| Action Date |
Action |
Description |
DEC Staff |
| 6/8/1994 |
Site Added to Database |
|
Former Staff |
| 6/8/1994 |
Leaking Underground Storage Tank Release Confirmed - Petroleum |
LUST Site created in CSP for source area ID 77315 |
Former Staff |
| 6/8/1994 |
Leaking Underground Storage Tank Cleanup Initiated - Petroleum |
|
Former Staff |
| 8/10/1995 |
Update or Other Action |
Tank 525B was located near the northwest comer of building 42-525. This single-walled carbon steel tank stored mogas (gasoline) for use in operations support vehicles and equipment on EAFB. Tank 525B was part of a two tank system. Tank 525A contained diesel and was located approximately four feet west of tank 525B. The dispensers for both tanks were located approximately 120 feet southeast of the tanks.
The Storage Tank Management Plan, ENSR (STMP) shows that tank 525B was installed in
1988. This UST remained active until 27 May 1994. The tank was scheduled for removal on
7 June 1994. There is no record of a tightness test for this UST.
Excavation and removal of tank 525B and both the gasoline and diesel dispensers began on 8
June 1994. Base personnel removed remaining tank fluids before the excavation began. The
tank appeared to be in good condition and there were no visual leak indications on the outside
of the tank. The excavated tank and dispenser were transported to the EAFB treatment storage
and disposal (TSD) facility at building 22-009, where they are stored pending demolition. A
portion of the piping was removed, while the remaining portion was closed in place. During
field activities, the adjacent UST (525A) was upgraded with spill and overfill protection and
leak detection equipment to meet 1998 EPA/ADEC UST compliance requirements.
Two soil samples were collected from the UST excavation at a depth of 10 feet below ground surface (bgs) and one sample was collected from the midpoint of the dispenser island at 2.5 feet bgs. Samples were analyzed for gasoline-range organics (GRO), diesel-range organics (DRO), and benzene, toluene, ethylbenzene, and total xylenes (BTEX).
The maximum contaminant concentrations were detected beneath the north end of the former UST and were 1,050 mg/kg GRO, 75 mg/kg DRO, 0.06 mg/kg benzene, 33.5 mg/kg toluene, 40.5 mg/kg ethylbenzene, and 304 mg/kg total xylenes. All other results were below ADEC 18 AAC 75 Method Two cleanup levels. After removal of the UST, the excavation was backfilled with clean fill material.
The ADEC cleanup matrix score for this site is 26, which classifies this site as a level C
cleanup. Laboratory analytical results from this site show that soils at the south end of the
excavation pit and soils from beneath the dispenser island meet the ADEC level C soil matrix
cleanup standards. Soils in the north end of the excavation pit do not meet the ADEC level C
soil matrix cleanup standards. Headspace analysis PID screening results along the piping run
show that soils meet ADEC level C cleanup standards.
RECOMMENDATIONS- Further delineation to determine the lateral and vertical extent of hydrocarbon contamination should be completed near the north end of the tank pit. Any further decision regarding soil remediation at this site should be made in light of the results of this evaluation. |
Louis Howard |
| 12/31/1996 |
Update or Other Action |
During the State-Elmendorf Environmental Restoration Agreement (SERA) Phase V investigation conducted in 1996, five borings were advanced to the groundwater table. A split spoon sampler was used to collect soil from the ground surface to the water table, which was encountered at approximately 18 feet bgs.
Two samples were collected from each boring and analyzed for GRO, DRO, residual-range organics (RRO), and BTEX. Elevated contaminant concentrations were detected in 4 of the 5 borings at depths between 15 and 19 feet bgs (smear zone). Maximum detected soil contaminant concentrations were 5,130 mg/kg GRO, 7,780 mg/kg DRO, 3.49 mg/kg benzene, 51.5 mg/kg toluene, 35.6 mg/kg ethylbenzene, and 157.9 mg/kg total xylenes. Field screening indicated that contamination was not present from 0-15 feet bgs in these borings and contaminant concentrations in two samples collected from 10-12 feet bgs were below ADEC 18 AAC 75, Method Two (January 2003) cleanup levels.
|
Louis Howard |
| 7/1/1997 |
Update or Other Action |
During the SERA Phase VI investigation conducted in 1997, a passive soil gas survey was conducted and soil borings were advanced to the groundwater table to delineate soil contamination. The results of the soil gas survey indicated that elevated levels of contamination were present south of the UST area and near former Hardstand A-6.
Three borings were advanced south/southwest of Building 15380. One was drilled in the former Hardstand A-6 area and the other two borings were advanced south of the building, adjacent to Taxiway J. Two to three samples were collected from each boring and analyzed for GRO, DRO, RRO, and BTEX. In the area of former Hardstand A-6, GRO, toluene, and ethylbenzene were detected in the smear zone above cleanup levels and benzene was detected in the vadose zone above the cleanup level. Near Taxiway J, GRO, DRO, and toluene were detected in the smear zone above cleanup levels. |
Louis Howard |
| 5/31/2000 |
Update or Other Action |
ST507/6/8 is the location of an active underground storage tank (UST) and a former UST
situated adjacent to the Air Freight Terminal, Building 15380 (formerly 42-525). The former
UST, STMP 525B, was a 1,000-gallon tank that provided unleaded mogas (gasoline) for use in
operations support vehicles and equipment. An associated dispenser island was located
approximately 120 feet southeast of the tanks along the west side of Building 15380. The UST .
and dispenser island were removed in June 1994. The remaining active 1,500-gallon UST,
STMP 525A, was upgraded and currently stores diesel fuel; a new dispenser is located nearby.
