High Line Canal

Developing practical solutions for repurposing the High Line Canal for collecting and treating stormwater runoff.

Denver, Colorado
Urban Drainage and Flood Control District

RESPEC prepared a one-of-a-kind feasibility study to confirm the practicability of repurposing the 66-mile-long High Line Canal to collect and treat the stormwater runoff that taxes the capacity of existing storm sewer systems. Additionally, RESPEC was tasked with developing practical solutions that can be implemented through engineering analysis and coordinating with the project sponsors and public.

The project included characterizing all of the watersheds that cross the High Line Canal; determining the canal’s treatment capacity; determining infrastructure needs; estimating the annual stormwater volume available for infiltration and evapotranspiration; estimating capital, operational, and maintenance costs; evaluating a framework for operating within the Colorado water-rights administration system; providing a conceptual design of a pilot project to reconfirm the project’s feasibility; and identifying future steps for project implementation. This project was coordinated with several governmental agencies, including their stormwater, public works, and parks and recreation staff.

The High Line Canal was divided into 52 design reaches. Each reach was evaluated to determine the amount of runoff that currently enters or could enter the canal, the storage volume available in the canal that could be used to treat for water quality, and the water quality capture volume for the area tributary to the canal.

This analysis showed that some canal reaches had an excess capacity while others lacked adequate capacity to fully treat the existing and proposed canal inflows. The segmented canal allows temporary storage of approximately 200 acre-feet of stormwater runoff, which represents approximately 68 percent of the total water quality capture volume of the defined tributary area.

The canal also provides the opportunity to infiltrate an additional 1,000 acre-feet of water in an average year that is then available for existing trees and shrubs, thus, assisting in preserving the canal’s recreational and aesthetic amenities. Adding small control structures in the bottom of the canal passively provide water quality and vegetation preservation benefits.