General Water

Lahontan Regional Water Quality Control Board Implementation of Statewide Water Quality Policy for Onsite Wastewater Systems

By Douglas F. Smith, Assistant Executive Officer

The Lahontan Regional Water Quality Control Board, known as the Lahontan Water Board, is a state agency whose mission is to protect surface and ground­water uses for current and future benefit of all Californians. The board has seven members appointed by the governor and confirmed by the Senate. Staff offices are located in South Lake Tahoe and Victorville.

This article’s focus is the implementa­tion of the State’s Onsite Wastewater Treatment System (OWTS) Policy as it affects the South Lahontan Basin. These onsite systems are more commonly re­ferred to as septic systems.

Sewered and Non-sewered Areas

In the Lahontan Region, both commu­nity wastewater treatment facilities and individual septic systems are used to manage domestic wastewater discharg­es. The Lahontan Water Board autho­rizes more than 100 discharges through individual waste discharge require­ments or orders. Most discharges of treated wastewater are applied to land as recycled water for crops, used in land­scape irrigation, or allowed to percolate through the soil to groundwater. Land applying such discharges helps to filter out pathogens and provides an effective method of groundwater recharge. Reg­ulated facilities are required to conduct monitoring and reporting to ensure the protection of water quality.

Where individuals or subdivisions do not have readily available community wastewater collection systems (sewers), individual septic systems are used. Es­timates of the number of septic systems in California are more than 1.2 million. Because the Lahontan Region is pre­dominately rural, the population served with septic systems is a significant frac­tion of the total population within the region.

Pre-policy Regulation of Septic Systems

Local jurisdictional agencies (local agencies) issue building permits for the construction of septic systems. The lo­cal agencies are counties and incorpo­rated cities/towns.

Conventional septic systems consist of a septic tank for solids removal and liq­uids disposal by sub-surface drain fields or seepage pits. To ensure protection of public health and safety, the Water Quality Control Plan for the Lahontan Region (Basin Plan) has specified mini­mum criteria that local agencies must follow before issuing building permits for new septic systems. Through the Basin Plan and implementing memoran­dums of understanding (MOUs) with lo­cal agencies, the Lahontan Water Board restricted septic system discharges to 500 gallons per acre per day or 250 gal­lons per day per two equivalent dwell­ing units per acre. Installation of septic systems were allowed on lots having a net area greater than or equal to 15,000 square feet at subdivisions approved be­fore 1988.

Emergence of the Statewide Policy

There have been occurrences in Califor­nia where septic systems, for a number of reasons, have not protected water quality and public health. Because of this concern, the Legislature amended the Porter Cologne Water Quality Act and required the state to adopt a state­wide policy for septic systems regula­tion. The State Water Resources Con­trol Board (State Water Board) adopted the OWTS Policy on November 13, 2012, and it became effective on May 13, 2013.

OWTS Policy Objectives, Scope, and Processes

The OWTS Policy allows the continued use of septic systems providing they are protective of water quality and public health. The OWTS Policy recognizes that existing local agencies are best to manage septic systems and relies upon existing local programs to improve these systems, with coordination between local agencies and the Water Board. To accomplish this, the OWTS Policy establishes a statewide, risk-based, tiered approach for the regulation and management of septic systems installations and replacements, consisting of Tiers 0 to 4. The OWTS Policy also sets the level of performance and protection expected from septic systems. General OWTS Policy information describing OWTS Policy Tiers is presented below and can be accessed on the Lahontan Water Board website at:­sues/programs/owts/index.shtml.

OWTS Policy Tiers

The OWTS Policy sets five different tiers for regulating septic systems, based on risk to water quality:

Tier 0 Properly functioning septic sys­tems and no impacts to water quality

Tier 1 Statewide standards for new or replacement septic systems

Tier 2 Local Agency Management Program (LAMP) to regulate septic systems

Tier 3 Specific standards for septic systems that may be affecting surface waters

Tier 4 Septic systems that require cor­rective action

Tier 1 sets prescriptive siting and design standards to assure short-term and long-term protection of water quality. Of significance is the allowable density for new septic systems. In the High Desert area, the minimum density under Tier 1 is one equivalent dwelling unit per 2½ acres for subdivisions created after May 13, 2013.

