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Site Report: MOA - AWWU Pump Station #12-UST

Site Name: MOA - AWWU Pump Station #12-UST
Address: 4501 West 100th Avenue, Anchorage, AK 99515
File Number: 2100.26.044
Hazard ID: 23877
Status: Active
Staff: Lisa Krebs-Barsis, 9072697691 lisa.krebs-barsis@alaska.gov
Latitude: 61.129256
Longitude: -149.962901
Horizontal Datum:NAD83

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

Problems/Comments

On 9/20/90 AWWU discovered a diesel fuel leak at their UST facility. Later in 1990 the UST was removed and some contaminated soil was excavated. Monitoring wells were installed in 1991 to help define the extent of the groundwater contamination. Additional contaminated soil was excavated in 1993. Up to 3,280 mg/kg DRO, 192 mg/kg GRO, and 0.09 mg/kg benzene remain in the excavation in the smear zone at 6.5 to 7.5 feet below ground surface on the west, northwest, and north portion of the excavation. The excavated contaminated soil was thermally treated. An on property drinking water well is located within 50 feet of the former leaking tank. Soil and groundwater contamination remain at this site. Groundwater and drinking water well monitoring continues at this site.

Action Information

Action Date Action Description DEC Staff
9/21/1990 Leaking Underground Storage Tank Release Confirmed - Petroleum LUST Site created in CSP for source area ID 77953 ADD; Former Staff
9/21/1990 Site Added to Database Former Staff
9/22/1990 Leaking Underground Storage Tank Cleanup Initiated - Petroleum Corrective action underway. This action was originally entered under reckey 92210028603.:LCAU Date changed DB conversion. Former Staff
10/16/1990 Update or Other Action ADEC letter to AWWU requesting corrective action and site information. Former Staff
11/16/1990 Document, Report, or Work plan Review - other Anchorage Water/Wastewater Utility sends in letter/report of corrective action to date & proposed cleanup activities at site including a schedule for installation of new tanks & temporary closure of the existing tanks. Former Staff
5/13/1991 Document, Report, or Work plan Review - other Two borings drilled. 14.5 mg/kg TPH in groundwater. 6,500 mg/kg TPH in soil at groundwater table interface. Former Staff
8/30/1992 Underground Storage Tank Site Characterization or Assessment Reviewed a phase 1 site assessment report. Former Staff
10/22/1992 Site Visit On site inspection, discussed monitoring well locations and soil borings with RP's consultant. Site was backfilled with clean fill and 400 cubic yards. of contaminated soil was removed. Former Staff
10/23/1992 Update or Other Action UST reported as a LUST. This action originally from reckey 92210028603. Former Staff
11/30/1992 Update or Other Action Original date when this site was added to database as reckey 92210028603. Former Staff
2/8/1993 Document, Report, or Work plan Review - other Reviewed a phase 2 site assessment report. Former Staff
2/24/1993 Update or Other Action Corrective action plan to excavate additional contaminated soil. Former Staff
11/20/1997 Update or Other Action ADEC sends Notification of Intent to Cost Recover Letter to Current Owner: ANCH. WATER & WASTEWATER UTILITY Former Staff
8/10/1998 Update or Other Action ADEC letter requested continued groundwater monitoring for BTEX, DRO, and PAH. Former Staff
9/30/1998 Document, Report, or Work plan Review - other AWWU sent ADEC 9/1/98 groundwater samples, flow, and elevation information. Former Staff
12/4/1998 Document, Report, or Work plan Review - other December 4, 1998 groundwater monitoring event. Up to 252 mg/l DRO and 13.5 ug/l benzene in the groundwater. Some PAH's over groundwater cleanup levels in monitoring well MWA. On property water well at the site continues to show non-detect levels. Depth to groundwater was 5.2 to 10.95 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
2/25/1999 Document, Report, or Work plan Review - other February 25, 1999 groundwater monitoring event. Up to 145 mg/l DRO and 14.6 ug/l benzene in the groundwater. Some PAH's over groundwater cleanup levels in monitoring well MWA. On property water well at the site continues to show non-detect levels. Depth to groundwater was 5.95 to 11.22 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
