The Stratton Lock and Dam is the lifeblood of the Chain O' Lakes.
Its gates push water south when the Chain is too full, while holding water in when rain stops falling through the hot summer months.
And, the McHenry facility is a vital means of transportation, helping move recreational boaters from the upper river to the lower river and back again.
But officials with the Illinois Department of Natural Resources say the gates are showing their age from natural erosion and use, and the boat lock is too small and antiquated to serve the 24,000 boats on the busy waterway.
"The structure is breaking down from years of wear, tear and age," said John Palmeiri, lockmaster of the Stratton Lock and Dam in McHenry. "The life expectancy of both structures are past due."
With millions of dollars in construction on the line, the Illinois Department of Natural Resources will host an informal meeting Monday to review several ideas to update the dam and build a bigger lock. The meeting begins at 6 p.m. at McHenry County College, 8900 Route in Crystal Lake.
Named after former Gov. William Stratton, the Stratton Lock and Dam is really two major pieces: the sluice gates or doors that control the flow of the river from the Chain and upper Fox River to the lower river, and the lock that allows boats to travel from one side of the dam to the other.
Officially, the dam was built in 1907, but not by the Illinois Department of Natural Resources, which currently owns it. The dam was donated to the IDNR in 1923 when it was just a spillway designed to hold back a certain amount of water from running downstream.
The gates were added in 1939 after major floods in November 1937 and July 1938 showed officials they needed to have the ability to release more water downstream to alleviate flooding.
Palmieri said the five sluice gates, located below a steel-and-concrete walkway on the western half of the river, are used to control the height of the river and the Chain above and below the dam.
The gates and how they are used to control flooding has been a point of controversy with boaters, residents and businesses on the lower river and the Chain for many years.
During large-scale floods since 1940, people on both sides of the dam have complained about how the doors -- and a third hydraulic gate erected in 2002 -- have released too much or too little water.
Depending on the plan approved by the IDNR, new gates could alleviate some of those problems, Palmieri said.
Meanwhile, the boat lock that was installed in 1960 as a way to allow boats to traverse from the lower river to the upper river and Chain, is not large enough to keep up with the size and number of boats on the popular waterway.
The lock operates like a "water elevator" to lift and drop boats between water levels on the lower and upper river, Palmieri said. If a boater wishes to get from the lower river to the upper river, the boat pulls into the lock and water rises slowly until it meets the height of the upper river. The reverse happens and water is released for a boat traveling in the opposite direction, he said.
Currently, only four boats can pass safely through the lock at one time, Palmieri said, while six could do so nearly a decade ago.
"Bottom line, the boats are much bigger now than they were a decade ago, and there are more larger boats on the river and Chain than ever before," he said. "Ideally, we'd like to double the amount of boats going through right now."
Ron Barker, the acting executive director of the Fox Waterway Agency in Fox Lake, said the average boat on the Chain is about 24 feet. The average boat size was 18 feet in the late 1990s, and even smaller when the lock was installed in 1960, he said.
Rita Lee, a water hydraulist from the IDNR, said the agency could rehab the current lock, expand the existing lock to double the number of boats able to pass through, or add a second lock.
However, Lee said, fixing the sluice gates will be more complex, and four options are under review.
The sluice gates could be rehabbed or the dam itself could be replaced to feature four larger gates instead of five medium-sized gates, she said.
Officials are also reviewing two alternate technology options -- a crest-hinged gate that lowers and raises the gates from under the water, and an "over-under gate" in which the doors are raised out of the water instead or swinging open to let water through.
Lee said all the options will be sufficient to let water flow through the dam at current levels, though the newer technologies could increase the flow of the river and displace water downstream quicker.
"Whatever plan is decided, it will be pretty expensive," she said. "But, we won't know how much exactly until after a plan is decided."
The cost would be covered through capital improvement dollars from the Illinois Department of Natural Resources, she said. The hope is to begin construction as soon as a final plan is determined.
The cost and time frame when the work is expected to be completed will be decided after Monday's meeting, Lee said.