Tier 2 is a LAMP, administered by local agencies, for new or replacement septic systems. Local agencies develop and maintain the LAMP. The LAMP pro­vides an alternative method of achiev­ing the OWTS Policy’s objective to protect water quality and public health. A LAMP may contain different siting and design requirements than Tier 1. Of interest to economic development, the tiers associated with the local agency approval of new and replacement septic systems are Tier 1 and Tier 2.

Tier 3 applicable in areas of impaired water bodies, does not currently apply in the High Desert, as there are no listed impaired surface water bodies.

Tier 4 applies to septic systems that are not properly functioning (failing). Fail­ure may be indicated by surfacing efflu­ent, wastewater backing up in plumb­ing fixtures, septic systems component/ piping structural failure, or significant groundwater or surface water degrada­tion.


While the OWTS Policy contains a number of milestones, it allows local agencies to manage their previous septic system program under the Basin Plan/ MOU until the Lahontan Water Board approves the local agency LAMP or May 13, 2018, whichever occurs first. After May 13, 2018, a local agency must regulate septic systems under either the Tier 1 restrictive requirement or the Tier 2 LAMP.

Summary of LAMP Submissions in the High Desert

The table below presents the eight local agencies in the High Desert portion of the South Lahontan Basin that propose to implement a Tier 2 LAMP.


These agencies have proposed different approaches to limit septic system den­sity but generally continue the existing Basin Plan/MOU density criteria: one dwelling unit per ½ acre and 15,000 ft² for some parcels. An up-to-date status of LAMP submission, review, and La­hontan Water Board approval is avail­able on the Lahontan Water Board web-site.

Septic Systems with Supplemental Treatment

In some cases, supplemental treatment is needed because of site conditions, such as rapid infiltration rates in underlying soil and shallow groundwater or a com­mercial site that does not meet the den­sity criteria. In these cases a developer may need to add supplemental treatment to septic systems to compensate for in­creased loading of pathogens and nutri­ents. Some local agencies will include these types of systems within the scope of the LAMP and require inspections, maintenance, and monitoring. Lahon­tan Water Board staff may review these proposed systems at the request of the local agency and will provide recom­mendations for the siting, construction, and ongoing maintenance of the system. However, if the local agency chooses not to regulate these systems, the de­veloper must obtain waste discharge requirements (e.g., permit) from the La­hontan Water Board.

Water Quality Assessment Program

As stated, local agencies with a LAMP must maintain a Water Quality Assess­ment Program to evaluate the impact of septic system discharges. A Water Quality Assessment Program must include surface and/or groundwater moni­toring, data collection, and assessment. However, local agencies may use data collected from other monitoring pro­grams or data sources to characterize the effect of septic system discharges on water quality. Additionally, Water Board staff supports and encourages local agencies to track and evaluate lo­cations and densities of septic systems and water supply wells to estimate and predict future adverse changes in water quality.

Lahontan Water Board staff recogniz­es that the Water Quality Assessment Program is an evolving process. Lo­cal agencies are encouraged to partner with other agencies, such as the Mojave Water Agency, who maintains a reposi­tory of groundwater quality data from its programs as well as data gathered by the United States Geological Survey (USGS). The State Water Board’s Divi­sion of Drinking Water also maintains data from regulated drinking water sys­tems.

Conditional Waiver of Waste Dis­charge Requirements

The State Water Board has waived the requirements for a septic system owner to submit a report of waste discharge, pay fees, and obtain waste discharge requirements from the Lahontan Water Board. The waiver applies to septic system discharges covered under the OWTS Policy, primarily domestic wastewater discharges of less than 10,000 gallons per day and less than “high-strength” water (less than 900 milligrams per liter of biochemical oxygen demand). Septic system owners with a design flow of greater than 10,000 gallons per day (or that meet other criteria – such as discharges of industrial wastewater) must obtain waste discharge requirements from the Lahontan Water Board.

Local Financial Effects

Local agencies are proposing LAMPs that comply with the OWTS Policy and, if accepted by the Lahontan Wa­ter Board, propose negligible effects on new developments. LAMP implementa­tion may increase tracking and monitor­ing by the local agencies and bear the cost of preparing and submitting Water Quality Assessment Program reports or supporting counties in preparing these reports. Future changes to LAMPs may be proposed to the Water Board. In­creases in local agency program costs are unknown. The Lahontan Water Board encourages developers to consid­er installing community sewer systems, where feasible, to allow for the re-use and recycling of such water for benefi­cial use of the public. In this manner the underlying high quality groundwater of the Mojave Desert can be protected and managed to provide safe drinking water to our communities for a long time to come.