Site Report: Alyeska PS 01 West Pad Area

Site Name:	Alyeska PS 01 West Pad Area
Address:	Pump Station 1, SW Area of Pad, Prudhoe Bay, AK 99734
File Number:	330.38.107
Hazard ID:	4057
Status:	Active
Staff:	Laura Jacobs, 9074512911 laura.jacobs@alaska.gov
Latitude:	70.256614
Longitude:	-148.620561
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.

Site Chronology
IC / Closure Details
Documents
Associated Sites

Problems/Comments

During the groundwater sampling for the Solar Generator project in 2003, a prominent synthetic chemical odor was noted in monitoring well B-MW-10. The odor was not identifiable and differed substantially from the odors associated with petroleum-contaminated purge water. This synthetic chemical odor was also noticeable while sampling monitoring well B-MW-GB, which is installed through the floor of the Gas Building. The samples collected from B-MW-10 were analyzed for a full range of volatile organic compounds. Numerous aromatic hydrocarbons associated with petroleum fuels were detected and assumed to originate from the Solar Generator release. The non-petroleum compounds detected included chloromethane, dichlorodifluoromethane (CFC-12), 1,2,3-trichlorobenzene, 1,1,1-trichloroethane (1,1,1-TCA), and trichlorofluoromethane (CFC-11. Because these compounds have not been documented as part of the Solar Generator or the Brine releases, investigation into the extent and potential sources of these contaminants is addressed at this site. File numbers 330.38.095, 330.38.107, and 330.38.110 are being monitored and reported together under this file number.

