary sampling indicates soil and water contamination due to AST release. Scott Rose
9/23/1993 Site Characterization Report Approved (Old R:Base Action Code = RI - Remedial Investigation). Remedial Investigation included installation of soil borings and monitoring wells. Benzene in groundwater at 1.1 mg/l. Scott Rose
8/1/1994 Site Characterization Workplan Approved (Old R:Base Action Code = SA2R - Phase II SA Review (CS)). Phase II assessment approved. The department requested additional borings and monitoring wells. Scott Rose
10/19/1995 Site Added to Database Site added. Scott Rose
10/19/1995 Site Ranked Using the AHRM Initial ranking. Scott Rose
1/17/2001 Update or Other Action 2000 Contaminated Soil Excavation and Groundwater Monitoring Report, PS 1 Former Gasoline Tank Area, Alyeska Spill Number 1992348 submitted to ADEC. Approximately 150 cubic yards of contaminated soil were removed from the excavation down to the suprapermafrost groundwater. An impermeable liner was installed after the excavation was complete, and the AS system was reassembled. Analytical results from groundwater samples indicate that petroleum hydrocarbon impact remains in the area north of the former gasoline ASTs site. DRO concentrations increased in MW-1, MW-2, MW-8, MW-9 and MW-10. GRO and benzene levels also increased in MW-9. MW-10 has increased GRO and BTEX concentrations as well. IT states that some of the increases seen in petroleum hydrocarbon concentrations in the immediate area of the AS system is likely due to the excavation activities releasing the contaminants from soil to the groundwater. IT recommends continued operation of the AS system and continued groundwater monitoring in the vicinity of the former gasoline tank area. Deborah Williams
8/6/2001 Cleanup Plan Approved Plan approval for start up of air sparging system and annual groundwater monitoring. Renee Evans
4/9/2003 Update or Other Action Alyeska submitted a groundwater monitoring report for the former PS1 Gasoline Tank Area. Analytical results from the groundwater samples collected at the site showed that the concentrations of petroleum hydrocarbons are relatively stable at most monitoring wells. The most significant exceptions include monitoring wells in the center of the contaminant plume (MW-8, MW-9, and MW-10), which may demonstrate a northeastern migration of the dissolved hydrocarbon plume. No petroleum hydrocarbons were detected in samples collected from the nearest surface water body off of the eastern edge of the tank farm gravel pad. Also, a small area of isolated DRO contamination east of Tank 117 seems to exist separately from the gasoline contamination resulting from the FGTA. SLR recommend the continuation of annual groundwater monitoring. Deborah Williams
3/30/2004 Update or Other Action Alyeska submitted report entitled 2003 Former Gasoline Tank Area Ground Water Monitoring Report, PS 1. Ground water samples collected from the PS 1 FGTA show that concentrations of dissolved petroleum hydrocarbons remain above ADEC ground water cleanup levels. Within the source area there were benzene levels up to 10.3 ppm and downgradient benzene up to 9.12 ppm. Samples collected in 2003 support previous observations of northeasterly migration of the petroleum contamination, notable in monitoring wells MW-8, MW-9, MW-15, and MW-19. Monitoring well MW-10, closest to the source, shows an overall reduction since 1994 in dissolved hydrocarbons, while monitoring wells MW-8, MW-9 and MW-15, downgradient from the source, exhibit overall increases. The area of ground water impacted above ADEC cleanup levels appears to have increased since the 2002 sampling. However, based on ground water samples collected from the edge of the pad and from surface water proximal to the PS1 pad, it is apparent that impacted groundwater is not currently migrating off pad. SLR recommends the continuation of the annual ground water and surface water sampling program in 2004, as well as the continued operation of the AS system. Deborah Williams
3/14/2005 Update or Other Action ADEC reviewed SLR's PS 1 Former Gasoline Tank Area 2004 Groundwater Monitoring and Remediation Report. Samples collected in 2004 support previous observations of a northeasterly migration of the petroleum contamination. Monitoring well MW-10, which is located closest to the source, shows an overall reduction in dissolved hydrocarbons since 1994. Downgradient monitoring wells MW-8 and MW-15 indicate consistently increased concentrations of dissolved hydrocarbons. In addition, the lateral extent of groundwater with concentrations exceeding ADEC cleanup levels has increased slightly during the last two years. Analytical results from groundwater and surface water samples collected adjacent to the pad, were non-detect. Therefore, there does not appear to be migration from the pad to the surface water. Deborah Williams
