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Site Report: Alyeska PS 09 Former Mainline Turbine Sump


Site Name: Alyeska PS 09 Former Mainline Turbine Sump
Address: Mile 258 Richardson Hwy., Pump Station 9, Delta Junction, AK 99737
File Number: 330.38.065
Hazard ID: 2681
Status: Active
Staff: Grant Lidren, 9072698685 grant.lidren@alaska.gov
Latitude: 63.931333
Longitude: -145.769408
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

Alyeska encountered petroleum-contaminated soil while removing the PS 09 Mainline Turbine (MLT) sump in October 1996. The petroleum source was later determined to be turbine fuel. The MLT sump had been buried at 6.5 feet Below Ground Surface (BGS). Three pipes and a tank were connected to the sump, including a vent pipe, pumpout pipe, and a blowdown pipe. The blowdown pipe and tank extended roughly 50 feet from the sump area and were buried 2-3' bgs. Leaks associated with breaks in the blowdown pipe were encountered. Impacted soil was excavated to the extent practical due to the presence of permanent structures; however, contaminated soil was left in place. Subsequent assessment efforts indicate petroleum contaminated soil (PCS) extends all the way to groundwater at approximately 110-120' BGS. Free product is typically noted on the water table at MWs 1, 5, & 6, and these wells have been converted into product recovery wells. Geochemical testing shows that oxygen is not a REDOX-limiting agent, which is why product skimmers (within Product Recovery Canisters; PRCs) were chosen as the preferred remediation/recovery method. An estimated 2,000 gallons of free product are thought to affect the water table, and a total of 1,079 gallons have been recovered through the end of 2012. Surface water flow is radial, away from the Control Bldg. Drinking water comes from an onsite well, screened in an aquifer approximately 390 feet bgs. File contents and info were combined with file number 330.38.093 (Alyeska PS 09 Turbine Fuel Spill) since that file previously tracked an August 1992 release, which is now thought to comingle with this plume. Separate files created redundancy. Suspected source of the 1992 contamination: On August 6, 1992, a 180-gallon turbine fuel spill occurred at the turbine fuel offloading building during offloading. Approximately 75 cubic yards of contaminated soils were removed. The excavation was discontinued at a maximum depth of approximately 4.5 feet BGS. Further excavation was not feasible because the contamination was beneath permanent structures. Alyeska PS 09 Fuel Handling Area (330.38.010) was also combined with the subject site since that case (330.38.010) tracked a May 1992 investigation and June 1992 removal action (1,200 cubic yards) from the same area. These earlier sources of contamination are likely co-mingled in the soil and groundwater. Ongoing groundwater monitoring and product recovery have been reported under the subject site's file (330.38.065).

Action Information

Action Date Action Description DEC Staff
6/20/1992 Cleanup Plan Approved Action originally entered under 330.38.010 by Mehrdad Nadem. On May 12, 1992 five test pits were excavated to a maximum depth of 8.5 feet in the vicinity of the Turbine Fuel Offloading Dispenser. Samples were collected and analyzed for BTEX, DRO and GRO. DRO values ranged from ND to 12,000 mg/kg, GRO ranged from ND to 375 mg/kg. Corrective action plan was to excavate soils and place into a bioremediation cell. Keather McLoone
7/1/1992 Update or Other Action Action originally entered under 330.38.010 by Mehrdad Nadem. Remedial Action Report Review (CS). Between June 14 and June 20, approximately 1,200 cubic yards of contaminated soils were excavated and stockpiled. The excavation stopped at a depth of 20 feet due to equipment constraints. DRO concentrations up to 4,350 mg/Kg remain at the floor of the excavation. Liner was placed in excavation and was then backfilled. Keather McLoone
8/2/1992 Update or Other Action Action originally entered under 330.38.010 by Mehrdad Nadem. Design document for exsitu biocell submitted to department. Keather McLoone