Action Information

Action Date	Action	Description	DEC Staff
8/3/2004	Site Added to Database	Unknown contaminant found in the suprapermafrost groundwater near the Gas Building at Pump Station 1.	Deborah Williams
8/3/2004	Site Ranked Using the AHRM	Preliminary ranking.	Deborah Williams
6/23/2005	Update or Other Action	ADEC received PS 1 Gas Building Area Investigation 2004 Monitoring Report. This reports involves the investigation of chlorofluorocarbons (CFCs) and chlorinated organic compounds in the suprapermafrost groundwater that was discovered in B-MW-10 in 2003. Results indicated the highest concentrations of CFCs from wells MW-10 and B-MW-5. Concentrations of methylene chloride, benzene, and toluene in one groundwater sample collected near the Compression Building (B-MW-6) exceeded ADEC groundwater cleanup levels. There will be a site investigation in the vicinity of monitoring well B-MW-6 on the south side of the Compression Building to assess extent of methylene chloride, benzene and toluene under a new project in 2005.	Keather McLoone
4/5/2006	Update or Other Action	ADEC received Pump Station 1 2005 Gas Building Area Groundwater Monitoring Report. The 2005 monitoring event was expanded from the 2004 effort to include thirteen wells in the vicinity of not only the Gas Building, but also the Solar Generator, Warehouse and Gas Compressor Building. All of the ground water samples contained detectable concentrations of CFC-11 and CFC-12. The specific source of these CFCs and other chlorinated organics is unknown. None of the groundwater samples, which were analyzed for VOCs, contained hydrocarbon concentrations at or above the ADEC water quality criteria. SLR recommends continued groundwater monitoring on an annual basis to assess extent of chlorinated organic compounds, VOCs and CFCs in ground water in the area between the Solar Generator and the Compression Building. SLR also recommends the inclusion of surface water monitoring on the west and south PS1 pad edges.	Deborah Williams
6/28/2006	Update or Other Action	The site name for this site was changed from "Alyeska PS 1 Gas Building site" to "Alyeska PS1 West Pad Area". This site is a combination of the Alyeska PS1 Solar Generator site and Alyeska PS1 Gas Compressor site.	Deborah Williams
3/14/2007	Update or Other Action	ADEC received the PS 1 2006 West Pad Groundwater Monitoring Report. According to the report, with exception of B-MW-6, BTEX concentrations appear to be relatively consistent or slightly decreasing across the West Pad site. Elevated levels of GRO and DRO constituents above ADEC cleanup levels were found. Each of the groundwater samples contained detectable concentrations of CFC-12, and CFC-11 was detected in each of the samples except MW-8 and CB-MW-2. The specific source of the CFCs and other chlorinated organics is unknown. SLR recomends continued groundwater monitoring on an annual basis. SLR recommends dropping the sampling for PAHs with the exception of naphthalene.	Deborah Williams
1/4/2008	Exposure Tracking Model Ranking	Initial ranking with ETM completed. Ranking for Gas Compressor Bldg (330.38.110/330.38.107) is currently under West Pad Area (330.38.107).	Keather McLoone
3/14/2008	Update or Other Action	Received Pump Station 1 West Pad 2007 Ground Water Monitoring Report. Sites that have been combined in this report are the Gas Building Site, the Solar Generator site, and the Gas Compressor Building Site. Fourteen of the 17 monitoring wells were dry in 2007 - the others were sampled for DRO, VOCs (chlorinated compounds including CFCs of particular interest), and naphthalene by 8270C (although lab reported naphthlane by 8260B). CFCs were detected in each of the 3 samples that were collected and methylene chloride was detected above Table C in 2 of the wells samples. SLR recommends continued groundwater monitoring. Report review including lab QA/QC conducted 3/27/08.	Keather McLoone
3/4/2009	Document, Report, or Work plan Review - other	Date of receipt of Pump Station 1 West Pad 2008 Ground Water Monitoring Report by SLR. Ten of 17 wells at this site contained water and were sampled. DRO, GRO, benzene, toluene, and ethylbenzene, and methylene chloride found above Table C. Monitoring to continue in 2009. Review included laboratory review checklist.	Keather McLoone
6/4/2009	Document, Report, or Work plan Review - other	Approval of 2009 Pump Station 1 West Pad Ground Water Monitoring Work Plan. Thirteen groundwater wells will be sampled for VOCs/GRO/DRO and Naphthalene by 8270CSIM. Surface water has not historically been sampled in conjunction with the West Pad monitoring projects but if feasible - two locations will be established and sampled for TAH/TAqH.	Keather McLoone
5/7/2010	Document, Report, or Work plan Review - other	Review of Pump Station 1 West Pad 2009 Groundwater Monitoring Report. Twelve of the 17 wells had enough water for sampling. Surface water along the edge of the pad was also sampled at two locations. Report states results were below Table C and water quality criteria, respectively. Groundwater samples were sampled for DRO, PAHs, and VOCs. Some wells also had GRO samples collected and analyzed. Monitoring will continue in 2010. It would appear that the report is in error and methylene chloride is above Table C in 3 wells sampled.	Keather McLoone
6/18/2010	Document, Report, or Work plan Review - other	Review of 2010 Pump Station 1 West Pad Water Monitoring Workplan received on 6/17/2010. A single suprapermafrost and surface water sampling event is planned for when the PS 01 gravel pad is thawed. An attempt to sample all 17 onsite wells will be made.	Keather McLoone
4/11/2011	Document, Report, or Work plan Review - other	Receipt of Pump Station 1 West Pad 2010 Water Monitoring Report. Groundwater results above Table C, surface water results continue to indicate that contaminants are not migrating off the site. Review included laboratory data review checklist. Methylene chloride was detected in two samples above Table C (the LOQ was equal to Table C level).	Keather McLoone
7/5/2011	Document, Report, or Work plan Review - other	Date of receipt of Pump Station 1 West Pad 2011 Water Monitoring Work Plan. Alyeska plans to conduct one suprapermafrost ground water and surface water sampling event.	Keather McLoone
3/23/2012	Document, Report, or Work plan Review - other	Date of receipt of 2011 Water Monitoring Report. Only seven out of 17 wells were sampled due to insufficient water (9) or well damage (1). All but one of the wells had an exceedance for either DRO (5) ranging from 83.9 (MW-8) to 1.93 mg/L or methylene chloride (1) at 0.0938 mg/L (duplicate) but not both constituents. The two surface water samples collected did not contain TAH or TAqH above applicable criteria. TAH and TAqH are still not being calculated correctly, but would not have exceeded regardless. This high of a DRO concentration suggests product is present and measuring product at this site in the future should be discussed.	Keather McLoone
6/5/2012	Document, Report, or Work plan Review - other	SLR plans to replace monitoring well B-MW-8 due to damage and replace MW-4, MW-6,MW- 11, CB-MW-1, CB-MW3, & CBMW4 due to historically insufficient water to permit testing/analyses. Replacement activities will occur if SLR and Alyeska can coordinate work schedules so that SLR doesn’t interfere. New well locations will be determined in the field, but should be near previous wells. One collection event will occur at all 17 MWs in 2012 to track trends and determine if contaminated groundwater is migrating offsite. Surface water will also be analyzed.	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