8/2/1999 Document, Report, or Work plan Review - other August 2, 1999 groundwater monitoring event. Up to 18.0 mg/l DRO and 11.7 ug/l benzene in the groundwater. Some PAH's potentially over groundwater cleanup levels in monitoring well MWA. On property water well at the site continues to show non-detect levels. Depth to groundwater was 6.09 to 11.11 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
9/22/1999 Update or Other Action ADEC conditionally approves workplan to excavate contaminated soil and monitor the groundwater. The replacement monitoring well is to be sampled for BTEX, GRO, DRO and PAH, monitoring well MW1 for GRO, and monitoring well MW2 for BTEX and GRO. Robert Weimer
10/12/1999 Update or Other Action ADEC approves direct haul for thermal treatment of contaminated soil to be excavated. Robert Weimer
10/25/1999 Update or Other Action 258.3 tons of contaminated soil were excavated and transported to ASR for thermal treatment. Robert Weimer
11/22/1999 Document, Report, or Work plan Review - other November 22, 1999 groundwater monitoring event. Up to 77.1 mg/l DRO and 24.8 ug/l benzene in the groundwater. Some PAH's over groundwater cleanup levels in monitoring well A2. On property water well at the site continues to show non-detect levels. Depth to groundwater was 5.96 to 10.85 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
12/22/1999 Document, Report, or Work plan Review - other Report of the results of the 1999 cleanup work. 258.3 tons of contaminated soil was removed and thermally treated. 880 pounds of ORC was added to the soil used for backfill to assist natural attenuation. Groundwater was encountered at 6.5 feet in the excavation. 2,000 gallons of contaminated water was pumped from the excavation and treated by AWWU. Monitoring well MW-A was removed during the excavation. A replacement monitoring well B1MW was drilled just north of monitoring well MW-A. Up to 3,010 mg/kg DRO, 115 mg/kg GRO, and non-detect (<0.089 mg/kg) benzene in the soil sample collected from the replacement monitoring well. Groundwater was encountered at 9 feet below ground surface at the monitoring well. Up to 3,280 mg/kg DRO, 192 mg/kg GRO, and 0.09 mg/kg benzene remain in the excavation in the smear zone at 6.5 to 7.5 feet below ground surface on the west, northwest, and north portion of the excavation. Further excavation could occur in the future in those directions. Robert Weimer
2/29/2000 Document, Report, or Work plan Review - other February 29, 2000 groundwater monitoring event. Up to 17.8 mg/l DRO and 23.8 ug/l benzene in the groundwater. On property water well at the site continues to show non-detect levels. Depth to groundwater was 5.85 to 10.43 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
5/30/2000 Document, Report, or Work plan Review - other May 30, 2000 groundwater monitoring event. Up to 9.04 mg/l DRO and 23.6 ug/l benzene in the groundwater. On property water well at the site continues to show non-detect levels. Depth to groundwater was 4.74 to 9.48 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
8/24/2000 Document, Report, or Work plan Review - other August 24, 2000 groundwater monitoring event. Up to 180 mg/l DRO and 16.2 ug/l benzene in the groundwater. On property water well at the site continues to show non-detect levels. Depth to groundwater was 5.85 to 10.89 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
7/11/2001 Document, Report, or Work plan Review - other July 11, 2001 groundwater monitoring event. Up to 4.91 mg/l DRO and 21.5 ug/l benzene in the groundwater. On property water well at the site continues to show non-detect levels. Depth to groundwater was 3.94 to 8.63 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
10/23/2001 Update or Other Action ADEC approves reduction in groundwater monitoring to semi-annual for MW1:DRO, MW2:DRO and BTEX, MW3: DRO, GRO, and BTEX, and Drinking water well:DRO, GRO, BTEX, and PAH's. Robert Weimer
1/24/2002 Document, Report, or Work plan Review - other January 24, 2002 groundwater monitoring event. Up to 10.6 mg/l DRO and 23.4 ug/l benzene in the groundwater. On property water well at the site continues to show non-detect levels. Depth to groundwater was 5.08 to 10.73 feet below ground surface. Groundwater has historically flowed toward the west to northwest. Robert Weimer
