DIXON – Engineers hired by the city have identified the ideal spot to build a detention pond on the west branch of Fargo Creek to alleviate flooding issues.
The City Council approved a flood study in October looking for improvements and priority areas along the creek, which splits into east and west forks and flows from Bloody Gulch Road to the Rock River.
Rock Island-based Veenstra & Kimm Inc., which is conducting the study for about $87,900, presented findings to about 15 community members Thursday during its second project meeting.
The east branch has a detention pond that was built in the early 1990s that helps to offset flooding, but the west end is where most of the problems are, Veenstra design engineer Jason McKenzie said.
The proposed detention pond would be located upstream of the creek just south of the C&NW Railroad and encompass about 30 to 40 acres.
It would cost about $850,000 for more of a natural pond that would hold water and then slowly drain over time, or about $2.77 million to build a recreational pond that would be surrounded by a path and other features.
The city received a $2.1 million Illinois Transportation Enhancement Program grant to extend the bike path about 2,800 feet east on River Road toward Raynor Garage Doors and west on River Road connecting to First Street and following the viaduct to Seventh Street.
McKenzie said the recreational pond could pair well with the bike path if the city chose to extend it farther south on the west side in future years.
"It would be the largest cost, but it may benefit the community in the future," he said.
Not counting the recreational option, he said it would cost an estimated $2.6 million during the next 10 years to replace and maintain creek infrastructure, and he recommended that the city evaluate the conditions once or twice a year.
Other improvements include bolstering the culverts at Monroe Avenue between Fifth and Sixth streets and at Ninth Street for $288,000 and $533,000, respectively.
They identified two other possible locations for the detention pond: slightly south of Bloody Gulch Road or in between the railroad and Bloody Gulch Road, but hydraulic engineer Tom Kirkeeng said it's more effective closer to the urban area.
"It covers more of the drainage basin, and the closer we can build it, the most impact it has in town," he said.
Part of the study work included assessing infrastructure along the creek, walking through the culverts, updating floodplain data, and analyzing channel flows and capacity.
They identified 10 possible alternatives to improving flood flow conditions but eliminated half of them because of a combination of excessive cost and little benefit to the situation.
The creek is normally dry, but is prone to flash flooding, which can take a toll on residents as well as city infrastructure, such as when heavy rain in August that left parts of Dixon under about 3 or 4 feet of water, and the summer of 2015 when a portion of West Seventh Street collapsed.
The next steps are for the consultants to create a draft report with findings and recommendations that will be presented to the City Council in early March followed by a final report with possible grant options, tentatively at the end of March.