12/1/1992 Update or Other Action Action originally entered under 330.38.010 by Mehrdad Nadem. Another spill (180 gallons) occurred at the turbine fuel offloading area on August 8, 1992. 75 cubic yards of contaminated gravel was removed to a depth of 4.5 feet. Contamination was left in place at depths greater than 4.5 feet and near buildings and piping. Additional Additional removal will be necessary upon decommissioning of the offloading area. 10 samples were collected from the excavation floor, 6 of the ten exceeded cleanup criteria for DRO with concentrations up to 10,100 mg/kg. Keather McLoone
12/1/1992 Report or Workplan Review - Other Action originally entered under 330.38.093 by Deb Williams - Turbine Fuel Spill Corrective Action Report: PS 9 - Turbine fuel contamination remains in the soils directly adjacent to the turbine fuel offloading building and the blow-down tank. The vertical depth of contaminated soils was not determined. Contaminated soils were excavated to the maximum extent practical considering the risk to undermining the structure foundations and buried piping. Lab results from bottom of excavation - DRO levels up to 7,100 ppm. The horizontal extent of contamination was limited. AN/E recommends that the remaining turbine fuel impacted soils be left in place due to extreme difficulty of excavating additional contaminated soils without disturbing the buried pipelines and structure foundations. Based on the limited aerial extent of the remaining soil contamination and the great depth to GW beneath the site, the risk of adverse GW impact appears to be minimal. Keather McLoone
7/28/1993 Update or Other Action Action originally entered under 330.38.010 by Mehrdad Nadem. Additional assessment work at the turbine fuel offloading area to determine the vertical and horizontal extent of contamination. DRO contamination extends to 45 feet below ground surface but the highest concentrations recorded were 422 mg/kg DRO. Keather McLoone
10/12/1994 Update or Other Action Action originally entered under 330.38.010 by Scott Rose. Biopile final report received by department. Several problems with the data quality but in general the pH concentrations had decreased significantly. One more year of treatment required. Keather McLoone
12/20/1996 Report or Workplan Review - Other Date of Pump Station 9 Mainline Turbine Sump Soil Sampling and Analysis Report. The excavation was about 60 ft by 25 ft and 2 to 20 feet deep. Excavation was limited by proximity to a nearby building and its stairwell to the south. Between 415 and 485 cubic yards of soil was removed. Three corrugated metal pipes were place into the excavation to use as potential dilling locations: one within the source area, one at the northeast corner and one in the northwest corner. Eight confirmation samples were collected. Keather McLoone
5/8/1998 Report or Workplan Review - Other Date of Final Contamination Assessment Report submitted by Emcon on behalf of Alyeska. This report contains well Borings were advanced to delineate the lateral and vertical extent of contamination. In July 1997, a hollow stem auger was used to advance three soil borings through corrugated metal pipe placed during 1996 excavation and samples collected at 5-ft intervals. Refusal was met at 30, 34.5, and 65 ft although PID readings and petroleum odors indicated that the vertical extent of contamination had not been delineated. All samples had a petroleum odor and all samples consisted of sandy gravels. In October 1997, an air rotary drill rig was used to advance borings. MW-1 was installed in the source area and screened from ~ 102 to 122 ft bgs. Free product was observed in this well. MW-2 was installed to the west, to a similar depth of screening. MW-3 was installed to the southwest, in between the source area and the PS 09 water supply well, and to a similar depth of screening. All wells were 2 in diameter wells. Soils are generally sandy gravels with a silt layer at about 80-90 ft bgs. A passive product recovery canister was installed into MW-1. It was checked twice after installation and found to have not yet recovered any product. Groundwater samples exceeded cleanup levels for benzene in MW-1 at 200ug/L and dibenzo(a,h)anthracene in MW-3 at 0.34 ug/L. Keather McLoone
