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Public Works proposes targeted updates to county engineering and drainage manuals to clarify standards and reduce surprises for developers
Summary
Coconino County Public Works presented proposed updates to the county’s Engineering Design and Construction Manual and Drainage Design Criteria Manual to clarify responsibilities, utility siting, grading permits, and traffic‑study rules.
Coconino County Public Works on April 1 presented a set of proposed revisions to two design manuals — the Engineering Design and Construction Manual (EDCM) and the Drainage Design Criteria Manual (DDCM) — intended to clarify standards and reduce surprises for developers and the public.
Public Works Director Christopher Tressler and County Engineer Chad Auker said the update is the result of industry feedback and internal review. Key proposed changes include a definitions/roles section that clarifies which decisions fall to the county engineer versus the Flood Control District’s engineer; preferred utility locations moved outside the roadway prism to reduce future pavement cutting; a graduated grading‑permit threshold (retain 50 cubic yards for parcels under 1 acre, raise to 100 cubic yards for parcels larger than 1 acre); and explicit asphalt‑binder specifications for elevation bands in the county.
On drainage, staff added a recommended erosion‑hazard setback for high‑flow channels and formalized a “no adverse impact” standard consistent with Association of State Floodplain Managers guidance. Traffic and access revisions include updated rules about when turn lanes are required: the county will relax automatic turn‑lane mandates on minor collectors and local streets when posted speeds are under 30 mph and sight distance is adequate, which officials said avoids costly mitigation that provides little safety benefit in low‑speed contexts. The manuals also move from average‑daily‑traffic triggers to peak‑hour criteria for traffic‑study scoping and add a trip‑generation requirement at conditional‑use review to scope future traffic analyses early in the process.
County staff said they had already solicited comment from more than 30 industry partners, retained Intellus (consultant) and CivilTech to compile feedback, and coordinated with Flood Control District staff. The documents will be circulated again for review before returning to the board as an action item; if the board adopts revisions, staff said there will be a 30‑day implementation window before the standards become effective.
Speakers quoted in this article are drawn from the meeting record: Christopher Tressler (Public Works Director); Chad Auker (County Engineer); Nate Reiser (Assistant County Engineer); representatives of the Flood Control District and the county’s community development division.
