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Site Report: ADOT&PF Willow Maintenance Station

Site Name: ADOT&PF Willow Maintenance Station
Address: Mile 71 Parks Highway, Willow, AK 99688
File Number: 2268.26.002
Hazard ID: 1809
Status: Cleanup Complete
Staff: ,
Latitude: 61.760806
Longitude: -150.064947
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 a 1,000-gallon heating oil tank, de minimis diesel contamination was encountered.

Action Information

Action Date Action Description DEC Staff
8/11/1993 Update or Other Action (Old R:Base Action Code = SA2R - Phase II SA Review (CS)). No Longer Assigned
9/22/1993 Site Added to Database No Longer Assigned
10/20/1993 Site Ranked Using the AHRM Initial ranking. No Longer Assigned
11/29/2006 Update or Other Action Staff transferred from Pikul to Jaynes. Aggie Blandford
6/1/2007 Update or Other Action NTP issued for Site Characterization David Allen
2/21/2008 GIS Position Updated position updated with SPAS GIS Statewide Locater Grant Lidren
9/11/2008 Exposure Tracking Model Ranking Initial ranking with ETM completed for source area id: 72787 name: auto-generated pm edit ADOT&PF Willow Maintenance Station Todd Blessing
3/26/2009 Update or Other Action DEC staff reviewed and approved Shannon and Wilson's Site Characterization and Cleanup Work Plan, dated March 12, 2009. Shannon and Wilson proposed to do the following: • Excavate contaminated soil from four areas: the former diesel and gasoline USTs, former heating oil UST, former holding tank, and dry well locations; • Stockpile excavated soil as “clean”, “potentially clean”, or “contaminated”; • Sample the on-site drinking water well and two existing wells for contaminants of concern; and • Decommission the on-site drinking water well Todd Blessing
1/14/2010 Update or Other Action DEC reviewed Shannon and Wilson's (S&W's) "Site Characterization and Cleanup, Former ADOT&PF Maintenance Station Willow, Alaska" dated December 2009. S&W excavated contaminated soil from the following areas: the former diesel and gasoline USTs, former heating oil UST, former holding tank, and dry well locations. Two soil stockpiles were generated (i.e. a potentially clean and contaminated) based on field screening results and placed on a concrete pad that is bermed with clean soil. Confirmation soil samples from each excavation confirmed that no contaminated soil remained in all excavation pits except the dry well location. This location contained levels of PCE, arsenic, DRO, and RRO at levels that exceeded 18 AAC 75.341 Table B1 and B2 values. The levels of these compounds were only detected adjacent to the former dry well. Based on these results and with DEC approval, S&W dewatered and exavated 8 additional cubic yards of contaminated material near the dry well location and place this soil on a liner adjacent to the other contaminated soil stockpile. Additional soil confirmation results from the dry well excavation pit suggested that all contaminated soil still remained near the former dry well. S&W backfilled all excavation pits with clean soil and brought each up to grade. S&W also sampled groundwater from the eight existing montoring wells and the drinking water well for contaminants of concern. Except for monitoring well MW-4, no COC's were detected above 18 AAC 75.345 Table C values in the monitoring wells and drinking water well. In monitoring well MW-4, benzene was detected at a level of 0.0245 mg/L. S&W decommissioned the drinking water well in accordance with DEC standards. Todd Blessing
6/23/2010 Site Characterization Workplan Approved DEC has reveiwed and approved of Shannon and Wilson’s “Site Characterization and Landfarming Work Plan, Former ADOT&PF Maintenance Station, Mile 71.4 Parks Highway, Willow, Alaska”. This work plan defined the means and methods to evaluate contaminant concentrations in soil and groundwater near the former excavated areas, characterize chlorinated solvent contaminated soil, and landfarm soil impacted with petroleum hydrocarbons. One monitoring well would be installed downgradient and north of the former dry well. Groundwater samples will be collected from 6 existing monitoring wells and the newly install monitoring well to be analyzed for GRO, DRO, RRO, and VOCs. Three soil samples will be collected from the 8 – cubic yard chlorinated solvent contaminated stockpile based on field screening results. These samples will be analyzed for GRO, DRO, and VOCs and potentially TCLP. Landfarmed soil will be tilled monthly and soil biodegradation will be enhanced by the addition of moisture and nutrients. Todd Blessing