4/2/1999 Report or Workplan Review - Other Contamination Assessment Report 1999 received on this date. Seven borings were advanced and six 4 inch diameter (but otherwise similar to those previously installed) monitoring wells installed - MW-4, MW-5, MW-6, MW-7, MW-8, and MW-10. During installation of MW-10 there was a release of hydraulic fluid from the rig into the well which was estimated to be small but resulted in DRO and RRO concentrations of 94 mg/L and 230 mg/L respectively. Two days later this well was sampled again and contained 10.8 mg/L DRO and 21.8 mg/L RRO. The other wells either contained product or were below cleanup levels. Product was observed in MW-5 and MW-6 as well as MW-1 and a product recovery canister was installed in MW-6. Product was recovered from the canister in MW-1. The free-phase product plume and the dissolved-phase product plume were estimated to extend between 70 and 140 feet in length from MW-1 to the NW. Keather McLoone
4/14/2000 Site Ranked Using the AHRM Initial ranking. Deborah Williams
4/20/2000 Site Added to Database Deborah Williams
5/9/2000 Report or Workplan Review - Other Date of receipt of Final Feasibility Study and Contamination Assessment Report 1999. A step-drawdown, aquifer pump test, aquifer slug test, product baildown and dual phase pump test, and soil gas testing were performed. The aquifer is reported to have a high transmissivity of 160 to 270 square feet/day which is why it was concluded that pumping water from the wells would not be effective in draw more product into the recovery wells. It was also determined that adding oxygen would not be effective as oxygen levels were not significantly depressed according to soil gas tests. The estimate of volume of free product present was 2,020 gallons and was based on the estimated area of free product, average thickness of product, and "effective porosity" of the aquifer and sediments. Keather McLoone
6/13/2001 Report or Workplan Review - Other Date of receipt of 2000 Corrective Action Report. Monitoring in May, July and October as well as installation of an automated product recovery system in three wells. Concentrations of DRO and RRO in MW-10 continued to show a decreasing trend. Keather McLoone
2/12/2002 Report or Workplan Review - Other Date of receipt of 2001 Groundwater Monitoring Report. Wells were sampled in March, July, September and November. Only exceedance was during July in MW-7 for DRO at 2.96 mg/L. Keather McLoone
4/9/2003 Report or Workplan Review - Other Date of receipt of 2002 Mainline Turbine Sump Product Recovery and Groundwater Monitoring report. During 2001 product recovery continued in MW-1 and MW-5 but MW-6 had persistent operational problems. Problems with recovery at MW-6 continued in 2002. Groundwater samples were collected in June and October of 2002. Keather McLoone
3/17/2004 Update or Other Action ADEC received the 2003 PS 9 Mainline Turbine Sump Product Recovery and GW Monitoring report. Continued groundwater monitoring is recommended at PS 9 on a semi-annual basis from all monitoring wells that do not contain free-phase product. Dissolved petroleum hydrocarbons were detected in samples from monitoring wells down and cross-gradient of the release site (MW-4, MW-8, and MW-10), but all concentrations were below ADEC cleanup levels. Petroleum hydrocarbons were not detected in the up-gradient well MW-3 and down-gradient wells MW-2 and MW-7. Because no PAH compounds have been detected in any samples since 2001, it is recommended that the analytes be changed to include only DRO and BTEX plus naphthalene in future groundwater monitoring events. The automated product recovery system has demonstrated continued effectiveness at reducing the volume of free-phase turbine fuel from the subsurface in the vicinity of the former PS 9 MLT sump. In 2003, 95 gallons of turbine fuel were recovered, for a total of 763 gallons recovered to date. The automated recovery system has accounted for 711 gallons of this recovery since it began operation in 2001. Deborah Williams
3/15/2005 Update or Other Action ADEC received the 2004 PS9 Mainline Turbine Sump Product Recovery and Groundwater Monitoring report. According to the report, dissolved petroleum hydrocarbons were detected in samples from monitoring wells MW-4, MW-7 and MW-10. One water quality criteria exceedance occurred at monitoring well MW-7, where benzene was detected above the ADEC criteria in October 2004. Other hydrocarbon detections at this site did not exceed the ADEC cleanup levels. The installation of the hydrophobic skimmers on the product recovery system appears to have increased the effectiveness of the system. During 2004 system operation, 117 gallons of product were recovered, bringing the total product recovered to date to 880 gallons. Deborah Williams