A release investigation was conducted at ST507/6/8 under the State-Elmendorf Environmental
Restoration Agreement (SERA) Phases V (1996) and VI (1997) with 8 borings drilled. Analytical
results indicated that the site was impacted by petroleum hydrocarbons in excess of the Alaska
Depa:rtment of Environmental Conservation (ADEC) Method One and Method Two soil cleanup
levels. As part of the SERA Phase VIII investigation, an additional soil boring was installed in
1999 and completed as a monitoring well to better characterize the subsurface conditions
beneath the northern portion of the former UST.
Groundwater samples from the newly installed monitoring well (507WL01) contained petroleum
hydrocarbons in excess of ADEC Table C groundwater cleanup levels. Concentrations of GRO
and benzene also exceeded 10 times the groundwater cleanup levels. Product was not
detected in 507WL01, but free-phase product was observed in monitoring well 43WL 11 located
approximately 30 feet southwest of the former UST. Free product has been detected in this well
since it was first sampled in 1995.
Results from the 1999 investigation (including a review of previous investigation results) indicate that petroleum hydrocarbons are present in both soil and groundwater at ST507/6/8 at levels in excess of ADEC Method Two cleanup levels for gasoline range organics (GRO), diesel range organiCS (DRO), and benzene. The petroleum-impacted soil, however, appears limited to the
smear zone. This area of smear zone contamination extends from an area upgradient of the
former tank southward towards Hardstand A-6 and Taxiway J. ST507/6/8 physically falls within the Operable Unit 5 (OU5) Model Area; therefore, any remaining petroleum hydrocarbons are expected to be addressed by the OU5 remedy. The recommended site disposition, therefore, is to include further consideration of this site as part of the OU5 remedy and to exclude this site from further investigations under SERA.
Based on analytical results obtained during the removal of STMP 525B, it is likely that fuel
associated with the former UST was released at ST507/6/8. Based on subsequent SERA release investigations, the soil column within the immediate vicinity of the former UST (above
the water table interface) does not contain levels of petroleum hydrocarbons in excess of
modified migration to groundwater cleanup levels. Petroleum hydrocarbons remaining in the
soil column therefore should not adversely impact groundwater quality (i.e., increase the
concentration of dissolved GRO and benzene contaminants above current levels). The current
concentrations of GRO and benzene in groundwater in the immediate vicinity of ST507/6/8
(507WL01) are above 10 ten times groundwater cleanup levels.
Petroleum hydrocarbons are present in soils at levels in excess of Method One and Method
Two cleanup levels, primarily at depths greater than 15 feet bgs (considered to be the smear
zone). Release investigation data has not adequately characterized the horizontal and vertical
extent of this smear zone contamination. What is clear at this site is that an extensive area beginning somewhere upgradient of ST507/6/8 and extending generally southward towards Taxiway J has been impacted at the water table. It is unclear whether any possible releases from the former UST or the currently active diesel UST (STMP 525A) contributed to the petrol.eum hydrocarbon impact observed in smear zone soils and groundwater surrounding ST507/6/8. More importantly, the contamination observed in the immediate vicinity of the former tank, generally beginning at the top of the smear zone, may be partially or completely the result of other source areas and not necessarily due to the tank(s). |
Louis Howard |
| 7/26/2004 |
Update or Other Action |
Staff reviewed and provided comments on: ST531 Bldg. 12763 Defense Reutilization Marketing Office, EC Contaminated Site Decision Documents, Elmendorf Air Force Base, AK Dated April 23, 2004 and Basewide Groundwater Monitoring Program for Sites that Require Monitoring.
Text states: “The Elmendorf AFB Basewide Groundwater Monitoring Program will be utilized to monitor the natural attenuation of the impacted groundwater. Well 43WL11 is located approximately 30 feet southwest of the former UST and is included in the Basewide Groundwater Monitoring Program. No additional wells will be added to the monitoring program due to the location of the site on the far side of the East/West Runway and within the OU5 modeling area. UST 525A is still active and is inspected, tested, and maintained in accordance with ADEC 18 AAC 78 to ensure that it does not contribute to contamination at this site.”
The Elmendorf AFB Basewide Groundwater Monitoring Program will no longer exist after this year. Please confirm that your contractor will be monitoring the wells specified in the closure document submitted for this site and that the zone project manager is aware that the monitoring requirements for the compliance wells may be different than what is being required for under the CERCLA program.
For the site known as ST507, the Department will require analyses for DRO, GRO, and BTEX in the monitoring well identified above. |
Louis Howard |
| 4/3/2007 |
Site Closure Approved |
See ST507 Hazard ID 24004 for further information on groundwater monitoring for WL43-11 |
Former Staff |
| 5/1/2007 |
Update or Other Action |
After 2006 Zone 2 annual report, the agencies agreed to monitor well WL43-11 under site ST507 (Environmental Compliance Program). See ST507 Hazard ID 24004 for further information on groundwater monitoring for WL43-11. |
Louis Howard |
