Managing Runoff from Development Activities

Reducing the impacts from development activities is crucial for preventing stormwater pollution, minimizing erosion and flooding and protecting aquatic habitat. From development plan review to construction site inspections, our program ensures compliance with City codes, drainage design and erosion control standards and Permit requirements for both private and public projects.

What we’re doing:

• Set standards and provide guidance on the measures necessary to control the quantity and quality of stormwater produced by new development and redevelopment projects through our Olympia’s Drainage Design and Erosion Control Manual (DDECM)
• In 2026, staff will begin updating our DDECM to meet requirements of the 2024 Stormwater Management Manual for Western Washington.
• Require the following activities on all private and public construction sites that meet the minimum thresholds outlined in the DDECM as required by the Permit:
  • Review of all stormwater site plans for proposed development activities.
  • Inspect all sites prior to clearing and construction and during construction.
  • Inspect all development sites upon completion of construction and prior to final approval or occupancy.
  • Verify that a maintenance plan is completed and responsibility for maintenance is assigned for stormwater facilities.
  • Implement an enforcement action against those failing to comply with requirements of the DDECM including sites that are also covered by stormwater permits issued by the Dept of Ecology.