5/24/2013	Site Characterization Workplan Approved	Received and approved a work plan to conduct a single ground and surface water sampling event.	Richard Bernhardt
2/24/2014	Site Characterization Report Approved	On this date, ADEC received the Pump Station 1 West Pad 2013 Water Monitoring Report submitted by SLR dated February 2014. Work included monitoring 17 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building, and two surface water locations near the PS 01 West pad site. Two of the 17 well were not sampled because one was destroyed (MW-10) and the other did not contain enough water (MW-15). Monitoring wells MW-4, MW-8, MW-12, MW-16, , B-MW-5, B-MW-10, and B-MW-GB contained contaminant concentrations above ADEC cleanup levels with, GRO up to 4.53 mg/L (MW-12), DRO up to 60.7 mg/L (MW-8), benzene up to 0.676 mg/L (MW-12), and CFC-12 up to 8.2 mg/L (B-MW-5). The two surface water samples collected did not contain TAH or TAqH above applicable criteria. Groundwater is generally toward the southwest. The GW elevations were higher than the 2012 GW elevations in all the MWs except for MW-15.	Grant Lidren
6/10/2014	Site Characterization Workplan Approved	On this date, ADEC approved the 2014 Water Monitoring Work Plan Pump Station 1 West Pad 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 West Pad submitted by SLR dated April 2015. Work included monitoring 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building, collecting two surface water locations near the PS 01 West pad site and decommissioning MW-10. Four of the 16 wells were not sampled due to insufficient water volumes. Monitoring wells MW-8, MW-12, MW-14, MW-16, B-MW-5, B-MW-6 and B-MW-GB contained contaminant concentrations above ADEC cleanup levels with, GRO up to 12.2 mg/L (MW-12), DRO up to 37.9 mg/L (MW-8), benzene up to 0.241 mg/L (B-MW-6), toluene up to 3.57 mg/L (B-MW-6), and EDB up to 0.00021 mg/L (B-MW-6). GRO exceedances were limited to MWs: MW-12, MW-14, and B-MW-6 all located on the Westside of the site. These GRO exceedances are an increase from historical results. DRO exceedances were limited to MWs: MW-8, MW-16, B-MW-GB, and B-MW-5 on the eastside of the site. The three surface water samples collected did contain TAH/TAqH above applicable criteria. These exceedances were driven by toluene, which was also detected in the TB. Groundwater is generally toward the southwest. The GW elevations were 0.5 feet lower than the 2013 GW elevations in all the MWs.	Grant Lidren
7/6/2015	Site Characterization Workplan Approved	The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2015 Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated May 2015. ADEC has no objections to the Work Plan and SLR may proceed.	Grant Lidren
3/29/2016	Site Characterization Report Approved	On this date, ADEC received the 2015 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated March 2016. Work included monitoring 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building, collecting two surface water locations near the PS 01 West pad site and decommissioning MW-10. One of the 16 wells (MW-4) was not sampled due to insufficient water volume. Monitoring wells MW-8, MW-12, MW-13, MW-14, MW-16, B-MW-5, B-MW-6 and B-MW-GB contained contaminant concentrations above ADEC cleanup levels. Monitoring well B-MW-6 contained the highest concentrations of GRO at 83.0 mg/L, benzene at 1.12 mg/L, toluene at 23.8 mg/L, ethylbenzene at 1.44 mg/L, xylenes at 10.6 mg/L, methylene chloride at 0.308 mg/L and EDB at 0.000562 mg/L. Monitoring well MW-8 contained the highest concentrations of DRO at 23.1 mg/L. GRO exceedances were limited to MWs: MW-12 and B-MW-6 all located on the Westside of the site. These GRO exceedances are an increase from historical results. DRO exceedances were limited to MWs: MW-8, MW-16, B-MW-GB, B-MW-5, and BMW-6 all located on the eastside of the site with the exception of B-MW-6. The two surface water samples collected contained toluene but below TAH/TAqH water quality standards. Groundwater is generally toward the southwest. The GW elevations were slightly higher than the average elevations recorded since 2012.	Grant Lidren
6/8/2016	Site Characterization Workplan Approved	The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2015 Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated May 2016. ADEC has no objections to the Work Plan and SLR may proceed.	Grant Lidren
2/15/2017	Site Characterization Report Approved	On this date, ADEC received the 2016 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated February 2017. Work included: monitoring 12 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad site. Monitoring wells MW-1, MW-2, MW-4, and MW-12 were not sampled due to insufficient water volume. Six monitoring wells: MW-8, MW-16, B-MW-5, B-MW-6, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well B-MW-6 contained the highest concentrations of GRO at 5.57 mg/L, benzene at 0.102 mg/L, toluene at 2.11 mg/L, ethylbenzene at 0.291 mg/L, xylenes at 1.774 mg/L, 1,2,4-trimethylbenzene at 0.157 mg/L and napthalene at 0.0122 mg/L. Monitoring well MW-8 contained the highest concentrations of DRO at 32.1 mg/L, 2-hexanone at 0.0927 mg/L and 1,3,5-trimethylbenzene at 0.244 mg/L. GRO exceedances were limited to B-MW-6 located on the Westside of the site. This GRO exceedances is a decrease from last year results. DRO exceedances were limited to MWs: MW-8, MW-16, and B-MW-GB, all located on the eastside of the site. The two surface water samples collected detectable levels of petroleum constituents, but below TAH/TAqH water quality standards. Groundwater is generally toward the southwest.	Grant Lidren
6/16/2017	Site Characterization Workplan Approved	The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2017 & 2018 Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated June 2017. This work plan is for GW sampling for 2017 and 2018. ADEC has no objections to the Work Plan and SLR may proceed.	Grant Lidren
4/15/2018	Site Characterization Report Approved	On this date, ADEC received the 2017 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated April 2018. Work included: monitoring 15 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad. Monitoring well MW-15 was not sampled due to an ice plug. Eight monitoring wells: MW-2, MW-4, MW-8, MW-12, MW-13, MW-16, B-MW-6, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well MW-12 contained the highest concentrations of GRO at 11.1 mg/L, toluene at 6.58 mg/L, ethylbenzene at 0.3490 mg/L, xylenes at 2.65 mg/L, EDB at 0.000168 mg/L, and methylene chloride at 0.484 mg/L. Monitoring well MW-13 contained the highest concentrations of benzene at 0.852 mg/L, 1,2-dichloroethane at 0.0062 mg/L, and 1,1 dichloroethane at 0.14 mg/L. Monitoring well MW-8 contained the highest concentrations of DRO at 59.5 mg/L and naphthalene at 0.277 mg/L. Monitoring well MW-4 contained the highest concentrations of 2-hexanone at 0.108 mg/L, 1,2,4-trimethylbenzene at 0.265 mg/L, and 1,3,5-trimethylbenzene at 0.238 mg/L. Monitoring well B-MW-10 contained the highest concentrations of CFC-12 at 4.49 mg/L. No petroleum hydrocarbon exceedances were noted for wells MW-1, MW-14, MW-17, B-MW-5, B-MW-7, and CB-MW-2. Of these seven wells, well CB-MW-2 was the only sampled well without any VOC exceedances. Cleanup level exceedances at downgradient wells MW-17 and B-MW-7 were limited to dichlorodifluoromethane (CFC-12). GRO exceedances were limited to MW-12 and MW-13 located on the Westside of the site (note: BMW-6 did not contain DRO concentrations above CLs). DRO exceedances were limited to MWs: MW-2, MW-4, MW-8, MW-16, MW-13, B-MW-10, and B-MW-GB, all located throughout the site. EDB exceedances were limited to MW-12 and MW-13. The two surface water samples collected contained detectable levels of petroleum constituents, but below TAH/TAqH water quality standards. Groundwater is generally toward the southwest.	Grant Lidren
