Oasis Mobile Home Park Public Water System; Thermal, CA
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Background
September 14, 2021
EPA issued an Emergency Administrative Order under Section 1431 of the Safe Drinking Water Act An Act passed by the US Congress in 1974. The Act establishes a cooperative program among local, state and federal agencies to insure safe drinking water for consumers. (SDWA) 42 U.S.C. § 300i to Oasis Mobile Home Park, Thermal, California. EPA determined that conditions exist at Oasis’ public water system that may present an imminent and substantial endangerment to the persons served by the public water system. EPA’s decision was based on sampling results that indicated high arsenic levels, that exceeded the maximum contaminant level (MCL) [1], in the distribution system (premise plumbing), well source water, and at the entry point to the distribution system.
The Order and its requirements are necessary to ensure adequate protection of public health at the public water system. The Order requires, in part, that Oasis provide alternative water, notify the public of the high levels of arsenic, identify and correct the cause of the high arsenic levels, and perform increased monitoring and reporting.
August 23, 2023
The United States Department of Justice (DOJ) filed a Civil Complaint, on behalf of EPA, against the operators of Oasis, alleging failure to properly maintain and operate Oasis’ primary drinking water well, treatment and distribution systems and wastewater system, and failure to perform corrective measures to protect the health of those who consume the drinking water.
January 23, 2025
EPA announced a consent decree with the operators of the Oasis Mobile Home Park to resolve violations of SDWA. The consent decree requires the Park’s operators to upgrade the Park’s drinking water and wastewater systems and pay a $50,000 penalty.
The consent decree requires extensive upgrades and operational improvements to the drinking water system at Oasis over the next two years. In addition to the $50,000 civil penalty, key requirements include:
- Installation of alarms on the drinking water treatment system to monitor its operation;
- Addition of at least 80,000 gallons of water storage capacity;
- Installation of a booster pump and purchase of critical replacement parts;
- Ensuring that qualified public water system operators are at the Park seven days per week until the Park’s operators install the alarm system;
- Development of comprehensive standard operating procedures for the public water system;
- Mandatory quarterly meetings with EPA to review compliance progress with the consent decree; and
- Notification to EPA as soon as possible and no later than twenty-four hours if consent decree violations or other issues pose an immediate threat to public health or the environment.
The consent decree also requires the operators to work with an EPA contractor to develop a wastewater system assessment, expected to be completed by March 2026. The operators must fix problems identified during the wastewater system assessment after the Oasis drinking water system improvements are completed.
Oasis, located in California's Eastern Coachella Valley, sits within the Torres Martinez Desert Cahuilla Indians Tribal Reservation boundaries. With an estimated population of 1,000 people, it is the valley's largest mobile home facility and primarily serves agricultural workers. While situated on Tribal land, the public water and wastewater systems at Oasis operate independently from Tribal control or ownership. The Park’s drinking water system uses groundwater that has high levels of naturally occurring arsenic. Arsenic is a known carcinogen, and drinking high levels over many years can increase the chance of lung, bladder, and skin cancers, heart disease, diabetes, and neurological damage.
Sampling Results
As part of EPA’s ongoing enforcement, EPA has taken arsenic [1] and iron [2] samples (iron levels were taken to better understand arsenic levels) at the kitchen taps of homes served by the Oasis public water system periodically since April 2023. The results, recorded in parts per billion (ppb), are below.
To protect resident privacy, EPA is committed to safeguarding sensitive information by not disclosing specific home numbers in the sampling results. Instead, EPA is using unique identifiers (such as Zone 3/A1) to publicly report changes in arsenic and iron levels for each home location without compromising individual privacy. For example, location Zone 3/A1 identifies home A1 is located in Zone 3. A map of Oasis divided between different zones for purposes of sampling within the distribution system can be viewed in the Sampling Zone Map. Additionally, location Z3/A1 represents the same home location in all sampling results. Home locations not included in any specific sampling event means that specific home location was not sampled during that specific sampling event (such as the resident was not home at the time of sample collection).
* Sample was compromised during the shipping and handling process. No data is available.
^ Sample was collected from the bathroom tap instead of the kitchen tap.
Sampling Zone Map
Below is a map of Oasis divided between different zones for purposes of sampling within the distribution system. Zones correlate with the sample location results above. To protect resident privacy, EPA is committed to safeguarding sensitive information by not disclosing specific home locations in the sampling results.
Documents
- DOJ Complaint Against Oasis Mobile Home Park for Alleged Safe Drinking Water Act Violations | Queja del Departamento de Justicia contra Oasis Mobile Home Park por presuntas violaciones de la Ley de Agua Potable Segura (pdf)
- Emergency Administrative Order: Oasis Mobile Home Park | Orden administrativa de emergencia: Oasis Mobile Home Park (pdf)
- Oasis Mobile Home Park Drinking Water Fact Sheet (pdf)
- Oasis Mobile Home Park Water Filtration System Fact Sheet (pdf)
- Residential Flushing Procedure Handout (pdf)
- Arsenic and your Distribution System Brochure (pdf)
Footnotes
- EPA has established National Primary Drinking Water Regulations (NPDWRs) under the Safe Drinking Water Act (SDWA) that set mandatory water quality standards for drinking water contaminants. These are enforceable standards called "maximum contaminant levels" (MCLs) which are established to protect the public against consumption of drinking water contaminants that present a risk to human health. An MCL is the maximum allowable amount of a contaminant in drinking water which is delivered to the consumer. EPA set the MCL for arsenic at 10 parts per billion (ppb) to protect consumers against the effects of long-term, chronic exposure to arsenic in drinking water.
- EPA has established National Secondary Drinking Water Regulations (NSDWRs) that set non-mandatory water quality standards for 15 contaminants. EPA does not enforce these "secondary maximum contaminant levels" (SMCLs). They are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. These contaminants are not considered to present a risk to human health at the SMCL. The SMCL for iron is 300 ppb.