2/6/2006 Update or Other Action ADEC received the 2005 Mainline Turbine Pump Station 9 Product Recovery and Ground Water Monitoring Report. In the report, SLR concluded that dissolved phase petroleum hydrocarbons were detected in all 2005 samples. Benzene concentrations in samples collected in the June and October sampling from MW-7 exceeded the ADEC ground water cleanup level. Bail down tests performed on recovery wells MW-5 and MW-6 indicated that actual product thickness is likely between 0.07 and 0.12 feet. During the 2005 system operation 77.5 gallons of product were recovered, bringing the total product recovered to date to 957.5 gallons. SLR recommends continued groundwater monitoring at PS09 on a semi-annual basis from all monitoring wells that do not contain free-phase product. They also recommend the reinstallation of the product recovery skimmers in the wells that exhibit free-phase petroleum. Deborah Williams
3/14/2007 Update or Other Action ADEC received the SLR Final 2006 Mainline Turbine Sump PS 9 Product Recovery and Groundwater Monitoring Report. According to the report, benzene contamination above ADEC cleanup levels was found in MW-7 during the June and October sampling. The source of the increase in benzene concentrations in MW-7 that began in October 2004 has not been determined. MW-8 is located downgradient of MW-7 and the benzene levels are below ADEC cleanup levels. SLR recommends continuing groundwater monitoring at PS 9 in 2007 but on an annual basis. At the beginning of the 2007 field season, a bail-down test will be performed. If the actual product thickness determined from the bail-down test is below 0.1 ft, SLR recommends the operation of the product recovery system to be discontinued. Deborah Williams
3/15/2007 Exposure Tracking Model Ranking Initial ETM completed. Deborah Williams
2/1/2008 GIS Position Updated Updated using Arc GIS SPAR_StatewideLocator (ArcReader) Grant Lidren
3/7/2008 Update or Other Action ADEC received the Pump Station 9: 2007 Mainline Turbine Sump Product Recovery and Ground water Monitoring Report. Bail-down test results indicated that true product thickness was greater than 0.1 ft in two of the product recovery wells; therefore, the product recovery system was operated in 2007. 68 gallons of product were recovered during the May 30 to October 5, 2007 operating period and were similar to recovery results for 2005. Recovery of 8 gallons in 2006 was likely due to suboptimal performance of system (repairs were made prior to operation in 2007). Will perform another baildown test in 2008 prior to operation of system. SLR recommends reduction of groundwater sampling frequency to annual. Only exceedance of Table C is again benzene in MW-7. Keather McLoone
6/10/2008 Update or Other Action Approved 2008 Pump Station 9 Mainline Turbine Sump Product Recovery and Groundwater Monitoring Work Plan received May 30 2008. Keather McLoone
2/13/2009 Update or Other Action Receipt of Pump Station 9 Mainline Turbine Sump 2008 Product Recovery and Ground Water Monitoring Report by SLR. In 2008, ten gallons of product were recovered by the system between June 2 and October 5. A total of 1,044.5 gallons have been recovered to date. Bail-down testing showed an "actual" thickness of approximately 0.1 ft (0.08, 0.11, and 0.06 ft). Conceptual site model included in report. Five groundwater wells sampled with one benzene result above Table C. SLR/Alyeska propose to discontinue operating product recovery system and continue groundwater monitoring. Requested a cleanup complete with ICs status. Review included laboratory review checklist. Keather McLoone
2/25/2009 Update or Other Action DEC letter to approve 2008 report stating "ADEC has no objections to the discontinuation of the automated product recovery system. Please address how product will be treated when encountered in the 2009 work plan document. ADEC will not be making a site status change at this time, but will consider a site status decision after reviewing results that will be reported following 2009 efforts. Please also note that ADEC is tracking this site under ADEC file number 330.38.065." Keather McLoone
