Civil engineers often encounter and are challenged to mitigate the effects of stormwater runoff, including erosion, flooding, and slope instability. In two recent projects, an easily installed ditch liner solved runoff problems that threatened homes and commercial structures.

Saturated soils
The historic Iron Horse Inn has been a fixture of the Durango, Colo., area for more than 40 years. Located along Highway 550 on the north edge of Durango, the hotel is situated along the Animas River. Running along a hillside and Highway 550, an earthen irrigation ditch borders the inn’s property. This ditch collects stormwater from the adjacent highway and conveys mountain water runoff to the farms downstream and eventually ties into the Animas River.

Workers install SmartDitch liners in a winding channel along the base of a slope near Durango, Colo.

During the spring runoff and wet season, when this ditch flows at near capacity, the hillside that supports the ditch would become saturated, causing water to migrate through the soil and drain into the inn’s parking lots. Flooding occasionally occurred. The velocity of the flow and the saturation also raised the prospect of the hillside eroding.

Through the years, the inn’s owners and management looked for many solutions to alleviate this problem, including sealing the ditch with bentonite clay or lining it with concrete. After reviewing multiple options, the owners chose to line the ditch with SmartDitch, a corrugated, high-density polyethylene (HDPE) liner that is designed to fit into an existing or new construction ditch.

SmartDitch’s benefits in this application include water-tight joints to reduce or eliminate the soil saturation, a stable channel design to prevent hillside erosion, improved water flow for drainage purposes, and a durable material that reduces maintenance issues.

The approximately 600-foot-long ditch is sandwiched between Highway 550 and the inn. For maximum flow capabilities, the 24-inch-deep Trapezoidal SmartDitch product was chosen. Vegetation and silt had to be cleared from the flow line of the earthen ditch before installation. A small backhoe and laborers with hand tools accomplished this task. The course of the ditch snaked along through the right-of-way, requiring the liner to be installed with several small curves. At each end of the line, the liner was connected to existing headwalls, where the ditch connected to concrete pipe used for road crossings. Sand backfill was brought in to fill in the voids along the sides of the channel sections before installing anchors.

Installation of the 600-foot-long ditch liner took approximately two days after clearing vegetation and debris from the existing ditch. The installation crew comprised two laborers with a skid-steer loader used to bring in the sand backfill. The curves were installed by offsetting the flow line of the sections a small amount at each joint. The anchors were easily installed using an electric powered hammer.

Natural vegetation along the sides of the ditch minimizes erosion.

Natural vegetation was encouraged to grow along the ditch to minimize the possibility of erosion along the sides and in the area between the ditch and the highway. During the following wet season, water flowed through the lined section with no difficulties and no detectable saturation of the surrounding soil.

Unstable slopes
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 clogged with vegetation. When the challenge of repairing and maintaining a ditch between their homes arose, some residents turned to SmartDitch.

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

SmartDitch was chosen for this application because it provides a stable channel design to prevent hillside erosion, improved water flow for drainage purposes, and lower installation and maintenance costs.

Approximately 135 feet of the 12-inch-deep Trapezoidal SmartDitch product was installed on the slope. Vegetation and debris were cleared from the flow line of the ditch prior to installation. The liner sections were positioned at the opening of the 15-inch CMP, allowing water to flow from the pipe to the liner. 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 empties into a natural drainage swale.

Installation of the ditch liner took a crew of local residents working with hand tools approximately two days, including clearing vegetation and debris from the existing ditch. 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 both the Iron Horse Inn and Santa Barbara ditches will be minimal, ensuring years of trouble-free operation.

Michael J. Livermore is the SmartDitch national sales manager for Penda Corporation. He can be contacted at michaellivermore@penda.com.