| Action Date |
Action |
Description |
DEC Staff |
| 4/18/1988 |
Update or Other Action |
AF (AAC) FY 1989 Military Construction (MILCON) Project Data for Bldg. 11-433 Storage Tank
UST (Bldg. 11-433)
Removal of Residue & Ground Contamination
Cut up tank for removal
Clean fill
Description of Proposed Remedial Action
The scope of restoration work includes the following major elements: remove and dispose of any ground contamination, remove and dispose of water and bottom residues, cut up buried tank and remove it, fill the tank void with 1,680 cubic yards of clean fill material, grade fill material to level ground surface, topsoil and seed disturbed ground surface.
Requirement
Project: Remove and dispose of 8,000 barrel vertical cylinder underground storage tank. Remove bottom Bunker C residue and any associated soil contamination, fill tank void, grade and reseed disturbed areas.
REQUIREMENT: Bldg 11-433 storage tank has been abandoned since 1981. The tank was used during the 1970's as a hazardous waste storage vessel for base waste products. Due to the tanks age and past usage, tank removal operations are essential to preclude possible future environmental
problems.
CURRENT SITUATION: The abandoned 8,055 barrel vertical cylinder underground fuel storage tank is located north of the old Power Plant site. The tank stored bunker C fuel oil for the power plant during the plant's operational years. Throughout the 1970's base organizations used
the tank as a common collection point for storage of waste fuels, used solvents, PCB'S and other hazardous materials generated on Elmendorf AFB.
The tank is an unpermitted storage vessel for hazardous vastes and a State of Alaska inspector verbally cited Elmendorf AFB on 22 Feb 85 for violation of RCRA tank storage requirements. Tank contents were disposed via DRMO channels during early 1986. Approximately 12"-l8" of water
overlay an undetermined quantity of semi-solidified bunker C oil.
IMPACT IF NOT PROVIDED: Residual water/bunker C mixture will remain in 40 year old plus tank. Potential tank leakage will increase, which could adversely impact area soils and/or groundwater.
ADDITIONAL: This is an RA IRP (old Phase IVB, Priority IC) project. Purposed actions will eliminate all environmental concerns for IRP Site S-5.
Signed
Terese D. LeFrancois, GS-12, DAF
AAC DERA Program Manager. |
Louis Howard |
| 6/8/1993 |
Document, Report, or Work plan Review - other |
Ron Klein sent letter to Claude Mayer (Air Force) re: Waiver of 15 day notification period for closure of USTs located at Elmendorf AFB, Facility ID# 1525, Tank IDs 3, 141, 142, 155, 736, 875B, 875D. The department has received a request for waiver of the 15 day notification period for closure of USTs located at the above location. The requested documentation as specified in 18 AAC 78.090(c)(1) has been satisfactorily furnished. The department grants the requested waiver for closure to occur beginning on June 9, 1993. Please note that the site assessment must be done in accordance with the approved QAPP. Please also note that closure activitites must be supervised by a person certified under 18 AAC 78.400-78.495.
Upon removal, the tanks must be emptied, cleaned, removed and disposed of as specified in 18 AAC 78.085. A site assessment as required by 18 AAC 78.090 must be performed with a post closure notice within 30 days of completing closure activities. Any release reporting and corrective action must be done in accordance with 18 AAC 78.220-18 AAC 78.280. |
Ron Klein |
| 9/8/1993 |
Underground Storage Tank Site Characterization or Assessment |
EAFB Environmental Compliance Program UST Site Assessment SOA UST register number 3, near building 22-004 received. This is a report of the excavation, sampling and analysis associated with the closure by removal of a 5,000 gallon underground storage tank (UST) at building 22-004 on Elmendorf Air Force Base, Anchorage, Alaska. The number registered with the state of Alaska for this tank is 3. The Elmendorf storage Tank Management: Plan (STMP) Identification number for this tank is 270; this is an old numbering system that will be phased out. The AK
UST Register number (3) will be used exclusively hereafter in this report.
Two tanks were closed at this site simultaneously. The second tank (STMP 271, tank number 4) never received product and therefore was not considered a regulated tank. The installation was designed and constructed as used oil and diesel holding tanks. The intent was to complement the natural gas fired boilers at 22-004 with used oil. Building 22-004 is the base power plant. Air quality problems prevented the project from being implemented. Tanks 3 and 4 were subsequently scheduled for closure. According to plant manager, Gary Lynch, tank 3 had only a single load of 2,500 gallons of diesel fuel processed through it during its tenure.
Soil sampling and testing was done in accordance with an approved quality assurance program plan (QAPP) held by EA Remediation Technologies Inc. Since the site history indicates that one single use of diesel product was used at Tank 3, that was the only hydrocarbon tested for. Also, there was never any indication of hydrocarbon contamination encountered throughout the excavation or field screening process. Soil cleanup levels for site remediation are not evaluated as part of this effort.
No contamination was found during the field screening process and lab results from 15 soil samples were all below 5 ppm TPHD. Recommendation is site be accepted for clean closure and no further action required. |
John Halverson |
| 2/15/1994 |
Update or Other Action |
1994 SERA Phases 1A & 1B Site Assessment report which includes site ST69. Groundwater results: 240 ug/L benzene, 82 ug/L toluene, 12 ug/L ethylbenzene, 30 ug/L xylenes.
The subsurface soils do not exhibit hydrocarbon concentrations requiring remedial efforts. The concentration of benzene and BTEX compounds in the groundwater immediately around the former tank location is greater than established Federal and State MCLs. Prior to a review of possible groundwater remediation alternatives, the hydrogeologic properties of the shallow unconfined aquifer (such as hydraulic conductivity, thickness, etc.) could be determined.
