| Action Date |
Action |
Description |
DEC Staff |
| 8/23/1993 |
Update or Other Action |
Site Assessment report received. On July 17. 1993. Oil Spill Consultants performed a site assessment and collected samples during the removal of an underground storage tank (UST) at Building 956 located at Fort Richardson. Alaska. Fort Richardson is owned by the United States Federal Govemment and is under the United States Department of Defense.
Mr. Randy Easley (Senior Engineer for Oil Spill Consultants) collected three samples from the
soil which previously contained the UST at Building 956. One sample was collected from the
soil overburden. One background sample was also collected. These samples were submitted to Commercial Testing & Engineering Co. (formerly Chemical & Geological Laboratories of Alaska) for diesel range hydrocarbon and total petroleum analysis using EPA Methods 8100M and 418.1. respectively.
The laboratory results indicate that the soil under and around the UST is heavily contaminated
with diesel range hydrocarbons. These results are supported by the strong petroleum hydrocarbon odor emitted as the soil was excavated. Additionally. the soil under the UST appeared to be saturated with diesel fuel.
Under guidelines published by the Alaska Department of Environmental Conservation. the maximum allowable level of diesel range hydrocarbons (from a spill or leak) that can remain without cleanup is 2,000 mg/kg. Since the diesel range hydrocarbons were 12,400 mg/kg in the soil under the UST for Building 956, cleanup is required.
It is recommended that the following steps be implemented for Building 956:
- Perform additional site sampling to identify the extent of ground contamination.
- Excavate all contaminated soil. ('Ft'fe soil should be placed on a 20 mil plastic liner be and covered as required by the Alaska Department of Environmental Conservation.)
- Backfill the excavated area with clean soil.
Visual inspection and laboratory analysis indicate the soil under and around the storage tank
for Building 956 is significantly contaminated with petroleum hydrocarbons. The Alaska
Department of Environmental Conservation has established 2,000 mg/kg as the maximum level of diesel range hydrocarbons that can remain in soil from leaking underground storage tanks without any cleanup actions. Since the diesel range hydrocarbon contamination for the Building 956 tank ranges from 1,370 to 12,400 mg/kg, cleanup action is required for the excavation created by tank removal.
The diesel range hydrocarbon level for the soil stockpile created during the excavation was 556 mg/kg. By comparison, it was 95.4 mg/kg for the project background sample. In view of this, it is recommended that the excavated soil be cleaned using procedures approved by the State of Alaska.
The total petroleum hydrocarbon (TPH) for the project samples ranged from 1,370 to 17,800 mg/kg with the maximum level in the soil one foot below the tank impression. The TPH level for the background sample was 2,690 mg/kg.
In view of the heavy petroleum contamination resulting from the UST at Building 956, soil
cleanup is required.
|
John Halverson |
| 9/21/1993 |
Update or Other Action |
A.G. letter (Breck Tostevin) to Tamela J. Tobia, OS Judge Advocate for the Army. Letter states that a separate petroleum site compliance agreement should be separate from the CERCLA federal facility agreement. The petroleum site restoration agreement would function as a "two-party agreement" under the FFA. It would track the basic provisions of the UST Agreement but be tailored to the State's contaminated site regulations and would interface with the FFA. All petroleum sites addressed under the Two Party agreement would be reviewed in the final operable unit of the FFA and actions taken would be memorialized in a Record of Decision (ROD) under the FFA. |
Louis Howard |
| 11/22/1993 |
Update or Other Action |
Notice of Release Letter sent.
Notice of Release/Request for Corrective Action, Building #956, UST #104 Facility IDN: 788 Spill #: 93-2-1-00-306-61
On November 2, 1993, our office received a site assessment report stating diesel range
petroleum hydrocarbon contaminated soil was discovered during closure of an underground storage tank (tank #104) located at building #956 at Fort Richardson. The tank was registered as a regulated underground storage tank and a closure notice was submitted to the Department, however, it appears the tank may not be regulated under 18 AAC 78. Please check your records to determine whether the cleanup will be conducted under Alaska's Oil and Hazardous Substance Pollution Regulations (18 AC 75) or Alaska's Underground Storage Tank (UST) Regulations (18 AAC 78).
