A nonprofit publication of the Kentucky Center for Public Service Journalism

Craig Frye of SD1 shows why and how to have a rain garden; help keep stormwater out of the system

By Hannah Carver
NKyTribune reporter

As green land space shrinks in Northern Kentucky, rainwater has fewer places to go, leading to an increase in unmanaged stormwater runoff that’s presenting greater threats of erosion, flooding, and pollution to the community.

“As we increase the impervious surface — the hard surface, concrete, asphalt — you’re going to increase the runoff,” said Craig Frye, who is the Environmental Compliance Coordinator for Sanitation District No. 1 of Northern Kentucky (SD1).

Part of Frye’s job is to put in place best practices for managing the region’s stormwater. For businesses, that means the required building of drainage area features that are intended to make up for the increase in hard surfaces, like parking lots and rooftops.

However, for residents of Northern Kentucky, there are no requirements, despite the fact that individual homes still do contribute to the problem. There are ways to help, though.

SD1’s Disconnection, Redirection, Infiltration Program, or DRIP, strives to prevent the destructive impact of stormwater runoff by enabling homeowners to better manage it. The goal of the program is the disconnection of homes’ downspouts from the combined sewage system, which currently becomes overwhelmed in wet periods, leading to the release of untreated wastewater into our creeks, rivers, and lakes.

“If you can take stormwater and keep it out of that system, you’re going to open up more storage, more capacity in that system,” Frye said.

Guidance documents on SD1’s website show residents how to properly disconnect their downspouts in accordance with zoning requirements. After that step, there are a couple options for people who don’t want or don’t have the space to have water just splash into their yards.

One of those options is rain barrels.

Craig Frye explains how the depth of the rain garden matters for filtration. (Photos and video by Hannah Carver)

“They’re not going to solve any problems because it’s just a small amount of water, but it’s something,” Frye said. “And we’ve actually seen rain barrels chained together… so depending on if you want a bunch of barrels at your site, you can have a couple hundred gallons of stored water for usage.”

Once again, though, if yard space is an issue, this may not be the best option, and that’s where rain gardens come into play.

A rain garden is a shallow area filled with plants, and it is designed to capture clean stormwater runoff, effectively protecting local waterways, while at the same time, beautifying a property. Even better, it creates a habitat, in which bees and butterflies can thrive, by bringing in pollinator plants.

“For the resident, it’s a benefit for them because they are outside gardening and doing what they enjoy to do,” Frye said. “You’re also reducing that stormwater from getting into the sewer system, which is going to help a lot of things downstream.”

There are a few questions to consider before building a rain garden, though.

Conduct an infiltration test to determine how quickly the water will drain.

“First and foremost, do you have the space for it? Are you going to affect anything or anybody downstream? Is it going to get into the street? Is it going to get into the sidewalk?” Frye said.

Once that’s figured out, check to see if there are any utilities below. Then, determine the soil type.

“You don’t want to put a rain garden in an area that’s all clay. You can amend [the soil] as much as you want, but if it’s really heavily ridden with clay, you’re not going to get infiltration no matter what you do,” Frye said. “That water is going to pond. You don’t want to create a pond. That’s bad stuff.”

To test the soil, Frye recommends an infiltration test:

1. Dig a hole that’s both eight inches deep and eight inches wide.
2. Fill it up with water, saturating the area around it, and give it time to all soak.
3. Then, once it’d drained, fill it back up and measure it.
4. Come back four hours later to see how much the level has dropped.
5. Whatever that number is, multiply it by six to estimate how much will drain in a 24-hour time period.

“That infiltration test will dictate, too, the depth of your rain garden,” Frye said. “If your water is gone within four hours, you know it does not have to be that deep. If it’s infiltrating, but not infiltrating great, you may need to make amendments.”

Frye suggests using string to lay out the rain garden before spray painting the lines for excavation. (Photo provided)

Those amendments can include tilling things like sand or organic matter into the soil to help the rain garden drain more quickly.

“That little infiltration test: It’s as basic as can be, but it tells you if the stuff will work or not,” Frye said.

Next, figure out the square footage of the area draining into the rain garden to determine how large it needs to be. SD1 has calculations and diagrams to help with this step on their website.

Then, the fun of designing the rain garden can begin. Frye’s tip: Use string or yarn to lay it all out, and adjust as needed. Once the path is decided, spray paint the area.

“Residential rain gardens, for the most part, are going to be about 100 feet square, so they’re not going to be too large,” Frye said. “So you can [excavate] it with a shovel. It requires some work, but it can be done.”

Let the soil settle after excavation and watch how it handles rain. While eventually, the plants will help with infiltration, it’s not going to happen right away, so this is the best time to make any amendments to the soil or size of the rain garden, based on observations. It’s also a good point to build a spillway.

Using a tiller, work the soil after excavation and increase the infiltration of the rain garden. (Photo provided)

“These rain gardens are small, so if you get a big, huge rain event, that rain garden isn’t going to be able to handle all that rain, so it’s got to find a place to go. Instead of going over the berms and going all over your yard, direct it out one location, a good safe location where it won’t affect anything downstream,” Frye said.

Once everything is built, it’s time to start planting. To help with selection, SD1 has an appendix of recommended plants on its website.

Frye’s advice is to put vegetation that loves water in the deeper areas of the garden, while placing plants that might not want so much, higher up on the berms.

Top everything off with two layers of mulch. That acts as a protective cap against erosion and helps keep the plants stay moist as they establish themselves.

As far as maintenance goes, once the rain garden is built, it’s pretty simple: Prune, replace plants, weed, and water as needed. It’s also recommended to replace the mulch layer every couple of years.

While a single rain garden may not be the “be all end all” solution to Northern Kentucky’s runoff problem, it is a helpful step to maybe one day, solving it.

“You are contributing to the problem, as well as everybody else, so you can take pride in that you’re doing your part to help manage some of that stormwater that’s coming off your site,” Frye said.

For more information on building rain gardens, check out SD1’s website or call them at (859) 578-7450.

Put water-loving plants in deeper areas of the garden, and others on the berms. For a list of recommended plants, see SD1’s website (Photo provided)

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