These properties may be used for determining remedial system design if appropriate. The limited
extent of groundwater contamination and steep groundwater gradient in the coarse-grained soil
of the site suggest that the contamination should have been dispersed and attenuated naturally
by this time. An additional round of groundwater sampling should be conducted to confirm this.
|
Louis Howard |
| 6/6/1994 |
Document, Report, or Work plan Review - other |
John Halverson sent letter to Claude Mayer (Air Force) re: Underground Storage Tank System (UST) Site Assessment Report, Registration Number 3, near building 22-004; dated September, 1993. ADEC received the report last fall. It summarizes information collected during closure of the UST #3, which was reported to be a 5000 gallon tank that contained diesel fuel. Reportedly the tank was only filled once and was taken out of service after that point in time.
UST#4 was located adjactent to UST #3 and was closed out at the same time. However, UST #4 was installed to contain used oil for fueling the power plant and it was never placed in service (no product was ever put in the tank). A site assessment was not conducted during closure of UST #4 and no contamination was evident during the field work.
Based on previous discussions with you and Kent Patrick-Riley of our office, the department is not requesting any additional site investigations associated with the former USTs #3 and #4 at this site. However, if in the future any contaminated soil or groundwater is encountered at the site, it will need to be handled in accordance with applicable state and federal regulations.
SITE closure withdrawn- 1995 decommissioning of Haz waste accumulation area shows petroleum contamination remains in ground.
Fax sent by John Mahaffey (Air Force) RE: Proposed remediation for POL contaminated soil from RCRA Closure Site at Building 22-004. Attached is the information relating to the sampling and analysis data to the boxes of soil and asphalt. Only soil boxes are proposed for thermal remediation. All other materials have been handled via other disposal methods. Borehole sampling yielded: maximum DRO=7,700 mg/kg and maximum lead = 36 mg/kg. |
John Halverson |
| 4/21/1995 |
Update or Other Action |
Air Force Memorandum to John Halverson re: UST meeting. Elmendorf AFB will accomplish the following actions regarding UST projects. These actions are based upon conversation between, John Mahaffey, Larry Opperman and yourself.
a. EAFB will make every effort to accomplish clean closure of a UST removal if possible.
b. UST removal locations requiring cleanup action will be transferred into the State Elmendorf Environmental Restoration Agreement (SERA). A list of sites requiring cleanup will be coordinated with your office.
c. The presumptive remedy for contaminated UST sites in the outwash plain only will be bioventing technology.
d. Contaminated soils exceeding cleanup levels may be placed back into the excavation only if the site assessment (SA) indicates a need for further action.
e. Contaminated UST sites not in the outwash plain will require further investigation to determine appropriate cleanup options.
f. We (Elmendorf) will make every attempt possible to assure new USTs or new aboveground tanks are not installed in any way that would hamper future access for cleanup.
g. The project will first accomplish removal of all the USTs. SA information will be used to prioritize sites for cleanup using existing project funds. Additional funding will be requested to complete cleanup if available. Sites not addressed for cleanup due to exhausted funding will be placed in SERA Phase IV.
John Halverson signed memorandum on April 21, 1995. Memorandum submitted by Douglas G. Tarbett, Maj. USAF, Chief Environmental Compliance (CCs 3 WG/JA and 3 SPTG/CE).
|
John Halverson |
| 5/3/1995 |
Document, Report, or Work plan Review - other |
John Halverson sent USAF review comments on the SERA Phase I Corrective Action Plan dated April 1995. As noted in comments on the draft workplan, the corrective action plan needs to include
schedules for conducting field work, monitoring and maintaining equipment, and submittal
of interim and/or final corrective action reports. We have previously requested quarterly
reporting of remedial efforts at each site where free product has been identified (ST 43 and
ST36).
The Air Force has proposed changes to the several of the tables that outline groundwater
monitoring plans. Unless specifically noted below, the department does not object to these
changes. The locations of substituted wells need to be shown on figures in the plan, if not
already present.
NFA Candidate Sites: ST69 - Diesel Leak (Building 76-520, UST #525)
Section 2.11.7 - The second sentence states cleanup efforts at the time of the tank removal successfully prevented soil contamination. Based on discussion with other program staff, it is my understanding that when the tank was removed a large volume of soil was excavated (to the depth of the water table) and hauled off-site. Therefore, it would be more appropriate to state that contaminated soil was "removed", rather than "prevented", during excavation of the tank.
Section 2.11.9 - The first paragraph states it appears ST41 is the source of groundwater
contamination beneath ST69. Based on the information that petroleum contaminated soil was excavated to the depth of the water table at the time the UST was removed, it appears the former UST is the likely source of groundwater impacts rather than ST41. Assessment work after the tank removal and excavation of soil has not located petroleum contaminated soil above the watertable at this site, however, the elevated concentration of benzene in the groundwater warrants further monitoring. Therefore, the department does not object to a no further action decision under SERA for soil at ST69 based on the condition that monitoring well 46WL01 be added to the groundwater monitoring program. |
John Halverson |
| 8/23/1995 |
Leaking Underground Storage Tank Release Confirmed - Petroleum |
LUST Site created in CSP for source area ID 77683 ADD; Site added to database. |
Louis Howard |
| 8/23/1995 |
Site Added to Database |
|
Former Staff |
| 9/6/1995 |
Update or Other Action |
March 2, 1995 Report for decommissioning the hazardous waste accumulation area at Bldg. 22-004. Cleaning of the asphalt concrete pavement (ACP) pad consisted of removing of the layer of fine soils and coal dust that had accumulated on the pad's surface over the years. 128 DOT shipping boxes (3/4 cubic yard each) of "sub-asphalt soil", 7 boxes of "non-stained soil" and 1 box "stained soil" were generated and segregated during these activities. Only one box holding soils were visually stained. The asphalt has been recycled or as appropriate-drummed up and turned in to the treatment storage disposal facility as hazardous waste. |
John Halverson |
| 9/7/1995 |
Update or Other Action |
Fax sent by John Mahaffey (Air Force) RE: Proposed remediation for Petroleum, oil and lubricants (POL) contaminated soil from RCRA Closure Site at Building 22-004. Attached is the information relating to the sampling and analysis data to the boxes of soil and asphalt. Only soil boxes are proposed for thermal remediation. All other materials have been handled via other disposal methods. Call with questions.
