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Site Report: Dutch Hbr-Humpy Cove Power Plant UST

Site Name: Dutch Hbr-Humpy Cove Power Plant UST
Address: Mile 8, Summer Bay Road, Unalaska Island, Unalaska, AK 99685
File Number: 2542.38.013
Hazard ID: 3066
Status: Active
Staff: Kathleen Iler-Galau, 9074512153 kathleen.iler-galau@alaska.gov
Latitude: 53.899568
Longitude: -166.431990
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

Diesel contaminated soil at the Power Plant UST area. This area is used for subsistence food gathering and fishing. The UST located at the former Power Plant was uncovered 28 July 1998, approximate capacity 1600 gallons. The UST was removed and disposed offsite. 540 cy of impacted soil were transported offsite for treatment. The vertical limits of POL contaminated soil extended to groundwater and DRO contaminated soil remains in place immediately above the groundwater table. The maximum concentration remaining is 11,000 mg/kg DRO. This site was the location of Fort Brumback and was a tactical artillery area during WWII. It included troop housing, a mess hall, latrines, power generation facilities, a dispensary and utilities. The U.S. Army Corps of Engineers had a contractor demolish and landfill the buildings and remaining debris in the mid - late 1980s. Underground fuel tanks were abandoned in place. In the mid- 1990's the Corps of Engineers initiated further site investigation work to locate and address any remaining military contamination or sources of contamination.

