Development Standards
Stormwater Development Standards
Our stormwater development standards ensure that new projects effectively manage runoff, reduce nutrient pollution, and protect local waterways. Below is an overview of the key requirements and guidelines:
Total Suspended Solids (TSS) Reduction
Developments must achieve a minimum 85% average annual removal of Total Suspended Solids (TSS) using structural or non-structural Best Management Practices (BMPs). This ensures cleaner runoff entering our waterways, improving water quality and aquatic ecosystems.
Nutrient Reduction Standards
To address nitrogen and phosphorus pollution, developments must meet strict nutrient export limits:
Nitrogen: Maximum of 4.0 pounds per acre per year (lbs/ac/yr).
Phosphorus: Maximum of 0.4 pounds per acre per year (lbs/ac/yr).
Compliance can be achieved through:
Onsite or Offsite Stormwater Management Facilities: Install BMPs such as retention basins, bioretention cells, or constructed wetlands.
Regional or Jurisdiction-Wide Strategies: Participate in approved regional stormwater plans.
Land Conservation: Dedicate open spaces or conservation easements, either onsite or offsite, with approval.
Offset Payments: Make a one-time payment for nutrient offsets, as specified in state regulations.
All BMPs must adhere to design standards outlined in the Stormwater BMP Manual and be approved by the stormwater administrator.
Peak Runoff Control
New developments must ensure no net increase in peak stormwater runoff compared to pre-development conditions for the one-year, 24-hour storm event. Key requirements include:
Runoff Volume Drawdown: Must occur over 24-120 hours, depending on the BMP used.
Hydrology Standards: Follow calculation methods outlined in the BMP Manual to ensure compliance.
Exceptions: Peak flow control is not required if one of the following applies:
Low Impervious Area: The site’s impervious area is less than 15%, and pervious areas are used for stormwater management.
Minimal Peak Flow Increase: The post-development peak flow increases by less than 10% compared to pre-development conditions.
Alternative Methods: In cases where detention may worsen flooding or erosion, the director of engineering may approve alternate strategies.
Ensuring Compliance
All stormwater facilities must meet city and state standards, providing long-term benefits for both the environment and the community. By adhering to these requirements, developments contribute to sustainable growth while protecting our natural resources.
For more information, refer to the city’s Stormwater BMP Manual or contact the stormwater administrator.