2/4/2004 Update or Other Action File number changed from L69.12 to 2100.26.044 Sarah Cunningham
3/26/2008 Exposure Tracking Model Ranking Site ranked on the new Exposure Tracking Model (ETM). The ETM is a new site ranking system that looks at, based on available data, the potential exposure pathways for the contamination remaining at the site. Robert Weimer
8/20/2008 Update or Other Action ADEC reviews request for No Further Action for this site. Based on the latest sample results soil contamination (up to 3,280 mg/kg DRO, 192 mg/kg GRO, and 0.09 mg/kg benzene) and groundwater contamination (up to 10.6 mg/l DRO and 23.4 ug/l benzene) remain at this site. ADEC requests continued groundwater monitoring at this site and prior to site closure the collection of confirmation soil samples demonstrating that soils meet default cleanup levels. The groundwater is currently being used by an on property drinking water well located within 50 feet of the former tanks. Discussed this with MOA-AWWU. Robert Weimer
11/4/2008 Update or Other Action ADEC approves groundwater monitoring workplan. The plan calls for sampling the three monitoring wells this fall for BTEX, GRO, and DRO. The plan also calls for sampling the on property drinking water well for DRO, GRO, and VOC's by EPA method 524.2. Robert Weimer
5/14/2010 Update or Other Action Teleconference with AWWU and their consultant (BGES) to discuss future site work. BGES will provide a workplan for installing a downgradient monitoring well to help define the extent of the remaining soil and groundwater contamination and to conduct semi-annual groundwater monitoring of the site monitoring wells and drinking water well. Robert Weimer
6/25/2010 Site Characterization Workplan Approved DEC conditionally approves workplan for the installation of an additional monitoring well, soil, groundwater, and drinking water well sampling. Robert Weimer
8/12/2010 Document, Report, or Work plan Review - other DEC approves alternative location for monitoring well MW-4. Robert Weimer
7/27/2011 Document, Report, or Work plan Review - other ADEC reviews and approves request to dispose of contaminated water that meets table C levels and consolidate other contaminated water into 1 drum. Robert Weimer
9/8/2011 Document, Report, or Work plan Review - other ADEC reviews and approves request to dispose of contaminated water that meets sanitary sewer levels (<5 mg/l BTEX). Robert Weimer
3/5/2012 Update or Other Action DEC approves request to suspend lead sampling in the groundwater at this site. Robert Weimer
7/1/2013 Document, Report, or Work plan Review - other February 9, 2006 groundwater monitoring event. Up to 2.49 mg/l DRO and 13.7 ug/l benzene in the groundwater. Concentration increased in 2 of the 3 monitoring wells sampled. Groundwater has historically flowed toward the west to northwest. Robert Weimer
7/1/2013 Document, Report, or Work plan Review - other November 6, 2008 groundwater monitoring event. Up to 4.53 mg/l DRO, 0.109 mg/l GRO, and 2.99 ug/l benzene in the groundwater. Concentration increased in 1 of the 3 monitoring wells sampled. Groundwater has historically flowed toward the west to northwest. Robert Weimer
7/1/2013 Document, Report, or Work plan Review - other September 28, 2010 groundwater monitoring event. Up to 3.25 mg/l DRO, 0.120 mg/l GRO, and 3.95 ug/l benzene in the groundwater. Concentration increased in 1 of the 3 monitoring wells sampled. Groundwater has historically flowed toward the west to northwest. Robert Weimer
7/1/2013 Document, Report, or Work plan Review - other December 14, 2010 groundwater monitoring event. Up to 3.27 mg/l DRO, 0.373 mg/l GRO, and 5.90 ug/l benzene in the groundwater. Concentration increased in 2 of the 4 monitoring wells sampled. Groundwater has historically flowed toward the west to northwest. Robert Weimer
7/2/2013 Document, Report, or Work plan Review - other June 14, 2011 groundwater monitoring event. Up to 9.53 mg/l DRO, 0.212 mg/l GRO, and 3.51 ug/l benzene in the groundwater. Concentration increased in all 4 monitoring wells sampled. Groundwater has historically flowed toward the west to northwest. Robert Weimer