Elmendorf AFB proposes to transport the soil in the boxes to Alaska Soil Recyling for thermal remediation and disposal. We further propose to add the site from which the soils were excavated to the SERA Agreement and to investigate the site as part of SERA IV field activities. 22 of 128 soil boxes were composite sampled-maximum DRO 3,900 mg/kg and non-detect for lead. Borehole sampling yielded: maximum DRO=7,700 mg/kg and maximum lead = 36 mg/kg. |
John Halverson |
| 9/8/1995 |
Offsite Soil or Groundwater Disposal Approved |
Ray Burger on behalf of John Halverson (ADEC) sent approval with the Air Force's request to thermally treat the petroleum contaminated soil at ASR. |
Ray Burger |
| 11/4/1996 |
Document, Report, or Work plan Review - other |
Letter from ADEC (J. Halverson) to USAF (C. Mayer): RE: SERA Projects - Decision documents ST69 and ST72 Thank you for submitting proposed no-further-action decision documents for SERA sites ST72 and ST69. I apologize for not formally responding to those submittal in a timely manner. Due to circumstances with the projects, the sites were not amenable to the simplest no-further-action decision process. Each site is addressed separately below.
ST 69
As you are aware, an underground storage tank (UST) and petroleum contaminated soil were removed
from this site in the past. Site investigation work following the removal did not identify contaminated soil above the watertable. However, elevated concentrations of BTEX and petroleum hydrocarbons were found in the shallow groundwater. Monitoring well 46WL01 was added to the basewide groundwater monitoring program [NOTE TO FILE-SEE Operable Unit 2 monitoring wells which include 46-WL-01 monitoring well].
Data from the well shows benzene concentrations have decreased from 240 ppb in 1993 to 27 ppb in March 1996. The well will remain in the monitoring program until the concentrations have decreased to below the MCL, as defined in the monitoring plan. Therefore, the department has no objection with the proposed no further action (NFA) decision at that site. Please see the attached signed decision document. |
John Halverson |
| 11/4/1996 |
Update or Other Action |
Institutional Controls established and entered into the database. Monitoring well 46WL01 was added to the basewide groundwater monitoring program. Data from the well shows benzene concentrations have decreased from 240 ppb in 1993 to 27 ppb in March 1996. The well will remain in the monitoring program until the concentrations have decreased to below the MCL, as defined in the monitoring plan. (as of 4/2012 groundwater cleanup levels have been reached for several years at the site-2007, 2010 and 2011). |
John Halverson |
| 11/4/1996 |
Update or Other Action |
Signed by USAF: William R. Hanson and by John Halverson on Nov. 4, 19996. No Further Action Decision Document for State-Elmendorf Environmental Restoration Agreement (SERA) Site ST69 STATEMENT OF BASIS: This decision is based on the results of SERA Phase I Corrective Action Plan (CAP), Final, dated April 1995. Also, reference your 3 May 95 letter, page four, No Further Action Candidate Sites section.
DESCRIPTION OF THE SELECTED REMEDY: Based on the current conditions at ST69, it has been
determined that no significant risk or threat to public health or the environment exists. Therefore, no further action (NFA) at this site is required.
DECLARATION:It appears the former UST is the likely source of groundwater impacts at this site and not from an off-site upgradient source. Assessment work after the tank removal and excavation of soil has not located petroleum contaminated soil above the water table at this site, however, the elevated concentration of benzene in the groundwater warrants further monitoring. Well 46WL01 is included in the Basewide Support Groundwater Monitoring Program.
Therefore, this NFA declaration represents the selected action for this site in accordance with SERA. It has been determined that the selected remedy of no further action is protective of human health and the environment, attains federal and state requirements that are applicable
or relevant and appropriate, and is cost-effective. The statutory preference for further treatment is not satisfied because further treatment was not found to be necessary. Contaminant levels at the site have been determined to present no significant threat to human health or the
environment; thus, no treatment is necessary. |
John Halverson |
| 5/1/1997 |
Update or Other Action |
BASEWIDE SUPPORT AND GROUNDWATER MONITORING PROGRAM, ANNUAL REPORT OF GROUNDWATER SAMPLING ACTIVITIES received. May 1997. Well 46WL-01 is part of Operable Unit 2 and the well is required to be monitored as part of the NFA decision granted by ADEC in 1996. Results: Round 1 5.9 mg/L DO and 27.7 ug/L. Round 2 1.3 mg/L DO and 20.4 ug/L benzene. TCE was non-detect.
Interpretive Conclusions of Groundwater Data for Each Program Area in 1996, Basewide Support Groundwater Sampling Program.
The following are conclusions derived from intuitive and statistical groundwater data analysis within OU 2:
* A significant correlation could not be established between dissolved oxygen levels and benzene concentrations, although natural attenuation does appear to be occurring to some degree;
* Benzene exceeded the MCL at six locations during 1996, however, TCE did not exceed the MCL historically or during 1996 at the OU 2 wells sampled;
* No statistically significant trend (increasing or decreasing) could be established for either benzene or TCE;
* The highest benzene concentrations were detected at well ST41-16;
* Six ST20 COCs, identified in the OU 2 ROD, were eliminated from the OU 2 program for 1996 because no wells within ST20 are in the sampling program, including: beryllium, bis(2-Ethylhexyl)phthalate, chromium, nickel, nitrate, and vanadium. In addition, thallium was
dropped as a COC in 1996 as a result of no detects above the MCL at any one location; and
* Continue monitoring for analytes which meet the criteria specified in the Decision Guide (Figure 3-1). At a minimum, sampling should continue for 1996 COCs. In addition, the analyte suite used to evaluate the occurrence of intrinsic remediation (methane, redox potential,
sulfate ion, and ferric iron) is a recommended addition to the current list of methods at OU 2. |
John Halverson |
| 3/25/1998 |
Leaking Underground Storage Tank Cleanup Initiated - Petroleum |
|
Former Staff |
| 1/29/1999 |
Update or Other Action |
Basewide Annual Tech Memo 1998 received. Description of Historical and 1998 Product presence (product thickness is provided in units of feet) OU2 46-WL-01 8/14/1998 - ND (Sheen Detected).