Action Information

Action Date Action Description DEC Staff
8/25/1999 Interim Removal Action Approved ADEC received the final report titled "1998 SI, RI, IRA Amaknak and Unalaska Islands" dated August 1999, by Jacobs Engineering. The report documents site investigation work, locating buried fuel tanks at the former mess hall, dispensary, power plant and two latrines. The fuel, tanks and contaminated soil were excavated. Contaminated soil was thermally treated in Unalaska. A fifth UST was located but not removed due to the isolated location and inability to remove it. Three of the four sites where tanks were removed have residual soil contamination at levels higher than ten times the method two migration to groundwater levels and soil was excavated to the water table. Visible groundwater contamination was present in two excavations. Well points were installed, but subsequent water level measurements indicate they may not be downgradient. Further investigation and possibly cleanup are needed. John Halverson
11/29/1999 Site Added to Database Diesel contaminated soil. John Halverson
12/14/1999 Site Ranked Using the AHRM Initial ranking by staff. John Halverson
12/15/1999 Site Ranked Using the AHRM Reranked. Changed GW Exposure Index Value to 0 because SW Usage Value = 0.2. John Halverson
2/11/2000 Update or Other Action Staff reviewed and commented on the draft Comprehensive Remedial Investigation Report for Amaknak and Unalaska Islands, dated December 1999. The report evaluated cleanup levels for this area using an assumption that groundwater is not a potential future drinking water source, however, the necessary steps to make such a determination have not been undertaken. ADEC requested the report be revised to consider groundwater as a drinking water source or that steps in 18 AAC 75.350 be addressed. Further groundwater monitoring was recommended and is necessary. John Halverson
6/5/2000 Site Characterization Report Approved ADEC received the final Comprehensive Remedial Investigation Report, dated May 2000, by Jacobs Engineering under contract to the Corps. Humpy Cove Mess Hall UST - a 300 gallon heating oil tank and ~200 cubic yards of diesel contaminated soil were removed. Contaminated soil was removed to a depth of 26 feet below the ground surface (bgs). Contaminated soil was thermally treated off-site. A sample from 26' bgs contained 400 mg/kg DRO. Sidewall samples met the cleanup levels. Approximately 50 cubic yards of soil used to backfill the excavation contained up to 890 mg/kg DRO. An alternative soil cleanup level, based on the migration to groundwater pathway, may be proposed later. Dispensary UST - a 680 gallon UST and ~430 cubic yards of contaminated soil were removed. DRO contaminated soil extended to the water table with the highest concentration measured being 7100 mg/kg at ~13' bgs. Groundwater was encountered at 13' bgs. Three well points were installed and sampled; no groundwater contamination was found above the Table C levels, however, none of the well points were directly downgradient from the source area. Additional groundwater monitoring is planned. Power Plant - a 1600 gallon UST and ~540 cubic yards of petroleum contaminated soil were removed. Diesel range organics (DRO) contaminated soil extends to the water table at ~14' bgs. A soil sample from 14' bgs contained 11,000 mg/kg DRO. Well points installed at the site did not contain contaminants above regulatory levels, however, no well points were installed within or directly downgradient of the source area. Further groundwater characterization is recommended. Latrine #3 - a 300 gallon UST and ~35 cubic yards of petroleum contaminated soil were removed. Soil containing up to 3,800 mg/kg DRO was used to backfill the excavation. Confirmation samples collected from the limits of the excavation contained up to 3,400 mg/kg DRO at a depth of 9' bgs. Groundwater characterization is recommended. Latrine #1 - a UST estimated to be ~300 gallons in capacity, was located about 250' up a vegetated hillside from the road. A soil sampled collected from ~5' bgs and 5' downhill from the tank contained 10,000 mg/kg DRO. Another sample collected about 10' further downhill and 5' bgs did not contain measurable DRO. The tank was emptied and left in place due to limited access (would need to cut in a road). The report recommends in-place closure of this UST. John Halverson
9/5/2001 Update or Other Action DEC received the final 2000 Island-wide SI/IRA/RI Report for Amaknak/Unalaska Islands, dated August 2001, by Jacobs Engineering. It documents the following work in the Humpy Cove area: Power Plant site - one soil boring was drilled to 24.5' and did not encounter water. A second boring was drilled to ~30' and groundwater rose to ~21.5' bgs in the well. Field screening indicated contaminated soil between 18 and 30' bgs. The water sample from MW1 did not contain measurable levels of DRO and only 640 ug/l RRO. The report recommends no further action with institutional controls. Dispensary - two soil borings were drilled to refusal at ~11' bgs, no water was observed in either and the borings were backfilled. The report recommends no further action. Latrine 1 - a soil boring was installed to 28.5' bgs. The boring was dry, but a MW was installed. The well remained dry in September and October, but did contain water in December. A water sample from the well contained 230 ug/l DRO and PAHs below applicable cleanup levels. The UST was emptied and filled with gravel. The report recommends no further action. Latrine #3 - two soil borings were installed to 8 and 9 feet bgs. Neither well encountered water or evidence of soil contamination. A soil sample from 7.5' bgs contained only 2.9 mg/kg DRO. The report recommends no further action. John Halverson
1/23/2003 Update or Other Action Humpy Cove expanded into five unique sites from one. John Halverson
11/21/2003 GIS Position Updated Using TopoZone, NAD 27. Debra Caillouet
12/8/2003 Site Number Identifier Changed Changed Reckey to reflect date the tank was pulled. Old Reckey was 199925X120601. Former Staff
6/10/2005 Update or Other Action File number issued 2542.38.013. Aggie Blandford
6/3/2008 Exposure Tracking Model Ranking Initial ranking with ETM completed. Jill Taylor
9/14/2010 CERCLA Proposed Plan ADEC received Proposed Plan # 8 which addressed the Summer Bay Management Area 13. The plan recommends Alternative 2 (Corrective Action Complete/Cleanup Complete with ICs)for the Power Plant becuase the primary and secondary sources of contamination were removed to the extent practicable and remaining contamination does not appear to be migrating to groundwater. Meghan Dooley
10/14/2010 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 74041 1600 Gal UST. John Halverson
8/13/2019 Update or Other Action Site location was updated on this date. Coordinates for this site are used to determine the presence and position of the site on BLM’s ANCSA Conveyed Land web map. Rebekah Reams
10/27/2023 Document, Report, or Work plan Review - other On this date, DEC reviewed the Site Investigation Visit Technical Memorandum: CON/HTRW, Limited Removal Action, Amaknak FUDS for the Summer Bay-Humpy Cove Power Plant UST, and Little South America Latrine 1 UST and Mess Hall sites. This tech memo is a field visit work plan with limited sampling to guide the 2024 field work and removal actions at the three sites. Cascade Galasso-Irish
3/27/2024 Document, Report, or Work plan Review - other DEC reviewed and provided comments on the Draft Work Plan, CON/HTRW Limited Removal Action, Amaknak FUDS F10AK0841-15, Summer Bay-Humpy Cove, and Amaknak FUDS F10AK0841-20 Little South America, Unalaska, Alaska, dated March 2024. The work plan describes the project approach and methods to be used while conducting environmental removal actions at select Amaknak Formerly Used Defense Sites (FUDS) on Unalaska and Amaknak Islands, Alaska during the 2024 field season. Sarah Bernhardt

Contaminant Information

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Control Type

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