Bend advisory group advances stormwater master plan, weighs centralized systems for denser development

City of Bend staff on Wednesday presented the draft stormwater master plan and used the Water Advisory Group meeting to press a policy discussion on how to manage stormwater as lot sizes shrink and infill increases.

The draft plan, which staff said must await a linked public facility plan before formal adoption, lays out 12 capital improvement projects to be implemented over the next 20 years and identifies program actions — including retrofits for failing UICs (underground injection controls), a major maintenance program, and updates to design standards — that could require new funding and operational capacity.

"The main purpose of the stormwater master plan was to identify ... our CIP program, particularly looking at improving the quality of stormwater runoff and reducing flooding," said Austin Sanhague, city engineering staff who led the presentation. The plan also documents level-of-service metrics staff intend to use in an upcoming stormwater rate study.

Why it matters

City staff warned that the traditional model — requiring each private lot to manage its own stormwater — is increasingly impractical as developers build smaller lots and attached housing. That difficulty prompted a sustained discussion about encouraging or requiring subdivision-level, privately owned but commonly maintained stormwater facilities (often managed by an HOA) or shifting some facilities to city ownership, and how to fund construction and long‑term maintenance.

What staff proposed and what was discussed

- Plan status and scope: Austin said the draft plan will be posted publicly and that adoption is delayed while the related public facility plan is completed so both can be approved together.

- Capital and program priorities: Staff said the master plan identifies 12 CIP projects over 20 years and that projected capital costs appear to align with the current stormwater program budget. Separate programmatic needs — UIC retrofits and a major maintenance program for nuisance flooding sites — were flagged as likely to increase operating demands.

- UICs and design standards: The group discussed updating setbacks around drinking water wells and incorporating deeper dry‑well options into standards after a study of time-of-travel to municipal wells.

- MS4 permit compliance and short-term actions: Elizabeth O'Keefe, stormwater program staff, told the group that "the requirement in our MS4 permit is for any project that creates or replaces 5,000 square feet of impervious surface has to meet post-construction requirements for stormwater." She said staff will close exemptions for single-family housing and add templates and maintenance‑agreement language to capture subdivisions where individual lots might each be under the 5,000‑square‑foot threshold but the overall development exceeds it. Staff set an operational target to implement those changes by a November 1 permit deadline.

- Drainage and density (centralized facilities): The discussion focused on whether the city should set a minimum lot size or another threshold below which on-site stormwater control is deemed infeasible and subdivision- or district‑level facilities would be required or preferred. Staff described four policy approaches ranging from "business as usual" to requiring centralized facilities in some circumstances; they emphasized clarifying code pathways so developers can pursue centralized on‑site options without a full master plan process.

- Funding, maintenance, and ownership: Participants discussed fee‑in‑lieu, special district or urban‑renewal approaches for central cores, whether the city should accept private runoff into public facilities, and how to handle long‑term maintenance when HOAs dissolve or fail. Staff said a rate study will use the plan's level‑of‑service work to quantify O&M impacts and potential rate adjustments. Developers and engineers at the meeting noted that on a typical single‑family lot, private stormwater disposal currently can cost several thousand dollars per lot.

- Infill and small lots: Participants recommended differentiated approaches for greenfield master plans, larger infill projects, and small lot one‑offs. Fee‑in‑lieu and district-based master plans were discussed as tools for addressing infill where space for conventional on‑site facilities is limited.

- Technical tools: porous (permeable) pavements, deeper dry wells, and additional local rain gauges (the city is pursuing five more gauges with the Bureau of Reclamation) were discussed as parts of the toolbox; staff cautioned porous pavement reduces impervious area but should not be used as a sink for additional runoff unless designed as such.

Quotes from participants

"The main purpose of the stormwater master plan was to identify ... our CIP program, particularly looking at improving the quality of stormwater runoff and reducing flooding," said Austin Sanhague, city engineering staff.

"The requirement in our MS4 permit is for any project that creates or replaces 5,000 square feet of impervious surface has to meet post-construction requirements for stormwater," said Elizabeth O'Keefe, stormwater program staff.

"All developers will tell you that they want maximum flexibility," said Brian Wilkinson, principal civil engineer at ATS Engineering, during the discussion of potential lot‑size thresholds.

"We have already kind of taken this approach. We do a lot of centralized on‑site stormwater management," said Ashlyn Dribbsko, development manager with Polished Homes, describing current private development practice in some local subdivisions.

Next steps and outstanding issues

Staff will post the draft plan to the project webpage, solicit written feedback (email preferred, with a Word version available for detailed edits), finalize the related public facility plan, and return to council for adoption. The water services group will continue the drainage-and-density work to inform the stormwater rate study, code and standards updates, and the Central Oregon stormwater manual update the city expects to help coordinate regionally.

Participants flagged several questions for follow-up: what numeric lot‑size or impervious‑coverage thresholds (if any) should trigger centralized management; whether cost calculations for fee‑in‑lieu should be based on marginal public costs or representative private construction costs; and how to track long‑term capacity and maintenance liabilities for subdivision‑level facilities.

The advisory group scheduled a follow‑up discussion in the October meeting series and noted the city will also address related water‑wise/fire‑wise topics in upcoming sessions.