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Site Report: Unocal - #4581(former)

Site Name: Unocal - #4581(former)
Address: 636 C Street, Anchorage, AK 99501
File Number: 2100.26.114
Hazard ID: 23364
Status: Cleanup Complete
Staff: No Longer Assigned, 9074655229 dec.icunit@alaska.gov
Latitude: 61.215838
Longitude: -149.887794
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

Gasoline contamination of soil and groundwater documented in 1986 during station assessment. During facility demolition and tank removal in 1987, 300 cubic yards contaminated soils removed. In-place soil contamination remediation by vapor extraction. Groundwater treatment by pumping to the surface and air stripping began in 1990. Operation of the remediation system continued until 2002. Groundwater is at about 22 feet below ground surface and flows towards the northwest. A portion of the excavated contaminated soil was treated in landfarming cell at 9760 Old Seward Highway. Confirmation soil samples collected in 2007 demonstated that the on-site soils had remediated to cleanup levels. The most recent groundwater sampling in 2007 shows that groundwater meets site cleanup levels. Confirmation soil samples collected in 2011 demonstated that the landfarm soils and surrounding soils at the 9760 Old Seward Highway had remediated to cleanup levels. Recommended for site closure. F.K.A. L35.04

Action Information

Action Date Action Description DEC Staff
10/21/1986 Underground Storage Tank Site Characterization or Assessment A subsurface petroleum hydrocarbon evaluation by RZA documents soil and groundwater contamination. Groundwater is at about 22 feet below ground surface and flows towards the northwest. Former Staff
7/20/1987 Release Investigation A well survey by RZA indicated no actively used water wells within a 500 foot radius of the site. Former Staff
11/12/1987 Site Visit Ron Godden discusses problem with field crew concerning soil contamination that was not properly addressed. Station being demolished. Former Staff
11/12/1987 Leaking Underground Storage Tank Release Confirmed - Petroleum LUST Site created in CSP for source area ID 77746 Petroleum contaminant. Former Staff
11/12/1987 Site Added to Database Former Staff
11/13/1987 Leaking Underground Storage Tank Cleanup Initiated - Petroleum LCAU Date changed DB conversion Former Staff
11/13/1987 Leaking Underground Storage Tank Corrective Action Underway The underground storage tank excavation must have contamination removed before placing clean backfill. Unocal consultant responds with 11/19/87 workplan. ADEC approves a plan on 11/24/87. Former Staff
3/24/1988 Document, Report, or Work plan Review - other ADEC approves plan to treat 152 cubic yards of contaminated soil at an off-site lined landfarm treatment cell at 9760 Old Seward Highway. Former Staff
4/26/1988 Document, Report, or Work plan Review - other Excavated contaminated soil is being treated in a land farming cell at Stephan's Rental on the Old Seward Highway. Former Staff
6/1/1988 Document, Report, or Work plan Review - other RZA subsurface petroleum hydrocarbon source investigation. Soil and groundwater contamination documented. Former Staff
6/7/1988 Document, Report, or Work plan Review - other RZA prepares a work plan for further site assessment. Former Staff
7/27/1988 Document, Report, or Work plan Review - other RZA sampling site groundwater. Sample MW-7 taken on 7/27/88 had 5,200 ppb benzene. Former Staff
8/31/1988 Document, Report, or Work plan Review - other RZA prepares remedial action plan; excavation of shallow contaminated soils; vapor extraction for in-situ soils; pumping and treating groundwater by air stripping. Plan resubmitted 10/7/88 with more details. Former Staff
9/19/1988 Document, Report, or Work plan Review - other Quarterly groundwater monitoring report. Sample MW-7 taken on 10/24/88 had 11,000 ppb benzene. Former Staff
10/19/1988 Document, Report, or Work plan Review - other RZA submits plan for removing and disposing of about 200 cubic yards of soil. Former Staff
10/19/1988 Document, Report, or Work plan Review - other RZA submits plan for removing and disposing of about 200 cubic yards of soil at the Anchorage Regional Landfill. Former Staff
11/11/1988 Document, Report, or Work plan Review - other The tank was removed during 1987. Removal of contaminated soils took place between 11/11/87 and 11/14/87. The excavation was backfilled on 11/15/87 with clean imported soils. Former Staff
3/28/1989 Update or Other Action Monitoring well MW-5 was severely damaged apparently during removal of waste oil tank. Sample of MW-7 taken on 3/28/89 had 8,900 ppb benzene. Former Staff
2/26/1990 Document, Report, or Work plan Review - other Consultant (RZA) anticipates that operation of groundwater withdrawal and treatment will start by 5/15/90. Two years of treatment are expected by RZA. Former Staff
2/3/1992 Document, Report, or Work plan Review - other Remediation system has been running since 4/90. Air stripper tower treats pumped water and it is then discharged in AWWU sewer. Seven monitoring wells are on-site. Groundwater contaminant levels up to 5.7 ppm Benzene, 60.2 ppm BTEX, 64 ppm GRO, 6.3 ppm DRO, 1.7 ppm TPH. Former Staff