5/20/2009 Report or Workplan Review - Other Approval of Pump Station 9 Mainline Turbine Sump 2009 Ground Water Monitoring Work Plan. One groundwater monitoring event and removal of the product recovery system for offsite storage are planned. Product thickness will also be measured. Keather McLoone
5/4/2010 Report or Workplan Review - Other Review of Pump Station 9 Mainline Turbine Sump 2009 Groundwater Monitoring report submitted on 4/27/10 by SLR on behalf of Alyeska. One event took place in July 2009 and five monitoring wells were sampled (MW-2, MW-3, MW-7, MW-8, and MW-10). Benzene is the only constituent detected above Table C. It was only above Table C in MW-7, although its concentration is 2-3 times higher than it has been in any past event. Report response letter stated that ADEC did not concur with decommissioning of MW-1, MW-5, and MW-6 at this time and requested that the 2010 workplan address how product would be removed from these wells. Previous approval to discontinue use of the automated system was based on its efficiency and not intended to be approval of discontinuation of product recovery. The United States Environmental Protection Agency’s Guidance on effective recovery of free product suggests that an actual product thickness of 0.1 foot, such as was demonstrated in 2008, is a reasonable benchmark for feasibility of active product recovery. However, other factors such as volume of product and thickness of accumulation in wells are to be considered in evaluating whether recovery of free product is necessary and feasible. It was also stated that a change in site status would remain pending. Keather McLoone
6/15/2010 Report or Workplan Review - Other Receipt and review of Pump Station 9 Mainline Turbine Sump 2010 Groundwater Monitoring Workplan. Planned activities include a single groundwater monitoring event and free-product recovery using a bailer. DEC approved this workplan with the condition that MW-2, MW-3, MW-8, and MW-10 be sampled for DRO and BTEX as well as MW-7. Keather McLoone
5/20/2011 Report or Workplan Review - Other Receipt of Pump Station 9 Mainline Turbine Sump 2010 Groundwater Monitoring Report. Review included laboratory data review checklists. Groundwater sampling and product recovery were conducted at this site during 2010. About 14 gallons of product was recovered. Five groundwater wells were sampled. MW-7 and MW-2 contained concentrations greater than Table C for benzene and DRO respectively. Concentrations of DRO in MW-2 were higher in 2010 than they had been since 1999 but still only slightly above Table C at 1.75 mg/L. Alyeska propose to continue monitoring and product recovery in 2011. Keather McLoone
6/9/2011 Report or Workplan Review - Other Receipt of Pump Station 9 Mainline Turbine Sump 2011 Groundwater Monitoring and Product Recovery Workplan. Alyeska proposes to recover product throughout the 2011 field season and conduct a single groundwater monitoring event. Photo in report of fuel being recovered (looks more clear than crude as the source is turbine fuel which is a refined jet fuel/diesel fuel-like product). Keather McLoone
11/7/2011 Exposure Tracking Model Ranking An updated ETM ranking has been completed for source area 73657 Mainline Turbine Sump. Ranking was revisited since two other sites (330.38.010 and 330.38.093) were merged with this record after it was determined their plumes were co-mingled. Keather McLoone
3/23/2012 Report or Workplan Review - Other Date of receipt of 2011 Ground Water Monitoring and Product Recovery Report. During a single event, 5 wells were sampled. Three other wells contained product ranging in thickness from 0.01 to 0.05 ft after product recovery was conducted and approximately 11.23 gallons removed. The wells sampled did not contain constituents above cleanup with the exception of MW-7 (and the sample duplicate) which had benzene above Table C. SLR recommend another single round of groundwater sampling and another product recovery effort next year. Groundwater gradient arrow not included on site figure, this information was requested via email to be included with next set of planning documents so that bounding of the plume can be evaluated. Keather McLoone
