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Site Report: Thrifty Rent a Car, 4000 gallon gasoline UST 2

Site Name: Thrifty Rent a Car, 4000 gallon gasoline UST 2
Address: 3730 Spenard Road, Anchorage, AK 99517
File Number: 2100.26.219
Hazard ID: 24015
Status: Cleanup Complete
Staff: No Longer Assigned, 9074655229 dec.icunit@alaska.gov
Latitude: 61.186807
Longitude: -149.914296
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

A 4,000-gallon gasoline underground storage tank (DEC Tank ID #2) was removed in 1992. Soil and groundwater contamination found. Some contaminated soil was excavated and subsequently thermally treated. The remaining contamination appears to be mostly associated with the adjacent Chevron - #9014 site (see 2100.26.057). In 1998 a used oil tank was removed and cleaned up (see 2100.26.275).

Action Information

Action Date Action Description DEC Staff
9/12/1989 Leaking Underground Storage Tank Release Confirmed - Petroleum LUST Site created in CSP for source area ID 77637 Petroleum contaminant. Former Staff
9/12/1989 Site Added to Database Former Staff
9/13/1989 Leaking Underground Storage Tank Cleanup Initiated - Petroleum LCAU Date changed DB conversion Former Staff
9/18/1989 Site Visit ADEC staff noted petroleum contamination at the site. Former Staff
9/19/1989 Update or Other Action Requested workplans for identification of vertical & lateral level of contamination & extent of surface/subsurface contamination, cleanup of soil & groundwater contamination. Former Staff
9/19/1989 Release Investigation Shannon & Wilson found gasoline had been released near north end of underground storage tank. Former Staff
11/13/1989 Document, Report, or Work plan Review - other AZIZ recommended drilling monitoring well for locating contamination and stated that the nearby Chevron possible offsite source of contamination. Monitoring well was installed. Former Staff
7/26/1990 Document, Report, or Work plan Review - other Monitoring well showed groundwater contamination suggest that Chevron is the larger source of contamination. Propose to use vapor extraction on monitoring well 1. Former Staff
10/24/1990 Leaking Underground Storage Tank Corrective Action Underway Request for plan for groundwater cleanup, well search, & a more developed vapor extraction program plus a soil disposal plan. Originally for 11-5-90 but extension granted to 11-30-90. Another letter sent 12/6/90 reiterating same points plus request for quarterly groundwater measurements beginning immediately. Former Staff
2/4/1992 Update or Other Action Letter requesting documentation of releases from adjacent Chevron station, site history, quarterly groundwater measurements, sample all 4 monitoring wells for BTEX. Soil disposal to AS&G is approved. Submit well search documentation that there is no wells within 1/4 mile. Former Staff
2/9/1993 Underground Storage Tank Site Characterization or Assessment 4,000 gal gasoline tank removed on 8/21/92. Excavated soils meet level A and were placed back in the excavation. One excavation soil sample (in vadose zone) shows 940 mg/kg GRO and 1.3 mg/kg benzene. Former Staff
2/9/1993 Document, Report, or Work plan Review - other RELR; All 4 monitoring wells sampled on 7/8/92, all have benzene contamination (6.2 to 8,900 ug/l) over cleanup levels (5 ug/l). Former Staff
7/25/1995 Document, Report, or Work plan Review - other Reviewed quarterly groundwater monitoring report. There appears to be some groundwater contamination from the upgradient Chevron site. Former Staff
11/20/1997 Update or Other Action ADEC sends Notification of Intent to Cost Recover Letter to Current Owner: FLOYD & SONS INC Former Staff
4/23/1998 Update or Other Action In a settlement reached between Thrifty Car Rental and Chevron, the responsibility for cleanup of this site has been assumed by Chevron. Former Staff
12/1/1998 Update or Other Action Used oil tank removed near shed. Daniel Rogers
10/16/2003 Update or Other Action Site being cleaned up and monitored by the upgradient Chevron next door. Robert Weimer
12/1/2004 Update or Other Action Site continues to be cleaned up and monitored by the upgradient Chevron next door. Robert Weimer
