Usually placid Lake Byllesby will be a hopping spot for construction in the coming years, with upgrades to the hydroelectric dam and a pedestrian bridge over the Cannon River in the works.

Together, the projects aim to improve safety and accessibility for park visitors and those who live nearby and downstream. Here's a look at the plans:

Byllesby Dam

The century-old Byllesby Dam still does its job, but federal regulators have said it needs to be beefed up to withstand a probable maximum flood -- a deluge never yet recorded that would require 16 inches of rain over 100 square miles in six hours.

Dakota County, which owns the dam, has been drafting plans to add to the spillway and build a perimeter dike along the northeastern side of Gerlach Way.

The spillway upgrade -- basically a new concrete apron with additional gates on the southern end of the dam -- will make it easier for the dam to release large amounts of water when necessary. The dike, an earthen berm about two feet high, will prevent water from spilling out of the lake onto nearby fields during a major flood.

The projects are expected to cost about $5.8 million, with construction starting in 2012 and continuing into 2013.

Trail bridge

The pedestrian bridge, long on the wish list of trail advocates, would be a key river crossing for the Mill Towns State Trail between Faribault and Cannon Falls.

The Minnesota Department of Natural Resources has $1.7 million to spend on the bridge and constructing nearby segments of the trail. Dakota County has a standing state bonding request that would make up the difference in the total project, expected to cost $2.8 million.

The bridge, measuring 14 feet wide and 295 feet long, would cross the river near the dam, connecting Lake Byllesby Regional Park on the northern shore with a trail leading to Cannon Falls -- and the popular Cannon River Trail downstream -- on the southern shore.

Trail alignments and final designs are still in the works, but construction for the bridge is slated for 2013.

Katie Humphrey • 952-746-3286