Fourteen OU 2 monitoring wells were sampled in 1998. The first sampling event took place from
May 29 to June 8, 1998, and the second sampling event took place from August 14-21, 1998.
Results for 46-WL-01: Benzene-Summer 2.45 ug/L Fall 5.51 ug/L.
Conclusions
The following are conclusions derived from intuitive and statistical groundwater data analysis
within OU 2:
As discussed in Section 3.3, intuitive and statistical conclusions were drawn from 1998 data. In
previous reports, more intuitive conclusions of the data were conducted; however, with the larger sample populations available in 1998 more robust statistical procedures were used to establish i significant statistical trends. Although the number of statistically valid trends are still somewhat limited, as more data become available in successive rounds of sampling, more statistically significant trends will be established and intuitive conclusions will only be used to support statistical data;
* A general trend could not be established for benzene across the entire program area due to the
high variability of the data. However, of the four individual wells which showed a significant statistical difference and exceeded the MCL, two displayed an increasing trend and two displayed
a decreasing trend;
* Benzene was detected at seven well locations within OU 2 with five locations below baseline and
* two locations above baseline;
* Benzene exceeded the MCL at six locations with the highest benzene concentrations detected at
well ST41-16 (16150 gg/L). This is the same number of MCL exceedances as 1997 and an increase of one location from 1996;
* Intrinsic remediation is effectively reducing contamination within OU 2 with BIOSCREEN
simulation results indicating that the BTEX plume has been reduced by 70% and is shrinking.
Recommendations: Continue monitoring for analytes that meet the criteria specified in the Decision Guide (Figure 3- 1). At a minimum, sampling should continue semi-annually for 1998 COCs. In light of the 1998 assessment, an evaluation will be made in 1999 to determine the value of collecting further intrinsic remediation data at this program area. It is possible that the extent of monitoring for these parameters could be scaled down to only include wells associated with documented plumes. |
Louis Howard |
| 1/28/2000 |
Update or Other Action |
Basewide Monitoring and Well Maintenance Program annual technical memorandum received. Historical Product Thickness Detected through field operations (measured in feet). May 199-non-detected, October 1999 Sheen and fuel odor noted in well for OU2: WELL ID 46-WL-01. |
Louis Howard |
| 3/31/2000 |
Update or Other Action |
1999 Annual Report of Groundwater Sampling Activities received. Fourteen OU 2 monitoring wells were sampled in 1999. The first sampling event took place from 9-14 June 1999, and the second sampling event took place from 17-20 August 1999.
As a result of the 1999 Decision Guide analysis of the OU 2 sampling program, one well met the
criteria for removal from the sampling program (see Table 4-5). The results of the 1999 evaluation and an overview of each OU 2 well function by category of upgradient, in-source, downgradient, or other condition are provided in Table 4-5. There were no analytical methods that met the Decision Guide criteria for removal from the OU 2 sampling program.
WELL ID 46-WL-01 sample results for Summer 1999 Benzene: 9.2 ug/L Fall 1999 13 ug/L ("B" flagged-The analyte was found in the associated blank, as well as the sample.)
Conclusions
The following are conclusions derived from intuitive and statistical groundwater data analysis
within OU 2:
* Based on the 1999 Decision Guide review of OU 2, well ST41-20 met the criteria for removal
from the sampling program (see Table 4-5). There were no analytical methods that met the
Decision Guide criteria for removal from the OU 2 sampling program;
* Measurable free product was found at wells ST41-28 and ST41-38. Thickness of the product
layer at ST41-28 increased by a minimum of 0.18 feet since the 1998 product survey. These
wells, and downgradient wells to the north, will be tracked closely during 2000 sampling;
* Of the 14 wells within OU 2, five displayed statistically valid trends with respect to benzene
concentrations. Three of these are increasing and two are decreasing;
* In 1999, benzene concentrations exceeded the MCL at six wells within OU 2. Of these, one had a
statistically increasing trend (46-WL-01), two have statistically decreasing trends (ST41-07 and
ST41-28), and a statistically significant trend could not be established at three locations (ST41-10R, ST41-16, and ST41-25); and
* Intrinsic remediation continues to be effectively reducing groundwater contamination within
OU 2. BIOSCREEN simulation results generated in the 1998 Annual Report (USAF, 1999b)
indicate that the BTEX plume has been reduced by 70% and is shrinking.
Recommendations: The following are recommendations for OU 2 from a review of analytical data gathered in 1999:
Maintain the OU 2 groundwater sampling program with the following modification. Based on the 1999 Decision Guide review ofOU 2, well ST41-20 met the criteria for removal from the sampling program (see Table 4-5). There were no analytical methods that met the Decision Guide criteria for removal from the OU 2 sampling program; therefore the 1999 methods should be maintained; and
Replace SW8015 methods for fuels with the State of Alaska "AK" methods with no further parallel testing. |
Louis Howard |
| 3/30/2001 |
Update or Other Action |
Basewide Annual Groundwater Report received. 46-WL-01 meets the criteria to retain as an in-source well for benzene levels above the MCL. MEMO TO THE FILE: Also, it should also be noted that the well is associated with ST69. ST 69 was an underground storage tank (UST) and petroleum contaminated soil was removed from this site in the past. Site investigation work following the removal did not identify contaminated soil above the watertable. However, elevated concentrations of BTEX and petroleum hydrocarbons were found in the shallow groundwater. Monitoring well 46WL01 was added to the basewide groundwater monitoring program. Data from the well shows benzene concentrations have decreased from 240 ppb in 1993 to 27 ppb in March 1996. The well will remain in the monitoring program until the concentrations have decreased to below the MCL, as defined in the monitoring plan as part of the 1996 NFA decision agreed to by the Air Force and ADEC.
