Idaho Environmental Guide for Local Governments: Wastewater
Wastewater is spent or used water, such as from households and businesses, that contains enough harmful material to damage water quality. Every building with running water generates some sort of wastewater.
Why Communities Should Care
If a city, district, or other entity owns and operates a wastewater collection or treatment system, it is responsible for protecting the health of its citizens and fulfilling the requirements of state and federal rules and permits for collecting, treating, and disposing of the wastewater. Similarly, individuals with wastewater systems discharging to drainfields on their lots are responsible for all wastes entering their systems because these wastes ultimately enter the ground water below the drainfields. Ground water is Idaho's main source for individual and community drinking water.
Wastewater may contain contaminants such as oil, dirt, human waste, and chemicals. Untreated wastewater can cause serious harm to the environment and threaten human health. Proper management and disposal of wastewater is essential to protect public health and Idaho's water quality.
What Communities Can Do
- Prior to project approval, request that project information specify applicability of requirements under Idaho's Wastewater Rules (IDAPA 58.01.16), Recycled Water Rules (IDAPA 58.01.17), and Individual/Subsurface Sewage Disposal Rules (IDAPA 58.01.03) apply.
- Plan ahead by developing and using a comprehensive land use management plan, which includes the impacts of present and future wastewater management. Generally, DEQ recommends that all new projects be served by existing approved wastewater collection systems or centralized community wastewater systems whenever possible.
- Local governments have authority to implement ordinances that go beyond federal and state laws and regulations for management of wastewater. Determine what is best for the health and welfare of the community.
- Understand the project's type of wastewater and its collection and treatment system prior to project approval. A project will generally fall under one of the following three categories:
- Projects that expand existing wastewater systems
- Projects that propose new wastewater systems
- Subsurface treatment and disposal system (SSDS)
- Community subsurface treatment and disposal systems
- Individual on-site wastewater systems
- The following information applies to owners (a city, district, or other entity) of an existing wastewater system:
- Understand responsibilities. If a city, district, or other entity owns and operates a wastewater collection or treatment system, it is responsible for protecting the health of its citizens and fulfilling the requirements set of state and federal rules and permits.
- Different rules apply to different types of wastewater collection, treatment, and disposal systems in Idaho. Determine which type of system is being operated. Wastewater collection, treatment, and disposal systems have five basic categories of requirements under Idaho's Wastewater Rules (IDAPA 58.01.16) and Recycled Water Rules (IDAPA 58.01.17):
- Engineering design and construction
- Construction and engineering
- Ongoing monitoring
- Operation and maintenance
- Understand the system by taking these steps:
- Talk to the operator of the wastewater system to determine the status of the system.
- Understand the certification requirements needed by an operator.
- Consider having a city and county elected official attend on-site inspections. While not required, it is a good idea for them to participate to understand the requirements and be aware of deficiencies.
- If correspondence from state or federal agencies such as DEQ or EPA is received, contact the agency directly with any questions.
- Meet with regulating agencies, such as the DEQ regional office or local Public Health District, to determine operating responsibilities, accountable parties, and issues affecting the wastewater system.
- Consider developing a facility plan for all wastewater systems, regardless of plans for growth. Doing so can help identify deficiencies in a system in advance of new projects so ample time is available to address problems or issues. Cities are responsible for continually ensuring adequate capacity.
- Contact a DEQ regional office with any questions regarding expanding or modifying existing systems.
- If a system has a lagoon, the Wastewater Rules require that all lagoons be tested for leakage prior to April 15, 2012. Plan ahead to meet this deadline.
- Identify and implement pollution prevention measures.
- Local governments have authority to implement ordinances that go beyond state and federal laws and regulations for management of wastewater. Determine what is best for the health and welfare of the community. Learn about wastewater treatment method benefits and drawbacks. DEQ's regional offices and state program personnel can help ensure applicable and effective ordinances are proposed and enacted.
Projects that Expand Existing Wastewater Systems
- DEQ recommends verifying that adequate sewer capacity is available to serve projects. Prior to project approval, the city and county may want to contact the sewer provider for three items:
- A capacity statement or declining balance report
- The system's willingness to serve the project
- The system's ability to serve the project
Note: These items are required by DEQ for project review/approval.
- All facilities should have a DEQ-approved facility plan that outlines current capacity and future expansions needed to expand capacity. If the existing facility plan is inadequate to cover new projects, a new facility plan must be prepared and submitted to DEQ unless the new project is classified as a simple wastewater main extension and capacity can be demonstrated without a new facility plan. Developing a facility plan can help identify deficiencies in a system in advance of new projects so ample time is available to address problems or issues.