In either case, it appears the Army did not notify the Department of the release in a timely
manner. Please note, according to state regulations most releases must be reported within 24
hours of discovery. In this case, the tank was removed on July 17, 1993 and no spill report
was submitted until the site assessment report was received on November 2, 1993. The
closure notice we received in June indicates USTs were also being removed at buildings 979,
952 and 756.
To date we have not received site assessment reports or notification of releases for these closures. Please note, according the recently signed UST Compliance Agreement, site assessment report are to be submitted within 60 days of completion of site assessment field work. The Department requests submittal of site assessment reports and any necessary release notifications as soon as possible, since this appear to be in violation of the regulations
and the compliance agreement.
Tank #104 was registered as an UST, thus this letter outlines requirements under 18 AAC 78
and the compliance agreement between the Amy and the Alaska Department of Environmental Conservation (ADEC).
In accordance with 18 AAC 78.220, within 24 hours of discovering a release the owner or
operator must report the release to the Department, take immediate action to prevent further
release and identify and reduce fire and safety hazards. In addition to reporting the release,
the owner or operator of the UST must perform Initial Abatement and a Site
Assessment/Release Investigation, in accordance with 18 AAC 78.230.
Enclosed is a Site Assessment/Release Investigation Summary Form to further assist you in
conducting work and reporting the required information. The compliance agreement contains
a schedule for submittal of additional work plan. According to that schedule, a draft release
investigation plan should be submitted by no later than March 2, 1994. The release investigation plan should include a schedule for implementing the field work.
In addition, upon confirmation of a petroleum release, the owner or operator of the UST
must undertake Corrective Action in accordance with 18 AAC 78.240.
Many of the corrective action requirements should conducted during the release investigation,
thereby allowing for development and implementation of a remedial action plan during the
next phase of the project.
Please include the facility name, facility ID number and the spill number as shown at the top
of this letter in all future correspondence and submit reports to:
Alaska Dept. of Environmental Conservation
Southcentral Regional Office
3601 C Street, Suite 1334
Anchorage, AK 99503
Attn: John Halverson
Based on the information that will be submitted, the Department may request additional
information and/or work plans which are determined necessary to respond to this release.
Enclosed are copies of a Preliminary Risk Evaluation Form, and a Site Assessment/Release
Investigation Summary Form to help you address this release. You will help satisfy both
state and federal regulations by following the requirements outlined above. |
John Halverson |
| 11/23/1993 |
Site Added to Database |
Diesel range petroleum hydrocarbon contamination. |
Louis Howard |
| 6/3/1994 |
Update or Other Action |
Site Assessment Report for UST 104 received. EMCON Alaska, Inc. (EMCON) was retained by the U.S. Anny Engineer District, Alaska (COE), under Delivery Order No. 0007, Contract No. DACA85-93-D-0013, to conduct a subsurface investigation in support of Release Investigations in the vicinity of former underground storage tank (UST) 104 at Building 956, Fort Richardson, Alaska.
The proposed soil boring locations were selected to define the vertical & horizontal extent of impact associated with UST 104. 8 soil borings were advanced & sampled at 5’ intervals beginning at the surface to a maximum depth of 32’ bgs. GW was not encountered during drilling. Soil samples were collected from the borings & submitted for lab analysis. Selected soil samples collected during the 1994 sampling program were analyzed using EPA Methods 8260 for VOCs, EPA 8100 Modified for DRO, EPA Method 9060 for total organic carbon (TOC), & for biofeasibility parameters.
Proposed cleanup levels for site soil were obtained for VOCs (other than petroleum hydrocarbons) from the EPA Region 10 Risk-Based Cleanup Levels (EPA, 1992). The proposed cleanup levels for BTEX, GRO, DRO, & RRO were based on the Matrix Score Sheet provided in the ADEC "UST Regulations" (ADEC, 1991).
Based on the results of the February 1994 investigation at this site in the vicinity of former UST 104, remaining site soils exceed ADEC cleanup criteria for petroleum hydrocarbons. EMCON conducted an exposure assessment for the development of alternative cleanup levels (ACLs) using the EPA numerical leaching model multimedia contaminant fate, transport, & exposure model (MMSOILS).