5/4/2012 Report or Workplan Review - Other Date of receipt of 2012 Groundwater Monitoring and Product Recovery Workplan. Activities planned include a single groundwater monitoring event and free-product recovery throughout the 2012 field season. Keather McLoone
2/1/2013 Report or Workplan Review - Other Receipt date for Alyeska's 2012 work report. SLR sampled 5 of 8 monitoring wells (MWs 2, 3, 7, 8, & 10) on 20 July 2012. The other three serve as product recovery wells and have contained free product every year since sampling began in 1997. Only MW-7 had detectable COCs (benzene & DRO), but both were below CUL. This is the 1st time MW-7 has been below CUL since 2004. SLR attempted product recovery from MWs 1, 5, & 6 on 11 occasions between 5 Jun and 22 Oct 2012, but MW-1 and MW-6 had ice plugs until 9 August. MW-5 had an ice plug through 20 July. Approximately 8.75 gallons of free product were recovered in 2012. Total recovery includes approximately 1,079 of the estimated 2,000 gallons that were released. MW-5 has been the most productive recovery well with one gallon collected on each visit. (One gallon is the maximum storage capacity for these Petroleum Recovery Canisters.) SLR recommends additional sampling and recovery efforts in 2013 with less frequent site visits if recovery rates continue to decline. Report included Laboratory Data Review Checklist. Richard Bernhardt
2/19/2013 Update or Other Action Updated geocoordinates based on comparison of 2012 work report and Google Earth imagery. Richard Bernhardt
5/23/2013 Report or Workplan Review - Other Received and approved the 2013 work plan to include multiple free product recovery events and continued groundwater monitoring. ADEC approved adding distilled water and removable heat tape to monitoring wells to melt ice plugs if they're encountered in 2013. ADEC recommended against abandoning/decommissioning product recovery wells so they can serve as potential future injection wells. ADEC is also receptive to the idea of reducing the frequency of product recovery deployments if recoverability decreases on par with rates noted in 2012. Richard Bernhardt
2/4/2014 Site Characterization Report Approved On this date, ADEC received the 2013 Groundwater Monitoring and Product recovery Report Pump Station 9 Mainline Turbine Sump dated December 2013. SLR sampled 5 of 8 monitoring wells (MWs 2, 3, 7, 8, & 10) on September 19, 2013. The other three serve as product recovery wells and have contained free product every year since sampling began in 1997. Only MW-2 and MW-7 had detectable COCs (benzene & DRO), but both were below CUL. SLR attempted product recovery from MWs 1, 5, & 6 on nine occasions between June 19th and October 17th 2013. An ice plug prevented free product recovery from MW-5 and MW-6 until August 2nd and July 19th respectively. Ice prevented deployment of an absorbent sock into MW-1 until August 29th. Approximately 28.3 gallons of free product were recovered in 2013. Total recovery includes approximately 1,107 of the estimated 2,000 gallons that were released. Heat trace was installed in the three product recovery wells on October 17, 2013 to allow for product recovery earlier in the season for future recovery events. Grant Lidren
5/27/2014 Site Characterization Workplan Approved On this date, ADEC approved the 2014 Groundwater Monitoring and Product Recovery Work Plan Pump Station 9 Mainline Turbine Sump submitted by SLR, dated May 2014. Grant Lidren
1/9/2015 Site Characterization Report Approved On this date, ADEC received the 2014 Groundwater Monitoring and Product Recovery Report Pump Station 9 Mainline Turbine Sump submitted by SLR dated December 2014. SLR conducted one baildown test, one groundwater sampling event, and seven free product recovery events in 2014. Prior to the bail down test, the measured apparent thickness of free product was 1.72 feet in MW-1, 1.98 feet in MW-5, and 0.28 feet in MW-6. The bail down test indicated the true product thickness was 0.30 feet in MW-1, 0.46 feet in MW-5, and 0.09 feet in MW-6. SLR attempted product recovery from MWs 1, 5, & 6 on seven occasions between June 4th and October 9th 2014. An ice plug prevented free product recovery from MW-1 and MW-5 for the first couple visits. Approximately 17.3 gallons of free product were recovered in 2014. This includes 4.7 gallons from MW-1, 11.9 gallons from MW-5, and 0.7 gallons from MW-6. Total recovery includes approximately 1,152 of the estimated 2,000 gallons that were released. Groundwater samples were collected from five of the eight monitoring wells (MWs 2, 3, 7, 8, & 10). None of the MWs contained detectable levels of contaminants except MW-7 which contained benzene at 0.00481 mg/L and DRO at 1.03 mg/L Monitoring wells MW-1, MW-5, and MW-6 serve as product recovery wells and have contained free product every year since sampling began in 1997. Grant Lidren