4/5/2006 Update or Other Action ADEC received PS 1 Former Gas Tank Area 2005 Groundwater Monitoring and Remediation Report. GW analytical results collected from monitoring wells in 2005 show that concentrations of dissolved petroleum hydrocarbons remain above ADEC groundwater cleanup levels. MW-10, which is located closest to the source, shows an overall reduction in dissolved hydrocarbons since 1994. However, downgradient MW-8 demonstrates consistently increased concentrations of dissolved hydrocarbons. From the data, it is apparent that impacted ground water currently is not migrating off-pad. SLR recommends the continuation of the annual groundwater and surface water sampling program in 2006, as well as the continued operation of the AS system. Deborah Williams
3/14/2007 Update or Other Action ADEC received the SLR report on the 2006 Groundwater Monitoring and Remediation for the PS 1 Former Gas Tank site. According to the report, there still appears to be a northeasterly migration of petroleum contamination. MW-10 which is located closest to the source shows an overall reduction in dissolved hydrocarbons since 1994. However, downgradient MW-8 demonstrates consistently increased concentrations of dissolved hydrocarbons. Deborah Williams
3/16/2007 Exposure Tracking Model Ranking Initial ranking completed. Deborah Williams
3/7/2008 Update or Other Action Receipt of Pump Station 1 Former Gasoline Tank Area 2007 Ground Water and Remediation Report. Nine groundwater wells and two surface water locations were sampled. Overall results appear to be fairly consistent with past years data, including no BTEX or PAH in surface water. Since its installation, MW-15 has exhibited particularily high DRO concentrations which is thought to be due to therminol contamination from a leaking pipe at Tank 117. DO results suggest that biodegradation may be occuring. Air sparging (AS) unit was not operated due to interference that was created by recent sludge treatment activities. SLR recommends continued monitoring with MNA parameters in groundwater and continued operation of AS or more excavation. Report review including laboratory QA/QC conducted 3/26/08. Keather McLoone
3/13/2009 Report or Workplan Review - Other Receipt of Pump Station 1 Former Gasoline Tank Area 2008 Ground Water Monitoring and Remediation Report by SLR. In 2008, soil was excavated (~150 cubic yards) from the original source area of the gasoline contamination. Contaminated soil above the suprapermafrost grond water table was removed but some contaminated soil remains beneath this depth. Eight excavation confirmation samples were collected from 2.5 - 4 ft bgs and all exceeded most conservative criteria (0.025 mg/kg) benzene. Two samples collected from 3.5 and 4 ft bgs also exceeded criteria for ethylbenzene, xylenes, and toluene. Samples were also analyzed for GRO, DRO, RRO, and PAHs. Groundwater, including natural attenuation parameters, and surface water monitoring. Impacted groundwater is not migrating off-pad. Results in MW-15 much reduced from historic data (2 orders of magnitude reduction). Monitoring to continue in 2009. The air sparging system was decommissioned during excavation of soil from within its footprint. Alyeska intends to install an AST in this vicinity in 2009. Review included laboratory review checklist. GRO/BTEX results for SS-2 should be considered rejected and usable as a screening value due to too much uncertainty in data quality. Methanol appeared to have leaked in transit and lab added another aliquot of MeOH (extract already extracted soil). Furthermore, the field surrogate recovery was outside of acceptance criteria (biased high). GRO/BTEX results for SS-3 should be considered estimated with a high bias due to surrogate recovery more than 2 times the upper limit of acceptance criteria and no dilution performed. DRO/RRO/PAH results for SS-2 should be considered estimated as prep and analysis were performed on container that was broken and 50 percent "salvageable" upon receipt. Keather McLoone
6/4/2009 Report or Workplan Review - Other Approval of 2009 Pump Station 1 Former Gasoline Tank Area Water Monitoring Work Plan. When the PS01 gravel pad has thawed, a groundwater and surface water event will be conducted, likely August or September. Thirteen groundwater locations and 2 surface water locations will be sampled. Groundwater sampling to include DO, ferric/ferrous iron, nitrite/nitrate, and sulfate/sulfide as it has in the past. Contaminant analyses to include BTEX/GRO/DRO/PAH in groundwater and TAH/TAqH in surface water. Two well installations are also planned - one to replace MW-10 which was destroyed and an additional well to be installed NE of MW-10. DEC comment on workplan regarding collection of MNA parameters and the importance of understanding the limitations and interferences of measurements made using techniques that expose the water to ambient air or ORP measurements are not stabilized. Keather McLoone
