The Arizona Department of Environmental Quality has given preliminary approval to a plan to clean up remnants of gasoline that leaked from an underground storage tank at a local gas station 30 years ago, and the department is seeking public comment before those plans are put into action.

The cleanup in question is at the Terrible’s gas station located at 60 N. Lake Havasu Avenue, regarding a leak that was discovered and reported to ADEQ in April of 1991. Although past efforts have been made to clean up the site in the 30 years since, the Westmark Group submitted a Corrective Action Plan to ADEQ in September, on behalf of Terrible Herbst, Inc., that is expected to return the soil and groundwater to within ADEQ’s established standards in about five years. Monitoring of the groundwater and soil in the area indicates that the contamination is fairly localized, and has not reached Lake Havasu.

The confirmed contaminants in the groundwater – about 58 to 65 feet below ground – are benzene, toluene, ethylbenzene and total xylenes (collectively called BTEX), 1,2-Dibromoethane/Ethylene dibromide (EDB), and benzo(a)pyrene. Confirmed contaminants in the soil include BTEX, Sec-butyl benzene, cumene, n-Propylbenzene, 1,2,3,4,5-Trimethylenzene, and naphthalene.

ADEQ has given preliminary approval to an estimated $1,637,600 plan to set up a multi-phase extraction system. The proposed system is designed to extract vapors from the soil, which will be treated prior to emission in accordance with air quality standards, and to pump out and treat the contaminated groundwater, before discharging into the city sewer system or the storm sewer after obtaining the proper permits.

“ADEQ has determined that multi-phase extraction should ensure the adequate protection of public health, welfare and the environment, provide for the maximum beneficial use of the soil and waters of the state, and be reasonable, necessary, technically feasible, and cost effective,” ADEQ wrote in a letter addressed to Terrible Herbst President Tim Herbst on Thursday.

ADEQ began accepting public comments about the proposal on Friday and the 30-day comment period will remain open through Nov. 8.

If approved, the multi-phase extraction system would be designed in December, followed by permitting and installation of the remediation system starting in January 2022. In the proposed corrective action plan, the Westmark Group estimates that the system will need to run for five years in order to achieve the goal of meeting ADEQ’s Tier 1 standards.

Comments can be emailed to, or mailed to Garrett Tabor, Waste Programs Division, 1110 W. Washington St., Phoenix, AZ, 85007. In the press release ADEQ says it may announce and hold a public meeting on the proposal if there is sufficient public interested during the public comment period.

“Following the public comment period, ADEQ will consider and respond to all public comments received in making a final determination on the corrective action plan,” said ADEQ spokesperson Caroline Oppleman.

 History of the site

According to the proposal, the groundwater has been monitored since 1991 and the underground storage tank systems were removed in November 1991, along with some impacted soil below the tanks and the piping.

“However, fuel from the release appears to have migrated down through the vadose zone and accumulated near the top of the groundwater table,” Westmark Group wrote in the corrective action plan.

The report says that historically, gasoline recovery efforts have primarily been accomplished by hand bailing or deploying produce recovery canisters. The report says such efforts at the Terrible’s on Lake Havasu Avenue have recovered an estimated 220 gallons of contamination as of September 2021.

The report says in response to a request from ADEQ in 2018, a pilot test was conducted that attempted to use a Solar Sipper hydrocarbon recovery system to remove the leftover contaminants, but the pilot tests ultimately proved to be unsuccessful.

Leaking USTs not uncommon

According to ADEQ’s website, leaking underground storage tanks (usually a petroleum leak) have been identified as a major source of soil and groundwater contamination. But in most cases, such leaks do not pose an immediate threat to public health.

ADEQ says there is little to no health risk posed by soil contamination unless there is contact with the skin, or it is ingested. The department also says that there is little to no risk for anyone connected to a public water system – such as Lake Havasu City’s water – because that water is filtered for residential and business use. But the department says anyone with a private well in the vicinity is encouraged to have their well water tested for possible contamination.

ADEQ is tracking lots of similar leaks throughout the city, county and state. There are currently three sites where an underground storage tank has leaked, or is leaking, within Lake Havasu City – one at the Terrible’s at 104 S. Acoma Blvd. and one at the Max Mini Mart at 1571 Palo Verde Blvd, in addition to the Terrible’s on Lake Havasu Avenue.

Other nearby sites being tracked by ADEQ include three in Bullhead City with another in Mohave Valley, four sites in Kingman, and three sites in La Paz County between the Parker Dam and the town of Parker. A map of all the sites in Arizona is available online at

 Terrible Herbst #148

The Terrible’s on South Acoma Avenue is also currently in the process of working with ADEQ on a corrective action plan for a 25-year old confirmed leak that was discovered on Nov. 6, 1996.

“When available [the corrective action plan] will provide the environmental data for the site and the proposed clean-up plan,” Oppleman said.

According to the original report in 1996, the gasoline contamination was discovered when three 10,000 gallon underground storage tanks used to store gasoline were removed at the business, along with one that stored used oil. The report also indicates that contaminated soil was removed and stockpiled on site in an attempt to limit contamination.

Max Mini Mart

The leak at the Max Mini Mart on S. Palo Verde Blvd. is a much more recent development than either of the other sites in Lake Havasu City.

According to the report sent to ADEQ on Jan. 22, 2020, the contamination was discovered the previous day involving three 10,000 gallon underground storage tanks and product piping near one of the business’s dispensers. Leaked contaminants include unleaded gas, unleaded premium, and diesel.

The report states that soil sampling was conducted on Jan. 16 and 17, 2020 at shallow and deep depths for each of the tanks, the piping, and the dispensers as part of the businesses action plan for permanent closure of the tanks. The leaks were discovered as the closure plan was enacted.

According to the original report, there is no known impact from the leak on drinking water wells, groundwater wells, or any daycare, hospital, park or school in the vicinity.

Oppleman said Max Mini Mart is doing clean-up work of the site under ADEQ’s underground storage tank preapproval program, which provides financial assistance for cleaning up releases from regulated underground storage tank systems – provided they can demonstrate compliance with financial responsibility requirements such as insurance.


(2) comments


I agree, a well written report by Michael. As a secondary note It sure would be nice if they could fix their asphalt. It is so rough in most places it almost becomes a walking hazard. Time for a skim coal of sand and alsphal to smooth out the blacktop.


very nice report sir.

Welcome to the discussion.

Keep it Clean. Please avoid obscene, vulgar, lewd, racist or sexually-oriented language.
Don't Threaten. Threats of harming another person will not be tolerated.
Be Truthful. Don't knowingly lie about anyone or anything.
Be Nice. No racism, sexism or any sort of -ism that is degrading to another person.
Be Proactive. Use the 'Report' link on each comment to let us know of abusive posts.
Share with Us. We'd love to hear eyewitness accounts, the history behind an article.