Scouts Rehabilitate Rain Garden

A rain garden at the Coon Lake Beach Community Center needed a little help. Originally constructed in 2015, maintenance had reached a point where a group effort was needed to reclaim the garden from weeds and silt overload. The Community Center leaders enlisted a local boy scout troop, their parents, and ACD to help.

The rain garden has an important function in the neighborhood as it is positioned near the bottom of a hill to collect street runoff. Instead of going into the lake at the bottom of the hill, the water and associated pollutants are treated by infiltration. The reduction in volume of water running towards the lake also helps alleviate shoreline erosion in specific problem spots.

In one-hour the scouts completed several renovations to bring back much of the original beauty and function. They removed four trailer loads of invasive trees including many thorny black locust. They removed sediment that had collected and was damming the rain garden entrance. Rocks and retaining walls were cleared of debris, leaving the garden with a more formal appearance and ready for the next rainfall. Great job scouts! 

September 2017 - Two years after installation
August 2023 - Overgrown with weedy vegetation
Rehabilitation work
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Happy 1st Birthday Rain Gardens

Six curb-cut rain gardens were installed approximately one-year ago and have been capturing runoff and its associated pollutants ever since. With each rainfall, runoff flowing in the street gutter is redirected into the rain gardens via a cut in the curb. Following a rain event, the water that enters the rain gardens is able to soak into the ground, which better mimics the natural hydrology before impervious surfaces (e.g. roofs, driveways, roads, etc.) and storm sewers directed runoff directly to Rice Creek. The rain gardens are able to store water and are filled with native species that were carefully selected for the site-specific conditions (e.g. light, soil type, and moisture).

Cumulatively, the six rain gardens are estimated to infiltrate 455,000 gallons of water, as well as remove 605 pounds of sediment and two pounds of phosphorus loading to Rice Creek annually. The native plants help to maximize infiltration and provide the co-benefit of pollinator habitat. One additional rain garden is located adjacent to a trail entrance into Locke County Park, providing an excellent public education opportunity.

These rain gardens were installed in partnership with the landowners, the City of Fridley, and the Rice Creek Watershed District. ACD provided design services and construction oversight.  

The rain garden shown in the pictures below was planted last summer and as you can see, it didn't look like much at the time. Now, it looks beautiful and is full of flowers which pollinators love! This rain garden captures curbside runoff from 6.5 acres of neighborhood which previously went untreated to the Rum River. The native plant's roots create channels through the soil and reduce compaction, ensuring a maximum amount of water can infiltrate into the ground. The homeowners who worked with ACD to make this rain garden a reality, kept weeds at bay, and provided irrigation for the new plants during drought conditions!

Project funding was from the Clean Water, Land, and Legacy amendment, and the Lower Rum River Watershed Management Organization. To see other rain gardens installed throughout Anoka County, please see the virtual project tour on ACD's website.

For more information on rain gardens in Anoka County contact Mitch Haustein at This email address is being protected from spambots. You need JavaScript enabled to view it. or 763.434.2030 x150

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Construction Underway for Anoka Rain Gardens

A thriving rain garden installed in Columbia Heights in 2018. With proper maintenance, native species planted in rain garden will fill the entire space within ~3 years.


Four rain gardens are being installed in a northern Anoka neighborhood as part of the City's 2022 Street Surface Improvement Project. Collectively, these gardens will capture nearly 10 acres' worth of stormwater runoff (over 700,000 gallons annually) which would otherwise drain untreated to the Rum River. Through this, sediment loading to the river will be reduced by 969 pounds/year, and total phosphorus loading will be reduced by 3 pounds/year.

Each garden will provide additional ecological benefits through the planting of a diverse range of native species, creating several hundred square feet of rich pollinator habitat within the Rum River corridor. 

The largest of the four Anoka rain gardens – a double inlet project which will treat stormwater from two adjacent roadways.

Funding for project design was provided by the Metropolitan Conservation Districts Engineering and Technical Assistance Program, and funding for construction is provided by the City of Anoka and State Watershed-based Implementation Funding. 

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Rain Gardens Benefitting the Rum River

Six new rain gardens will be installed this summer in Anoka and Ramsey to benefit the Rum River. The first of them, on Washington Street, was completed the first week of June. Each curb-cut rain garden captures water from the neighborhood streets, driveways, roofs and other surfaces. Prior to these projects, the stormwater is discharged directly to the Rum River without treatment. Rain gardens are ideal in built-out neighborhoods where space is not available for stormwater ponds or other larger practices.

Funding for two rain gardens is a state Clean Water Fund grant and the Lower Rum River Watershed Management Organization. Funding for the other four is the City of Anoka as part of their 2022 street renewal project. 

Bowler family members Amanda and Connor at the newly constructed rain garden in their front yard (not pictured: Daniel Bowler). The Bowlers will own and maintain the rain garden which treats stormwater from 2.2 acres of their neighborhood.
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RAIN GARDENS IN THE CITY OF ANOKA

Street reconstruction projects often provide opportunities to install new projects that can benefit water quality in nearby waterbodies. In the City of Anoka, four curb-cut rain gardens are currently being designed in conjunction with a street reconstruction project. The designs are being done by ACD in partnership with the City of Anoka and landowners. The rain gardens will capture stormwater runoff before it enters the storm sewer system, which discharges to the Rum River.