5/10/2010 Report or Workplan Review - Other Review of Pump Station 1 Former Gasoline Tank Area 2009 Remediation and Groundwater Monitoring Report. Groundwater sampling, surface water sampling, and monitoring well installation was conducted in 2009. MNA parameters were also assessed. Surface water results do not indicate offsite migration. Groundwater results contain benzene, toluene, ethylbenze, xylenes, GRO, and DRO above Table C. No remediation was conducted during 2009. Keather McLoone
6/18/2010 Report or Workplan Review - Other Review of Pump Station 1 Former Gasoline Tank Area 2010 Water Monitoring Workplan received June 15, 2010. A single groundwater event of all onsite wells and including MNA parameters is planned when the PS 01 gravel pad thaws. Keather McLoone
4/11/2011 Report or Workplan Review - Other Date of receipt of Pump Station 1 Former Gasoline Tank Area 2010 Water Monitoring Report. Eight groundwater and two surface water locations were sampled in 2010. Groundwater samples were also collected for MNA parameters. Groundwater results are still above Table C but surface water samples suggest that contamination is not migrating off the pad. Keather McLoone
7/5/2011 Report or Workplan Review - Other Date of receipt of Pump Station 1 Former Gasoline Tank Area 2011 Water Monitoring Workplan. Alyeska plans to conduct a single suprapermafrost and surface water sampling event. Keather McLoone
3/23/2012 Report or Workplan Review - Other Date of receipt of 2011 Water Monitoring Report. Only nine of 17 wells were sampled due to insufficient water (7) or well damage (1). Exceedances for GRO, DRO, benzene, and/or toluene were found in samples collected from five of the nine wells. High DRO concentrations suggest product present which should be measured in the future. Two surface water samples collected showed concentrations below applicable criteria. TAH and TAqH are still not calculated correctly but would not have exceeded regardless. MNA parameters also collected at the nine wells sampled. Ferric iron, alkalinity, and nitrite were performed using field test kits. Evaluation of quality of MNA data also made difficult because calibration information, etc. for field measured parameters not included with report. Total iron, sulfate, sulfide, and total nitrate plus nitrite were performed by the laboratory. SLR plans to resurvey the wells due to frost jacking issues. Keather McLoone
6/19/2012 Site Characterization Workplan Approved Approved workplan to monitor groundwater and surface water, perform maintenance on monitoring wells, and measure Monitored Natural Attenuation (MNA) parameters, to include NOx, SO4, Fe2/Fe3. SLR plans to measure PAHs in 20% of wells this year, so I requested measurement at key wells downgradient of source area (MW-9, 19, & 17) as a minimum to track plume migration. Richard Bernhardt
2/26/2013 Site Characterization Report Approved Field work occurred between 2 & 6 Aug 2012. Eleven of 17 MWs and 2 surface water locations were sampled. The remaining MWs were either dry or damaged. GRO remained over cleanup levels in MWs 8, 9, & 91. DRO remained over cleanup levels in MWs 3, 9, 14, & 15. Benzene remained over cleanup levels in MWs 8, 9, 18, 19, & 20. Maximum COCs were detected as follows: GRO - MW-19 = 14.4mg/L; DRO - MW-15 = 206mg/L; and Benzene - MW-9 = 3.91mg/L. COCs (including PAHs) were not detected in surface water samples. Richard Bernhardt
3/15/2013 Update or Other Action Updated coordinates based on comparison between the 2012 work report and Google Earth imagery. Richard Bernhardt
4/23/2013 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 72719 Benzene contamination. Richard Bernhardt
5/24/2013 Site Characterization Workplan Approved Received and approved a work plan to conduct a single groundwater and surface water monitoring event, install up to three new monitoring wells, and decommission two wells. Richard Bernhardt
2/24/2014 Site Characterization Report Approved On this date, ADEC received the 2013 Water Monitoring Report Pump Station 1 Former Gasoline Tank Area dated February 2014 submitted by Alyeska. Groundwater and surface water monitoring activities were conducted on August 3rd and 4th. Only 15 out of 17 wells were sampled due to inaccessibility to MW-10 and MW-21. Additionally due to inaccessibility, MW-4, MW-16, and MW-17 were not replaced and MW-10 and MW-13 were not decommissioned. Monitoring wells MW-8, MW-9, MW-14, MW-15, MW-18, and MW-19 contained contaminant concentrations above ADEC cleanup levels with GRO up to 19.2 mg/L (MW-19), DRO up to 102 mg/L (MW-15) and benzene up to 4.97 mg/L (MW-19). The two surface water samples collected did not contain TAH or TAqH above applicable criteria. Groundwater is generally flat with a trend toward the northeast or edge of pad. The GW elevations were generally lower than the 2012 GW elevations. Grant Lidren
