Town gets master plan for stormwater

During particularly heavy rain — especially during leaf-peeping season — Nashville’s side streets can resemble rivers more than roads.

People living on the south and west sides know that when the creek starts rising, they need to pay attention. More than once, residents near the end of West Washington have been rescued by boat.

Nashville has some stormwater collection infrastructure underground, but not all over downtown.

Last month, the council heard a presentation from an engineering firm about how to fix the drainage problems.

There’s one big problem, though: It would cost $11.1 million — more if the council delays it, which it must.

That’s nearly 15 times the town’s annual general fund budget.

“I think I saw (town Clerk-Treasurer) Brenda (Young) choke a little,” joked Huck Lewis, with DB Engineering.

The town retained the firm in November 2020 to create a stormwater master plan, which cost about $128,000.

The town has been fighting drainage problems for at least 20 years, said council member David Rudd.

Now that the town has a utility service board and has been creating various utility master plans, the town’s municipal adviser, Dax Norton, recommended the council look at this, too.

The council has not done anything to try to fund a future stormwater project since hearing the presentation about it in July from DB Engineering. The town’s utility service board has looked at it, but since there isn’t a town stormwater utility yet, that board isn’t doing anything with it right now either, Norton said last week.

Other town utility projects are in front of this one, such as work necessary to fix the town’s wastewater plant and bring it up to state standards, and to bring the state park fully onto the town’s water and wastewater systems. Both of those projects could start later this year.

Once they are clear, the council could look at possibly applying for a grant or loan to get started on some of the stormwater work.

User fees also could fund stormwater construction projects and the maintenance of the new utility.

Recommendations

Throughout the fall and spring of 2021, DB Engineering did an overall evaluation of the current drainage system and the problems and coverage gaps it has. Employees made sure to be here when they could observe heavy rain.

Project engineer Whitney Neukam described three main areas of concern to the council:

  • along Old 46/Main Street from Locust Lane to Hard Truth Hills;
  • the northern half of downtown bounded by Main Street to the south, Mound Street to the north, Jackson Branch Road to the west, and Locust Lane to the east; and
  • the southern half of downtown bounded by Pat Reilly Drive/Schoolhouse Lane and North Fork Salt Creek to the south, Main Street to the north; and Old School Way to the east.

Three different watersheds affect the town, and the southern and western edges of it are bordered by Salt Creek, making it imperative that water is purposely directed.

As it is now, a “significant drainage area” comes off the northern hills and enters a storm sewer and conveyance ditch system, Neukam said. That ditch terminates north of Old School Way.

East-west on Old State Road 46/Main Street, the engineers noticed collapsed and undersized culverts in that area. On the west side near Jackson Branch, they identified a storm sewer outlet near the bottom of the road that doesn’t allow other channeled water to escape. That causes water to bubble up from manholes and other outlets upstream, Neukam said.

They also noticed a lack of or undefined curbs and gutters, which causes water to channel itself off roads and into people’s yards.

In the near term, DB Engineering recommended that the town keep the drainage system on the north end of town but improve the ditches and channels that it drains into so that it can flow more efficiently, like removing overgrown vegetation.

In the northern half of downtown, the firm recommended installing or upgrading drainage structures along nearly every east-west road from Main Street to Mound Street as well as sections of some north-south roads to handle the runoff coming from the high point in town, North Jefferson Street, and other watersheds. The structures would be designed to direct water ultimately to North Fork Salt Creek south of town.

Work on the south end would include installing new drainage structures north-south on Jefferson and Johnson streets and east-west on parts of Franklin and Washington streets, Pat Reilly Drive and Schoolhouse Lane.

But first, the firm recommended that the town do GIS mapping of all the structures it has underground. That would be important regardless of whether the town had the money to go forward with other work because town leaders need to know what they have to maintain and the condition those structures are in, Neukam said. The town does not have good records of where its water and sewer lines are either, and the mapping project could help with that.

The cost for projects suggested in Area 1 was estimated at $1,167,000; Area 2 at $5,740,000; and Area 3 at $4,217,000.

A new utility?

The only money the town has directed specifically to stormwater now is one-quarter of its cumulative capital development fund, which builds up over time. At the end of 2020, the stormwater portion had about $70,000.

Grants can become available for stormwater work as well. The county is using one now from the Indiana Office of Community and Rural Affairs to finish a stormwater project in Helmsburg that was started about 20 years ago.

What some communities do to fund their stormwater work and its maintenance is to start a utility specific to it, the engineering firm told the town council.

Basically, the town would set up a formula to charge a monthly user fee to properties in town limits.

To determine that rate, the town would gather a sample size of residential properties and measure their impervious area — hard surfaces that shed water — and get an average for one ERU, or equivalent residential unit, Neukam explained.

Commercial properties, which typically have greater impervious areas like parking lots and roofs, would have a multiplier added to them to determine their rate, because they create higher runoff, he said.

Those calculations could be made with the help of a rate consultant.

Neither the engineers in the room nor council members would speculate what the monthly stormwater rate would be, saying that they didn’t want to make any promises when they didn’t have any data yet.

The creation of this stormwater master plan was one step in a multi-year process to deal with drainage problems the town has had for decades.

Rudd asked if it would help stop the flooding in people’s basements that he hears about, and Huck Lewis, a DB Engineering employee and former mayor, said that it did help that problem when his town of Lebanon redid its stormwater lines.

The council has not taken any further steps since hearing the July presentation.

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Read the stormwater master plan draft: townofnashville.org/town-council

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