Luke Waterdog Recreation Annex

Luke Waterdog Recreation Annex | Site History: Page 2 of 2

2002: The system operated using the submersible pumps through the second quarter of the year. Influent concentrations ranged from 300 to 500 parts per million per unit volume (ppmv) volatile fuel hydrocarbons (VFHs). The system proved effective at the site; however its efficiency was greatly dependent on the dewatering component, which was limited by the depths of available wells. As a result, only a fraction of the smear zone could be dewatered.

The second system configuration involved soil vapor extraction (SVE) and dewatering was implemented in the third quarter of the year. Under this configuration, atmospheric air was drawn into the drop tube using formation vacuum. The sparge configuration results were mixed. The initial response was effective due to the temporary volatilization of dissolved phase contaminants which increased influent vapor concentrations. However, the sparge tubes could be submerged no deeper that 15-17 inches in each well, due to limited total vacuum.

A Complex Resistivity (CR) survey was conducted in November. Resistivity was mapped in ten foot “slices” of the aquifer from depths of 25 to 55 feet bgs. The results of this mapping identified preferentially fractured zones near the former UST location. These zones were targeted for installation of monitoring wells, and MW-8 and MW-9. MW-8 and MW-9 were installed in December. Optical televiewer logs were run in both wells to identify lithology, degree of fracturing, and orientation of fracturing.

2001: A passive soil gas survey was conducted in February and March. The primary goal of the survey was to screen locations for additional monitoring wells. In general, the survey results documented low levels of hydrocarbons in the soil gas. Based on these results, three additional monitoring well locations were selected at distances 150-200 feet from the former LUST. Three additional groundwater monitoring wells were installed at the site in April.

Installation of the SVE system was initiated on June 5. The SVE design included a 100 cfm electric catalytic oxidation unit (catox), along with well head modifications, three pneumatic groundwater submersible pumps, air compressor, two-inch PVC surface piping, and one-inch air line and water line piping. The SVE was intended to operate in conjunction with groundwater pumping, in order to influence the bedrock aquifer. Based on groundwater monitoring results, and historic lake level information, it was believed that gasoline hydrocarbons had become smeared in the weathered/fractured bedrock below the water table. At that time, the smear zone was submerged, and acted as a continuing source of dissolved benzene. Groundwater pumping was intended to dewater the bedrock, allowing vacuum flow to volatilize and capture hydrocarbon vapors within the system’s radius of vacuum influence (ROI). The vapors would be oxidized by the catox unit, which was the primary component of the SVE system.

In October, an electric catox unit, air compressor, and power drop were installed at site. The system was started in November. At start up, the initial influent air concentrations contained approximately 500 ppmv  VFHs.

1999: On July 30, groundwater samples were analyzed for BTEX, total petroleum hydrocarbons (TPHs), and attenuation parameters (nitrate, sulfate, and alkalinity). The results indicated that the sampled monitoring wells had TPH concentrations in excess of Arizona Aquifer Water Quality Standards (AWQS). Methane levels were found to be elevated in all wells, which may indicate that degradation of hydrocarbons due to aerobic activity was occurring at the site.

1997: In March, the bioventing system was converted to a  SVE system and operated until May. Soil vapors were extracted at a rate of 34 standard cubic feet per minute (scfm) for 35 days. After 35 days, vapor samples were collected and no volatiles were detected in the vapors. The soil bioventing/SVE system was shut down in May.

1995 – 1996: In order to remediate the contaminated soils at the site a soil bioventing system was installed, and operated. Remediation of the soils at the site using bioventing began in June 1995. The bioventing system consisted of a single air injection well, one background well, and two vapor monitoring wells. The injection well was 15 feet deep. The bioventing system operated from June 1995 to January 1996.

In January 1996, groundwater and surface water samples were collected from monitoring wells and Apache Lake. The samples were analyzed for BTEX. Benzene was detected above state standards in one of the wells. BTEX compounds were not detected in the surface water sample.

1994: A field investigation was completed at the site to determine the extent of soil contamination. The investigation consisted of a soil gas survey, drilling, and sampling of soil borings. This investigation indicated subsurface petroleum hydrocarbon soil contamination exists. 30 soil gas survey points were sampled at the UST and AST sites, each point were analyzed for, toluene, ethylbenzene, and xylenes (BTEX). Based on results of the soil gas survey, a total of five boreholes (four at UST site and one at the AST site) were drilled and then sampled. A preliminary site characterization report was issued in May.

1993: Williams AFB was Congressionally-mandated to close on September 30. Waterdog was then closed to visitors and Luke AFB assumed responsibility for the complex.

1991: In June, Williams AFB personnel noticed a strong fuel odor and sheen on Apache Lake, as well as stained soil within the UST valve vault. Sorbent booms were installed to contain any fuel that may have leached into the lake. The release was reported to ADEQ (Report Number 91-056-A) and a LUST number (LUST 4715.1933.01 to 03) assigned. In December, approximately 135 cubic yards of petroleum contaminated soil were excavated, disposed at a licensed disposal facility (Century Materials), and the excavation was backfilled with clean fill.

1979 – 1984: Four underground storage tanks (USTs) with piping to the boat dock were constructed and added to the complex. The USTs were used to store gasoline and pre-mix for the boating operation and consisted of one 3,750-gallon regular gasoline UST, one 2,000-gallon mixed gas/oil UST and two 550-gallon mixed gas/oil USTs. Two above-ground storage tanks (ASTs) were located approximately 500 feet east-southeast of the USTs. In the early 1980s, 18 of the 21 cabins were torn down, and new slump block cabins were built in their place.

1957 – 1958: Williams Air Force Base (Williams AFB) received a special use permit for the Waterdog property in 1957 from the National Forest Service (NFS) to be used for the enjoyment of military personnel stationed at the base. Several buildings, including the recreational building, 21 cabins, the maintenance building, two maintenance sheds, and the old water treatment shed were built in 1958. A floating dock was constructed at the lake shore directly in front of the recreational building. A fuel pump was located near the floating dock for boat refueling.