A report made by The Army Corps of Engineers addressed unacceptable risk in the Rough River Lake Dam due to foundation conditions. The recommendation was major rehabilitation to ensure the structure's integrity and lower the risk.
Background
The contractor was to carry out the first phase of drilling & grouting and collect data as a input for the later coming main rehabilitation work.
Non-potable water was taken directly from the lake and used for the drilling. Even if it looked dirty, water analysis proved it good enough to use for drilling without any pretreatment.
Water treatment solution
Since the drilling took place during winter time the water was heated before used for drilling and grouting. The collected drill water at the drill site was then pumped back thru isolated pipes to the water treatment plant to be treated before discharge back to the lake. Removal of particles was done with 80 m3 (21 000 gallon) settling tanks and by adding of additives. Since the drilling was performed in a limestone formation, the drill water was treated with CO2 to correct the pH.
The contractor used a settling tank from Adler (www.adlertankrentals.com). Similar tanks are also availble at Rain for rent (www.rainforrent.com).
If the water analysis of the non-potable water would have shown too high particle levels, the solution would have been to use an automatic sand filter.