5/25/2018	Document, Report, or Work plan Review - other	On this date, ADEC received the addendum to Water Monitoring Work Plan for 2017 & 2018, Pump Station 1 West Pad_Revision 1 submitted by SLR and dated May 25, 2018. Petroleum VOCs analysis will be added to all MWs for 2018.	Grant Lidren
7/31/2018	Site Visit	Visited site on this date with Alyeska and SLR.	Grant Lidren
3/4/2019	Site Characterization Report Approved	ADEC received the 2018 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated February 2019. Work included: monitoring 14 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad. Monitoring well MW-15 was not sampled due to an ice plug and MW-12 was dry do to dewatering of an adjacent excavation. Ten monitoring wells: MW-2, MW-4, MW-8, MW-14, MW-16, MW-17, B-MW-5, B-MW-7, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well MW-16 contained the highest concentrations of ethylbenzene at 0.0177 mg/L. MW-8 contained the highest concentration of DRO at 35.3mg/L, xylenes at 0.67 mg/L mg/L, 1,3,5-trimethylbenzene at 0.187 mg/L and naphthalene at 0.206 mg/L. MW-4 contained the highest concentration of 1,2,4-trimethylbenzene at 0.157 mg/L. MW-14 contained the highest concentration of concentrations of dichlorodifluoromethane (CFC-12) at 2.46 mg/L and methylene chloride at 0.356 mg/L. DRO exceedances were limited to: MW-2, MW-4, MW-8, and MW-16 all located throughout the site. Xylene exceedance was limited to MW-8. Ethylbenzene exceedance was limited to MW-16. Cleanup level exceedances at downgradient wells MW-17 and B-MW-7 were limited to CFC-12. The two surface water samples collected contained detectable levels of toluene, but below the summation of TAH/TAqH water quality standards. Groundwater is generally toward the southwest.	Grant Lidren
5/29/2019	Site Characterization Workplan Approved	On this date, ADEC received the Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated June 2019. The Groundwater is approved to be monitored in 2019, 2020, and 2021.	Grant Lidren
12/18/2019	Site Characterization Report Approved	ADEC received the 2019 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated December 2019. Work included: monitoring 15 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad. Monitoring well MW-15 was not sampled due to an ice plug. Fourteen monitoring wells: MW-1, MW-2, MW-4, MW-8, MW-12, MW-13, MW-14, MW-16, MW-17, B-MW-5, B-MW-6, B-MW-7, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well MW-12 contained the highest concentrations of GRO at 9.08 mg/L, benzene at 0.126 mg/L, ethylbenzene at 0.154 mg/L, toluene at 1.57 mg/L, xylenes at 2.125 mg/L, EDB at 0.000166 mg/L, and methylene chloride at 0.529 mg/L. MW-8 contained the highest concentration of DRO at 35.9 mg/L and naphthalene at 0.234 mg/L. MW-4 contained the highest concentration of 1,2,4-trimethylbenzene at 0.292 mg/L and 1,3,5-trimethylbenzene at 0.319 mg/L. B-MW-6 contained the highest concentrations of 1,1,2-trichloroethane at 0.00064 mg/L. MW-12 and B-MW-5 contained the highest of concentrations of dichlorodifluoromethane (CFC-12) both at 3.99 mg/L. DRO exceedances were limited to: MW-4, MW-8, B-MW-GB, MW-12, and MW-16 all located throughout the site. Xylene exceedances were limited to MW-12, B-MW-6, MW-14, MW-13, MW-16 and MW-8 all located throughout the site. Ethylbenzene exceedance was limited to MW-12, MW-13, MW-14, MW-16, B-MW-6, and BMW-10 all located throughout the site. 1,1,2-trichloroethane exceedances were limited to B-MW-6, MW-13, and MW-14 all located adjacent to each other on the west side of the site. GRO exceedances were only in MW-12 and MW-14 located near each other on the west side of the site. Cleanup level exceedances at downgradient wells MW-17 and B-MW-7 were limited to CFC-12 only. The two surface water samples did not contain detectable concentrations of contaminants. Groundwater is generally toward the southwest.	Grant Lidren
5/21/2021	Document, Report, or Work plan Review - other	The Pump Station 1 West Pad 2020 Water Monitoring Report and the Water Monitoring Work Plan, Pump Station 1 West Pad were reviewed. Groundwater monitoring is proposed to continue for the next two years in the work plan at the existing sixteen wells and two surface water sample sites across the combined sites: Gas Compressor, Solar Generator, and the Gas Building. There was a release of refrigerant brine from the Gas Compressor site. Turbine fuel was the release from the Solar Generator site. Chlorofluorocarbons were detected in groundwater samples collected from monitoring wells in the vicinity of the Gas Building during the 2003 site investigation. The source of CFCs in this area has not been identified to date. ADEC requested this effort be added to the work plan.	Laura Jacobs
10/24/2022	Long Term Monitoring Workplan or Report Review	The 2021 Water Monitoring Report for PS01 West Pad includes the monitoring sites and results from the other sites included (Solar Generator and Gas Compressor Building). Groundwater samples were collected from 14 of 16 monitoring wells and two surface water locations. Results showed a slight increase in groundwater impacts from 2020. Exceedances included petroleum hydrocarbons (diesel range organics, benzene, ethylbenzene, and xylenes) and volatile organic compounds (CFC-12 and naphthalene). Surface water quality is not affected by impacted groundwater.	Laura Jacobs
7/14/2023	Document, Report, or Work plan Review - other	DEC has completed a review of the 2022 Water Monitoring Report submitted to our office on January 23, 2023 and is approving it. Groundwater samples were collected from 15 of the existing 16 monitoring wells and two surface water samples were collected from two water bodies west of the site. Overall, sample results trend towards a slight increase in contaminant levels across the site. Specifically, the quantity and magnitude of Volatile Organic Compound (VOC) exceedances decreased in MW-1, MW-2, MW-4, MW-8, MW16, and B-MW-BG. Surface water samples were below DEC water quality standards at both sample locations. DEC also reviewed the 2023 Water Monitoring Work Plan received by our office March 31, 2023. DEC is also approving the work plan which proposes to continue monitoring for the next two years.	Laura Jacobs
10/2/2023	Document, Report, or Work plan Review - other	DEC reviewed the additional information provided by the RP's consultant to explain the site history use of Chlorofluorocarbons (CFCs) that have been found on site in the form of CFC-11 and CFC-12. The additional information included plume maps over time, and a Mann-Kendall trend analysis. Ultimately, it was recommended and DEC agrees that monitoring the plume over time while observing natural attenuation processes is the best strategy twenty some years after the discovery.	Laura Jacobs
8/22/2024	Document, Report, or Work plan Review - other	The field efforts in 2023 included sampling of 14 of the 16 remaining monitoring wells and two surface water locations. Although the number of exceedances of the Groundwater Cleanup Levels has remained consistent during the last three years, there are more analytes exceeding this year than in the past. The petroleum hydrocarbon exceedances increased above historic ranges at MW-12, MW-13, MW-14, B-MW-6, B-MW-GB, and CB-MW-2 during the 2023 sample effort. Hydrocarbon concentrations in surface water samples were below the Alaska Water Quality exceedance criteria. Samples were collected in August19-20, 2023. DEC approves the 2023 report as submitted.	Laura Jacobs

