Repairs & Current Work

Localized erosion

Basic repair items that are being addressed now are erosion along the downstream embankment in localized areas. Eroded areas will be backfilled and compacted, after proper surface preparation has taken place - removing grasses and leveling uneven and gullied soil. Erosion along the downstream wing wall returns will be filled in with rip-rap. Erosion has occurred here because it is exposed to foot traffic, fishermen who climb down the rip-rap along the side.

Erosion below Monitoring Well #4B

Each set of monitoring wells had an additional well installed at the downstream toe. Now there are four sets of three wells per set. This well will give a third plotting point on the phreatic line graphs, which we use to show the behavior of the water through cross sections of the embankment at four locations. The data will also help us in determining the most effective elevation to locate a toe drain just above the downstream toe.

As may have been mentioned at some point on this blog, there has been some leakage visible at the downstream embankment. We have monitored it visually and through the readings captured at the Monitoring Wells. For the last few months, the conditions have remained stable, which is a good thing, however it can't be left to leak for the long term. Our plans to plug the leaks have taken several twists and turns. The best case scenario for fixing the leaks has always included Bentonite, a naturally occurring clay which carries the unique inherent property that upon contact with water, it can swell up to 16x its original size. We would be using sodium bentonite in either powder or pellet form, and would spread it over the upstream embankment and insert it into potential inflow points to form a "plug" that would seal reservoir water from traveling through the embankment. However, Bentonite is not commonly used in Cambodia, and so we had to look elsewhere for material suppliers. We have just received pricing from a Thai supplier, and looks like we could receive material within two weeks. (PS, if any of our blog readers have information on bentonite suppliers in this region of the world, we would love to hear from you, for future reference.)

While this may solve the problem on our hands now, once the reservoir is fully turned over to the community, it will not be so easy to reach out to a Thai supplier, purchase material, and get it to the site... Something we're trying to start, as we perform maintenance and repairs on the embankment now, is getting the high level FWUC members involved directly. Participation of the FWUC is essential now, because they will be responsible for operating, maintaining, and inspecting the dam and watergate in the long term. A long period of overlap with EWB, HT, and FWUC all participating in routine dam inspections and monitoring procedures will help to ensure the success of the project's future management.