2000 no sheen was observed in well 46-WL-01. Results from 2000-Benzene: Summer 1 ug/L Fall 7.4 ug/L. Seven wells at OU 2 contained statistically valid trends using current available data for benzene. Of these, two had increasing trends (46-WL-01 and ST41-07).
Conclusions
The following are conclusions derived from intuitive and statistical groundwater data analysis
within OU 2:
* As a result of the 2000 Decision Guide analysis of the OU 2 Program Area, it is recommended
that all wells and methods remain for the 2001 program year.
* For wells in the OU 2 Program Area, a measurable free product layer was detected at two well
locations during the 2000 field season (ST41-16 and ST41-28). In addition, a sheen and/or fuel
odor was noted at three well locations (ST41-10R, ST41-25, and T40001).
Four organic COCs (benzene, ethylbenzene, toluene, and xylene) exceeded MCLs in 2000. Benzene exceeded the MCL at six locations (46-WL-01, ST41-07, ST41-10R, ST41-16, ST41-25, and ST41-28); ethylbenzene exceeded the MCL at three locations (ST41-16, ST41-25, and ST41-28); and toluene and xylene MCLs were exceeded at one location (ST41-16). Although manganese exceeded the secondary MCL (0.05 mg/L) at 12 locations, none of the levels were detected above the manganese background concentration of 64 mg/L.
* Seven wells at OU 2 contained statistically valid trends using current available data for benzene.
Of these, two had increasing trends (46-WL-01 and ST41-07); three had decreasing trends
(ST41-10R, ST41-28, and T40001); and two are maintaining stable concentrations (ST41-30 and
ST41-34).
* Intrinsic remediation continues to be effectively reducing groundwater contamination within
OU 2. BIOSCREEN simulation results generated in the 1998 Annual Report (USAF, 1999b) indicate that the BTEX plume has been reduced by 70% and is shrinking.
Recommendations: Maintain the OU 2 groundwater sampling program in its current form for 2001. Continue to closely monitor free product presence and the trends of organic COCs. |
Louis Howard |
| 3/29/2002 |
Update or Other Action |
Basewide Annual Groundwater Report received. Twelve groundwater monitoring wells were sampled at OU 2 in 2001. The first sampling event took place June 13-19 and the second sampling event took place from August 24-30, 2001.
One well, ST41-27, is specified for monitoring in the OU 2 ROD and was added in 2001. Well 46-WL-01 is located downgradient of "Four Million Gallon Hill" (the ST41 source area) and has been sampled as part of the OU 2 program area since 1996. The well was originally installed as an in-source well for Site ST69 in the SERA IA program area. This was the site of a 500-gallon diesel
spill that reportedly occurred between 1989 and 1990. For 2001, the well was again sampled as part of the OU 2 program area and tested under the OU 2 suite of analytes. This was done to obtain a full suite of analytical Method 8260B for the five-year review, which will occur in 2003.
For the 2002 Basewide Program, this well [46-WL-01) will be moved to the SERA Miscellaneous program area, which does not include TCE in the analyte suite. This well is no longer considered necessary for downgradient monitoring for the ST41 source area, but will be used to continue monitoring at Site ST69. As a result of the 2001 Decision Guide analysis of the OU 2 program area, it is recommended that wells ST41-24, ST41-26, ST41-27, ST41-30, ST41-37A, and T40001 be removed from the 2002 program year. Six wells remain for the 2002 program year. It is also recommened to sample for only the ROD specified ARARs, benzene, ethylbenze, toluene, and total xylenes in 2002.
A sheen and/or fuel odor was noted at four well locations (46-WL-01, ST41-1OR, ST41-25, and T40001). NOTE TO FILE: A significant increase of benzene has been noted in well 46-WL-01 comparted to the last 4 years. 2001 results: Benzene Summer 24 ug/L and Fall 50 ug/L.
Conclusions
The following are conclusions derived from intuitive and statistical groundwater data analysis
within OU 2:
* As a result of the 2001 Decision Guide analysis of the OU 2 program area, it is recommended that wells ST41-24, ST41-26, ST41-27, ST41-30, ST41-37A, and T40001 be removed from the 2002
program year. Five wells remain for the 2002 program year. It is also recommended to continue
sampling for only the ROD specified ARARs, benzene, ethylbenze, toluene, and total xylenes.
* For wells in the OU 2 program area, a measurable free product layer was detected at two well
locations during the 2001 field season (ST41-16 and ST41-28). In addition, a sheen and/or fuel
odor was noted at four well locations (46-WL-01, ST41-10R, ST41-25, and T40001).
* Three organic COCs (benzene, ethylbenzene, and toluene) exceeded MCLs in 2001. Benzene
exceeded the MCL at six locations (46-WL-01, ST41-07, ST41-10R, ST41-16, ST41-25, and
ST41-28); ethylbenzene exceeded the MCL at two locations (ST41-16, and ST41-28); and
toluene exceeded MCL at one location (ST41-16).
* Seven wells at OU 2 contained statistically valid trends using current available data for benzene. As indicated on Table 4-8, 46-WL-01, ST41-07, ST41-1OR, ST41-16, ST41-25, and ST41-28
exceeded the benzene MCL in 2001. Four of these wells, ST41-07, ST41-10R, ST41-25, and
ST41-28 showed statistically significant decreasing trends in benzene. The remaining wells with
concentrations above MCLs, 46-WL-01 and ST41-16 had no statistical trend.
A review of 2001 natural attenuation data from OU 2 indicates a high level of microbial activity
in all contaminated wells. Natural attenuation appears to be working well in this program area.
* Well 46-WL-01 was installed as an in-source well in the SERA IA program area but was sampled
in the OU 2 program area from 1996 though 2001 to provide an additional downgradient location
for ST41. 46-WL-01 is, however, an in-source well for the SERA site ST69. The well will be reclassified into the SERA Miscellaneous grouping in 2002.
