Water Infrastructure

Stormwater Facility Retrofit and Performance Optimization Plan

Location: Clackamas County, Oregon

Clackamas County Water Environment Services (WES) engaged in a comprehensive review of its approach to stormwater management. They undertook several key projects to guide them through the technical steps to an updated program with a new vision and expected outcome. The DEA team worked with WES to execute these new approaches. The program included three key projects:

Upgrades and Enhancements to Older Facilities: Many of these facilities were designed and constructed under older ordinances and guidelines that have since been updated to provide better and more comprehensive stormwater management benefits, such as water quality improvements and stream protection. The process included modeling existing systems against new standards to evaluate flow control deficiencies; evaluating existing watershed conditions to prioritize the greatest needs for upgrades; selecting hydromodification improvements, water quality improvements or a combination of both; preparing retrofitting alternatives that could be applied to each facility depending on site conditions and configuration; and developing a tool to assist field staff with making design modifications to meet updated performance expectations. DEA reviewed the monitoring data from the hydromodification retrofit and established recommendations to the modified standards and control approaches. WES gained a prioritized program for retrofitting neighborhood stormwater ponds, design templates for similar facilities from different eras, and recommendations for system improvements including a design tool to execute those modifications without process delays.

Evaluation for Performance Retrofitting of Phillips Creek Regional Detention Facility and Three Creek Regional Detention Facility: The DEA team considered alternative strategies to optimize flow control, stream protection standards, and improved water quality performance. WES gained confirmation that each of its facilities and properties was being optimized for the greatest stream health need. In addition, the flood control performance of the Three Creeks Regional Detention Facility was reevaluated to determine whether the area was optimized for flood control and downstream habitat protection.

Adaptive Management Basin Plan for the Cedar Creek Watershed: Over time, WES collected data, inventoried resources, evaluated collected data, identified needs and opportunities, and made improvements. The purpose of this test plan was to develop an effective strategy for connecting retrofit actions to stream impacts and stream health. The DEA team reviewed and commented on the direction of the proposed approach and provided peer review of interim and draft final products. A key element of this program was to define stream health targets and select the appropriate basin retrofitting approach to achieve those goals.