• Salmon Creek Treatment Plant

    Salmon Creek Treatment Plant

    2026 Online Open House

  • Welcome!

  • The Salmon Creek Treatment Plant is a vital part of the wastewater system, helping to keep our community livable and protect the environment. This online open house will provide an opportunity to learn more about the Discovery Clean Water Alliance, the plant and projects in the works.

    We’ll also share our plans for the future as we grow with the community, and we’ll share some ways you can support our work keeping our waterways clean and safe. Thank you for participating!

  • Visit the stations to learn more about:

    1. Who We Are
    2. The Treatment Plant
    3. Planning for the Future
    4. Construction Projects
    5. Protect Our Water
    6. Stay in Touch - Be sure to fill out the questionnaire and we'll send you a thank you gift!

  • Illustration of the Salmon Creek Treatment Plant

  • Note: This online open house should take about 10 minutes to view. You may use the links at the top of the page to skip to specific information. Please participate by Thursday, July 2.

  •  

  • Who We Are  

  • The Alliance is a regional partnership created to improve sewer service delivery through joint ownership and management of regional wastewater assets. 

    The Salmon Creek Treatment Plant is owned by the Discovery Clean Water Alliance, which is a partnership consisting of Clark County, the Clark Regional Wastewater District, and the cities of Battle Ground and Ridgefield. The Alliance was formed in 2013 to jointly manage wastewater infrastructure critical to the region’s economic and environmental health. 

  • Partner logos: City of Battle Ground, City of Ridgefield Washington, Clark County Washington, Clark Regional Wastewater District

  • Members

    • City of Battle Ground
    • City of Ridgefield
    • Clark County
    • Clark Regional Wastewater District

    Service Area Assets

    • Gravity interceptors
    • Pump stations
    • Force mains
    • Treatment plants
  • Map showing the Salmon Creek Treatment Plant service areas with highlights around Ridgefield, Battle Ground, and north Vancouver Washington.

    This map shows the Alliance’s service area (Click the image to enlarge and open in a new tab)

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  • The Treatment Plant

  • Providing Reliable Wastewater Service

    The Salmon Creek Treatment Plant is the last part of the system that moves your wastewater. The plant receives and treats roughly 9–13 million gallons of wastewater per day from homes and businesses. An estimated 120,000 residents living in unincorporated Clark County and the cities of Battle Ground and Ridgefield rely on this important facility every day.

  • Illustrated aerial map of the Salmon Creek Treatment Plant showing eight numbered facility components across the site, surrounded by trees and a nearby residential area.

  • What happens at the treatment plant

  • 1. Preliminary Treatment/Screening

    Preliminary treatment involves screening out objects such as personal hygiene products, wipes and other debris. Trash that is removed from the system is taken to the landfill. Each year, almost 200 tons are removed. Additionally, odorous gases from wastewater are pumped through a biotrickling filter to reduce odors. After the flow passes through the screening systems, it is ready for the primary treatment process.

    Close-up of a bar screen covered in debris removed during preliminary treatment screening.

  • 2. Primary Treatment

    In this phase, gravity causes the solid waste to settle to the bottom of the tank, allowing for efficient removal of more than half of the solid material coming into the plant. These solids are transferred to the solids process for further treatment. Aluminum covers help reduce the escape of odors.

    Exterior view of the Salmon Creek primary treatment facility showing covered settling tanks and the treatment building.

  • 3. Secondary Treatment

    Secondary treatment creates ideal food and oxygen conditions that allow bacteria and other microscopic organisms to quickly and efficiently digest dissolved waste. This process is similar to what happens in a natural environment but on a much larger scale. At the end of secondary treatment, nearly all waste has been removed from the water.

    Overhead view of a circular secondary treatment clarifier with a mechanical scraper arm, part of the biological treatment process.

  • 4. Disinfection

    Disinfection is the final step in the liquids treatment process. Water passes through chambers containing ultraviolet lamps that kill any remaining disease-causing bacteria and pathogens. The plant uses ultraviolet lamps, a safer option than chemical disinfection. Washington State Department of Ecology closely monitors the treatment process to ensure all treated wastewater meets strict environmental standards.

    Exterior view of the UV disinfection chambers.

  • 5. Discharge

    Following treatment, effluent (treated wastewater) from the plant is transported by pipeline and released into the Columbia River through a diffuser, which dilutes the effluent as it mixes into the river water. The diffuser is periodically inspected by a diver to ensure it is not damaged in any way.

    View of the Columbia River where treated effluent from the Salmon Creek plant is discharged through an underwater diffuser.

  • 6. Solids Processing

    All solids collected during the primary and secondary treatment process are further processed by mixing and heating for one month in large tanks called digesters. This process is called anaerobic digestion, where microorganisms further stabilize the organic material in a process similar to composting. This treatment meets state and federal standards and produces biosolids, which have beneficial agricultural uses. Additionally, two carbon adsorbers collect and remove odorous air from this process.

    Large cylindrical anaerobic digester tanks at the Salmon Creek Treatment Plant used for solids processing.