2/12/1996 Document, Report, or Work plan Review - other Reviewed a quarterly groundwater sampling and vapor extraction and groundwater pumping system reports. Former Staff
7/31/1996 Update or Other Action The soil vapor extraction and groundwater treatment system was decommissioned. Robert Weimer
11/20/1997 Update or Other Action ADEC sends Notification of Intent to Cost Recover Letter to Current Owner: UNOCAL - CLOSED FACILITIES Former Staff
9/12/2003 Update or Other Action Approved reduction in groundwater monitoring. Robert Weimer
2/6/2004 Update or Other Action ADEC can't grant NFRAP status without confirmation soil samples. Robert Weimer
7/13/2004 Document, Report, or Work plan Review - other Semi-annual monitoring report for June 24, 2004. Up to 4.31 ug/L benzene, .325 mg/L GRO, and 1.26 mg/L DRO. Trends are decreasing. Robert Weimer
9/13/2004 Document, Report, or Work plan Review - other Additional groundwater monitoring conducted on June 1, 2004. Up to 1.19 mg/l GRO, 1.09 mg/l DRO, and 2.96 ug/l benzene. Trends appear to be decreasing. Robert Weimer
1/7/2005 Document, Report, or Work plan Review - other Additional groundwater monitoring conducted on December 4, 2004. Up to .672 mg/l GRO, .995 mg/l DRO, and 4.80 ug/l benzene. Trends appear to be stable. Robert Weimer
4/25/2005 Update or Other Action Reviewed confirmation sampling workplan. Provided comments in a meeting with RP and consultant. They are to provide a revised workplan. We also discussed the cold asphalt and soils at Stephan Tool Rental site. Robert Weimer
5/27/2005 Update or Other Action Discussions with Unocal on the status of the soils at the Stephan's Tool Rental (now United Tool Rental) site. Unocal could not find the soils, and the current owner has no knowledge of it. Unocal will check with past owners/operators and submit a plan to assessing the area where the cell used to be. Robert Weimer
8/26/2005 Document, Report, or Work plan Review - other Groundwater monitoring conducted on June 21, 2005. Up to .071 mg/l GRO, 1.23 mg/l DRO, and 2.34 ug/l benzene. Trends appear to be stable. Groundwater flows to the northwest. Robert Weimer
5/4/2006 Document, Report, or Work plan Review - other Groundwater monitoring conducted on December 28, 2005. Up to 0.0615 mg/l GRO, 0.761 mg/l DRO, and 1.06 ug/l benzene. Trends appear to be decreasing. Groundwater flows to the west by northwest. Robert Weimer
9/25/2006 Update or Other Action Talked with RP's consultant. He will provide a revised workplan. We also discussed the cold asphalt (it will be verified during the soil sampling) and soils at Stephan Tool Rental site. Robert Weimer
12/19/2006 Document, Report, or Work plan Review - other Groundwater monitoring conducted on June 29, 2006. Up to <0.05 mg/l GRO, 0.507 mg/l DRO, and 1.09 ug/l benzene. Trends appear to be decreasing. Groundwater flows to the north by northeast. Depth to groundwater was around 18 feet below ground surface. Robert Weimer
3/13/2007 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
3/27/2007 Document, Report, or Work plan Review - other Groundwater monitoring conducted on December 31, 2006. Up to 0.082 mg/l DRO. Trends appear to be decreasing. Groundwater historically flows to the north by northeast. Depth to groundwater historically is around 18 feet below ground surface. Robert Weimer
4/2/2007 Update or Other Action Meeting with RP to discuss site. They are to locate Stephan's Tools property soils, to submit a revised confirmation sampling workplan, and information regarding status of cold asphalt at the site. Robert Weimer
8/7/2007 Update or Other Action Review and approve revised confirmation sampling workplan. Robert Weimer
9/6/2007 Update or Other Action Approved corrective action plan for the thermal treatment of three drums of contaminated soils. Robert Weimer
1/8/2008 Document, Report, or Work plan Review - other Groundwater monitoring conducted on June 28/30, 2007. Up to 0.72 mg/l DRO, 0.3 mg/l GRO, <0.0097 ug/l EDB, and <0.5 ug/l 1,2,DCA. Trends appear to be increasing. Groundwater historically flows to the north by northeast. Depth to groundwater was 23.78 to 24.88 feet below ground surface. Robert Weimer
3/3/2008 Document, Report, or Work plan Review - other Groundwater monitoring conducted on August 15/16, 2007. Up to 0.16 mg/l DRO, and 0.2 mg/l GRO in the one monitoring well samples (MW-3). Groundwater historically flows to the north by northeast. Robert Weimer
3/5/2008 Update or Other Action Meeting with Chevron and their consultants. They do follow up work to locate and assess the soils that went to Stephan's Tool Rental in 1988. Robert Weimer
6/5/2008 Site Visit Site visit with UNOCAL/Chevron's consultant (CRA) to observe the condition of the soil treatment cell at Stephan's/United Tool Rental and to conduct confirmation sampling. Confirmation sampling was not done at this time because of changes in site conditions. The soil treatment cell had been graded and spread over a larger area, there may have been fill placed over portions, there were trailers and equipment were parked on portions of the treatment cell area, and there were some visibly stained soil in the cell area some of which was under the stored equipment. There were also some visibly stained soil under some equipment stored to the east of the treatment cell area. CRA said they would talk with the property owner and Chevron about what they observed. Robert Weimer