Results of the assessment indicate that the potential for human & ecological receptors to be exposed to contaminants in the impacted zone located at Building 956 is very low. The results of the assessment & the findings of the release investigation indicate that GW is not being influenced by DRO present in the contaminated zone at this site.
The cooler temperature (6.3°C) for the cooler containing samples 94FRU187SL, 94FRU189SL, 94FRU190SL, 94FRU193SL, 94FRU195SL, 94FRU206SL, 94FRU208SL, 94FRU200SL, 94FRU202SL, 94FRU201SL, & 94FRU711RB exceeded the recommended 4°C requirement. All samples, except 94FRU201SL, were analyzed for EPA Method 8100M (DRO), & samples 94FRU206SL & 94FRU201SL were also analyzed for ASTM Method D4129-82 Modified for TOC, & EPA Methods 350.3M, 351.4M, 353 .2M, 365.3M, & 9045 for inorganics. EPA Method 305.1 for ammonia ion salicylate was requested for samples 94FRU206SL & 94FRU201SL, but not analyzed.
All results were non-detect for these target analytes except for DRO in samples 94FRU187SL (16,000 mg/kg), 94FRU206SL (6,000 mg/kg), & 94FRU200SL (252 mg/kg). Low concentrations of DRO may not have been detected due to the elevated cooler temperature. The cooler temperature (15 .7 °C) for the cooler containing samples 94FRU298SL & 94FRU300SL also exceeded the recommended requirement. These samples were analyzed for EPA Method 8100M (DRO) & EPA Method 8270 (semi-volatiles). All analytical results were reported as non-detect. Low concentrations of DRO may not have been detected due to the elevated cooler temperature.
15 soil samples were submitted from the 8 borings for DRO analysis. Five samples contained detectable levels of DRO. The levels ranged from 5.4 mg/kg in sample 94FRU257SL to 16,000 mg/kg in sample 94FRU187SL [AP3377(FRU-30)] at approximately 15’ bgs. Detected DRO concentrations exceeded the ADEC soil target cleanup level of 1,000 ppm in two samples (94FRU206SL & 94FRUI87SL). 94FRU206SL is AP-3378 (FRU-31) sample results for DRO were 6,000 mg/kg at approximately 15’ bgs.
Based on the results of this subsurface investigation, the investigation at Building 952 (approximately 400’ NE of this site), & the modeling results, potential impacts to GW are unlikely. GW at Building 952 was encountered at approximately 144’ bgs, & the analytical information collected in April 1994 indicated that VOCs, & metals were not detected in the GW. DRO were detected in GW at Building 952 at 140 ug/L. No GW was encountered during subsurface investigation at Building 956.
The results of the modeling conducted at Building 952 & 956 indicate that the impacted soils identified at these buildings would not be expected to impact GW through hydraulic loading. The depth to GW for Building 956 was assumed to be approximately 145’ bgs based on the depth to water observed in monitoring well AP3375, which is located near building 952.
EMCON recommends that remedial action not be performed at this site and that the site
be considered for closure. |
Louis Howard |
| 6/16/1994 |
Update or Other Action |
Release investigation - Soil samples taken during removal contained diesel range organics (DRO) ranging up to 12,100 milligrams per kilograms (mg/kg). Eight (8) soil borings were installed at the site in 1994 as part of a release investigation. Samples from these borings, advanced to 32 feet below ground surface, contained DRO at up to 16,000 mg/kg. A soil leaching potential assessment was conducted and indicated that contamination at this site would not pose a risk to groundwater at the site. |
Louis Howard |
| 7/25/1994 |
Institutional Control Record Established |
ICs are required since level of soil contaminated with petroleum is above those levels which would allow for unrestricted use. Dig permit required for any soil activity in area managed by Public Works Environmental staff. Area noted on Post Management plans and maps as an area requiring ICs and waste management and disposal at a permitted facility if soil were to be excavated at any time in the future. |
Louis Howard |
| 7/25/1994 |
Conditional Closure Approved |
Jennifer Roberts sent letter to Army-RE: June 1994 Draft Release Investigation report, Building 956, Former UST 104 Contract No. DACA85-93-D-0013 Delivery Order No. 0007.