Action Date

Action

Description

DEC Staff

8/3/2004

Site Added to Database

Unknown contaminant found in the suprapermafrost groundwater near the Gas Building at Pump Station 1.

Deborah Williams

8/3/2004

Site Ranked Using the AHRM

Preliminary ranking.

Deborah Williams

6/23/2005

Update or Other Action

ADEC received PS 1 Gas Building Area Investigation 2004 Monitoring Report. This reports involves the investigation of chlorofluorocarbons (CFCs) and chlorinated organic compounds in the suprapermafrost groundwater that was discovered in B-MW-10 in 2003. Results indicated the highest concentrations of CFCs from wells MW-10 and B-MW-5. Concentrations of methylene chloride, benzene, and toluene in one groundwater sample collected near the Compression Building (B-MW-6) exceeded ADEC groundwater cleanup levels. There will be a site investigation in the vicinity of monitoring well B-MW-6 on the south side of the Compression Building to assess extent of methylene chloride, benzene and toluene under a new project in 2005.

Keather McLoone

4/5/2006

Update or Other Action

ADEC received Pump Station 1 2005 Gas Building Area Groundwater Monitoring Report. The 2005 monitoring event was expanded from the 2004 effort to include thirteen wells in the vicinity of not only the Gas Building, but also the Solar Generator, Warehouse and Gas Compressor Building. All of the ground water samples contained detectable concentrations of CFC-11 and CFC-12. The specific source of these CFCs and other chlorinated organics is unknown. None of the groundwater samples, which were analyzed for VOCs, contained hydrocarbon concentrations at or above the ADEC water quality criteria. SLR recommends continued groundwater monitoring on an annual basis to assess extent of chlorinated organic compounds, VOCs and CFCs in ground water in the area between the Solar Generator and the Compression Building. SLR also recommends the inclusion of surface water monitoring on the west and south PS1 pad edges.

Deborah Williams

6/28/2006

Update or Other Action

The site name for this site was changed from "Alyeska PS 1 Gas Building site" to "Alyeska PS1 West Pad Area". This site is a combination of the Alyeska PS1 Solar Generator site and Alyeska PS1 Gas Compressor site.

Deborah Williams

3/14/2007

Update or Other Action

ADEC received the PS 1 2006 West Pad Groundwater Monitoring Report. According to the report, with exception of B-MW-6, BTEX concentrations appear to be relatively consistent or slightly decreasing across the West Pad site. Elevated levels of GRO and DRO constituents above ADEC cleanup levels were found. Each of the groundwater samples contained detectable concentrations of CFC-12, and CFC-11 was detected in each of the samples except MW-8 and CB-MW-2. The specific source of the CFCs and other chlorinated organics is unknown. SLR recomends continued groundwater monitoring on an annual basis. SLR recommends dropping the sampling for PAHs with the exception of naphthalene.

Deborah Williams

1/4/2008

Exposure Tracking Model Ranking

Initial ranking with ETM completed. Ranking for Gas Compressor Bldg (330.38.110/330.38.107) is currently under West Pad Area (330.38.107).

Keather McLoone

3/14/2008

Update or Other Action

Received Pump Station 1 West Pad 2007 Ground Water Monitoring Report. Sites that have been combined in this report are the Gas Building Site, the Solar Generator site, and the Gas Compressor Building Site. Fourteen of the 17 monitoring wells were dry in 2007 - the others were sampled for DRO, VOCs (chlorinated compounds including CFCs of particular interest), and naphthalene by 8270C (although lab reported naphthlane by 8260B). CFCs were detected in each of the 3 samples that were collected and methylene chloride was detected above Table C in 2 of the wells samples. SLR recommends continued groundwater monitoring. Report review including lab QA/QC conducted 3/27/08.

Keather McLoone

3/4/2009

Document, Report, or Work plan Review - other

Date of receipt of Pump Station 1 West Pad 2008 Ground Water Monitoring Report by SLR. Ten of 17 wells at this site contained water and were sampled. DRO, GRO, benzene, toluene, and ethylbenzene, and methylene chloride found above Table C. Monitoring to continue in 2009. Review included laboratory review checklist.

Keather McLoone

6/4/2009

Document, Report, or Work plan Review - other

Approval of 2009 Pump Station 1 West Pad Ground Water Monitoring Work Plan. Thirteen groundwater wells will be sampled for VOCs/GRO/DRO and Naphthalene by 8270CSIM. Surface water has not historically been sampled in conjunction with the West Pad monitoring projects but if feasible - two locations will be established and sampled for TAH/TAqH.

Keather McLoone

5/7/2010

Document, Report, or Work plan Review - other

Review of Pump Station 1 West Pad 2009 Groundwater Monitoring Report. Twelve of the 17 wells had enough water for sampling. Surface water along the edge of the pad was also sampled at two locations. Report states results were below Table C and water quality criteria, respectively. Groundwater samples were sampled for DRO, PAHs, and VOCs. Some wells also had GRO samples collected and analyzed. Monitoring will continue in 2010. It would appear that the report is in error and methylene chloride is above Table C in 3 wells sampled.

Keather McLoone

6/18/2010

Document, Report, or Work plan Review - other

Review of 2010 Pump Station 1 West Pad Water Monitoring Workplan received on 6/17/2010. A single suprapermafrost and surface water sampling event is planned for when the PS 01 gravel pad is thawed. An attempt to sample all 17 onsite wells will be made.

