Amston Lake Dam Repair
Work on the dam is nearly complete and LR Enterprises has done an excellent job performing the repair. They have been doing dam repairs for many years and their experience showed throughout the repair process. It is typical for dam repairs to encounter unplanned additional work because until the dam is opened, the construction of the dam is unknown and problems are hidden.
This was the case for our dam. Here are some of the things we found:
The current dam is a rubble construction. That is to say, it is constructed from stones and earth, and to this a cement veneer (very thin in some areas) was applied.
We were not able to put the new the new sluice box (drain system) next to the current dam end wall as planned because this would disturb the rubble wall and create new leaks.
A new extension wall was needed between the current dam and the relocated sluice box.
A large undermined area was found next to the current dam downstream end wall and the undermined area extended well under the spillway. This was a leakage path for the leak we were trying to repair.
The repair plans were modified to inject cement under the spillway to fill a large cavity (about 3 cubic yards).
Impervious material (clay type) was added at the spillway side wall in the area of the leakage path. Foot drains were installed to lead away any leakage from the end wall.
A new extension wall was added to run between the current spillway rear end wall and the new 18 inch drain pipe end wall.
We found an old concrete wall which extended parallel to the current spillway. To help prevent leakage between this wall and the new sluice box, we added a large concrete fill between the old wall and the sluice box.
Usually a picture is much easier to understand than words, so you may wish to review the attached slide show which presents highlights from the repair process.
As you can see, we needed to modify the plan several times to correct problems as they were exposed. We have also made some repairs to the top of the spillway in locations were the concrete was cracking and chipping away. This was followed by a special cement over coating to seal cracks and give the dam a unifying appearance. (Please discourage any local artists from adorning the clean wall.) We have also graded and hydro seeded the earthen part of the dam.
One item which remains to be completed in the next couple of months is the installation of a slide gate valve which is being fabricated. This will provide a backup method to the weir boards for regulating water flow.