Sandoval County, NM Environmental Rules: Stormwater Management (2026)

Sec. 34-78(k), Storm drainage plan, requires that subdivisions and developments be planned, constructed and maintained to protect and preserve existing natural drainage channels except where erosion and water control measures are found necessary and approved by the local district. Developers must provide temporary measures to keep damaging runoff from leaving the site until construction is finished and permanent controls are installed, and must protect structures from flood hazards using the 100-year frequency storm to calculate flood levels. The system must remove runoff from within the subdivision without causing harm inside or outside its boundaries, and the county requires assurance that water leaving the site carries no more pollutants or sediment, and causes no more erosion, than would occur without the subdivision.

All storm drainage systems must be built to the standards of the local soil and water conservation district, and if the surrounding drainage basin is only partially developed, the district can require the system to be sized for the entire basin on the assumption it will eventually be fully built out. The plan must also address road drainage: ponding from road construction must be avoided or addressed, road-collected runoff must be designed to prevent erosion and sedimentation at outlets, and culverts must be properly sized, located and protected at their inlets and outlets.

Subsection (j) folds floodplain compliance into the same plan, requiring every subdivision to conform to the county's flood damage prevention ordinance in Chapter 18, tying the stormwater plan directly to the county's floodplain permit process.