Newberg engineers caution that curb‑tight sidewalks complicate stormwater treatment; council leaves option as exception

Newberg leaders heard technical advice on Nov. 3 about whether the city should allow "curb‑tight" sidewalks — sidewalks built directly at the curbline without the typical planting strip — as part of updated typical street cross sections.

Keller Associates acting city engineer Travis Smith and design lead TJ Centanni told the joint City Council–Planning Commission work session that Oregon statutes do not prohibit curb‑tight sidewalks, but state stormwater treatment standards administered by the Department of Environmental Quality mean curb‑tight sections require additional localized or regional pretreatment before stormwater can be discharged to the storm system. Centanni said those requirements make curb‑tight sidewalks more complicated to build and to maintain than separated sidewalks with planter strips.

Why it matters: planter strips behind the curb serve multiple functions (stormwater pretreatment space, a buffer that increases pedestrian safety, space for street trees, lighting and furnishings, and room for gentler ADA ramp transitions). Keller presented two basic compliance approaches: 1) provide localized treatment within the planter or in a trench drain behind a curb‑tight sidewalk; or 2) route runoff to a regional water‑quality facility that treats flows for a larger project. The localized approach can require trench drains, special grading, and maintenance access across the back of the sidewalk; engineers warned those features can be unsightly and more costly over time.

Council and planning commissioners asked detailed questions about maintenance responsibilities, right‑of‑way ownership and public perception. Staff clarified that the city typically owns stormwater controls placed in the public right‑of‑way, and that putting treatment facilities behind a curb‑tight walk can make the line between private property and public infrastructure less clear for homeowners. Staff also reminded the group that the development code already contains a limited exception that allows curb‑tight sidewalks in certain affordable‑housing projects, and that the city engineer can approve design variances for constrained sites on a case‑by‑case basis.

Throughout the session council members emphasized two recurring concerns: (1) long‑term sidewalk damage from tree roots and the city’s costs to repair ramps and sidewalks, and (2) ADA and pedestrian‑safety implications of placing pedestrians immediately adjacent to moving traffic. Engineers said selecting appropriate deep‑rooting tree species, installing linear root barriers, and other construction details can reduce root damage but acknowledged there are tradeoffs, including cost and site suitability.

Outcome and next steps: the council did not adopt a formal ordinance or change to the municipal code at the meeting. Instead, members signaled mixed sentiment — roughly half the council indicated they wanted curb‑tight sidewalks kept as an optional code route or design exception, while others favored default separated sidewalks for safety and stormwater reasons. Staff will bring revised cross‑section options back to the planning commission and city council for further review; no formal code change was adopted Nov. 3.

What was not decided: no new mandatory requirement for curb‑tight sidewalks was adopted, and staff said existing curb‑tight conditions will be maintained where they already exist. Any future curb‑tight installation will require a demonstrated stormwater solution and may be handled through design exceptions or site‑specific approvals.

Key quotes

"There aren't any ORS codes restricting sidewalk from being curb tight. However, due to treatment requirements for stormwater, it does make curb‑tight [construction] more complicated to execute, difficult to maintain, potentially unsightly for property owners, and less safe for pedestrians," said TJ Centanni, design lead for Keller Associates.

"If we have conditions that are currently curb tight, we're gonna maintain them as they are. This is thinking about future developments and of the larger scale," said the city engineer (Travis Smith).

Clarifying details and local context

- State stormwater rules require a level of pretreatment prior to discharging to waters of the state; the two main compliance approaches discussed were localized planter treatment or discharge to a regional treatment facility. (Keller Associates presentation.) - Planner strip width example given: 5‑foot planter strips were discussed as a workable typical width in many situations; linear root barriers and deep‑rooting trees were proposed mitigation techniques to limit long‑term sidewalk damage. (Keller memo and Q&A.) - The council noted approximately 60 ADA ramps are planned for next year and that ramp workload affected the city's approach to sidewalk maintenance and design sequencing. (Public works / capital projects discussion.)

Local proper names referenced in the discussion: Keller Associates; Crestview Crossing; Newberg (city).