. 1 The D&C has a number of Drivers including: Watershed Based - PDF document

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The D&C has a number of Drivers including: • Watershed Based Permit • Operating and Maintenance considerations for our system • Regulations from other entities that have an effect, including Army Corps of Engineers, Department of State Lands and Metro • And we are an Agent for DEQ on the 1200 ‐ C Erosion Control Permit As a result we have Standards for: • Post development stormwater runoff and treatment control • Site development and construction erosion control • Vegetated Corridors (upland buffers to protect Water Quality Sensitive Areas, such as streams and wetlands) • Standards for permitting process • Construction of sanitary sewer pump stations • Development requirements for and construction of public sanitary sewer and storm water conveyance. 2

The D&C is for the entire District Service Area including both incorporated and unincorporated areas within the urbanized portion of Washington County as well as small portions of Multnomah and Clackamas counties that drain to the Tualatin River. The 7 cities that Co ‐ Implement the Watershed Based permit (Hillsboro, Beaverton, Forest Grove, Cornelius, Tigard, Tualatin and Sherwood) implement the standards within their own jurisdictional boundaries. The D&C sets the minimum standards; however, cities can adopt a more stringent standards. 3

The Design and Construction Standards have evolved over the years in response to new permits, other regulatory agency rule changes and as technology and construction practices advance. The last major update to the standards was in 2007. There have been a couple of minor updates to specific sections since then, but not a large update. Some of you may recall our last update effort in 2012 and 2013. That effort was delayed as we didn’t get the new Watershed Based permit as quickly as we hoped. But now we do have the new permit! …and we hope to build on our prior effort so as to not be starting from scratch. This is important because Updates usually take 18 to 24 months, while the first major deadline for the current process is in April 2017. 4

The District received the new Watershed ‐ Based Permit in April of this year. The permit covers discharges from our four wastewater treatment facilities as well as discharges from the MS4 or Municipal Separate Storm Sewer System. 5

The new watershed based permit has three requirements that will necessitate updating the D&C to be in compliance. • Each requirement triggers on an anniversary of the permit issuance date. The first of which is April 22 nd of 2017, so you can see we already have less than a year • to implement this first requirement All three of the requirements are related to stormwater. 1 st Anniversary = 1,000 SF Treatment Threshold • 2 nd Anniversary = LIDA Prioritization – prioritize LIDA above other treatment methods • 3 rd Anniversary = Hydromodification Plan; requires a standard to deal with the water • “quantity” component of runoff from development and redevelopment Because of how the permit requirements work with triggers on the anniversaries, we are proposing a two phase approach to updating the standards over the next two to three years. Phase 1 will address: 1 st Anniversary Treatment Threshold • 2 nd Anniversary LIDA prioritization • • As well as a number of items we had been working on during the 2012/2013 update effort Phase 2 will be primarily focused on developing a Hydromodification Standard 6

Phase 1 Timeline The plan for Phase 1 is to address the specific Watershed ‐ Based Permit requirements due by the first and second anniversary of issuance and as many of the topics from the 2012/2013 update effort that we can reasonably accomplish within the limited timeframe of Phase 1. Those 2012/2013 update topics we can’t accomplish as part of Phase 1 will be addressed as part of Phase 2. 7

The Primary Drivers for the D&C Update are the new requirements within the Watershed Based Permit. The First and Second Anniversary permit requirements are the primary topics for Phase 1. Water Quality Treatment Threshold (Required by First Anniversary) The new Watershed ‐ Based Permit requires that the District implement a water quality treatment threshold for new development and redevelopment that either creates or replaces 1000 sf or more of impervious area. A treatmernt requirement already exists for commercial/industrial developments and residential subdivisions. What would be new would be to require post ‐ development on ‐ site treatment of stormwater for new/modified single family residences and duplexes on an existing lot of record as well as partitions when exceeding the 1,000 sf threshold. LIDA Prioritization (Required by Second Anniversary) The implementation of a Low Impact Development Approaches (LIDA) prioritization for post ‐ construction stormwater runoff treatment is also a requirement of the new watershed based permit. The standards must include a description of conditions where LIDA is not practicable. This could have an impact on when and or where other treatment approaches such as filter vaults or fee ‐ in ‐ lieu are allowed. While this standard is not required to be in place until April of 2018, working on it now will help avoid updating the standards a third time in the next two and a half years. While included in Phase 1 update, implementation of this section could potentially be delayed until April of 2018. 8

Additional update topics from the 2012/2013 effort could be included in Phase 1. We want to build on the 2012/2013 effort and not lose the hard work that was put in during that time. Since it has been nearly 10 years since our last large update there are many things that we want to improve based on what we have learned, new technology and changing development patterns and practices. Some of the Topics we talked about last time were: • Stormwater Treatment Redevelopment Standard, • EC Best Management Practices for in stream/wetland work • Adjusting our standards to be consistent with State Plumbing Code • Many procedural or housekeeping items not intend to change standards as much as clarify or update based on common practice Procedure wise, if some of these topics become contentious or otherwise too involved to meet the Phase 1 timeline it may become necessary to move them to Phase 2 to ensure that we can implement the Permit Driven updates items on time. 9

While we are not going to be including Hydromdification in the Phase 1 update, I did want to say a little bit about it as it is going to be the primary focus of Phase 2. What is hydromodification? Simply, Hydromodification is the alteration of the natural flow of water through a landscape, and often takes the form of channel modification or channelization. As we talk about Hydromodification in the urban area we are really talking about the alteration of flow due to development. This picture shows a possible result of hydromodification – down cutting of the channel 10

What tools do we have to offset the effects of Hydromodification? The most prevalent tool to counter Hydromodification resulting from development is the upland detention facility, …but the upland detention facility only addresses hydromodification that is occurring as a result of that development. It does not address existing channel degradation or other impacts within the stream channel or riparian corridor. 11

There are a variety of situations that can exist within the landscape. You can have anything from new development in a greenfield with intact streams to infill within developed areas where the adjacent streams are already degrading. Detention can’t address all of the problems and/or situations and a variety of tools is needed (one size doesn’t fit all). 12

That’s why over the next couple of years the District will be working to develop a range of tools to address hydromodification in a holistic way. Some of these tools may include: • Co ‐ located facilities (such as park areas that can also provide detention) • Facilities that are optimized to hold or release water based on the weather forecast • Floodplain reconnection • And Stream Enhancement to provide greater resiliency within our stream corridors Already piloting some of these new tools or approaches in River Terrace and North Bethany Responding to Hydromodification, done right, requires a complex solution with many tools; which takes time to develop but will provide for more resilient stream systems But in the short term… 13

We will be working through key topic discussions and beginning to draft updates for Phase 1 this fall. 14

Meeting dates have not been identified yet, but we intend to have key topic (technical) discussion meetings with the public on these key topics. Are there other topics from the 2012/2013 update effort that anyone feels warrants a key topic discussion meeting? 15

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