Development in River Terrace will be required to manage stormwater using new and updated standards. The strategies recommended in the River Terrace Stormwater Master Plan are based upon Clean Water Services (CWS) Design and Construction Standards and the CWS Low Impact Development Approaches (LIDA) Handbook.

Tigard’s intention is to adopt new design standards which implement the Master Plan in collaboration with CWS on or before River Terrace Community Plan adoption. Several factors motivating this change include:

  • The community’s desire to preserve and protect existing natural resources in the River Terrace and Bull Mountain area
  • The city’s recent experiences dealing with channel stability problems near the River Terrace area
  • Anticipated changes to CWS’s Design and Construction Standards to address pending requirements under their National Pollutant Discharge Elimination System (NPDES) permit.

At a minimum, new design standards will include the following:

  • Requirement to minimize stormwater impacts caused by development through use of best practices for water quantity management, even when a downstream analysis shows that the downstream system has adequate conveyance capacity. A new continuous simulation model will be developed for this purpose, which development will be required to use.
  • Development of a minimum facility size standard for regional water quality and quantity (i.e. detention) facilities to allow flexibility in the implementation of this plan.
  • Allowance for smaller regional facilities in locations not anticipated by this plan where it can be shown that development of the recommended regional facility is either not timely or feasible and the proposed facility meets the minimum facility size standard.
  • Allowance for interim facilities where regional facilities are recommended in instances where it can be shown that development of a regional facility is not timely and the proposed interim facility meets the minimum facility size standard.
  • Requirement to design regional stormwater management facilities as community amenities that provide aesthetic, educational, and/or recreational benefits.