Recommendations: Remove wells ST41-24, ST41-26, ST41-27, ST41-30, ST41-37A, and T40001from the 2002 Basewide Program. Sample for only the ROD specified ARARs, benzene, ethylbenze, toluene, and total xylenes. Continue to closely monitor free product presence and trends of organic COCs. Move well 46-WL-01 to the SERA Miscellaneous program area. Initiate seep sampling as outlined in the OU 2 Record of Decision.
|
Louis Howard |
| 3/28/2003 |
Update or Other Action |
2003 Basewide Annual Report received. Well 46-WL-01 is added to the SERA Miscellaneous Wells along with ST69 well 46-WL-02, & well WGN-01. Three SERA Miscellaneous monitoring wells were sampled in 2002 for the Basewide Program. SERA Miscellaneous sites are located throughout EAFB & are primarily associated with former fuel storage tank sources. Wells sampled during 2002 are located in the Outwash Plain deposits.
GW flow characteristics & the location & depth of the Bootlegger Cove Formation are similar to those described for SERA Phase I. The purpose of GW monitoring at SERA sites is to monitor natural attenuation & monitor contaminant plumes to ensure protection of receptors such as Ship Creek, the Knik Arm, & Hillberg Lake.
In 2002, fuel odor was noted in 46-WL-01. Sampling was only conducted in the summer for 2002: 8.5 ug/L benzene was detected. The ST69 Plume is located in the western portion of EAFB on Fairchild Ave. It is approximately 1,000 feet south west of the 26th Ave. & Fairchild intersection. This is an isolated plume found in the shallow unconfined aquifer which ranges from 5 to 15 feet thick in this region of the base.
This aquifer is underlain by the Bootlegger Cove Formation. The source for this plume was a 500-gallon diesel fuel spill which reportedly occurred between 1989 & 1990. During the site investigation benzene levels were reported at 240 µg/L at 46-WL-01. Benzene remains the contaminant of concern for this site.
Well 46-WL-01, the in-source location, & Well 46-WL-02, the downgradient location, were sampled twice during the 2002 Basewide Program. An evaluation of natural attenuation parameters from these wells shows strong evidence for natural attenuation.
Levels have greatly decreased since the site investigation & the presence of ferrous iron indicated ferric iron has been used as an electron acceptor. Even with the process historically occurring, electron acceptors remain elevated & it is likely that microbes will continue to utilize the acceptors.
Downgradient, Well 46-WL-02 shows no sign of contaminant migration. However, electron acceptors also are elevated at this well &, should migration occur, benzene should continue to degrade through natural attenuation processes.
Figure 3-24. shows high levels of benzene in 1993 & generally decreasing thereafter. A spike in levels was detected in data from the second round of sampling in 2001, which may be the effect of smear zone soil contamination. Statistical analysis of benzene in this well from 1996 through 2002 is inconclusive. No statistical trend can be established for this data set.
The site assessment for ST69 recommends continued monitoring at 46-WL-01. With an acceptable rate of natural attenuation occurring, monitoring for this well will continue on a 5-year basis. Downgradient Well 46-WL-02 will be monitored every 2 years to track any migration.
Overall Performance of Natural Attenuation as Compared to Guidance Documents
The selected remedies for ST69 call for GW monitoring until sampling determines that the remediation goals have been reached & risks are acceptable. As previously stated, there are remediation goals for several analytes: benzene, DRO, & GRO. Of these, only benzene remains above regulatory levels. The natural attenuation assessment for the benzene plume at ST69 indicated that remediation is occurring & conditions remain favorable for further breakdown. It is recommended to continue monitoring on a reduced frequency until benzene is below regulatory levels at this plume.
The following are conclusions & recommendations derived from the 2002 GW data analysis for the SERA Miscellaneous program area:
• A measurable product layer was not detected at any well in the SERA Miscellaneous program in 2002. A fuel odor was reported at Well 46-WL-01.
• The only COC reported above cleanup levels was benzene. Benzene levels at 46-WL-01 were reported at 8.5 µg/L. The level in 2002 was lower than last year but is consistent with the other sampling events.
• An assessment of natural attenuation at SERA Miscellaneous wells indicates that natural attenuation is occurring & conditions remain favorable for continued breakdown of benzene.
• In 2002, none of the SERA Miscellaneous wells met the criteria for removal. Two of the current wells will be monitored on a reduced frequency: 46-WL-01 once every 5 years & 46-WL-02 once every 2 years. Natural attenuation parameters will be taken at these wells every 5 years. Well WGN-01, the sentry well location at Hillberg Lake, will continue to be monitored annually for COCs.
• It is recommended to sample the ST69 downgradient location, 46-WL-02, every two years to ensure no contaminant migration is occurring & that levels continue to decline. It is also recommended to sample 46-WL-01 every 5 years to provide information for the 5-Year Review & to update the assessment of natural attenuation. |
Louis Howard |
| 5/28/2004 |
Update or Other Action |
2003 Annual Report Basewide Groundwater Monitoring Program received. Field Activities and Results: There were no field activities conducted at the ST69 Plume during 2003. Well 46-WL-02 will be sampled for COCs and natural attenuation parameters every other year, with the next round of sampling occurring next year. In addition, 46-WL-01 will also be sampled for COCs and natural attenuation parameters every five years with the next sampling event occurring in 2007.
Benzene concentrations have undergone a steady decline and natural attenuation is very active at
the ST69 Plume. As such, COC concentrations in this plume should continue to move toward
ADEC closure requirements and groundwater monitoring should continue in its current form
with no alterations.
Recommendations: A cleanup date for this plume should be determined. With no predicted closure date in place, groundwater monitoring should continue in its current form. |
Louis Howard |
| 7/29/2005 |
Update or Other Action |
2004 Phase I RPO Annual Report Groundwater Performance Optimization Monitoring Program received. Performance monitoring is conducted at the ST69 Plume to determine data needs and assessment methods useful for evaluating the monitoring network and determining remedy effectiveness. To achieve this goal, narrowly defined monitoring objectives have been created and precise performance criteria have been established to define the endpoint of performance monitoring.