7/3/2013 Document, Report, or Work plan Review - other March 8, 2012 groundwater monitoring event. Up to 3.9 mg/l DRO, 0.244 mg/l GRO, and 4.13 ug/l benzene in the groundwater. Concentrations decreased in all 4 monitoring wells sampled. The on-property water well at the site continues to show non-detect levels. Depth to groundwater was 5.87 to 10.43 feet below ground surface. Groundwater has historically flowed toward the west to northwest. The monitoring wells were purged prior to sampling with a bladder pump. Robert Weimer
9/20/2013 Update or Other Action DEC approves request to suspend PAH sampling, and suspend sampling for DRO in monitoring well MW-1. Robert Weimer
11/1/2013 Offsite Soil or Groundwater Disposal Approved DEC has no objection to the proposal for discharge the development and purge water into the AWWU sanitary sewer. Robert Weimer
8/25/2014 Update or Other Action DEC requests that complete copies of field notes be included with the monitoring reports. The field notes and the report need to document that the groundwater samples were collected after purging, and the sample interval was within the top 1 foot of water in the monitoring well during sampling. The volatile sampling needs to be done with a sampling method that minimizes the loss of volatiles (such as an in-well pump or bladder pump). Robert Weimer
10/1/2014 Offsite Soil or Groundwater Disposal Approved DEC has no objection to the proposal for discharge the development and purge water into the AWWU sanitary sewer. Robert Weimer
5/4/2015 Document, Report, or Work plan Review - other September 30, 2013 groundwater monitoring event. Up to 4.93 mg/l DRO and 5.19 ug/l benzene in the groundwater. Concentrations increased in all 3 monitoring wells sampled. Robert Weimer
5/4/2015 Document, Report, or Work plan Review - other September 5, 2014 groundwater monitoring event. Up to 2.08 mg/l DRO and 3.11 ug/l benzene in the groundwater. Concentrations decreased in all 3 monitoring wells sampled. Monitoring well MW-3 had a sheen on the purge water with a hydrocarbon odor. The on-property water well at the site continues to show non-detect levels. Depth to groundwater was 5.80 to 10.26 feet below ground surface. Groundwater flow direction was toward the west. The monitoring wells were purged prior to sampling with a mini whale pump with the intake near the soil/water interface. Robert Weimer
5/4/2015 Document, Report, or Work plan Review - other December 4, 2014 groundwater monitoring event. Up to 1.30 mg/l DRO and 3.25 ug/l benzene in the groundwater. Concentrations increased in 2 of the 3 monitoring wells sampled. The on-property water well at the site continues to show non-detect levels. Depth to groundwater was 5.80 to 10.26 feet below ground surface. Groundwater flow direction was toward the west. The monitoring wells were purged prior to sampling with a mini whale pump. Robert Weimer
5/12/2015 Meeting or Teleconference Held Meeting held with Consultant. Items discussed include suspending GW monitoring for MW-1, MW-2, and MW-4, and drinking water well sampling during first three quarterly monitoring events due to continued non-detect results, or results less than ADEC Table C cleanup levels. GW samples from MW-2 and MW-4, and samples from the drinking water well will be collected during fourth quarterly monitoring event and tested for DRO and BTEX. MW-3 will be sampled on a quarterly basis for DRO and BTEX. Lisa Griswold
2/3/2016 Document, Report, or Work plan Review - other Work plan for quarterly groundwater monitoring approved. Plan includes details on sampling MW-3 on four occasions, with MW-2, MW-4 and the drinking water well to be sampled during the last sampling event. Sampling is tentatively scheduled for February, May, August and November 2016. Lisa Griswold
4/12/2016 Document, Report, or Work plan Review - other Data package for the first quarter GW monitoring event reviewed and approved on this date. Sampling was completed in MW-3 as indicated in the work plan. This event indicated DRO (1.16 mg/L) benzene (0.002 mg/L) Ethylbenzene (0.00571 mg/L), and total xylenes (0.0103 mg/L), were detectable but below ADEC cleanup levels. Toluene was non-detect (<0.000500 mg/L). Lisa Griswold
