City working to optimize stormwater system performance
With a record-breaking 58.55 inches of rain so far this year, many islanders have been inquiring about the standing water on the roadways and Shared Use Path system on Sanibel.
“We are getting rainfall totals we have not been seeing for a very long time,” Public Works Assistant City Engineer Oisin Dolley said. “The vast majority of the areas I have looked at are saturated from record rainfalls.”
According to city staff, it is the highest amount of rainfall on Sanibel in 20 years — even with 8 more inches over the next four months, Sanibel will set a 10-year record for the year.
There are several areas that have localized drainage and do not have design overflow. The areas were full and overflowing, causing major impacts.
Dolley said the roadside swales on West Gulf Drive have certain amounts of storage and are designed to a certain point, but when full they are not designed for excess water to be released.
“Most areas where necessary, we put out warning signs to make sure drivers were aware,” he said of standing water.
The stormwater infrastructures are also monitored and evaluated to ensure there are no clogs, as well as maximizing the storage as much as possible. Dolley said there are areas under a lot of stress.
The weir structures for the Sanibel Slough are a major stormwater infrastructure for the island. There are also hundreds of culverts, catch basins, roadside swales and retention areas for the stormwater infrastructure.
“Our staff has been monitoring those areas to ensure things are open and not clogged and nothing is contributing to more issues than the record rainfall we have had,” he said, adding that it is an ongoing effort as they check as often as possible.
A large portion of the island uses the Sanibel Slough system, as there is a west and east basin for the stormwater infrastructure. Tarpon Bay Road operates as the dividing line. The freshwater environment is the large part that makes the island a sanctuary.
The slough operates as an avenue for excess stormwater and freshwater holding, which maintains the environment through the dry season.
“There are water control structures that do overflow naturally on its own, and water control gates to lower the levels when needed to reduce flooding through those areas,” Dolley said. “It’s very dependent on tides when we can and cannot open (the gates).”
Dolley said they started working on updating the stormwater master plan at the beginning of the summer and anticipate working on it through late spring of next year. The process will include public input, which will most likely occur after the holidays.
He said they are evaluating Hurricane Ian impacts, as well as looking at how Sanibel manages stormwater in balance between flood protection and the environment. In addition, they will look at how sea level rise and resiliency measures can be looked at to modernize the system when possible.
An engineering firm is also evaluating issues and collecting data from ground level and slough levels.
“We have already handled several issues we identified couldn’t wait, but also have a larger repair project that involves going through and addressing issues that maybe came from Hurricane Ian regarding swales, unclogging catch basins and culverts,” Dolley said.
Those who have noticed standing water persisting for more than 72 hours are asked to email sanpw@mysanibel.com for the Public Works Department to investigate.