The monitoring objectives for the ST69 Plume are as follows:
• Reduce benzene concentrations in groundwater to ADEC cleanup levels (5 ug/L) for this (benzene) plume
• Verify that plume expansion is not occurring and that the monitoring network is sufficient
for this purpose.
Decision documents have identified several POL contaminants as groundwater COCs at the ST69 Plume and created cleanup levels for these compounds. These COCs and their associated ADEC cleanup levels represent the performance criteria against which analytical results will be compared to measure progress toward achieving the monitoring objectives at the ST69 Plume. Currently all COCs except benzene have remained either undetected or below cleanup levels. Therefore, benzene is the only COC currently monitored. The specified cleanup level for benzene is 5 µg/L. There is no predicted cleanup date for this plume. 46WL-01 Sampling results from 2004- Summer: 4.3 ug/L. Well 46WL-02 was non-detect.
Inorganic MNA samples were collected from two plume wells, 46WL-01 and 46WL-02, in 2004. These two wells are crossgradient and in-source, and their COC levels have recently fallen to levels beneath cleanup standards. There is no upgradient or downgradient well for comparison of these results. Natural attenuation parameters at the cross-gradient and in-source wells show excellent evidence for biodegradation of fuels. Within the plume, electron acceptor concentrations are low and the oxidation-reduction potential indicates the presence of an anaerobic environment within the center of the plume. Cross-gradient of the plume, electron acceptor concentrations are higher and the aquifer appears to be aerobic (based on oxidation reduction potential).
Based on this information, it can be concluded that microbes are using several biodegradation pathways to reduce the contaminant mass of this plume. The aquifer appears to be aerobic outside of the plume and microbes are likely utilizing dissolved oxygen as an electron acceptor at the plume margins. Within the plume, the aquifer is anaerobic and microbes appear to be utilizing nitrate, ferric iron, and sulfate as electron acceptors during the breakdown of fuel. Qualitatively, this indicates that the rate of biodegradation of fuels at this location is likely stable.
Remedial activities at the ST69 Plume are ongoing. Of the original COCs outlined in the decision documents, only benzene has historically remained above its specified cleanup level of 5 µg/L. In 2004 however, levels fell below the cleanup criteria for the ST69 Plume. Future remedial activities at the ST69 Plume will consist of performance monitoring to verify this decreasing benzene trend continues.
Benzene is the final COC currently monitored at this plume. Benzene concentrations have also already fallen beneath the cleanup level of 5 µg/L. The benzene concentration during 2002, the previous sampling event, was 6.4 µg/L. By 2004, this concentration had decreased to 4.3 µg/L. No predicted cleanup date exists for this plume. Because the benzene concentration has recently fallen below its cleanup level, it is recommended that performance monitoring continue in its current form at this plume. Software modeling efforts have been recommended at other plumes to optimize various performance monitoring components such as well selection and sample frequency, cleanup time predictions, and contaminant mass calculations. Similar refinement of these performance monitoring components is not recommended at the ST69 Plume.
This plume appears on course to reach ADEC cleanup standards and does not require these optimization efforts at this time. Those resources should be allocated to plumes with more sharply elevated COC concentrations and cleanup dates that occur sooner. The next monitoring event for COC samples should be performed in 2005, as opposed to the specified date of 2006. This will allow for accelerated site closure. It is also recommended that inorganic MNA samples no longer be collected at the ST69 Plume. Resources required for MNA monitoring should not be used at this plume, provided that COCs remain below cleanup standards. |
Louis Howard |
| 5/1/2006 |
Update or Other Action |
2005 Annual Basewide Groundwater Monitoring Field Report received. 46WL-01 is in Zone 1. The benzene concentration in the in-source well, 46WL-01, was below the cleanup level in 2004. This well was not sampled in 2005, but the 2006 analytical results (next sampling event) will be compared to the established baseline in 2007 to assess the plume’s performance (within acceptable range or not). If the plume is performing as predicted, no changes to the program would be required at this site. The plume will be scheduled for further evaluation, beginning with a CSM review, to determine what changes might be warranted to the monitoring program if the plume is not performing as predicted.
The selected remedy for the ST69 Plume is MNA with removal of free product. The current
groundwater monitoring network for this plume is adequate to track migration of contaminants
toward potential human or ecological receptors. Current land use at Site ST69 is recreational.
This site is located within the Outwash Plain south of the Elmendorf Moraine and use of the
shallow aquifer for any purpose is strictly prohibited. The Base General Plan indicates that this is also the anticipated future land use. Based on this land use scenario, and because benzene concentrations are currently beneath State cleanup levels, no human or environmental exposure to the contaminated groundwater at ST69 is expected. Remediation workers are adequately
protected and follow established health and safety procedures. This remedy is therefore
considered protective of human health and the environment. This remedy was not evaluated in
the 2002 Five Year Review.
One round of monitoring data (2004) from groundwater samples collected at the ST69 Plume
show that benzene concentrations are currently beneath ADEC-specified cleanup levels.
Monitoring of this plume is on-going per the Final SERA Phase I Corrective Action Plan (USAF,
1995a). In-place land use controls are strictly enforced, preventing human or ecological
exposure to contaminated groundwater.
Recommendations: Change to annual sampling frequency for ST69 plume wells (46WL-01 and 46WL-02); Sample for all SERA Phase I required COCs. Justification: to potentially accelerate site closure since 2004 results were below action level. Implementation date: 2006. Cost increase: $11,438 for an annual sampling event. Anticipated life-cycle cost for 14 years of monitoring is $160,132. |
Louis Howard |
| 10/5/2007 |
Update or Other Action |
2006 Zone 1 Activities report received. The in-plume well (46WL-01) has commonly exceeded the 5-µg/L cleanup level whereas the leading-edge well (46WL-02) has generally been ND; the 2006 results contained the first cleanup-level exceedance. Figure 6-2 presents these results logarithmically as plots of concentration versus time. From 1999 onward, there is no discernable trend for the in-plume well and therefore no basis for empirically estimating a cleanup date. For the downgradient well, the 2006 exceedance appears to be an anomaly but might be an indication of plume migration; further data are needed.
