1. Exact Code Language
TMC 17.10.060 – Buffer establishment, management, and maintenance
(b) The following structures, practices, and activities are permitted in the buffer, with specific design or maintenance features, subject to the review of the Director of Utilities or designee:
(1) Pedestrian bridges, foot paths, and utilities.
This is the key enabling provision. It does not say utilities are allowed by right with no oversight. It expressly conditions them on:
- Specific design or maintenance features, and
- Review (and therefore approval) by the Director of Utilities or designee.
The surrounding subsections reinforce the controlled nature of this permission:
- Subsection (a) lists the things that are prohibited without written approval (clearing existing vegetation, grading/stripping/soil disturbance, filling, dumping, draining, etc.). Installing a sewer line almost always triggers one or more of those prohibited activities, so the “permitted” status in (b)(1) does not eliminate the need for written approval of the disturbance itself.
- Subsection (d) requires a permanent Stream Buffer Easement for the buffer area included in the project design.
TMC 17.10.050 – Design standards for buffers
The buffer is divided into two zones with different widths, vegetation targets, and allowable uses:
| Zone | Type I | Type II | Type III | Vegetation Target | Allowable Uses | Primary Function |
|---|---|---|---|---|---|---|
| Streamside Area | 50 ft | 25 ft | 15 ft | Native vegetation | Streambank stabilization, flood control, utility corridors | Protect the physical and ecological integrity of the stream ecosystem |
| Outer Area | GIS-based | GIS-based | GIS-based | Native vegetation or managed lawn (Type II/III) | Biking/hiking paths, flood control, detention/retention, utility corridors, stormwater BMPs, residential yards, landscape areas | Protect key components of the stream and filter/slow runoff |
Key observation: “Utility corridors” are listed as an allowable use in both the stricter streamside zone and the outer zone. This is deliberate. The City recognized that linear utilities (sewer, water, storm, electric, gas, etc.) frequently must cross streams and that completely prohibiting them would be impractical.
2. What “Utility Corridors” and “Utilities” Practically Mean
The code does not define “utility corridors” or expand on what “specific design or maintenance features” means. In practice (based on the permanent Stream Buffer Easement form, subdivision checklists, and stormwater review materials), this language is interpreted as follows:
- A utility corridor is a linear pathway through the buffer for underground (or occasionally overhead) infrastructure.
- The corridor itself is allowed, but the method of installation and the restoration after installation are tightly controlled.
- The City expects the utility to be placed and maintained in a way that does not permanently destroy the buffer’s water-quality, bank-stability, or habitat functions.
Common expectations that emerge from the review process and related documents:
- Prefer trenchless methods (directional boring, jack-and-bore, etc.) over open-cut trenching whenever feasible, especially in the streamside zone.
- If open-cut is used, the trench must be as narrow as practical, backfilled properly, and the surface fully restored with native vegetation.
- No permanent above-ground structures or heavy equipment access roads are allowed to remain in the buffer.
- The Stream Buffer Easement language typically grants the City (and sometimes the utility owner) the right to enter for construction, reconstruction, inspection, repair, and maintenance of the utility.
3. How the Two Sections Work Together
| Aspect | 17.10.050 (Design Standards) | 17.10.060(b)(1) (Management) | Practical Result for a Sewer Crossing |
|---|---|---|---|
| Status of utilities | Explicitly listed as allowable use in both zones | Explicitly listed as a permitted activity | Allowed in principle |
| Approval required? | Implied by the overall buffer-plan requirement | Explicitly requires review by Director of Utilities | Yes – written approval needed |
| Design control | “Utility corridors” must still meet vegetation and function goals | “Specific design or maintenance features” required | Plans must show construction method, restoration, and ongoing maintenance |
| Easement | Required for the entire buffer | Reinforced in (d) | Permanent Stream Buffer Easement must be recorded |
| Disturbance of vegetation/soil | Not prohibited if it is part of an allowed use | Still needs written approval under (a) | Buffer Plan + written approval covers both |
In short: 17.10.050 tells you that a utility corridor is a legitimate land use inside the buffer. 17.10.060(b)(1) tells you that you still have to get the Director of Utilities to sign off on the specific design and how you will maintain the buffer afterward.
4. Interaction with Other Requirements
- Buffer Plan (17.10.040): Required for any development inside the buffer. The plan must delineate both the streamside and outer zones and show the proposed utility alignment.
- Stream Buffer Easement: Mandatory. The standard form used by the City already contemplates utility corridors and grants access rights for construction and maintenance.
- Grading / Stormwater Management Plan: The utility crossing is almost always reviewed as part of the larger stormwater package. The Stormwater Quality and Quantity Review Checklist specifically flags sites that contain mapped stream buffers.
- Water Pollution Hazards (17.10.050(d)): On-site septic drainfields have large setbacks (200–500 ft), but a public sanitary sewer line is treated as a utility corridor, not a pollution hazard under that subsection.
5. Bottom-Line Practical Interpretation for a Sewer Line Crossing
The code intentionally creates a pathway for utilities rather than forcing every sewer (or water) line to obtain a formal variance under 17.10.080. However, that pathway is not automatic:
- You must submit a Buffer Plan showing the crossing.
- The plan must demonstrate “specific design or maintenance features” that protect the buffer’s functions (method of installation, erosion control, native vegetation restoration, long-term maintenance responsibility).
- The Director of Utilities (or designee) must review and approve it in writing.
- A permanent Stream Buffer Easement must be granted and recorded.
If the proposed crossing is unusually wide, involves permanent surface disturbance, or cannot be designed to minimize impact, staff can still require a formal waiver/variance under 17.10.080 (with alternatives analysis and mitigation).
This structure is typical of modern stream-buffer ordinances: utilities are recognized as necessary linear infrastructure and are therefore listed as permitted uses, but they remain subject to site-specific design review so the buffer’s primary environmental purposes are not lost.
