Bloomfield Hills drainage requirements reviewed
By Kevin Elliott
Heavy rainfall, storms and flooding will be more frequent in the future, leading to more potential drainage problems – and opportunities for mitigation – in residential neighborhoods like Bloomfield Hills, according to consultants working with the city to help improve residential drainage issues.
James Burton, vice president of Hubbell Roth & Clark (HRC) consulting engineers, recommended on Tuesday, March 14, to Bloomfield Hills city commissioners at their meeting to consider the creation of a policy that incorporates drainage requirements into residential site development and construction.
“Rainfall is getting more frequent, more intense every year out there. What used to be a 100-year storm is now a 25-year storm,” Burton said. “We are going to see more and more flooding, more and more regularly throughout this community and every community. It’s what’s happening out there.”
The commission requested Hubbell, Roth & Clark review the city’s current drainage requirements of residential lot development to determine if further requirements are needed as part of the process. The request was part of the commission’s 2023 city goals.
Under the city’s National Discharge Elimination System permit for releasing stormwater pollutants, the city is required to enforce stormwater standards for development projects. As the city’s stormwater consultant, HRC recommends stormwater management improvements. However, additional requirements to the city’s grading ordinance, Burton said, would help mitigate drainage impacts in single-family areas.
Burton recommended the city institute requirements for more unconventional projects, as a way to begin the process. Those projects could include lot split applications; landscape open space variance requests; accessory structure and building applications; and for projects such as sports courts or pools that generate runoff during rain events.
Further, he recommended the city encourage developments incorporate measures to help reduce the impact of stormwater runoff, such as rain gardens, bioswales, French drains, leaching basins, and dry wells. Additionally, he said the city should require such measures be maintained to ensure their effectiveness.
“If you don’t maintain these things, they aren’t going to do any good after a while, so we have to make sure homeowners are maintaining, and we have the ability to do that,” he said. “How we do that is to meet with code enforcement, the city attorney and city manager, and go through that.”
City commissioner Sarah McClure said the city should also be looking at large redevelopments, where the footprint of a home is increased by several thousand square feet, thus creating more impervious surface.
“With a lot split, we wouldn’t know the purpose of what they are going to put on the lot, and what the requirement would be,” she said.
Burton and commissioners discussed the possibility of establishing volumetric requirements for certain types of developments.
“If the average sports court generates an average of say, 5,000 gallons (of runoff), then I would make the requirement that they provide mitigation for 5,00 gallons,” he said. “A pool or structure may require x gallons.”
“So if someone is building a sports court or pool or patio, or whatever – you want something in (the ordinance) that says they are required to put in drainage,” commissioner Susan McCarthy asked. “For example, we had a resident who expanded their house, and then wanted a pool and a pickleball court, and we never addressed drainage. I don’t see a problem saying if you put ‘this’ thing in, you need ‘this.’”
McClure questioned how to determine volumetric requirements, and that the process seems to be overly complicated, which may dissuade residents from complying.
The discussion ended without a formal motion, but with an agreement from HRC to incorporate the discussion into revised recommendations and further discussion.