12/16/2005 Update or Other Action Site continues to be cleaned up and monitored by the upgradient Chevron next door. The September 22, 2005 groundwater monitoring event had up to 10 mg/l GRO, 2,600 ug/l benzene, and 3 ug/l MTBE in the groundwater at the Thrifty Rent-A-Car site. Groundwater flows to the southwest and the depth to groundwater is 11 to 12 feet below ground surface. Robert Weimer
2/14/2007 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
9/17/2008 Document, Report, or Work plan Review - other September 17, 2008 groundwater monitoring event conducted by Chevron's consultant. Up to 110 mg/l GRO, 5600 ug/l benzene, non-detect (<10.0 ug/l) 1,2-DCA, non-detect (<0.0098 ug/l) EDB, and non-detect (<200 ug/l) MTBE in the groundwater. Concentrations increased in 2 of 11 total project monitoring wells sampled by Chevron. Depth to groundwater was 11.47 to 13.28 feet below ground surface. Groundwater flow direction was to the southeast. Chevron continues to do semi-annual groundwater monitoring at the site as they treat the contaminated soil and groundwater with their air sparge vapor extraction system. Robert Weimer
5/20/2009 Document, Report, or Work plan Review - other May 20, 2009 groundwater monitoring event conducted by Chevron's consultant. Up to 62 mg/l GRO, 2200 ug/l benzene, non-detect (<3.0 ug/l) 1,2-DCA, non-detect (<0.0097 ug/l) EDB, and non-detect (<63 ug/l) MTBE in the groundwater. Concentrations increased in 4 of 9 total project monitoring wells sampled by Chevron. Depth to groundwater was 11.58 to 13.34 feet below ground surface. Groundwater flow direction was to the southeast. Chevron continues to do semi-annual groundwater monitoring at the site as they treat the contaminated soil and groundwater with their air sparge vapor extraction system. Robert Weimer
9/3/2009 Document, Report, or Work plan Review - other September 3, 2009 groundwater monitoring event conducted by Chevron's consultant. Up to 100 mg/l GRO, 3500 ug/l benzene, non-detect (<5.0 ug/l) 1,2-DCA, non-detect (<0.0098 ug/l) EDB, and non-detect (<130 ug/l) MTBE in the groundwater. Concentrations increased in 4 of 11 total project monitoring wells sampled by Chevron. Depth to groundwater was 11.60 to 13.58 feet below ground surface. Groundwater flow direction was to the southeast. Chevron continues to do semi-annual groundwater monitoring at the site as they treat the contaminated soil and groundwater with their air sparge vapor extraction system. Robert Weimer
1/11/2011 Document, Report, or Work plan Review - other May 2010 groundwater monitoring event conducted by Chevron's consultant. Up to 97 mg/l GRO, 1400 ug/l benzene, and 22 ug/l MTBE in the groundwater. Concentrations increased in 1 of 11 total project monitoring wells sampled by Chevron. Depth to groundwater was 11.75 to 13.2 feet below ground surface. Groundwater flow direction was to the southeast. Chevron continues to do semi-annual groundwater monitoring at the site as they treat the contaminated soil and groundwater with their air sparge vapor extraction system. Robert Weimer
4/28/2011 Update or Other Action Chevron's Third quarter 2010 remediation system report. The upgraded system includes 10 new air sparge wells and 4 existing soil vapor extraction wells which began operation on June 26, 2008. The system operated 85% of the planned time and removed 7.2 pounds of GRO during this period. To date the systems have removed 8,877 pounds of GRO and 691 pounds of benzene. The air sparge system is pulsed between 3 banks of air sparge wells. The consultant recommends in the future shutting down the system and check for any rebound in groundwater contamination and system vapors. A workplan for the rebound study is to be submitted. Existing remediation system is to be upgraded to treat a larger area of the soil and groundwater contamination. Robert Weimer
9/29/2011 Update or Other Action DEC approves Chevron's request to shut down SVE/AS system for 6 months to conduct a rebound study, then turn the system back on and take air samples. Robert Weimer
10/19/2011 Document, Report, or Work plan Review - other September 8, 2010 semi-annual groundwater monitoring event conducted by Chevron's consultant. Up to 120 mg/l GRO, 2,500 ug/l benzene, and non-detect (<130 ug/l) MTBE. Concentrations increased in 7 of the 19 total project monitoring wells sampled by Chevron. Groundwater flows to the southwest. Depth to groundwater is 11.46 to 13.55 feet below ground surface. Naphthalene 22 ug/l, cleanup level (730 ug/l). Robert Weimer