6/22/2016 Document, Report, or Work plan Review - other Second Quarter Groundwater Monitoring (conducted on May 23, 2016) data package reviewed and approved on this date. Diesel Range Organics was detected in MW-3 at 1.31 mg/L, Benzene at .00206 mg/L, Ethylbenzene at 0.00570 mg/L, Xylenes at 0.00906 mg/L, while Toluene was non-detect. All detected contaminants are below ADEC Table C cleanup levels. Lisa Griswold
10/3/2016 Document, Report, or Work plan Review - other Third Quarter 2016 Groundwater Monitoring Data Package approved on this date. Diesel Range Organics (DRO) was detected in MW-3 up to 1.42 mg/L, Benzene up to 0.00201 mg/L, Ethylbenzene up to 0.00282 mg/L, and xylenes up to 0.00660 mg/L. Toluene was non-detect. All detected contaminants are below ADEC Table C cleanup levels. Lisa Griswold
12/21/2016 Offsite Soil or Groundwater Disposal Approved ADEC approves the disposal of 30 gallons of purge/decontamination water to the wet well at pump station 12. Lisa Griswold
1/17/2017 Document, Report, or Work plan Review - other 2016 Quarterly Groundwater Monitoring Report reviewed on this date. ADEC had requested that one year of quarterly groundwater monitoring be completed and this report summarizes the entire year of groundwater monitoring done in February, May, August and November 2016. The first three events sampled MW-3 due to its high incidence of exceeding ADEC cleanup levels since sampling on the well began in 1999. The last sampling event in November 2016, sampled MW-2 through MW-4, as well as the drinking water. MW-3 contained Diesel Range Organics (DRO) at detectable, but below ADEC cleanup levels (up to 1.42 mg/L) until November 2016 when the concentration increased to 3.79 mg/L, approximately 2.5 times more than the ADEC cleanup level of 1.5 mg/L. MW-2 through MW-4 and the drinking water samples were either non-detect or detected contaminants below ADEC cleanup levels in November 2016. A review of previous DRO concentrations in MW-3 showed an increase in DRO concentration in the Fall/Winter sampling events since 1999. Due to the spike in DRO concentration, ADEC requests that yearly groundwater monitoring be completed on MW-3 in November in order to establish a trend of Fall/Winter DRO concentration. Lisa Griswold
2/13/2017 Meeting or Teleconference Held Meeting with RP and consultant held on this date. Items discussed included a path forward to closure. Consultant is to submit a letter explaining rationale for requesting for cleanup complete with institutional controls. Lisa Griswold
3/2/2017 Update or Other Action ADEC notified of new spill discovered on site. 150 gallons diesel inside pump house. Product seeped through expansion cracks in floor and has contaminated soil. Lisa Griswold
4/14/2017 Document, Report, or Work plan Review - other Work Plan for Release Investigation approved on this date. Three soil borings are to be advanced. One within the building; one to the north of the building; and one to the west. If contamination is found in the boring within the building, an additional boring will be advanced to the south of the building. A boring cannot be advanced to the east of the building due to the slope present. The borings outside of the building will be completed as monitoring wells, while the interior boring will be completed as a temporary monitoring well. This work plan is approved with the following comments:1) The work plan states that one analytical soil sample will be collected from each soil boring. According to ADEC’s 2016 Field Sampling Guidance: two samples should be taken from each boring. ADEC would like to comment that only taking one soil sample per boring increases the likelihood that site characterization could be considered incomplete and require further sampling. 2)The work plan did not specify what kind of sand was going to be used in the monitoring well installation. According to ADEC’s Monitoring Well Guidance, it is recommended that 20-40 sand be used with a 0.010 slotted well screen. 3)Before sampling of the wells takes place, an interface probe should be used to gauge presence/absence/thickness of free product in the well. If any free product is detected, it should be recovered per 18 AAC 75.325. 4)The use of a disposable bailer in the temporary monitoring well is discouraged due to loss of volatiles; and possible presence of free product. However it is ADEC’s understanding that sample is intended to indicate the presence/absence of contamination rather than a quantitative evaluation. Lisa Griswold