3/21/2011 Site Characterization Report Approved DEC has completed a review of Shannon and Wilson's "Site Characterization and Landfarming, Former ADOT&PF Maintenance Station Willow, Alaska." This report was recieved on February 24, 2011. The report documented site characterization and landfarming activities. The levels of contaminants of concern in two soil samples collected from the sole soil boring near the former dry well did not exceed applicable cleanup values. The landfarming soil was also sampled and DRO was detected at values ranging from 1,370 to 6,170 mg/kg. Contaminants of concern were detected in three (i.e. MW3, MW4, and MW9) of the seven groundwater monitoring wells sampled. These wells were positioned at the the former heating oil tank, the former gasoline and diesel USTs, and the former dry well. Only one groundwater sample exhibited levels of contaminants of concern above DEC cleanup criteria. DRO and benzene were detected above DEC cleanup criteria in well MW-4, which was located near the former gasoline and diesel UST. Todd Blessing
5/2/2011 Update or Other Action DEC staff requested that Shannon and Wilson (S&W) continue tilling the landfarmed soil during the summer of 2011 under the current Notice to Proceed. S&W will provide a memo to DEC as a final deliverable that discussess the frequency and duration of the tilling efforts. Todd Blessing
12/1/2011 Site Characterization Report Approved DEC staff reviwed Shannon and Wilson's (S&W's) November 22, 2011 "Landfarm Tilling and Confirmation Sampling..." report. S&W documented that landfarmed soil was tilled four times in the summer of 2011. Newman’s Hilltop (Newman’s) of Willow, Alaska provided an excavator and personnel to till the soil on June 6, July 7, August 4, and August 30, 2011. A S&W representative was on site to observe the soil tilling activities. The full depth of the landfarmed soil was turned over with the excavator during each tilling event. S&W collected field screening and confirmations samples from the landfarmed soil on October 5, 2011. Fifteen soil samples were collected from the landfarm at a depth of approximately 0.5 to 0.7 foot below the landfarmed soil surface. The samples were screened for organic vapors with a photoionization detector (PID) using a headspace sampling method. The sample locations and headspace screening results are shown in Figure 1. Based on headspace results, four samples plus one field duplicate sample were collected for potential analytical testing. The sample with the highest headspace result (Sample LF-115) was analyzed for gasoline range organics (GRO) by Alaska Method 101 (AK101), DRO by Alaska Method 102, RRO by Alaska Method 103, and volatile organic compounds (VOC) by Environmental Protection Agency Method 8260B. The remaining samples were not analyzed because the results of Sample LF-115 indicated further remediation was necessary. Sample LF-115, collected from the northeast corner of the landfarm, near where the former dry well stockpile was incorporated into the landfarm cell, contained an J-flagged estimated concentration of 1.18 mg/kg GRO, 1,720 mg/kg DRO, 3,610 mg/kg RRO, and J-flagged estimated concentrations of six VOC constituents (0.00899 mg/kg toluene, 0.00924 mg/kg 1,4¬dichlorobenzene, 0.0199 mg/kg 1,3,5-trimethylbenzene, 0.0180 mg/kg naphthalene, 0.0367 mg/kg xylenes, and 0.0379 mg/kg 1,2,4-trimethylbenzene). The DRO concentration is greater than the most stringent ADEC Method 2 cleanup criterion (18 AAC 75.341, October 2011). Based on the results of Sample LF-115, the DRO concentrations in the landfarm have decreased, but remain above the ADEC cleanup criterion. Todd Blessing
1/4/2012 Update or Other Action DEC issued a request for proposal to three term contractors to till landfarmed soil on a monthly basis from May until October 2012, decommission up to nine groundwater monitoring wells, and analyze groundwater from monitoring well MW-4 for contaminants of concern to evaluate whether the site can be closed. Todd Blessing
3/22/2012 Update or Other Action Exposure tracking model ranking updated. Todd Blessing
4/3/2012 Report or Workplan Review - Other DEC staff reviewed and approved of Shannon and Wilson Inc.'s work plan titled "Work Plan For Site Characterizartion at The Former ADOTIPF Maintenance Station, Mile 71.4 Parks Highway Willow, Alaska. The work plan was dated April 03, 2012 and discusses the decommissioning of nine groundwater monitoring wells, sampling monitoring well MW-4, landfarming soil during the summer, and sampling the landfarm area during the fall 2012. Todd Blessing
4/2/2013 Update or Other Action Updated database to reflect correct RP/Landowner Jacob Gano
6/6/2013 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 72787 Leaks from floor drains and dry well. Jacob Gano
6/14/2013 Cleanup Complete Determination Issued Jacob Gano

Contaminant Information

Name Level Description Media Comments
DRO Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil

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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