ADEC has received on June 16, 1994, a copy of the referenced report. ADEC will consider tank 104 closed out based on the data and conservative assumptions used in the leaching model analyses presented in the report. For your information, ADEC is currently using the SESOILS model to evaluate leaching assessment models. Closing out this site does not preclude ADEC from requesting further remediation or site investigation at a later date. If new information indicates that previously undiscovered contamination or exposures lead to groundwater contamination above the applicable water quality criteria (18 AAC 70) or pose a risk to human health, wildlife or the environment, then future investigation and/or remedial actions will be required by ADEC. |
Louis Howard |
| 7/25/1995 |
Document, Report, or Work plan Review - other |
Staff reviewed and commented on the June 1994 Draft Release Investigation report, Bldg 956, Former UST 104 Contract No. DACA85-93-D-0013 Delivery Order No. 0007
The Alaska Department of Environmental Conservation-Defense Facilities Oversight group (ADEC)
has received, on June 16, 1994, a copy of the above referenced report. ADEC will consider tank
104 closed out based on the data and the conservative assumptions used in the leaching model
analyses presented in the report. For your reference, ADEC is currently using the SESOILS model
to evaluate leaching assessment models.
Closing out this site does not preclude ADEC from requesting future remediation or site investigation at a later date. If new information indicates that previously undiscovered contamination or exposures lead to groundwater contamination above the applicable water quality criteria (18 AAC 70) or pose a risk to human health, wildlife or the environment, then future investigation and/or remedial actions will be required by ADEC. |
Jennifer Roberts |
| 4/21/1998 |
Site Ranked Using the AHRM |
Ranking action added now because it was not added when the site was originally ranked. |
Bill Petrik |
| 9/14/2001 |
Update or Other Action |
Institutional controls report received for several sites which include this building. DRO was detected up to 16,000 mg/kg, a leachability study was used to obtain site closure (NFA actually). This closure does not preclude future remediation or site investigation if new information indicates there is previously undiscovered contamination or exposures which cause an unacceptable risk to human health or the environment. ADEC requests any monitoring wells installed as a part of the investigation be added to the Post-wide monitoring network established under the CERCLA Federal Facility Agreement. ICs tracked under Fort Richardson Master Plan (GIS). |
Louis Howard |
| 9/28/2001 |
Update or Other Action |
Staff commented on the ICs report which included this site. ADEC does not concur that the Army does not need to conduct a five-year review for this site. Hazardous substances remain above levels that would allow for unlimited use and unrestricted exposure. Please refer to the potential leaching assessment included in the Draft Release Investigation Report June 1994 where the Army proposed an alternative cleanup level for diesel range organics at 16,000 mg/kg. ADEC concurred with the proposed cleanup level on July 25, 1994. As an alternative cleanup level, ADEC expects the Army to impose institutional controls upon the contaminated soils at the site to reduce exposure of workers to contamination at the site.
Also, ADEC expects any excavated soils, which are contaminated to be treated and disposed of in accordance with 18 AAC 78 Underground Storage Tank regulations. Hazardous substances remain at the site above levels, which would allow for unlimited use and unrestricted exposure.
A review will need to be conducted within five years after commencement of the remedial action to ensure that the remedy continues to provide adequate protection of human health and the environment. |
Louis Howard |
| 12/12/2001 |
Update or Other Action |
1. All organizations conducting activities on United States Army Alaska (USARAK) controlled land are responsible for complying with established institutional controls (ICs). ICs are administrative, procedural, and regulatory measures to control human access to and usage of property. They are applicable to all known or suspected contaminated sites where contamination has been left in place.
2. These controls have been established to implement the selected remedial actions agreed upon by the U.S. Army (Army), the U.S. Environmental Protection Agency (USEPA), and the Alaska Department of Environmental Conservation (ADEC) in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) as amended by the Superfund Amendment Reauthorization Act (SARA). These controls also apply to remedial actions agreed upon under Two-Party Compliance Agreements. These agreements are concluded between USARAK and ADEC and apply to petroleum/oil/lubricants- (POL) contaminated sites.
3. ICs such as limitations on access, water use, excavations, and property transfers will supplement engineering controls as appropriate for short-term and long-term management to prevent or limit human and environmental exposure to hazardous substances, pollutants, or contaminants. Specific ICs include, among other things: limitations on the depth and location of excavations, prohibition of or restrictions on well drilling and use of ground water, requirements for worker use of personal protective equipment, site monitoring, and prohibition of certain land uses, types of vehicles, etc.
