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:	Bill O'Connell, 9072693057 bill.oconnell@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.

Site Chronology
IC / Closure Details
Documents
Associated Sites

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

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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2019 Additional Site Characterization Activities Report

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Alaska Department of Environmental Conservation

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

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2019 Additional Site Characterization Activities Report

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State of Alaska Department of Environmental Conservation