  • 7. Biosolids Recycling

    Biosolids can be used as a nutrient-rich fertilizer that reduces soil erosion and provides micronutrients and nitrogen to the soil. Biosolids removed from the plant are regularly applied to farmlands in accordance with federal and state requirements. During dry weather, the biosolids are taken to farms in Lewis County, near Centralia. During the remainder of the year, biosolids go to other farms near Goldendale, where the weather and agricultural practices can support a nearly year-round operation.

    Covered biosolids storage at the treatment plant, where processed biosolids are prepared for agricultural application.

  • 8. Monitoring & Quality Control

    Plant operation requires constant monitoring and quality control testing. Liquids and solids are carefully monitored by certified operations staff who test and evaluate the liquids and solids at each stage of the process to ensure effective treatment and compliance with strict regulatory requirements.

    Interior of the plant's monitoring and quality control laboratory where certified staff test water and solids samples.
  •  

  • Planning for the Future

  • The Alliance is updating its General Sewer Plan

  • This plan will guide sewer system decision-making over the next 20 years, providing a road map for expansion of the wastewater system and ensuring reliable service as our region grows. It will also help us better understand and plan for future capital improvements and ensure regulatory compliance.

    In a survey last summer, our customers asked us to prioritize the following values in the new plan:

    1. Affordability
    2. Reliability
    3. Environmental stewardship
    4. Sustainability

  • Aerial photo of the Felida neighborhood showing the Salmon Creek Treatment Plant labeled in the upper left, surrounded by fields, residential areas, and Salmon Creek.

    This aerial photo shows the Felida neighborhood, where NW 36th Avenue crosses Salmon Creek.

  • Future Needs and Potential Solutions

  • Our community is growing. Half of all Clark County growth happens in the Alliance service area. The amount of wastewater we handle is expected to increase by nearly 70% by 2045. We’re planning ahead to ensure we can grow with the community.

  • Line graph showing Alliance Service Area population growth projection from 2025 to 2045, with population rising from approximately 150,000 to 275,000.

    We’re considering improvements to:

    • Increase wastewater capacity and reliability
    • Meet future federal and state regulations
    • Align with community values

    Potential updates to keep up with the increased flow:

    • More transmission system capacity
    • New liquids process improvements
    • New solids process improvements
    • New maintenance spaces and staff facilities
  • Map showing the Salmon Creek Treatment Plant service areas with highlights around Ridgefield, Battle Ground, and north Vancouver Washington.

    This map shows the Alliance’s service area (Click the image to enlarge and open in a new tab)

  • Potential Transmission System Improvements

  • We’re considering improvements to the transmission system, which could include upgrades to our pipelines, pumps and storage facilities. These improvements would increase capacity for our service area, particularly for Battle Ground, one of our fastest-growing communities.

    • Option A: New pipe from Battle Ground running parallel to existing pipe
    • Option B: Increase storage in existing system
    • Option C: New pipeline from west Battle Ground
    • Option D: Build new pipe to Neil Kimsey Pump Station

    Each option will be evaluated on construction complexity, operational needs, and cost to help us make a recommendation.

  • Map of potential transmission system improvements in the Alliance service area. Key labeled infrastructure includes the Salmon Creek Treatment Plant in the west, the 36th Ave Pump Station and 117th St Pump Station in the central-west area, the Neil Kimsey Regional Pump Station in the north-central area, and the Battle Ground Pump Station/Flow Equalization Basin in the far northeast. Existing pipes are shown in solid blue feeding the Salmon Creek Treatment Plant. Four improvement options are color-coded on the map. Option A, shown in green dashes, would add a new pipe from Battle Ground parallel to the existing pipe. Option B, shown in pink dashes around the Battle Ground Pump Station and Equalization Basin, would increase storage in the existing system. Option C, shown in red dashes, would add a new pipeline from the 92nd Ave Pump Station to the existing pipe. Option D, shown in light blue dashes, would build a new pipe from the 92nd Ave Pump Station to the Neil Kimsey Pump Station.
    (Click the image to enlarge and open in a new tab)

  • Salmon Creek Treatment Plant Potential Improvements

    To meet the needs of our growing community, over the next 20 years, we are planning to expand and improve the following sections of the plant:

    • Liquids treatment
    • Solids treatment
    • Support facilities
    • Maintenance spaces

  • Illustrated aerial map of the Salmon Creek Treatment Plant with color-coded zones indicating areas planned for improvement: Liquids Treatment, Solids Treatment, and Support/Maintenance Facilities.
    (Click the image to enlarge and open in a new tab)

  • How and When Decisions Will Be Made

    As we develop General Sewer Plan recommendations for the Alliance Board of Directors, we are seeking input from technical experts, partner agencies and community members. These considerations are shaping our recommendations:

    • Community values: affordability, reliability, environmental stewardship and sustainability
    • Long-term ongoing maintenance needs
    • Public impacts
    • Risks

    Timeline

    • Summer 2027: Plan finalized
    • Fall 2027: Plan sent to Alliance Board for adoption
    • Winter 2027: Plan sent to Washington Department of Ecology for approval

    Stay Engaged

    Attend Alliance Board meetings quarterly during the planning period. Meeting information is available on the Alliance website: discoverycwa.org/about/meetings

  • Construction Projects

  • Entrance Gate

    We are replacing the entrance gate to the plant after it was damaged late last year. Below are renderings of the new gate in both the day and night.