Keather McLoone

4/11/2011

Document, Report, or Work plan Review - other

Receipt of Pump Station 1 West Pad 2010 Water Monitoring Report. Groundwater results above Table C, surface water results continue to indicate that contaminants are not migrating off the site. Review included laboratory data review checklist. Methylene chloride was detected in two samples above Table C (the LOQ was equal to Table C level).

Keather McLoone

7/5/2011

Document, Report, or Work plan Review - other

Date of receipt of Pump Station 1 West Pad 2011 Water Monitoring Work Plan. Alyeska plans to conduct one suprapermafrost ground water and surface water sampling event.

Keather McLoone

3/23/2012

Document, Report, or Work plan Review - other

Date of receipt of 2011 Water Monitoring Report. Only seven out of 17 wells were sampled due to insufficient water (9) or well damage (1). All but one of the wells had an exceedance for either DRO (5) ranging from 83.9 (MW-8) to 1.93 mg/L or methylene chloride (1) at 0.0938 mg/L (duplicate) but not both constituents. The two surface water samples collected did not contain TAH or TAqH above applicable criteria. TAH and TAqH are still not being calculated correctly, but would not have exceeded regardless. This high of a DRO concentration suggests product is present and measuring product at this site in the future should be discussed.

Keather McLoone

6/5/2012

Document, Report, or Work plan Review - other

SLR plans to replace monitoring well B-MW-8 due to damage and replace MW-4, MW-6,MW- 11, CB-MW-1, CB-MW3, & CBMW4 due to historically insufficient water to permit testing/analyses. Replacement activities will occur if SLR and Alyeska can coordinate work schedules so that SLR doesn’t interfere. New well locations will be determined in the field, but should be near previous wells. One collection event will occur at all 17 MWs in 2012 to track trends and determine if contaminated groundwater is migrating offsite. Surface water will also be analyzed.

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

5/24/2013

Site Characterization Workplan Approved

Received and approved a work plan to conduct a single ground and surface water sampling event.

Richard Bernhardt

2/24/2014

Site Characterization Report Approved

On this date, ADEC received the Pump Station 1 West Pad 2013 Water Monitoring Report submitted by SLR dated February 2014. Work included monitoring 17 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building, and two surface water locations near the PS 01 West pad site. Two of the 17 well were not sampled because one was destroyed (MW-10) and the other did not contain enough water (MW-15). Monitoring wells MW-4, MW-8, MW-12, MW-16, , B-MW-5, B-MW-10, and B-MW-GB contained contaminant concentrations above ADEC cleanup levels with, GRO up to 4.53 mg/L (MW-12), DRO up to 60.7 mg/L (MW-8), benzene up to 0.676 mg/L (MW-12), and CFC-12 up to 8.2 mg/L (B-MW-5). The two surface water samples collected did not contain TAH or TAqH above applicable criteria. Groundwater is generally toward the southwest. The GW elevations were higher than the 2012 GW elevations in all the MWs except for MW-15.

Grant Lidren

6/10/2014

Site Characterization Workplan Approved

On this date, ADEC approved the 2014 Water Monitoring Work Plan Pump Station 1 West Pad 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 West Pad submitted by SLR dated April 2015. Work included monitoring 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building, collecting two surface water locations near the PS 01 West pad site and decommissioning MW-10. Four of the 16 wells were not sampled due to insufficient water volumes. Monitoring wells MW-8, MW-12, MW-14, MW-16, B-MW-5, B-MW-6 and B-MW-GB contained contaminant concentrations above ADEC cleanup levels with, GRO up to 12.2 mg/L (MW-12), DRO up to 37.9 mg/L (MW-8), benzene up to 0.241 mg/L (B-MW-6), toluene up to 3.57 mg/L (B-MW-6), and EDB up to 0.00021 mg/L (B-MW-6). GRO exceedances were limited to MWs: MW-12, MW-14, and B-MW-6 all located on the Westside of the site. These GRO exceedances are an increase from historical results. DRO exceedances were limited to MWs: MW-8, MW-16, B-MW-GB, and B-MW-5 on the eastside of the site. The three surface water samples collected did contain TAH/TAqH above applicable criteria. These exceedances were driven by toluene, which was also detected in the TB. Groundwater is generally toward the southwest. The GW elevations were 0.5 feet lower than the 2013 GW elevations in all the MWs.

Grant Lidren

7/6/2015

Site Characterization Workplan Approved

The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2015 Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated May 2015. ADEC has no objections to the Work Plan and SLR may proceed.

Grant Lidren

3/29/2016

Site Characterization Report Approved

On this date, ADEC received the 2015 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated March 2016. Work included monitoring 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building, collecting two surface water locations near the PS 01 West pad site and decommissioning MW-10. One of the 16 wells (MW-4) was not sampled due to insufficient water volume. Monitoring wells MW-8, MW-12, MW-13, MW-14, MW-16, B-MW-5, B-MW-6 and B-MW-GB contained contaminant concentrations above ADEC cleanup levels. Monitoring well B-MW-6 contained the highest concentrations of GRO at 83.0 mg/L, benzene at 1.12 mg/L, toluene at 23.8 mg/L, ethylbenzene at 1.44 mg/L, xylenes at 10.6 mg/L, methylene chloride at 0.308 mg/L and EDB at 0.000562 mg/L. Monitoring well MW-8 contained the highest concentrations of DRO at 23.1 mg/L. GRO exceedances were limited to MWs: MW-12 and B-MW-6 all located on the Westside of the site. These GRO exceedances are an increase from historical results. DRO exceedances were limited to MWs: MW-8, MW-16, B-MW-GB, B-MW-5, and BMW-6 all located on the eastside of the site with the exception of B-MW-6. The two surface water samples collected contained toluene but below TAH/TAqH water quality standards. Groundwater is generally toward the southwest. The GW elevations were slightly higher than the average elevations recorded since 2012.