In 2006, low DO concentrations and moderately reducing ORP values in both wells indicated
that the plume was anaerobic and therefore undergoing little biodegradation except around the
fringes, where oxygen can be supplied by advection and diffusion. In addition, a strong odor was noted in downgradient well 46WL-02. These observations suggest that dissolved benzene could be advecting more rapidly than it can be attenuated by biodegradation and dispersion.
6.6 SUMMARY OF PERFORMANCE AND RECOMMENDATIONS AT ST69
Conditions and trends in the ST69 plume are as follows:
-Upgradient—The source has been removed, and no additional sources are anticipated.
-In plume—A cleanup prediction remains elusive in the absence of a significant declining
trend.
-Downgradient—A benzene exceedance in 2006 could reflect contaminant migration or
merely the variability inherent in this plume.
Historical data indicate that contamination has been localized around the in-plume well
(46WL-01), but 2006 results suggest that the leading edge of the ST69 plume may have
reached the downgradient sentry well (46WL-02). Additional data are needed to evaluate the
downgradient detection; it may reflect plume migration or it may be a statistical artifact
reflecting the intrinsic variability of contaminant concentrations near the plume. Anaerobic,
moderately reducing conditions in both wells suggest that biodegradation rates are minimal
within the plume, although significant biodegradation may be occurring at the fringes of the
plume, where oxygen is available through advection and diffusion.
The 2006 RPO Report (Appendix A) developed two recommendations for Site ST69, to be
implemented in 2007 (Table 6-5). Based on the recommendations of the RPO Report, water
sampling in 2007 will be the same as that conducted in 2006 (Table 6-6). Although cleanup
no longer appears to be imminent, as anticipated by the 2005 RPO Report (USAF 2006c), the
need to understand the significance of the benzene exceedance in the downgradient well
argues for continuing to sample these wells annually. |
Louis Howard |
| 3/7/2008 |
Exposure Tracking Model Ranking |
Intitial Ranking Complete for Source Area: 77683 (Autogenerated Action) |
|
| 9/15/2010 |
Update or Other Action |
2007 Zone 1 Field Activities report received.
Site ST69 is located in the western portion of EAFB on Fairchild Avenue, approximately
1,000 feet southwest of the intersection with 26th Avenue. The site is approximately 0.5 mile
west of the east-west runway. A 500-gallon diesel fuel spill reportedly occurred at this site
between 1989 and 1990. In addition, 50 gallons of motor vehicle gasoline spilled from a
ruptured standpipe associated with a UST near the site on 22 April 1991. The UST was
removed at the time of the spill. Hydrocarbon sheen was noticed on the groundwater during
excavation and removal of the tank. One plume, the ST69 Plume, comprises Site ST69.
6.2 SITE ST69 SITE MONITORING OBJECTIVES
The remedy for Site ST69, set forth in the Final SERA Phase I Corrective Action Plan (USAF
1995a), consists of removal of free product from groundwater-monitoring wells followed by
MNA for remediation of groundwater contamination. Benzene is the only COC at the site. Ongoing monitoring will verify that the plume is not expanding and will track benzene concentrations in groundwater until they are below the cleanup level of 5 µg/L.
6.3 2007 SITE ACTIVITIES AT ST69
In 2007, in-plume Wells 46WL-01 and 47WL-02 were sampled using PDBs placed 1.5 feet bswl and analyzed for benzene. Field and MNA parameters (pH, DO, ORP, conductivity, and ferrous iron) were collected conventionally using a submersible pump. Synoptic water-level measurements were made at all site wells within 48 hours of sampling.
6.6 SUMMARY OF PERFORMANCE AND RECOMMENDATIONS AT ST69
Conditions and trends in the ST69 plume are as follows:
• Upgradient—The source has been removed, and no additional sources are anticipated.
• In-plume—Well 46WL-01 now exhibits a downward concentration trend but a cleanup date remains uncertain.
• Downgradient— Well W6WL-02 can be considered remediated. A benzene exceedance in 2006 could reflect variability inherent in this plume.
Historical data indicate that contamination has been variable in the in-plume well (46WL-01),
but 2007 results suggest that an overall downward trend continues. The 2007 RPO Report develops three recommendations for Site ST69 to be implemented in 2008. Although cleanup may not be imminent, the need to understand the significance of the variability in benzene exceedances argues for continuing to sample these wells annually.
Although MNA is the selected remedy for all contaminated groundwater in Zone 1, it appears
to be currently effective at only three of the groundwater plumes: ST41 North, ST69, and
PL81 South. ST69 contaminant concentrations were below cleanup levels in both wells for the first time in 2007. Predicted cleanup-possibly 2012. Plume core is anaerobic, inhibiting rapid biodegradation. Results have exhibited wide variability but are below cleanup levels in 2007 in both wells. |
Louis Howard |
| 2/24/2011 |
Document, Report, or Work plan Review - other |
Staff reviewed and approved the recommendations in the draft field activities report for this source area in SERA Phase I. |
Louis Howard |
| 4/26/2012 |
Cleanup Complete Determination Issued |
ADEC has received the final version of the ST69 Site Closure Report and will approve it as submitted. The status for ST69 in the Contaminated Sites database will reflect a “cleanup complete” designation. Based on the information proveded, groundwater and soil at this site is no longer contaminated above cleanup levels. This decision may be reviewed and modified in the future by the Department [in accordance with 18 AAC 75.380(d)(1)], if additional information becomes available that indicates the presence of contaminants or exposures at ST69 cause an unacceptable risk to human health or the environment. In this case, the United States Air Force will conduct additional actions to meet the requirements of the current site cleanup rules in effect at that time. |
Louis Howard |
| 8/21/2014 |
Exposure Tracking Model Ranking |
Initial ranking with ETM completed for source area id: 77683 name: Surface release |
Louis Howard |
| 8/1/2019 |
Institutional Control Record Established |
Institutional Controls established and entered into the database. |
Louis Howard |
