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Site Report: ADOT&PF Ninilchik Maintenance Facility

Site Name: ADOT&PF Ninilchik Maintenance Facility
Address: 15560 Sterling Highway, Ninilchik, AK 99639
File Number: 2325.26.001
Hazard ID: 24698
Status: Cleanup Complete
Staff: ,
Latitude: 60.045500
Longitude: -151.669000
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.


During the removal of one 2,000 gallon unleaded gasoline and one 2,000 gallon diesel underground storage tank, DRO concentrations ranging from 33 to 24,000 ppm, GRO concentrations ranging from 13 to 11,000 ppm, BTEX from 3.67 to 2,887, and Benzene from .24 to 47 mg/Kg were encountered. Eighteen cubic yards of impacted soil was removed and stock piled on site. Further site assessment and cleanup added an additional 1,100 cubic yards of contaminated soil, that was stored on site. Detectable concentrations of GRO, DRO, and BTEX ranging from 3.20 ppm to 15.7 ppm GRO, 0.447 to 3.58 DRO, and 1.62 to 2.372 BTEX was encountered in the groundwater, and four groundwater monitoring wells were installed. The total of 1,120 cubic yards of impacted soils was thermally remediated by FMW LLC Thermal Operations portable soil treatment at the ADOT&PF Ninilchik facility. Updated 11/29/05 Alyce Hughey.