6/30/2008 Update or Other Action RP's consultant provides documentation on the correct sample preservation for the 8/15/07 groundwater samples. Robert Weimer
12/4/2008 Document, Report, or Work plan Review - other Review of subsurface investigation report. Confirmation soil samples were collected on the site property in August 2007. Four soil borings were sampled. All samples meet default cleanup levels. Up to 160 mg/kg DRO (250 mg/kg cleanup level), 11 mg/kg GRO (300 mg/kg cleanup level), and 0.008 mg/kg benzene (0.025 mg/kg cleanup level) in the soil samples collected. Robert Weimer
2/25/2009 Meeting or Teleconference Held Meeting with Chevron and their consultants. They do follow up work in 2009 to assess and cleanup the soils that went to Stephan's Tool Rental in 1988. We discussed that it appears based on the sampling data submitted that the soil and groundwater at 636 C Street meet cleanup levels. Robert Weimer
3/11/2010 Meeting or Teleconference Held Meeting with Chevron and their consultants on 3/10/10. We discussed that assessment work still needs to be done at the Stephan's Tool site, the owner of the property also participated in the meeting. We discussed that PAH would be required in 10% of the soil samples. Robert Weimer
4/6/2010 Document, Report, or Work plan Review - other DEC review of Site Vapor Intrusion Evaluation report for this site. The report concluded that this site does not have a potential for vapor intrusion based on the remaining concentrations in the soil and groundwater at this site. Robert Weimer
10/19/2010 Site Characterization Workplan Approved DEC conditionally approves revised Soil Investigation and Management Workplan to assess the 1988 soil treatment cell and area at the Stephan Tool/United Tool property (see file number 2100.38.479). Robert Weimer
12/21/2010 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 77746 1987 UST contamination. Updated ETM to reflect recent soil and groundwater data. BTEX, GRO, and DRO contamination in the soil at an off property location that needs confirmation sampling and assessment(Stephan's Tool Rental). On property soil and groundwater meet cleanup levels. Robert Weimer
6/3/2011 Update or Other Action ADEC approves workplan for the decommissioning of the 4 remaining monitoring wells at the site. Robert Weimer
10/28/2011 Update or Other Action Need results of the Fall 2011 assessment of the 1988 soil treatment cell and area at the Stephan Tool/United Tool property (see file number 2100.38.479) to evaluate site for closure. Robert Weimer
11/4/2011 Document, Report, or Work plan Review - other ADEC approves treatment of 6 drums of contaminated water generated during the September 2011 subsurface investigation work. Robert Weimer
12/20/2011 Update or Other Action ADEC receives documentation of the decommissioning of the last 4 monitoring wells at the site on June 3, 2011. Robert Weimer
2/29/2012 Meeting or Teleconference Held Meeting with Chevron and their consultants on 2/28/12. DEC is to review the February 2012 report for the sampling of the landfarm soils at the Stephan's (United) Tool Rental property. Robert Weimer
10/8/2012 Document, Report, or Work plan Review - other Review of Soil Cell Assessment Report for the September 2011 sampling of the soil treatment cell at the 9760 Old Seward property. The cell contained contaminated soil from several Unocal sites. Two visibly stained areas were sampled had up to 4,000 mg/kg DRO and 12,000 mg/kg RRO. The contaminated soil from these locations was excavated and thermally treated. Confirmation soil samples were collected from within the cell, under the cell liner, and around the perimeter of the cell. Up to 120 mg/kg DRO, 1,600 mg/kg RRO, background metals concentrations, non-detect PCBs, non-detect HVOCs, low concentrations of PAHs, and 0.006 mg/kg benzene in the soil samples collected. Robert Weimer
2/26/2013 Meeting or Teleconference Held Meeting with Chevron and their consultants on 2/26/13. We discussed that DEC would be issuing a Corrective Action Complete letter soon for this site. Robert Weimer
6/12/2013 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 77746 1987 UST contamination. Robert Weimer
6/25/2013 Site Visit Site visit to observe current site conditions. Robert Weimer
7/2/2013 Cleanup Complete Determination Issued Robert Weimer
8/7/2015 Update or Other Action This file has been archived at Alaska Archives Barcode: 795759 Box 388 and 795758 Box 387 Susan Carberry

Contaminant Information

Name Level Description Media Comments
GRO < Table C Groundwater
GRO < Method 2 Most Stringent Soil
DRO < Table C Groundwater
DRO < Method 2 Most Stringent Soil
RRO < Table C Groundwater
RRO < Method 2 Most Stringent Soil
Benzene < Table C Groundwater
Benzene < Method 2 Most Stringent Soil

Control Type

Type Details
No ICs Required

Requirements

Description Details
Advance approval required to transport soil or groundwater off-site.

No associated sites were found.

Missing Location Data

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State of Alaska Department of Environmental Conservation

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