- According to Idaho's Wastewater Rules, all systems proposing major wastewater system collection projects, pump station projects, treatment plant designs or upgrades, or new septage transfer stations are required to submit a project-specific preliminary engineering report for DEQ review and approval prior to submitting project specific plans and specifications for the project.
- All projects involving wastewater collection systems, wastewater treatment plants, or wastewater disposal systems must be designed by a professional engineer registered in Idaho. Plans and specifications need to be approved prior to construction. Refer to Idaho Code §39-118 and Section 440.03 of the Wastewater Rules to determine design review authority.
- For existing wastewater systems with adequate capacity, the plans for simple wastewater main extensions may qualify to be reviewed and approved by a Qualified Licensed Professional Engineer (QLPE) prior to initiation of construction. Refer to Idaho Code §39-118 and Section 440.03 of the Wastewater Rules for applicability and requirements. These simple wastewater main extensions are the only wastewater projects that do not require DEQ plan review and approval. Additionally, at the discretion of any city, county, quasi-municipal corporation, or regulated public utility, projects that fall under Idaho Code §39-118 may be referred to DEQ for approval. However, upon project completion project as-built drawings must be submitted to DEQ.
- DEQ does not review plans for gravity service lines serving residences; these should be reviewed by the State Plumbing Bureau and/or the local building department. Contact DEQ to discuss requirements on any other service line that includes mechanical components.
Projects that Propose New Public Wastewater Systems
- All projects involving new wastewater collection, treatment, or disposal systems must be designed by a professional engineer registered in Idaho. Refer to Idaho Code §39-118 to determine applicability of DEQ design review.
- According to Idaho's Wastewater Rules, DEQ recommends that a city or county consider the following when approving or constructing new public wastewater collection, treatment, or disposal systems:
- Schedule a pre-design meeting with DEQ prior to preparing facility plans, engineering reports, or plans and specifications for a new public wastewater collection system.
- Plans and specifications must be approved by DEQ prior to construction.
- Before submitting plans and specifications for the wastewater collection, treatment, or disposal system for DEQ review and approval, all new systems must have a current facility plan, a Technical, Financial, and Managerial (TFM) document, and a project-specific engineering report approved by DEQ.
- The facility plan is a planning document that covers items such as the project's location, population, demographics, and the overall wastewater system configuration (collection, treatment, and disposal components). The facility plan should be prepared and submitted to DEQ prior to design of the wastewater infrastructure. Ideally, a facility plan would also be used to support and supplement planning and zoning requests. Facility plans are sometimes referred to as master plans or facilities planning studies.
- The TFM demonstrates a systems ability to construct, own, and operate a wastewater system, and documents the capabilities required of a wastewater system to achieve and maintain compliance with the Wastewater Rules.
- The project-specific preliminary engineering reports are engineering documents used to establish the detailed design basis for individual wastewater components such as pumping stations and treatment works.
- If a project includes a private municipal wastewater treatment plant, the minimum design capacity for such plants is 25,000 gallons per day based on average day flows.
- Per the Idaho Wastewater Rules, owners of municipal wastewater treatment plants must receive a
- draft National Pollutant Discharge Elimination System (NPDES) permit
- a draft wastewater reuse permit or
- a final subsurface treatment and disposal system (SSDS) permit
Plans and associated specifications for collection and treatment systems must be approved by DEQ. Communities approving projects should consider this requirement when scheduling timelines and understand the wastewater treatment plant's effluent discharge proposed for a project.
- NPDES permit. If wastewater treatment plant effluent will reach state waters, an NPDES permit issued by EPA will be required for the proposed discharge. Permits may be difficult and time-consuming to obtain.
- Wastewater reuse permit. If a project proposes reuse of wastewater (for irrigation or land application, for instance), a wastewater reuse permit is required from DEQ.
- Subsurface treatment and disposal system (SSDS). If effluent from the wastewater treatment plant will be discharged to ground water through a subsurface disposal system, a permit from the Public Health District is required. DEQ review and approval may also be necessary.
Subsurface Treatment and Disposal System (SDDS)
Subsurface sewage disposal systems can service the needs of various wastewater generators ranging from individual homes to small communities. Where and how the wastewater is generated establishes the type of subsurface sewage system while the wastewater volume determines whether enhanced drainfield configurations are required.
There are two common types of subsurface treatment and disposal systems: 1) Individual on-site wastewater systems and 2) Central subsurface treatment and disposal systems, commonly referred to as a Community SSDS.
Additionally, if wastewater volumes of 2,500 gallons per day (GPD) or more are received by the SSDS, the drainfield is classified as a Large Soil Absorption System (LSAS) and must meet enhanced design, construction, monitoring and reporting requirements.
