Strategic Green Infrastructure Planning for Denver’s MS4 Program

Projects

Client

Department of Transportation & Infrastructure

Timeline

2024–2025

Location

Denver, Colorado

A street view of two brick houses with porches and leafless trees in winter; a traffic light and street signs are visible on the right; the sky is mostly clear with some clouds.
Two houses with front porches and leafless trees sit along a quiet street on a sunny day. A green street sign reads York. There are some brown and yellow leaves on the ground and sparse plants in the yards.
A city street with two parked vehicles—an SUV on the left and a white pickup truck on the right—in front of a modern building with large windows, trees on the sidewalk, and yellow road lines in the foreground.
A city street with two parked vehicles—an SUV on the left and a white pickup truck on the right—flank a median with small trees and shrubs in front of a modern brick and glass building.
A wide concrete sidewalk runs alongside a parking lot with several parked cars, bordered by brick buildings and trees under a sunny sky. Red markings are visible on the sidewalk.
A city sidewalk with a small planted area featuring tall grasses and a young tree in the center, bordered by parked cars and brick buildings under a sunny sky.

Meeting Stormwater Requirements While Investing in Greener, More Equitable Streets

Turning MS4 Compliance into An Early Planning Decision

Meeting Municipal Separate Storm Sewer System (MS4) requirements in Denver had become a coordination problem, not a technical one. Green infrastructure was often considered late in project development, after transportation designs were largely set, limiting feasibility and diluting water quality benefits. Denver’s Department of Transportation & Infrastructure (DOTI) needed a defensible way to decide where green infrastructure belonged, how it aligned with other City priorities, and how to justify those decisions under regulatory review.

Without a clearer framework, investments risked becoming reactive—meeting permit language without improving outcomes for water quality, heat mitigation, or equity.

Building A Defensible, Cross-Department Framework

DOTI manages a 6-year transportation capital program spanning hundreds of projects, each with different right-of-way constraints, schedules, and funding sources. Stormwater goals had to align with street design, tree canopy targets, heat reduction priorities, and equity commitments, all within fixed capital timelines. Any planning approach had to work across departments and remain transparent to both regulators and the public.

RESPEC partnered with DOTI to move green infrastructure decisions upstream. The team evaluated projects in the six-year transportation plan and developed a GIS-based planning framework to identify where green infrastructure could deliver the greatest combined benefit.

Using layered datasets, including tree canopy coverage, street-level temperatures, right-of-way constraints, flood history, and social equity indicators, RESPEC built scoring tools that rank candidate projects and recommend appropriate green infrastructure practices. The framework also identifies opportunities to bundle water quality benefits across multiple projects, improving coordination and investment efficiency.

From Reactive Mitigation to Repeatable Investment

DOTI now uses a repeatable planning framework to guide green infrastructure investment in support of MS4 compliance. The approach strengthens cross-department coordination, improves accountability, and helps ensure stormwater investments deliver measurable water quality benefits alongside community and environmental value as City priorities evolve.