4. Organizational units, tenants, and support/contractor organizations must obtain an Excavation Clearance Request (ECR) for all soil disturbing activities impacting soils six inches or more below the ground surface. The review process for approval of an ECR begins with the identification of the current status (known or suspected hazardous waste site or “clean” site) of a work location. ECR’s for work in known or suspected hazardous waste sites:
a. will include specific limitations and controls on such work;
b. will include specific IC procedures, and notification, monitoring, reporting, and stop work requirements;
c. may include procedures for management, characterization, and disposal of any soil or groundwater encountered or removed;
d. will identify “project managers” for both the unit/contractor requesting the work and DPW Environment Resources.
5. The DPW project manager will conduct on-site inspections of each work site (at which ICs apply) to determine continued compliance with the terms and conditions of the approved ECR. DPW has the authority to revoke ECR approval if the specified terms and conditions are not being met. ECR forms are available at the Customer Service Desks at: a. Building 730 at Fort Richardson; b. Building 3015 at Fort Wainwright; c. Building 605 at Fort Greely.
6. USARAK has negotiated (with USEPA and/or ADEC) decision documents and/or Records of Decision (RODs) that mandate the implementation of ICs USARAK Directorate of Public Works, Environmental Resources Department (PWE), maintains copies of all decision documents and RODs requiring ICs in its real property files. PWE provides regularly updated post maps showing all areas affected by ICs. These maps can easily be accessed by using an approved intranet mapping interface application. Copies of these maps will be available to each directorate, activity, and tenant organization. To ensure the effectiveness of ICs, all organizational units and tenant activities will be informed on an annual basis of ICs on contaminated soils and groundwater in effect near their facilities.
7. ICs are enforceable by the U.S. Environmental Protection Agency (USEPA) and the Alaska Department of Environmental Conservation (ADEC). Failure to comply with an IC mandated in a decision document or ROD will violate the USARAK Federal Facility Agreement and may result in stipulated fines and penalties. This does not include the costs of corrective actions required due to violation of an established IC.
|
Louis Howard |
| 8/30/2007 |
GIS Position Updated |
61.2664 N latitude -149.6943 W longitude |
Louis Howard |
| 6/11/2013 |
Exposure Tracking Model Ranking |
Initial ranking with ETM completed for source area id: 72769 name: auto-generated pm edit Ft. Rich Bldg. 956 UST 104 |
Louis Howard |
| 8/1/2013 |
Update or Other Action |
Draft UFP-QAPP received for review and comment.
The overall objective for the site is to meet “unrestricted or residential site use” criteria and achieve a “cleanup complete without institutional controls (ICs)” determination. To meet this objective, soil samples will be collected to characterize risk to human health and the environment within the framework of the ADEC site cleanup process (Title 18 Alaska Administrative Code Chapter 75 [18 AAC 75] Sections 325 to 390 and 18 AAC 78 Section 600) (ADEC, 2012a; ADEC, 2012b).
If 18 AAC 75 Method Two criteria are exceeded, the Hydrocarbon Risk Calculator (HRC) approach under Method Three will be used to assess whether site conditions meet ADEC risk criteria (in which case, a “cleanup complete without ICs” determination will be requested) or whether the site poses unacceptable risk (in which case, further remediation may be required).
If unacceptable risk is indicated by the HRC or if vadose zone soils exceed maximum allowable concentrations, then remedial options will be evaluated that address the contaminants of concern and associated exposure routes that contribute enough risk to cause the cumulative
risk estimate to exceed the risk standard.
One boring will be drilled at former location AP-3377 to resample the soil at the location and
depth where previous sampling showed exceedances of the migration to groundwater criteria
for DRO and to collect source area soil samples for PAHs, VPH, and EPH analysis.
?
One boring will be drilled west of former sample 93FRB956-RB-14-1 to assess the lateral
extent of contamination.
?