Grant Lidren

6/8/2016

Site Characterization Workplan Approved

The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2015 Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated May 2016. ADEC has no objections to the Work Plan and SLR may proceed.

Grant Lidren

2/15/2017

Site Characterization Report Approved

On this date, ADEC received the 2016 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated February 2017. Work included: monitoring 12 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad site. Monitoring wells MW-1, MW-2, MW-4, and MW-12 were not sampled due to insufficient water volume. Six monitoring wells: MW-8, MW-16, B-MW-5, B-MW-6, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well B-MW-6 contained the highest concentrations of GRO at 5.57 mg/L, benzene at 0.102 mg/L, toluene at 2.11 mg/L, ethylbenzene at 0.291 mg/L, xylenes at 1.774 mg/L, 1,2,4-trimethylbenzene at 0.157 mg/L and napthalene at 0.0122 mg/L. Monitoring well MW-8 contained the highest concentrations of DRO at 32.1 mg/L, 2-hexanone at 0.0927 mg/L and 1,3,5-trimethylbenzene at 0.244 mg/L. GRO exceedances were limited to B-MW-6 located on the Westside of the site. This GRO exceedances is a decrease from last year results. DRO exceedances were limited to MWs: MW-8, MW-16, and B-MW-GB, all located on the eastside of the site. The two surface water samples collected detectable levels of petroleum constituents, but below TAH/TAqH water quality standards. Groundwater is generally toward the southwest.

Grant Lidren

6/16/2017

Site Characterization Workplan Approved

The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2017 & 2018 Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated June 2017. This work plan is for GW sampling for 2017 and 2018. ADEC has no objections to the Work Plan and SLR may proceed.

Grant Lidren

4/15/2018

Site Characterization Report Approved

On this date, ADEC received the 2017 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated April 2018. Work included: monitoring 15 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad. Monitoring well MW-15 was not sampled due to an ice plug. Eight monitoring wells: MW-2, MW-4, MW-8, MW-12, MW-13, MW-16, B-MW-6, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well MW-12 contained the highest concentrations of GRO at 11.1 mg/L, toluene at 6.58 mg/L, ethylbenzene at 0.3490 mg/L, xylenes at 2.65 mg/L, EDB at 0.000168 mg/L, and methylene chloride at 0.484 mg/L. Monitoring well MW-13 contained the highest concentrations of benzene at 0.852 mg/L, 1,2-dichloroethane at 0.0062 mg/L, and 1,1 dichloroethane at 0.14 mg/L. Monitoring well MW-8 contained the highest concentrations of DRO at 59.5 mg/L and naphthalene at 0.277 mg/L. Monitoring well MW-4 contained the highest concentrations of 2-hexanone at 0.108 mg/L, 1,2,4-trimethylbenzene at 0.265 mg/L, and 1,3,5-trimethylbenzene at 0.238 mg/L. Monitoring well B-MW-10 contained the highest concentrations of CFC-12 at 4.49 mg/L. No petroleum hydrocarbon exceedances were noted for wells MW-1, MW-14, MW-17, B-MW-5, B-MW-7, and CB-MW-2. Of these seven wells, well CB-MW-2 was the only sampled well without any VOC exceedances. Cleanup level exceedances at downgradient wells MW-17 and B-MW-7 were limited to dichlorodifluoromethane (CFC-12). GRO exceedances were limited to MW-12 and MW-13 located on the Westside of the site (note: BMW-6 did not contain DRO concentrations above CLs). DRO exceedances were limited to MWs: MW-2, MW-4, MW-8, MW-16, MW-13, B-MW-10, and B-MW-GB, all located throughout the site. EDB exceedances were limited to MW-12 and MW-13. The two surface water samples collected contained detectable levels of petroleum constituents, but below TAH/TAqH water quality standards. Groundwater is generally toward the southwest.

Grant Lidren

5/25/2018

Document, Report, or Work plan Review - other

On this date, ADEC received the addendum to Water Monitoring Work Plan for 2017 & 2018, Pump Station 1 West Pad_Revision 1 submitted by SLR and dated May 25, 2018. Petroleum VOCs analysis will be added to all MWs for 2018.

Grant Lidren

7/31/2018

Site Visit

Visited site on this date with Alyeska and SLR.

Grant Lidren

3/4/2019

Site Characterization Report Approved

ADEC received the 2018 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated February 2019. Work included: monitoring 14 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad. Monitoring well MW-15 was not sampled due to an ice plug and MW-12 was dry do to dewatering of an adjacent excavation. Ten monitoring wells: MW-2, MW-4, MW-8, MW-14, MW-16, MW-17, B-MW-5, B-MW-7, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well MW-16 contained the highest concentrations of ethylbenzene at 0.0177 mg/L. MW-8 contained the highest concentration of DRO at 35.3mg/L, xylenes at 0.67 mg/L mg/L, 1,3,5-trimethylbenzene at 0.187 mg/L and naphthalene at 0.206 mg/L. MW-4 contained the highest concentration of 1,2,4-trimethylbenzene at 0.157 mg/L. MW-14 contained the highest concentration of concentrations of dichlorodifluoromethane (CFC-12) at 2.46 mg/L and methylene chloride at 0.356 mg/L. DRO exceedances were limited to: MW-2, MW-4, MW-8, and MW-16 all located throughout the site. Xylene exceedance was limited to MW-8. Ethylbenzene exceedance was limited to MW-16. Cleanup level exceedances at downgradient wells MW-17 and B-MW-7 were limited to CFC-12. The two surface water samples collected contained detectable levels of toluene, but below the summation of TAH/TAqH water quality standards. Groundwater is generally toward the southwest.

Grant Lidren

5/29/2019

Site Characterization Workplan Approved

On this date, ADEC received the Water Monitoring Work Plan Pump Station 1 West Pad submitted by SLR and dated June 2019. The Groundwater is approved to be monitored in 2019, 2020, and 2021.