5/9/2017 Document, Report, or Work plan Review - other Email approval given to sample wells MW1 and MW-3 according to ADEC field sampling guidance. MW-6 will have a free product bail down test conducted in order to measure the rate of product recovery. Any purge water or product is to be containerized and a disposal plan submitted once contaminants and quantities are known. A work plan for additional release investigation activities is to be submitted. Lisa Griswold
5/12/2017 Update or Other Action Letter sent to RP summarizing the email approval on 5/9/17 and to inform that project management was being transferred to Rodman. Lisa Griswold
5/12/2017 Update or Other Action Site transferred to Rodman Lisa Griswold
9/7/2017 Site Characterization Workplan Approved August 2017 work plan approved. Proposed activities generally consist of advancing soil borings, installing groundwater monitoring wells, collecting soil and groundwater samples for laboratory analysis, and managing investigation-derived waste (IDW). Select soil and water samples will be analyzed by the project laboratory for one or more of the following: gasoline range organics (GRO), diesel range organics (DRO), benzene, toluene, ethylbenzene, and xylenes (BTEX), and polynuclear aromatic hydrocarbons (PAHs). VOC's will be sampled in soil and groundwater samples with high PID readings. Amy Rodman
2/1/2019 Site Characterization Report Approved ADEC reviewed the “Release Investigation Activities: 4501 West 100th Avenue Anchorage, Alaska” (report) dated October 2018 for the MOA – AWWU Pump Station #12-UST site in Anchorage, AK. The report was submitted via email on December 18, 2018 by Shannon & Wilson, Inc. The described field effort was conducted in April & September 2018 and generally consisted of advancing soil borings, completing the soil borings as groundwater monitoring wells, field-screening and sampling soil and groundwater for laboratory analysis. On March 1, 2017, approximately 150 gallons of diesel was released from a ruptured pipe within the onsite generator building. Eight soil borings were advanced (B5 through B12) and seven groundwater monitoring wells (MW-5, MW-6, and MW-8 through MW-12) were completed. Soil was field-screened with a photo-ionization detector prior to sample collection for laboratory analysis. Work plan due March 15, 2019 for remaining soil and groundwater contamination. Amy Rodman
5/31/2019 Site Characterization Workplan Approved ADEC approved work plan to advance two soil borings to be completed as groundwater monitoring wells, groundwater sample collection from new and existing groundwater monitoring wells, soil sample collection from both new soil borings, and managing investigation-derived waste (IDW). Amy Rodman
10/30/2019 Update or Other Action Soil and groundwater laboratory data reviewed. Approval granted for transport & disposal of four 55-gallon drums of investigation-derived water to NRC Alaska. Approval granted to transport and disposal of two 55-gallon drums to Columbia Ridge Landfill (Arlington, OR) via NRC Alaska. Approval granted to landspread soil cuttings from soil boring 14 and discharge GW from MW-14 to ground. Amy Rodman
1/8/2020 Site Characterization Report Approved ADEC's Contaminated Sites Program reviewed and approved the “Additional Site Characterization Activities: 4501 West 100th Avenue” (report) dated December 2019 for the Municipality of Anchorage - Anchorage Water & Wastewater Utility by Shannon & Wilson, Inc. (S&W). The described field effort was conducted on June 19, 2019 and generally consisted of advancing soil borings, installing pre-pack groundwater monitoring wells, and sampling (soil and groundwater) for laboratory analysis. Soil and groundwater contamination confirmed above respective ADEC cleanup levels. Annual GW sampling of relevant onsite wells has been recommended to establish steady or decreasing trend. WP for next round of GW sampling due February 14, 2020. Amy Rodman
12/28/2021 Exposure Tracking Model Ranking Initial ranking with ETM completed for source area id: 80342 name: Generator Building Julie Fix

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