Up to approximately 10 primary soil samples will be collected and analyzed for GRO, DRO,
RRO, PAHs, and petroleum-related VOCs (BTEXN). One of the soil samples will also be analyzed for EPH and VPH. One of the soil samples will be analyzed for soil bulk density, grain size distribution, specific gravity, and soil moisture content. One of the soil samples will be collected from below the contaminated soil source and analyzed for foc.
?
If either boring is drilled to groundwater, a groundwater sample will be analyzed for
petroleum-related VOCs, GRO, DRO, RRO, PAHs, VPH, and EPH. |
Louis Howard |
| 8/12/2013 |
Document, Report, or Work plan Review - other |
Staff provided review comments on the draft UFP-QAPP
WS #17 Sampling Design & Rationale
Results of the HRC calculations for petroleum hydrocarbons are applicable only for those alternative cleanup levels allowed by regulation for Method Three - 18 AAC 75.340(e):
Under method three, a responsible person may propose a site-specific alternative cleanup level that modifies
(1) the migration to groundwater or inhalation levels in Table B1 of 18 AAC 75.341(c) or Table B2 of 18 AAC 75.341(d), based on the use of approved site-specific soil data, & the equations set out in the department’s Cleanup Levels Guidance, dated June 9, 2008, adopted by reference; the alternative cleanup level that then applies at the site for a hazardous substance is the most stringent of the Table B1 direct contact or Table B2 ingestion level & the site-specific calculated levels for inhalation or migration to groundwater;
(2) the migration to groundwater levels in Table B1 or Table B2 based on approved site-specific soil data & an approved fate & transport model that demonstrates that alternative soil cleanup levels are protective of the applicable groundwater cleanup levels under 18 AAC 75.345 if the alternative migration to groundwater cleanup level does not exceed
(A) the direct contact level in Table B1 or the ingestion level in Table B2;
(B) the inhalation level in Table B1 or Table B2; or
(C) a site-specific inhalation level calculated under (1) of this subsection; the level that applies at the site is the most stringent level; or
(3) the direct contact level or the inhalation level in Table B1 or the ingestion level or the inhalation level in Table B2 based on use of commercial or industrial exposure parameters listed in Appendix B of the Cleanup Levels Guidance, adopted by reference in (1) of this subsection, if the department determines that the site serves a commercial or industrial land use, & if the alternative direct contact level or inhalation level does not exceed the migration to groundwater cleanup level in Table B1, the alternative ingestion level or inhalation level does not exceed the migration to groundwater cleanup level in Table B2 or the alternative level does not exceed a site-specific migration to groundwater level calculated under (2) of this subsection.
The Site Cleanup Rules for Method Three do not allow for changes to Table C groundwater cleanup levels or calculation of risk based groundwater cleanup levels (“exposure point concentrations”). ADEC will not recognize the use of HRC for calculation of risk of groundwater contamination at TU074 or any site on JBER-E or JBER-R, except through the use of Method Four [risk assessment as allowed by 18 AAC 75.325(h)].
Therefore, Table C Groundwater Cleanup levels will apply at all JBER sites with no alternative or “risk-based” groundwater cleanup levels allowed via Method Three (e.g. HRC). Where the HRC guidance & user manual conflict with existing promulgated regulations, the regulations will be applicable & supersede or override any guidance, manuals or technical memoranda.
Site Specific Sampling Plan
JBER may collect one foc soil sample for whatever purpose it desires, however, the results for the one foc sample may not be used to derive any cleanup level under the Site Cleanup Rules (Method Three or Method Four). WS #15 states that the foc samples will be collected & analyzed in accordance with ADEC Technical Memorandum 08-002, Guidelines for Total Organic Carbon (TOC) Sample Collection & Data Reduction for Method Three & Method Four (ADEC, 2008).
If JBER is proposing using the foc data for Method Three or Method Four, then the 2008 ADEC Guidelines for TOC Sample Collection must be followed.
For example:
4) TOC samples must be collected from a minimum of four (4) borings or test pits adjacent to but outside of the zone of contamination. Soil type(s) analyzed for TOC must be representative of the impacted soil type(s). It is recommended that the sampling locations be selected at points surrounding (on each side of) the contaminated zone to ensure adequate characterization of the soil TOC variability. If the zone of contamination extends over a significant area, additional samples may need to be collected from the soil horizon below the impacted soils.