6/10/2014 Site Characterization Workplan Approved On this date, ADEC approved the 2014 Water Monitoring Work Plan Pump Station 1 Former Gasoline Tank Area submitted by SLR, dated May 2014. Grant Lidren
4/24/2015 Site Characterization Report Approved On this date, ADEC received the 2014 Water Monitoring Report Pump Station 1 Former Gasoline Tank Area submitted by SLR dated April 2015. Groundwater and surface water monitoring activities were conducted on August 21st and 24th. Seven out of the eleven monitoring wells sampled contained concentrations of contaminants above ADEC cleanup levels. These seven MWs: MW-3, MW-8, MW-9, MW-15, MW-18, MW-19, and MW-20 contained GRO up to 40.7 mg/L (MW-9), DRO up to 120 mg/L (MW-15), benzene up to 6.58 mg/L (MW-9), toluene up to 10.4 (MW-9), and ethylbenzene up to 0.732 (MW-9). Note: benzene and GRO concentrations in MW-19 have increased since 2009. Due to inaccessibility, MW-4, MW-16, and MW-17 were not replaced and MW-10 was not decommissioned as planned. However, the monitoring wells MW-14 and MW-21 were decommissioned. Two surface water samples collected did not contain TAH or TAqH above applicable criteria. Groundwater is generally flat with a trend toward the northeast or edge of pad. The GW elevations were generally lower than the 2012 GW elevations. Grant Lidren
7/6/2015 Site Characterization Workplan Approved ADEC Received and reviewed the 2015 Water Monitoring Work Plan Pump Station 1 Former Gasoline Tank Area submitted by SLR and dated May 2015. Grant Lidren
3/29/2016 Site Characterization Report Approved On this date, ADEC received the 2015 Water Monitoring Report Pump Station 1 Former Gasoline Tank Area submitted by SLR dated March 2016. In November 2015, seven MWs were installed replacing five historic wells adding two new MWs on the eastern side of the pad Groundwater and surface water monitoring activities were conducted between August 24th and 27th 2015. Thirteen MWs sampled including: MW-2, MW-3, MW-4, MW-8, MW-9, MW-12, MW-13 and MW-15 through MW-20; contained GRO up to 16.8 mg/L (MW-9), DRO up to 69 mg/L (MW-15), benzene up to 3.93 mg/L (MW-19), and toluene up to 2.27 (MW-9). MW-7 and MW-14 were not sampled due to damage. These monitoring wells and monitoring well MW-4, MW-16, and MW-17 were replaced with MW-4R, MW-7R, MW14R, MW16R, and MW-17R. MW-10 was not replaced as planned due to lack of access. Additionally, MW-22 and MW-23 were installed along the eastern edge of the pad. Two surface water samples collected did not contain TAH or TAqH above applicable criteria. Groundwater is generally flat with a trend toward the northeast or edge of pad. The GW elevations were generally higher than the 2012 GW elevations. Grant Lidren
6/29/2016 Site Characterization Workplan Approved ADEC Received and reviewed the 2016 Water Monitoring Work Plan Pump Station 1 Former Gasoline Tank Area submitted by SLR and dated June 2016. Grant Lidren
2/15/2017 Site Characterization Report Approved On this date, ADEC received the 2016 Water Monitoring Report Pump Station 1 Former Gasoline Tank Area submitted by SLR dated January 2017. A total of 16 MWs and two SW locations were sampled and the three damaged MWs: MW-4, MW-16, and MW-10 were decommissioned. The 16 MWs sampled including: MW-2, MW-3, MW-4R, MW-8, MW-9, MW-12, MW-13, MW-14R, MW-15R, MW-16R, MW-17 through MW-20, MW-22 and MW-23. Groundwater samples collected from seven of these 16 MWs contained contaminant concentrations above ADEC clean levels with GRO up to 30.8 mg/L (MW-9), DRO up to 106 mg/L (MW-14R), benzene up to 3.96 mg/L (MW-9), toluene up to 5.18 (MW-9) and xylenes up to 8.31 mg/L (MW-9). Note: newly installed MW-23 installed to the east edge of plume contained benzene at 0.0107 mg/L. Two surface water samples collected did not detectable concentrations of TAH or TAqH. Groundwater is generally flat with a trend toward the northeast or edge of pad. The GW elevations were 1.01 ft. lower than the 2015 GW elevations. Grant Lidren
6/6/2017 Site Characterization Workplan Approved ADEC received and reviewed the 2017 Water Monitoring Work Plan Pump Station 1 Former Gasoline Tank Area submitted by SLR and dated May 2017. MW-9 and MW-14 will be analyzed for petroleum VOCS by method 8260. This work plan is for approval of groundwater monitoring for three years: 2017, 2018, and 2019. Grant Lidren

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