May 03, 2011

Calming the Storm Water

HDPE ditch lining for residential and industrial applications

Dealing with storm water in industrial and residential settings simply cannot be avoided. Runoff and perimeter drainage plans usually consist of a series of shallow earthen trenches. Similarly, residential areas are confronted with flow control issues; culvert pipes often disperse large amounts of water, potentially causing serious erosion. Two recent projects made use of a high-density polyethylene (HDPE) ditch-lining system to help control storm water flow.

Santa Barbara Neighborhood

Living with unstable slopes and erosion is an all-too-common reality in the crowded neighborhoods of Santa Barbara, Calif. Homes are built with minimal separation, and drainage systems often become disrupted with vegetation. When the challenge of repairing and maintaining a ditch between their homes arose, residents turned to SmartDitch.

Between residential homes, a 15-in. corrugated metal pipe (CMP) drained from the roadway into a vegetated ditch running along property lines. During heavy rain events, the flow was disrupted by vegetation, causing flooding in yards and erosion at the bottom of the slope. After giving consideration to extending the pipe down the slope or lining the ditch with concrete, a third option of using SmartDitch was chosen.

An open HDPE ditch was considered the best management practice for several reasons, including:

  • A stable channel design to prevent hillside erosion;
  • Superior flow characteristics to improve the flow of the water for drainage purposes; and
  • Lower installation and maintenance costs.

Approximately 135 ln ft of the 12-in.-deep trapezoidal SmartDitch product was to be laid on the slope. The liner sections were positioned at the opening of the 15-in. CMP, allowing water to flow in. The course of the ditch followed the original drainage ditch, requiring the liner to be installed with several small curves. Stone embedment material was brought in to fill the voids of the original ditch along the sides of the channel sections for slope stabilization. At the bottom of the slope, the new lined ditch emptied into a natural drainage swale.

A crew comprised of local residents working with hand tools installed the ditch liner in approximately two days. The curves were installed by offsetting the flow line of the sections a small amount at each joint, creating a natural-looking flow path. Because of SmartDitch’s HDPE construction, maintenance on this ditch will be minimal, ensuring years of trouble-free operation.

Rocky Mountain Power Substation

When Rocky Mountain Power’s White Rock power substation was constructed in northern Utah, it included a storm water drainage system that met the local guidelines and regulations. What was not known or taken into account at the time, however, was additional, unregulated hillside storm water runoff that was comingling with the site’s regulated storm water, subsequently increasing the owner’s disposal costs.

To arrest this, Power Engineers, the consulting engineering firm on the project, specified the installation of 800 ln ft of 12-in. SmartDitch to keep the hillside drainage separate from the site’s mandatory storm water drainage system. The addition of the HDPE ditch liner also helped stabilize this new perimeter drainage system’s sidewalls, and it minimized any future erosion or sediment runoff.

Typical Installation Scenario

In both projects, the installation process was similar. Once the contractor excavates and cleans out the existing ditches/swales, the 10-ft ditch liner sections are dropped into place. Gaskets then are applied to the upstream end of each section. Once that is complete, the downstream end of another 10-ft liner section is overlapped and joined with a series of stainless steel self-tapping screws. This process is continued until the job is finished. A cable anchoring system (similar to that of a retention wall anchoring system) is used to secure the HDPE ditch liner into the ground.