Please refer to the TOC sampling guidance for additional requirements. |
Louis Howard |
| 7/21/2014 |
Update or Other Action |
Draft SC Report received for review and comment.
The NAPL source area at Building 956 associated with former UST 104 is defined by DRO
concentrations above screening levels. Current data indicate DRO within the soil source area
ranges up to 5,370 mg/kg and covers a lateral extent of approximately 40 by 50 feet (Figure 4-3).
Sample results from within the former tank footprint that were collected in 1993 and 1994 are
not considered representative of current conditions because they are more than 19 years old and
the former tank footprint was re-sampled in 2013. The highest concentration representative of
current conditions was recorded in boring TU074-SB06 (located within the former excavation
footprint) at a depth of 25 to 30 feet bgs. Contamination extends from 10 to 30 feet bgs
(Figure 4-6) for a total of approximately 40,000 cubic feet (1,500 cubic yards) of impacted soil.
No other compounds were detected above screening levels. Data indicate that contamination has not reached groundwater. Groundwater was measured at approximately 138 feet bgs (greater than 105 feet below the depth of contamination at Building 956) based on groundwater sampling conducted in November 2013 at monitoring well AP-3375 (located approximately 400 feet north-northeast of Building 956 at Building 952).
A nondetect (reported at the LOD) above the project screening level was reported for one result for benzene in soil at Building 956. This sample had a low percent solids (Table 4-6). In 2013,
12 samples (including three duplicates) were submitted from the three TU074 source areas; of
these, nine had nondetect results with LODs below the project screening level. Benzene has not
been detected in any samples from the historical or 2013 site characterization samples and is not
considered a COPC.
The NAPL source area at Building 956 associated with former UST 104 is defined by DRO
concentrations above screening levels. Current data indicate DRO within the soil source area ranges up to 5,370 mg/kg and covers an area of approximately 40 by 50 feet. Contamination extends from 10 to 30 feet bgs for a total of approximately 1,500 cubic yards of impacted soil. No other compounds were detected above screening levels.
The potential future indoor air exposure pathway (vapor intrusion) is considered insignificant
because volatile petroleum-related compounds in soil were not detected above the most stringent 18 AAC 75.345 Table B1 cleanup levels. |
Louis Howard |
| 5/21/2015 |
Cleanup Complete Determination Issued |
Cleanup complete determination provided for TU074. The cleanup level for soils at TU074 containing DRO is 10,250 mg/kg in the Under 40-inch Zone based on the ingestion pathway within the 0 to 15’ interval below ground surface (bgs). The cleanup level for soils at TU074 containing GRO is 1,400 mg/kg in the Under 40-inch Zone based on the maximum allowable concentration, ingestion & inhalation pathways within the 0 to 15’ interval below ground surface (bgs).
Based on the analytical data for soil samples collected, leachability study results, GW samples collected, depth to GW, modeling using the Hydrocarbon Risk Calculator (HRC), the residual GRO & DRO contamination in soil does not pose a migration to GW concern. The HRC was used to evaluate risk from petroleum contamination at TU074. The HRC is designed for sites with petroleum contamination—specifically the petroleum fractions, BTEX, PAHs, & other compounds dissolved in petroleum—with the intention & purpose of assessing human health risk from this type of contamination. In 2014, a follow-up soil gas study was conducted & the results of the study show no vapor intrusion risk for both residential & industrial scenarios is insignificant. Concentrations of 2-methylnaphthalene in soil gas at 8’ bgs are below ADEC’s shallow soil gas target levels, well-oxygenated soil & the presence of elevated CO2 levels indicate that the subsurface conditions are sufficient to support biodegradation & attenuation of 2-methylnaphthalene.
Based on a review of the environmental records, ADEC has determined that TU074 has been adequately characterized & has achieved the applicable requirements under the site cleanup rules. ADEC is issuing this written determination that cleanup is complete, subject to a future department determination that the cleanup is not protective of human health, safety, welfare, or of the environment [18 AAC 75.380(d)]. A “cleanup complete” designation will be entered for TU074 in the Contaminated Sites Database.
|
Louis Howard |
| 5/21/2015 |
Institutional Control Record Removed |
Institutional Controls have been removed. |
Louis Howard |