  • Daytime photo-rendering of the proposed entrance gate to the Salmon Creek Treatment Plant, showing a black metal gate spanning a two-lane road. The following components are labeled: Proposed Brick Columns, Knox Box for Fire Access, Warning Sign on Exit Side of Gate, Magnetic Gate Lock, LED Stop Signs, Reflective Strip Mounted to Gate, Landscape Uplights for Brick Columns, Proposed Gates to be Mounted to Existing Posts, Warning Sign, Camera Mounted to New Light Post, and Directional Light on 12 Ft. Post.
  • Nighttime rendering of the proposed entrance gate to the Salmon Creek Treatment Plant, showing the LED stop signs illuminated.

  • Biosolids Dewatering Equipment Replacement

    This equipment helps turn liquid wastewater into a semi-solid state for land application. The dewatering process reduces costs for trucking. Replacing the nearly 30-year-old equipment will boost system performance and reliability.

    Construction is scheduled for summer 2026-spring 2028.

  • Before

    Interior of the existing biosolids dewatering facility showing the aging equipment.

  • After

    Rendering of the new biosolids dewatering equipment, showing a large cylindrical screw press unit with a blue motor, replacing the existing 30-year-old system.

  • Salmon Creek Treatment Plant Ultraviolet System Replacement Project

    The Alliance is replacing our 20-year-old ultraviolet (UV) disinfection system used to disinfect treated wastewater before it reaches the Columbia River. UV disinfection benefits public health by reducing the release of potentially disease-transmitting pathogenic organisms to waterways.

    We are replacing this system because it is near the end of its useful life and is not as energy efficient as newer systems.

  • Before

    Existing UV disinfection equipment at the Salmon Creek Treatment Plant showing aging UV lamp assemblies and control infrastructure.

  • After

    Rendering of the new UV disinfection system showing angled UV lamp banks submerged in a water channel alongside a modern control cabinet, with a technician for scale.

  • Benefits of new system:

    • More reliable - protects water quality of flow reaching the Columbia River
    • More energy-efficient (reducing plant’s greenhouse gas emissions)
    • Fewer repairs needed
    • Lower operating costs - helps to keep rates affordable

    This project is funded in part by the U.S. Environmental Protection Agency.

  • Additional Projects

    The Alliance is continually assessing and updating our operations facilities to ensure they are efficient and meet regulatory guidelines.

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  • Protect Our Water

  • Each of us plays an important role in keeping our waterways healthy. From the products we purchase to how we dispose of them, our choices impact what ends up in our water. Below are some simple changes you can make around the house to help keep our water healthy and safe.

  • In the bathroom

    • Only flush toilet paper, everything else goes in the trash.
    • Don’t flush prescription drugs or other medications.
    • When shopping:
      • Choose products with the EWG VERIFIED™ mark.
      • Avoid products with plastic micro-beads, synthetic fragrances, parabens, or phthalates.

  • In the kitchen

    • Put fats, oils, grease, and grit in the trash—not down the sink.
    • Cook at lower temperatures if using older non-stick pans.
    • When shopping:
      • Look for products with the EPA Safer Choice label.
      • Choose stainless steel, cast-iron, or cookware with a ceramic coating.
      • Avoid products with “PTFE” or “FLOURO.”

  • In the garden

    • Use pesticides carefully and as a last resort.
    • If you must, spot-spray on pests; don’t spray pesticides over large areas.
    • Dispose of pesticides at your local household hazardous waste facility.
    • Scoop, bag, and trash pet waste.
    • When shopping:
      • Choose neem tree oil as a natural pesticide.

  • Learn more at crwwd.com/pollution-prevention link opens in a new tab

    For more information, contact Leanne Mattos, Administrative Supervisor & Board Clerk at Clark Regional Wastewater District, at lmattos@crwwd.com link opens in a new tab or 360-993-8823.

    See a printable version of this information link opens in a new tab (PDF, 355.1 KB)

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  • Stay in Touch

  • Thank you for taking an interest in the Salmon Creek Treatment Plant and participating in our online open house.

    To receive your free gift, please complete the following questions.

  • Where do you live relative to the treatment plant?
  • If you visited each of the previous pages, then we'd like to send you a gift for your time! What would you like? (We'll do our best to get you what you want, but we may need to make substitutions.) All participants will receive a magnet
  • image of sctp canvas bag gift image of sctp canvas bag gift image of sctp canvas bag gift
  • Would you like to sign up for project emails?
  • Would you be willing to answer some demographic questions about yourself?

  • Demographic Questions (Optional)

  • The following questions are optional and will help us understand who we are hearing from and whether we are reaching a wide range of people in the community. The identity of individuals is kept confidential. The results are reported as totals only and will be used solely to help improve future community engagement.

  • How do you describe your race or ethnicity? (Check all that apply.)
  • What is your age?
  • How many children under age 18 live in your household?
  • What are the primary languages that you speak? (Check all that apply.)
  • Should be Empty: