2023 Stormwater Changes

CHANGES TO BENTON COUNTY’S STORMWATER MANAGEMENT (NPDES) PERMIT REQUIREMENTS AS OF MARCH 2023

What has changed?

Benton County is permitted through the Oregon Department of Environmental Quality (OR DEQ) for stomrwater quality measures. The County's National Pollutant Discharge Elimination System (NPDES) permit has two new requirements (“control measures”) that went into place as of March 1, 2023.

These two control measures relate to:

• Construction Site Runoff and
• Post-Construction Site Runoff Control for New Development and Redevelopment

These two control measures include mandatory requirements for construction site runoff control and post-construction monitoring and maintenance of stormwater treatment and detention facilities for new development and redevelopment. To remain in compliance with the County's OR DEQ permit, amendments were made to Benton County Development Code and the County Erosion and Sediment Control permitting process.

Why were they necessary?

These changes to Benton County Erosion and Sediment Control permit and development code are part of compliance with Benton County’s Oregon Department of Environmental Quality (OR DEQ) National Pollutant Discharge Elimination System (NPDES) Phase II MS4 permit for small communities.

What is the National Pollutant Discharge Elimination System (NPDES)?

The NPDES is a component of the Clean Water Act (CWA). The CWA was the first major US law to address water pollution – it was enacted in 1948 as the Federal Water Pollution Control Act, and then amended in 1972. One way that the NPDES prevents water pollution is through permits and regulations for development and construction.

How NPDES program goals fit within Benton County’s 2040 Thriving Communities Initiative core values:

• Clean water is key for community health and makes Benton County a Vibrant, Livable Community.
• Benton County staff are at your service, every day with Supportive People & Resources to help you navigate new stormwater regulations and permitting.
• NPDES regulations help make Benton County a healthier place for people, fish, wildlife and the environment promoting High Quality Environment & Access to be enjoyed by all Benton County residents.
• A healthy environment is economically valuable and promotes a Diverse Economy that Fits.
• Environmental protections are important economic and community health aspects of retaining Community Resilience in the face of natural disasters, climate change and threats.
• Everyone deserves access to safe, clean and thriving natural resources - promoting Equity for Everyone and Health in All Actions.

CONTROL MEASURE: CONSTRUCTION SITE RUNOFF

Language from Benton County’s NPDES Permit:

“The permit registrant (Benton County) must implement and enforce a construction site runoff control program to reduce discharges of pollutants from construction sites in its coverage area. Existing permit registrants must continue to implement their construction site runoff program as they develop, and implement the requirements of Schedule A.3.d (See Benton County’s 2021-2023 NPDES Permit pg. 20)."

*‘Permit registrant’ refers to Benton County, and the property owners and developers in Benton County who conduct work under this permit and Benton County’s Erosion and Sediment Control and Stormwater Management permitting system.

What does this mean for development projects in Benton County?

• The Benton County Code (Chapter 99.650-680) was modified to meet these NPDES requirements. The code amendments were presented to the Benton County Planning Commission, the Board of Commissioners and were open for public comment before they went into effect on March 23, 2023.

• The ‘disturbed area threshold’ for Benton County Erosion and Sediment Control (ESC) permits has dropped from one acre (43,560 sq. ft.) to one quarter acre (10,980 square feet or approximately 104’x104’). This means that any development or construction project that disturbs more than 10,980 square feet must obtain an Erosion and Sediment Control permit from Benton County and implement measures to prevent the runoff of sediment from the construction site. There are exceptions for agricultural buildings proposed outside the urban growth boundaries of Philomath, Corvallis and North Albany.

• The creation of one quarter acre (10,980 square feet) or more of impervious surface during development or re-development triggers the need for stormwater detention and treatment systems that are now included in Benton County's Erosion & Sediment Control and Stormwater Management permitting.

• Projects that create one full acre or more shall be referred to the Oregon Department of Environmental Quality (OR DEQ) for prior to application for Benton County permits.

• If ground disturbance for a proposed project is less than one acre, but is part of a Common Plan of Development (CPOD) such as a partition or subdivision which cumulatively disturbs more than one acre, the project may also be subject to Benton County permitting in addition to OR DEQ permitting.

• Erosion and Sediment Control Plans (ESCP's) must be:

  • Submitted and deemed complete prior to building permit application;

  • Inspected by Public Works staff to ensure proposed/required ESC measures are in place prior to any clearing or disturbance activities by the applicant or their contractor(s)

  • Maintained and udated by the operator through all activity;

  • Kept onsite and available for inspection purposes through the life of the project.

• All ESCP’s are reviewed prior to issuance of a Benton County ESC permit, and the permitted site will be subject to inspections by trained Benton County staff tin order to ensure compliance with ESC measures. Minimum triggers for site visits are:

  • Initial inspection to confirm required measures as outlined in permit application are in place;

  • At least one inspection shall occur during the process of project implementation;

  • Precipitation events that result in stormwater discharge from the site;

  • Visible sediment in stormwater discharge or dewatering;

  • A report or complaint about pollution discharge from the site.

NEW CONTROL MEASURE: POST-CONSTRUCTION SITE RUNOFF CONTROL FOR NEW DEVELOPMENT AND REDEVELOPMENT

Language from Benton County’s NPDES Permit:

“Existing permit registrants* must continue to implement their post-construction stormwater pollutant control program as they develop programs to meet the requirements of Schedule A.3.e to reduce discharges of pollutants and address stormwater runoff from new development and redevelopment project sites in is coverage area. New registrants must develop programs to meet Schedule A.3.e requirements to reduce discharges of pollutants and address stormwater runoff from new development and redevelopment project sites in its coverage area. All registrants must describe their programs in the Stormwater Management Program (SWMP) Document.”

*‘Permit registrant’ refers to Benton County, and the property owners and developers in Benton County who conduct work under this permit and Benton County’s Erosion and Sediment Control and Stormwater Management permitting system.

What does this mean for development projects in Benton County?

Project sites that create or replace 10,980 sq. ft. or more of impervious surface area, and that discharge stormwater into the County’s stormwater system (also known as Municipal Separate Storm Sewer Systems, or ‘MS4’) shall:

• Work with Benton County to mitigate for these impacts using low impact development or green stormwater infrastructure, or obtain a Stormwater Management permit.

• Implement stormwater controls at all qualifying sites.

• Employ a site-specific approach that targets the use of natural surfaces or pre-development hydrologic function through the installation and long-term operation and maintenance of structural stormwater controls.

• Provide long-term operation and maintenance of structural stormwater controls at project sites that are under the ownership of a private entity.

  • Benton County shall use appropriate enforcement procedures and actions to ensure compliance with Schedule A.3.e.iv (See Benton County’s 2021-2023 NPDES Permit pg. 23; Benton County Code Chapter 31.020 for escalating enforcement procedures).

  • Benton County has created an ordinance to meet the requirements of Schedule A.3.e.ii-vi (See Benton County’s 2021-2023 NPDES Permit pg. 23).

Benton County has created a system for long-term operation and maintenance (O&M) of stormwater systems which:

• Documents efforts to obtain legal authority for Benton County to inspect and require effective O&M of privately owned and operated structural stormwater controls as allowed under state and federal law.

• Includes mechanisms for inspections, reporting and tracking long-term O&M for privately owned and operated stormwater controls.

• Includes a mapped inventory of all public and private stormwater structural controls installed in compliance with the NPDES permit.

• Involves adequate staff training for all County staff involved with ESC and NPDES measures within 30 days of hire.