Crews are scheduled to begin preliminary work on a nine-foot-tall dam on the north side of Folsom Lake Thursday.
Kyle Keer with the Bureau of Reclamation says the work will prevent water that has seeped through the dike from pooling.
"We're going to take off the downstream face of that dam and we're going to replace it with some sand and gravel filter layers. So when that water does come through the dike as it is now, it will hit that gravel and sand, and being the path of lowest resistance, it will follow that gravel and sand down as we direct it.
Keer says the water from the lake is rarely higher than the base of the dike and some seepage is normal.
Engineers have determined that an impermeable wall inside the dike would stop the seepage, but isn't necessary or cost-effective.
Keer expects the work to be completed by the end of April.
There are eleven earthen dikes around Folsom Lake.