5/28/2015 Site Characterization Workplan Approved On this date, ADEC received the 2015 Groundwater Monitoring and Product Recovery Work Plan Pump Station 9 Mainline Turbine Sump submitted by SLR date May 2015. Groundwater will be monitored from MW-2, MW-3, MW-7, MW-8, and MW-10. Product will be recovered from MW-1, MW-5, and MW-6. Grant Lidren
3/18/2016 Site Characterization Report Approved On this date, ADEC received the 2015 Groundwater Monitoring and Product Recovery Report, Pump Station 9 Mainline Turbine Sump submitted by SLR dated March 2016. SLR conducted one baildown test, one groundwater sampling event, and up to six free product recovery events in 2015. Prior to the bail down test, the measured apparent thickness of free product was 0.48 feet in MW-1, 0.89 feet in MW-5, and 0.11 feet in MW-6. The bail down test indicated the true product thickness was 0.30 feet in MW-1 and 0.31 feet in MW-5, however true product thickness could not be determined in MW-6 due to insufficient product thickness. SLR attempted product recovery from MWs 1, 5, & 6 on eight occasions between June 4th and October 1st 2015. An ice plug prevented free product recovery on MW-1 , MW-5 and MW-6 on the first visit and prevented the recovery on the second visit from MW-1 and MW-5. Approximately 15.1 gallons of free product were recovered in 2015. This includes 1.3 gallons from MW-1, 13.5 gallons from MW-5, and 0.3 gallons from MW-6. Total recovery includes approximately 1,167of the estimated 2,000 gallons that were released. Groundwater samples were collected from five of the eight monitoring wells (MWs 2, 3, 7, 8, & 10). None of the MWs contained detectable levels of contaminants except MW-7 which contained benzene at 0.00122 mg/L and DRO at 0.867 mg/L Monitoring wells MW-1, MW-5, and MW-6 serve as product recovery wells and have contained free product every year since sampling began in 1997. Grant Lidren
5/25/2016 Report or Workplan Review - Other The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2016 Groundwater Monitoring and Product Recovery Work Plan Pump Station 9 Mainline Turbine Sump 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 Groundwater Monitoring and Product Recovery Report, Pump Station 9 Mainline Turbine Sump submitted by SLR dated February 2017. SLR conducted one groundwater sampling event, ten free product recovery events, and replacement of sorbent socks in 2016. The measured free product thickness in MW-1, MW-5, and MW-6, prior to the ten recovery events, are as follows: 0.07 to 0.76 feet in MW-1, 0.21 to 1.48 feet in MW-5, and 0.0 to 0.10 feet in MW-6. No bail down test were conducted in 2016. Approximately 17.8 gallons of free product were recovered in 2016. This includes 2.6 gallons from MW-1, 14.6 gallons from MW-5, and 0.6 gallons from MW-6. Total recovery includes approximately 1,185 of the estimated 2,000 gallons that were released. Groundwater samples were collected from five of the eight monitoring wells (MWs 2, 3, 7, 8, & 10). None of the MWs contained detectable levels of contaminants above the LOQ except MW-7 which contained benzene at 0.00057 mg/L and DRO at 0.887 mg/L. Monitoring wells MW-1, MW-5, and MW-6 serve as product recovery wells and have contained free product every year since sampling began in 1997. MW-6 did not contain measurable product thickness during 1 out of the 10 measuring events in 2016. Grant Lidren
6/7/2017 Site Characterization Workplan Approved The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2017 Groundwater Monitoring and Product Recovery Work Plan Pump Station 9 Mainline Turbine Sump submitted by SLR and dated May 2017. This work plan is approved conditionally on sampling MW-7 for petroleum VOCs by method 8260. Grant Lidren

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