11/29/2011 Document, Report, or Work plan Review - other June 21, 2011 semi-annual groundwater monitoring by Chevron's consultant. Up to 100 mg/l GRO, and 4,700 ug/l benzene. Concentrations increased in 5 of the 19 total project monitoring wells sampled by Chevron. Groundwater flows to the southwest. Depth to groundwater is 10.87 to 13.47 feet below ground surface. PAH's were below cleanup levels in groundwater this monitoring event. Robert Weimer
3/1/2012 Meeting or Teleconference Held Meeting with Chevron and their consultants on 2/28/12. Chevron is to abandon damaged monitoring well T-4 and repair monitoring well monuments. The remediation system is currently down for the ongoing rebound study. They are to continue semi-annual groundwater monitoring. They are to add a rose diagram to the monitoring figure. Thrifty is to remove the two underground storage tanks and associated piping in their property in 2012. Robert Weimer
8/28/2012 Document, Report, or Work plan Review - other May 22, 2012 semi-annual groundwater monitoring conducted by Chevron's consultant. Up to 25 mg/l GRO, and 140 ug/l benzene. Concentrations increased in 5 of the 18 total project monitoring wells sampled by Chevron. Groundwater flows to the south by southwest. Depth to groundwater is 10.67 to 12.92 feet below ground surface. Robert Weimer
2/26/2013 Meeting or Teleconference Held Meeting with Chevron and their consultants on 2/26/13. Chevron proposes to continue semi-annual groundwater monitoring, is approved to remove the unused SVE/AS shed to use on a Fairbanks site, and provide missing reports. They are to add a rose diagram to the monitoring figure. The next groundwater sampling event they will sample both using no purge and purge help evaluate that the past no purge results were providing comparable data. We discussed that Thrifty's consultant has not provided a revised UST assessment work plan yet. Robert Weimer
4/11/2013 Document, Report, or Work plan Review - other September 20, 2012 semi-annual groundwater monitoring conducted by Chevron's consultant. Up to 130 mg/l GRO, and 320 ug/l benzene. Concentrations increased in 12 of the 19 total project monitoring wells sampled by Chevron. Groundwater flows to the south by southwest. Depth to groundwater is 10.43 to 12.73 feet below ground surface. Groundwater sampling was conducted with no purge using bailers. Since bailers were used the BTEX and GRO results may be biased low. Robert Weimer
2/10/2014 Document, Report, or Work plan Review - other May 13, 2013 semi-annual groundwater monitoring conducted by Chevron's consultant. Up to 79.7 mg/l GRO, and 1,610 ug/l benzene. Concentrations increased in 6 of the 17 total project monitoring wells sampled by Chevron. Groundwater flows to the south west. Depth to groundwater was 11.05 to 13.09 feet below ground surface. Samples were collect by both no-purge (Hydrasleeve) and purge (bladder pump) methods. The sampling interval for the hydrasleeve and bladder pump was not documented in the field notes. The sample results between to the two methods were not consistent (for example MW-11 was non-detect (<0.1 mg/l) GRO and non-detect (<1.0 ug/l) benzene with the no-purge hydrasleeve but was 6.19 mg/l GRO and 19.4 ug/l benzene with the purged bladder pump sampling). Robert Weimer
4/25/2014 Document, Report, or Work plan Review - other September 23, 2013 semi-annual groundwater monitoring by Chevron's consultant. Up to 218 mg/l GRO, and 594 ug/l benzene. Concentrations increased in 5 of the 19 total project monitoring wells sampled by Chevron. Groundwater flows to the south west. Depth to groundwater was 10.06 to 12.31 feet below ground surface. Samples were collect by no-purge (Hydrasleeve) method. Because the sampling interval for the hydrasleeve was not documented in the field notes the results are considered biased low. Robert Weimer
5/12/2014 Site Visit Site visit to observe current site conditions. Robert Weimer
12/10/2014 Conceptual Site Model Submitted August 2014 Conceptual Site Model (CSM) identified completed pathways for soil, groundwater, and air for the remaining contamination at this site. Robert Weimer
1/5/2015 Document, Report, or Work plan Review - other May 14, 2014 semi-annual groundwater monitoring by Chevron's consultant. Up to 7.99 mg/l GRO, and 160 ug/l benzene. Higher concentrations may exist because some samples arrived frozen/broken at the lab and were not analyzed. Two samples were not properly preserved in the field. Three samples were analyzed outside holding times. Concentrations increased in 9 of the 18 total project monitoring wells sampled by Chevron. Groundwater flowed to the south west. Depth to groundwater was 10.64 to 12.74 feet below ground surface. Samples were collect by purge method using a bladder pump. Samples were collected from within the top foot of the water column. Robert Weimer
5/27/2015 Document, Report, or Work plan Review - other October 15, 2014 semi-annual groundwater monitoring by Chevron's consultant, which includes 10 monitoring wells currently being monitored on the Thrifty property. Up to 52.3 mg/l GRO, and 436 ug/l benzene. The highest concentrations were on the Thrifty property. Concentrations increased in 8 of the 19 total project monitoring wells sampled by Chevron. Groundwater flowed to the south west. Depth to groundwater was 10.44 to 12.55 feet below ground surface. Samples were collect by no-purge method using Hydrasleeves. Samples were collected at the top of the water column as required. Robert Weimer
11/16/2015 Document, Report, or Work plan Review - other April 21, 2015 semi-annual groundwater monitoring by Chevron's consultant, which includes 4 monitoring wells currently being monitored on the Thrifty property. Up to 56.0 mg/l GRO, and 1,900 ug/l benzene. The highest concentrations were on the Thrifty property. Concentrations increased in 2 of the 4 monitoring wells sampled on the property. Groundwater flowed to the south west. Depth to groundwater was 11.72 to 12.97 feet below ground surface. Samples were collect by no-purge method using Hydrasleeves. Samples were collected at the top of the water column as required. Robert Weimer
6/22/2016 Site Visit Site visit to check on current site conditions. Robert Weimer
6/9/2017 Document, Report, or Work plan Review - other June 27-28, 2016 semi-annual groundwater monitoring by Chevron's consultant, which includes 8 monitoring wells currently being monitored on the Thrifty property. Up to 56.0 mg/l GRO, 6,500 ug/l toluene, and 620 ug/l benzene. The highest concentrations were on the Thrifty property. Concentrations increased in 4 of the 8 monitoring wells sampled on the property. Groundwater flowed to the southwest this monitoring event. Groundwater flowed to the south west this monitoring event. Depth to groundwater was 11.36 to 13.15 feet below ground surface. Samples were collect by no-purge method using Hydrasleeves. Samples were collected at the top of the water column. Robert Weimer
6/15/2017 Document, Report, or Work plan Review - other September 13-14, 2016 semi-annual groundwater monitoring by Chevron's consultant, which includes 8 monitoring wells currently being monitored on the Thrifty property. Up to 78.0 mg/l GRO, 6,000 ug/l toluene, 3,200 ug/l ethylbenzene, 14,000 ug/l xylenes, and 520 ug/l benzene. The highest concentrations were on the Thrifty property. Concentrations increased in 4 of the 8 monitoring wells sampled on the property. Groundwater flowed to the southwest this monitoring event. Depth to groundwater was 10.98 to 12.85 feet below ground surface. Samples were collect by no-purge method using Hydrasleeves. Samples were collected at the top of the water column except for monitoring well MW-27. Robert Weimer
1/16/2018 Document, Report, or Work plan Review - other September 11-13, 2017 semi-annual groundwater monitoring by Chevron's consultant. Up to 44 mg/l GRO, 3,800 ug/l toluene, 2,000 ug/l ethylbenzene, 10,000 ug/l xylenes, 2 ug/l MTBE, 5 ug/l 1,2-DCA, and 410 ug/l benzene. Concentrations increased in 4 of the 8 monitoring wells sampled on the Thrifty property. One of the monitoring wells (MW-27) was sampled for PAHs and had up to 36 ug/l Naphthalene, 0.33 ug/l Flurene, 0.67 ug/l Phenanthrene, 0.11 ug/l Acenaphthene, and 0.014 ug/l Acenapthylene. Groundwater flowed to the south west this monitoring event. Depth to groundwater was 10.89 to 12.72 feet below ground surface. Samples were collect after purging with a bladder pump at the top of the water column. Robert Weimer
4/11/2019 Document, Report, or Work plan Review - other May 16-18, 2018 semi-annual groundwater monitoring by Chevron's consultant. Up to 88 mg/l GRO, 7,400 ug/l toluene, 3,800 ug/l ethylbenzene, 20,000 ug/l xylenes, 1 ug/l MTBE, 5 ug/l 1,2-DCA, and 460 ug/l benzene. Concentrations increased in 3 of the 9 monitoring wells sampled on the Thrifty property. Four of the monitoring wells were sampled for PAHs and had up to 110 ug/l Naphthalene (1.7 ug/l cleanup level). The other detected PAH compounds were below current cleanup levels. Groundwater flowed to the south west this monitoring event. Depth to groundwater was 10.97 to 12.79 feet below ground surface. Samples were collect after purging with a bladder pump at the top of the water column. Naphthalene results were missing from the VOC 8260 analysis. Robert Weimer
5/16/2019 Document, Report, or Work plan Review - other September 26-28, 2018 semi-annual groundwater monitoring conducted by Chevron's consultant. Up to 77 mg/l GRO, 12,000 ug/l toluene, 3,800 ug/l ethylbenzene, 20,000 ug/l xylenes, 1 ug/l MTBE, 5 ug/l 1,2-DCA, and 800 ug/l benzene. Concentrations increased in 5 of the 10 monitoring wells sampled. Seven of the monitoring wells were sampled for PAHs and had up to 120 ug/l Naphthalene (1.7 ug/l cleanup level). The other detected PAH compounds were below current cleanup levels. Groundwater flowed to the south west this monitoring event. Depth to groundwater was 10.96 to 12.81 feet below ground surface. Samples were collect after purging with a bladder pump at the top of the water column. Naphthalene results were missing from the VOC 8260 analysis. Robert Weimer
1/10/2020 Document, Report, or Work plan Review - other May 8-10, 2019 semi-annual groundwater monitoring conducted by Chevron's consultant. Up to 33 mg/l GRO, 4,200 ug/l toluene, 1,900 ug/l ethylbenzene, 11,000 ug/l xylenes, 0.7 ug/l MTBE, 5 ug/l 1,2-DCA, and 500 ug/l benzene. Concentrations increased in 3 of the 10 monitoring wells sampled on the Thrifty property. Some of the monitoring wells were sampled for PAHs and had up to 23 ug/l Naphthalene (1.7 ug/l cleanup level). The other detected PAH compounds were below current cleanup levels. Groundwater flowed to the south west this monitoring event. Depth to groundwater was 11.26 to 13.03 feet below ground surface. Samples were collect after purging with a bladder pump. Since the samples were not collected at the top foot of the water column as required the results may be biased low. Naphthalene results were missing from the VOC 8260 analysis despite it being requested on COC. Robert Weimer
3/11/2020 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 77637 gasoline contamination. Robert Weimer
6/28/2024 Cleanup Complete Determination Issued DEC issued a cleanup complete letter. Soil contamination remained near the groundwater table after the 1992 UST removal. Groundwater monitoring in this area continues through the Chevron - #9014 site (Hazard ID 23570). Janice Wiegers

Contaminant Information

Name Level Description Media Comments
Benzene Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil Present in 1992 at 10 ft bgs at 1.3 mg/kg.
Ethylbenzene Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil Present in 1992 at 10 ft bgs at 22 mg/kg.
Toluene Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil Present in 1992 at 10 ft bgs at 53 mg/kg.
Xylenes (total) Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil Present in 1992 at 10 ft bgs at 160 mg/kg.
GRO Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil Present in 1992 as VPH at 10 ft bgs at 940 mg/kg.

Control Type

Type Details
No ICs Required

Requirements

Description Details
Advance approval required to transport soil or groundwater off-site.
Movement or use of contaminated material (including on site) in a manner that results in a violation of the water quality standards is prohibited (18 AAC 70)
Hazard ID Site Name File Number
26404 Thrifty Car Rental USTs 3 & 4 2100.26.589
23023 Thrifty Car Rental, 1000 gallon used oil UST 1 2100.26.275
23570 Chevron - #9014 2100.26.057

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State of Alaska Department of Environmental Conservation

P.O. Box 111800
Juneau, AK 99811-1800
Phone: 907-465-5066
Fax: 907-465-5245
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