Grant Lidren

12/18/2019

Site Characterization Report Approved

ADEC received the 2019 Water Monitoring Report Pump Station 1 West Pad submitted by SLR dated December 2019. Work included: monitoring 15 of 16 wells in the vicinity of the Solar Generator, Gas Compressor Building, and Gas Building; and collecting two surface water locations near the PS 01 west pad. Monitoring well MW-15 was not sampled due to an ice plug. Fourteen monitoring wells: MW-1, MW-2, MW-4, MW-8, MW-12, MW-13, MW-14, MW-16, MW-17, B-MW-5, B-MW-6, B-MW-7, B-MW-10 and B-MW-GB; contained contaminant concentrations above ADEC cleanup levels. Monitoring well MW-12 contained the highest concentrations of GRO at 9.08 mg/L, benzene at 0.126 mg/L, ethylbenzene at 0.154 mg/L, toluene at 1.57 mg/L, xylenes at 2.125 mg/L, EDB at 0.000166 mg/L, and methylene chloride at 0.529 mg/L. MW-8 contained the highest concentration of DRO at 35.9 mg/L and naphthalene at 0.234 mg/L. MW-4 contained the highest concentration of 1,2,4-trimethylbenzene at 0.292 mg/L and 1,3,5-trimethylbenzene at 0.319 mg/L. B-MW-6 contained the highest concentrations of 1,1,2-trichloroethane at 0.00064 mg/L. MW-12 and B-MW-5 contained the highest of concentrations of dichlorodifluoromethane (CFC-12) both at 3.99 mg/L. DRO exceedances were limited to: MW-4, MW-8, B-MW-GB, MW-12, and MW-16 all located throughout the site. Xylene exceedances were limited to MW-12, B-MW-6, MW-14, MW-13, MW-16 and MW-8 all located throughout the site. Ethylbenzene exceedance was limited to MW-12, MW-13, MW-14, MW-16, B-MW-6, and BMW-10 all located throughout the site. 1,1,2-trichloroethane exceedances were limited to B-MW-6, MW-13, and MW-14 all located adjacent to each other on the west side of the site. GRO exceedances were only in MW-12 and MW-14 located near each other on the west side of the site. Cleanup level exceedances at downgradient wells MW-17 and B-MW-7 were limited to CFC-12 only. The two surface water samples did not contain detectable concentrations of contaminants. Groundwater is generally toward the southwest.

Grant Lidren

5/21/2021

Document, Report, or Work plan Review - other

The Pump Station 1 West Pad 2020 Water Monitoring Report and the Water Monitoring Work Plan, Pump Station 1 West Pad were reviewed. Groundwater monitoring is proposed to continue for the next two years in the work plan at the existing sixteen wells and two surface water sample sites across the combined sites: Gas Compressor, Solar Generator, and the Gas Building. There was a release of refrigerant brine from the Gas Compressor site. Turbine fuel was the release from the Solar Generator site. Chlorofluorocarbons were detected in groundwater samples collected from monitoring wells in the vicinity of the Gas Building during the 2003 site investigation. The source of CFCs in this area has not been identified to date. ADEC requested this effort be added to the work plan.

Laura Jacobs

10/24/2022

Long Term Monitoring Workplan or Report Review

The 2021 Water Monitoring Report for PS01 West Pad includes the monitoring sites and results from the other sites included (Solar Generator and Gas Compressor Building). Groundwater samples were collected from 14 of 16 monitoring wells and two surface water locations. Results showed a slight increase in groundwater impacts from 2020. Exceedances included petroleum hydrocarbons (diesel range organics, benzene, ethylbenzene, and xylenes) and volatile organic compounds (CFC-12 and naphthalene). Surface water quality is not affected by impacted groundwater.

Laura Jacobs

7/14/2023

Document, Report, or Work plan Review - other

DEC has completed a review of the 2022 Water Monitoring Report submitted to our office on January 23, 2023 and is approving it. Groundwater samples were collected from 15 of the existing 16 monitoring wells and two surface water samples were collected from two water bodies west of the site. Overall, sample results trend towards a slight increase in contaminant levels across the site. Specifically, the quantity and magnitude of Volatile Organic Compound (VOC) exceedances decreased in MW-1, MW-2, MW-4, MW-8, MW16, and B-MW-BG. Surface water samples were below DEC water quality standards at both sample locations. DEC also reviewed the 2023 Water Monitoring Work Plan received by our office March 31, 2023. DEC is also approving the work plan which proposes to continue monitoring for the next two years.

Laura Jacobs

10/2/2023

Document, Report, or Work plan Review - other

DEC reviewed the additional information provided by the RP's consultant to explain the site history use of Chlorofluorocarbons (CFCs) that have been found on site in the form of CFC-11 and CFC-12. The additional information included plume maps over time, and a Mann-Kendall trend analysis. Ultimately, it was recommended and DEC agrees that monitoring the plume over time while observing natural attenuation processes is the best strategy twenty some years after the discovery.

Laura Jacobs

8/22/2024

Document, Report, or Work plan Review - other

The field efforts in 2023 included sampling of 14 of the 16 remaining monitoring wells and two surface water locations. Although the number of exceedances of the Groundwater Cleanup Levels has remained consistent during the last three years, there are more analytes exceeding this year than in the past. The petroleum hydrocarbon exceedances increased above historic ranges at MW-12, MW-13, MW-14, B-MW-6, B-MW-GB, and CB-MW-2 during the 2023 sample effort. Hydrocarbon concentrations in surface water samples were below the Alaska Water Quality exceedance criteria. Samples were collected in August19-20, 2023. DEC approves the 2023 report as submitted.

Laura Jacobs

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2019 Monitoring Report

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Site Report: Alyeska PS 01 West Pad Area

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State of Alaska Department of Environmental Conservation