DEQ has established minimum standards, the Individual/Subsurface Sewage Disposal Rules (IDAPA 58.01.03), for the design, construction, siting, and use of individual and subsurface sewage disposal systems. These rules also establish requirements for obtaining an installation permit and an installer's registration permit. These rules are administered by Idaho's seven Public Health Districts through a Memorandum of Understanding with DEQ. Contact the local Public Health District during initial project planning efforts to understand site and wastewater system requirements.
- Individual on-site wastewater systems. Individual septic systems are on-site wastewater systems that discharge wastewater into an underground tank where solids are separated from the effluent and the clarified water is dispersed into a subsurface drainfield located on the same property where the wastewater is generated. These on-site systems predominantly service residences in areas without access to municipal wastewater treatment plants and have historically been known as septic systems.
- On-site SSDS have the potential to transport pollutants from sewage to ground water. To help prevent this, nutrient-pathogen evaluations (N-P evaluations) may be required for certain proposed on-site wastewater disposal systems. If an N-P evaluation is not required by Public Health Districts, the local government may decide to assess a project's impacts to groundwater and request an N-P evaluation. Requiring an N-P evaluation may be prudent, especially if the subsurface disposal of sewage is to occur in a Public Drinking Water System's source water recharge area.
- On-site SSDS may also service commercial, industrial and institutional facilities. Care must be taken in designing and constructing a SSDS that receives wastewater from these facilities due to the potential for chemical contamination of ground water. SSDS serving these facilities are classified as non-domestic SSDS and must preprocess any wastewater generated to domestic wastewater strength prior to discharging to the drainfield. Furthermore, due to the potential for undesirable chemicals to enter these systems, the Idaho Department of Water Resources (IDWR) may have additional requirements as specified in the IDWR Rules and Minimum Standards for the Construction and Use of Injection Wells in the State of Idaho (IDAPA 37.03.03). The Public Health District coordinates system review with DEQ. DEQ coordinates the jurisdictional issues with IDWR for permitting of these non-domestic on-site SSDS.
- Central (Community) SSDS. A community SSDS is any wastewater treatment system that receives wastewater from more than two dwelling units or more than two buildings under separate ownership. These types of systems are analogous to more well known municipal wastewater collection and treatment systems with which they share many characteristics, but they discharge the processed wastewater to a subsurface drainfield. If a project indicates that a community SSDS will be used, details on this system need to be provided to the local Public Health District. The Public Health District will coordinate the review of all project submittals with DEQ so that the community SSDS meets all applicable Rules.
- Since Community SSDS share multiple characteristics with municipal wastewater treatment systems, they must also meet the regulatory requirements in the Idaho's Wastewater Rules (IDAPA 58.01.16). Specifically, the project needs to submit technical, financial and managerial documentation (IDAPA 58.01.16.409), a preliminary engineering report (IDAPA 58.01.16.411), and plans and specifications (IDAPA 58.01.16.420) that meet the minimum requirements specified in subsections for pipelines (IDAPA 58.01.16.430) and, if present, pump stations (IDAPA 58.01.16.440) and private wastewater treatment plants (IDAPA 58.01.16.455).
- Community SSDS may also service commercial, industrial and institutional facilities and, since the wastewater is coming from multiple sources, the likelihood that some of these sources are commercial, industrial and institutional facilities is increased. Consequently, additional care must be taken in designing and constructing a Community SSDS that receives wastewater from these facilities due to the potential for chemical contamination of ground water. DEQ recommends that Community SSDS receiving these mixed wastewater streams have the wastewater from these non-domestic sources evaluated prior to allowing them to connect to the collection system. DEQ and IDWR Rules may apply. Contact the DEQ regional office or IDWR for assistance.
- LSAS. Any individual or community SSDS that will receive wastewater volumes of 2,500 gallons per day or more must be designed and constructed to meet the additional configuration requirements specified in the Individual/Subsurface Sewage Disposal Rules (IDAPA 58.01.03.013) subsection on Large Soil Absorption System Design and Construction. The Public Health District coordinates system review and approval with DEQ prior to the Health District's issuance of necessary installation permits.
- Due to the large wastewater volumes discharged to the ground water at an LSAS, DEQ requires the developer to generate and submit a N-P evaluation. DEQ evaluates the N-P study to verify that the proposed system will not significantly degrade the beneficial uses of the ground water. It is recommended that an N-P study be successfully performed and approved prior to any system design activity start.
- All LSAS must be designed by an Idaho licensed professional engineer. Construction must be performed by a registered complex system installer or a licensed public works contractor who has experience in subsurface system installation and the installation, must be performed under the direction of a licensed professional engineer.