Action Information

Action Date Action Description DEC Staff
1/8/1998 Leaking Underground Storage Tank Release Confirmed - Petroleum LUST Site created in CSP for source area ID 77634 * Not Assigned
1/8/1998 Site Added to Database * Not Assigned
10/11/1999 Leaking Underground Storage Tank Cleanup Initiated - Petroleum * Not Assigned
12/1/2003 Update or Other Action Four Groundwater monitoring wells were installed , developed and sampled December 2003. Quarterly GW montioring events scheduled. Excavation scheduled for May 04. David Allen
12/1/2003 Update or Other Action A conditional approval letter was sent by Monica English from the Groundwater Monitoring Plan received October 23, 2003. Alyce Hughey
6/1/2004 Leaking Underground Storage Tank Corrective Action Underway Staff reviewed and provided comments to a Soil Remediation work plan and a Thermal Operations Plan. Review comments letter sent by Paul Horwath. Monica English
6/9/2004 Update or Other Action File number assigned and entered into the Fileroom DB and LUST DB. Alyce Hughey
6/23/2004 Leaking Underground Storage Tank Corrective Action Underway Conditional approval letter sent by Monica English for soil remediation work plan. Monica English
7/24/2004 Update or Other Action Requested Public Notice for Soil Remediation and Thermal Operations David Allen
2/14/2005 Report or Workplan Review - Other December 30, 2004 Shannon & Wilson report indicated 1120 cubic yards of soil was thermally treated on site. There was a slight exceedance of benzene above cleanup levels in one sample of post treated soil. The groundwater monitoring indicated B1MW and B3MW had detectable concentrations of petroleum (whereas B2MW and B4MW did not). Benzene was the contaminant of concern and was only detected in B3MW during the last event (October 2004). There appears to be a decreasing trend in contaminatioin and continued monitoring is recommended until Table C levels are met. An on-site drinking water well and an adjacent private well were sampled but were reported to be clean. Treated soil is proposed to be used on site. NFRAP status may be appropriate now and closure should be considered when groundwater cleanup levels are achieved. Jim Frechione
7/6/2005 Conditional Closure Approved File & reports reviewed. Current site conditions are protective of human health and the environment. Treated soils may be used on-site as base material for grading. They may not be removed off site without ADEC written approval. Natural attenuation will further degrade in-situ soils with residual contaminant concentrations exceeding ADEC cleanup levels. Analytical data showing contaminant levels are below ADEC soil and groundwater cleanup levels are required for site closure. GW monitoring program to continue on an annual basis until two consecutive sampling events show all GW sampling points are below cleanup levels. Soil and GW contaminant levels must all be below cleanup levels for site closure. Donald Seagren
7/6/2005 Institutional Control Record Established * Not Assigned
11/29/2005 Update or Other Action Using Figure 1 from a Water Sampling and Soil Remediation, ADOT&PF Ninilchik Maintenance Station, from Shannon & Wilson, dated December 30, 2004, in conjunction with TopoZone Pro and the KPB Parcel Lookup, entered the coordinates for this site. Metadata includes No Topo Basemap, TopoZone Pro Street Maps, Black and White Aerial Photo, on a Medium Size Map, View Scale 1:10,000, Coordinated Datum NAD83. High degree of confidence in accuracy of location. Alyce Hughey
2/16/2006 Update or Other Action Reviewed and approved S&W work GW monitoring work plan. Monitoring event tentatively scheduled for May 06. Donald Seagren
2/14/2007 Exposure Tracking Model Ranking * Not Assigned
7/5/2007 Report or Workplan Review - Other Reviewed monitoring report. B1MW contained benzene exceeding groundwater cleanup levels. Possible cross-contamination due to benzene being detected in MW and DW at low levels for the first time. Pending funding approval, wells will be sampled again to determine benzene concentrations. Annual monitoring will continue. Donald Seagren
6/17/2008 Update or Other Action Site transferred from Don Seagren to Paul Horwath per Linda Nuechterlein. Alyce Hughey
12/28/2010 Report or Workplan Review - Other Term contractor SLR's 2010 Ground Water Monitoring Report for this site, dated September 2010 was reviewed. Only GW MW B4MW was sampled and no contamination was detected in the July 2010 sampling event. Monitoring wells B1MW and B3MW were the only MWs that ever exceeded ADEC GW cleanup levels at this site. These two MWs were found to be covered with asphalt paving during the 2010 GW sampling event performed by ADEC term contractor SLR. These MWs were last sampled in 2006 and only B1MW exceeded cleanup levels at that time, at 13 ug/L benzene. The groundwater likely meets ADEC GW cleanup levels at this time, however MWs B1MW and B3MW may never be sampled again due to damage or the inability to locate them at the facility, since they are now covered with asphalt pavement. This site should be considered for site closure without the need for ICs or any further GW quality monitoring. The remaining GW MWs will need to be properly decommissioned. Paul Horwath
12/29/2010 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 77634 USTs. Paul Horwath
10/12/2011 Long Term Monitoring Complete No further soil or groundwater sampling is planned at this site at this time. Any residual contamination will continue to degrade over time, and is very unlikely to pose any unacceptable risk to any future use of the property. To reiterate the final work task associated with this project site; An ADEC Term Contractor should now be hired to locate and properly decommission the 4 groundwater monitoring wells present at this site. Two of these four monitoring wells (B1MW and B3MW) are now reportedly covered with asphalt pavement. If horizontal survey coordinates are unavailable for these two MWs, we may not be able to excavate, locate, and properly decommission these two wells. Paul Horwath
10/12/2011 Institutional Control Record Removed A State term contractor should now be hired to locate properly decommission the 4 groundwater monitoring wells present at this site. Two of the monitoring wells (B1MW and B3MW) are now reportedly covered with asphalt pavement. If survey coordinates are not available for these two MWs, we may not be able to excavate, locate, and properly decommission these two wells. Paul Horwath
4/3/2012 Update or Other Action A term contractor should be hired to properly decommission the groundwater monitoring wells. Paul Horwath
4/3/2012 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 77634 USTs. Paul Horwath
6/25/2014 Report or Workplan Review - Other Paul Horwath approved the Shannon & Wilson's June 9, 2014, Work Plan for Groundwater Monitoring Well Decommissioning for the ADOT&PF Ninilchik site. Alyce Hughey
12/10/2014 Update or Other Action All groundwater monitoring wells that could be located were decommissioned under the oversight of ADEC term contractor Shannon & Wilson in July, 2014. Paul Horwath

Contaminant Information

Name Level Description Media Comments
Benzene Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil
Benzene > Table C Groundwater Last sampling, 4 years ago in 2007, resulted in the detection of benzened in MW B1MW was 6.35 ug/L. The concentration of benzene in groundwater has clearly been decreasing over time, and likely now meets the Table C cleanup level. Howver B1MW has been paved over and is no longer available for additional water sample collection and analysis.

Control Type

Type Details
No ICs Required


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

Missing Location Data

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