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Concrete Cloth Culvert Remediation

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In November 2014, Concrete Cloth (CC) was used to reline a steel corrugated culvert pipe . The existing pipe had broken down through flow erosion and weathering. Water was flowing through the bottom of  the culvert and was compromising the base soils below which, in turn, threatened the integrity of the road above which needed to bear heavy loads from logging activities.

This culvert rests below a rural  country road, heavily used by logging trucks. A road closure, which would be required to replace the culvert, was  not an option at this time. Concrete Cloth was a much more cost effective solution for this problem and was chosen due to its  speed of installation, its ability to easily accommodate changes in culvert profile and its minimal environmental impact.

Concrete Cloth is recognized for use in live water courses by the UK Environment Agency  on previous projects. This was important as this project was located in an environmentally sensitive fish habitat.

To facilitate installation, a stream bypass was installed to divert water around the work zone. The  work zone was isolated with cofferdams, fish rescue was performed, and the site dewatered. Sediment laden  water was pumped downstream to a grassy area where water was filtered prior to rejoining the stream channel. Prior to placement of the Concrete Cloth, sand was placed below the culvert and within the scour hole, using only hand tools.

Installation took two days with a crew of five workers. On the first day of installation the cloth was laid out, screwed into the culvert, wet, and let to set and harden. The second day was used to caulk the edges of the cloth  to the sides of the culvert, and to test pH. The culvert dimensions were 5 ft in height, 7 ft in width, and 34 ft in length. The concrete lining covered  approximately 10 feet in width and the entire length of the culvert (34 ft). A 4” minimum overlap of Concrete Cloth was placed at all seams. Self tapping stainless steel screws were placed to anchor the concrete  fabric to the culvert. Screws were placed approximately every four inches along the sides of the culvert and every 18 inches within the center. Where the Concrete Cloth reached the sides of the culvert tar was spread to ensure a water tight seal.

At the inlet and outlet of the culvert Concrete Cloth was wrapped beneath the culvert and substrate was placed to fill existing voids. Monitoring for pH was carried out as water was introduced into the fabric. Any excess water in the work zone was pumped to an upland where it would infiltrate. Once the concrete hardened water was pumped through the culvert within the work zone, tested, and pumped to an upland until pH readings were within 0.5 units of the background readings between 6.5 to 8.5 units. Once work was complete and pH met the aforementioned surface water quality standards cofferdams were removed and the stream was allowed to flow freely within the culvert.

According to the client, the material was delivered on time and the packaging was in good order. Workers  were trained on-site and the project went smoothly. After numerous high flow events, over the past few  months, the cloth is performing well. The general consensus of the maintenance crew and environmental  personnel was satisfaction with the product. Overall, Lewis County rates this project a success.