High priority properties with large contributing drainage areas were targeted. Those properties with landowners willing to transition some yard space out near the road from turf grass to garden area and agree to provide maintenance are being considered for rain garden installation. Funding for design is provided by a Metropolitan Conservation Districts Engineering and Technical Assistance Program, and installation funding will be provided by the City of Anoka.

Watch for additional updates as designs are finalized and the rain gardens are installed. To see other rain gardens already installed throughout Anoka County, please see the virtual project tour on ACD's website. 

Curb-cut rain garden example
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Rain Gardens for Rice Creek

Street reconstruction projects often provide opportunities to install new projects that can benefit water quality in nearby waterbodies. In the City of Fridley, up to six curb-cut rain gardens are currently being designed in conjunction with a street reconstruction project. The designs are being done by ACD in partnership with the City of Fridley, the Rice Creek Watershed District, and landowners. The rain gardens will capture stormwater runoff before it enters the storm sewer system, which discharges to Rice Creek.

Depending on the underlying soils at each site, rain gardens with sandy soils will use infiltration (i.e. the water will soak into the ground) while those with finer soils (e.g. silty soils) will filter the runoff before discharging the cleaner water to the storm sewer system. In both cases, Rice Creek will benefit from reduced loading of sediment and nutrients.

High priority properties with large contributing drainage areas were targeted. Those properties with landowners willing to transition some yard space out near the road from turf grass to garden area and agree to provide maintenance are being considered for rain garden installation. Funding will be provided by the City of Fridley and the Rice Creek Watershed District.

Watch for additional updates as designs are finalized and the rain gardens are installed. To see other rain gardens already installed throughout Anoka County, please see the virtual project tour on ACD's website.

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Riverbanks, Lakeshores, and Rain Gardens, Oh My! - It's Been a Busy Spring

Anoka Conservation District staff have had a busy spring providing technical assistance to landowners for projects related to water resources. Inquiries about riverbanks, lakeshores, and rain gardens have been particularly common. In total, technical assistance has been provided to over 40 individual property landowners.

Active erosion is the primary reason that prompts people to reach out for assistance with their riverbanks and lakeshores. ACD staff have expertise in a wide variety of stabilization methods and know what it takes to complete a successful project. For example, stabilization projects typically require a formal design and coordination with a qualified contractor for installation. There are also a number of permits commonly required, which ACD staff have experience coordinating. Thus far in 2020, technical assistance has been provided for 13 riverbanks and 12 lakeshores.

Technical assistance has also been provided for 16 rain gardens so far in 2020. Rain gardens are generally categorized as either rooftop disconnect or curb-cut. Rooftop disconnect rain gardens receive runoff from downspouts. Driveway runoff could also be directed to rooftop disconnect rain gardens via a trench drain.Rooftop disconnect rain gardens can be a great do-it-yourself project. Curb-cut rain gardens direct water from the curb and gutter system into a shallow depression in your yard near the road and are primarily constructed by landscape contractors. Once the rain garden fills (typically 1' deep), the runoff bypasses the inlet so there is no risk of flooding your yard. This allows the 'first flush' to be treated, which typically has the most pollutants.

Available funding can be limited, but it's always a good idea to check because new grants may become available from year to year. If funding is unavailable, ACD staff can minimally provide technical assistance. That process typically begins with a phone call or email to learn about the site. ACD staff then conduct a desktop site assessment using available mapping data and schedule site visits when necessary. ACD will also provide assistance with design and construction management, which are sometimes covered by grants.

If you have questions about your property, please contact us. In addition to assistance with projects related to water resources, ACD staff are also available to assist with habitat restoration projects. 

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What we wish we knew: lessons for rain garden implementation

Over the last decade the Anoka Conservation District (ACD) has been involved in the design and construction of over 100 rain gardens in Anoka County. While the overwhelming majority fall closer to the 'ideal' end of the spectrum, we've been party to a few on the 'nasty' end as well. Properly functioning rain gardens often go unnoticed because they blend in with other landscape amenities. In contrast, the small fraction of 'nasty' rain gardens get the public's attention with nasty smells and mosquito problems. Rest assured, we've learned from our mistakes, refined our process, corrected the problematic rain gardens, and can confidently say we're now able to avoid the 'nasties'.

The lessons learned over the years have improved every aspect of rain garden location, design, installation, maintenance, and follow-up. These are our suggestions for other organizations designing and installing rain gardens.

Failed rain garden that doesn't drain between rain events

Design

  • For a standard rain garden, the water table should be at least five feet below the bottom of the garden. This will require an eight-foot-deep soil boring during the design process because the bottom of the garden is often two to three feet below the original ground elevation. Rain gardens with shallower water tables are feasible, but require an underdrain to function properly.
  • Soils should have high infiltration rates, generally one to three inches per hour. Rain gardens can be built in soils with lower infiltration rates, but may require an underdrain or a ponding depth shallower than 12".
  • If an underdrain is needed, install a control mechanism that allows variable draw down rates and levels. This provides a mechanism to capitalize on natural infiltration that may increase as the deep root structure of the native plant community matures and creates pathways for infiltration.
  • Water must be able to get into the garden consistently, predictably, and without causing erosion. The curb-cut should be sized to safely pass sufficient water volumes.
  • Utilizing a retaining wall along the back of the garden can improve the aesthetic appeal and allow the garden to store more water. Rain garden side slopes should be no steeper than 3:1. Therefore, for every foot of wall height, three feet of rain garden bottom is gained. In many cases this simple addition more than doubles the size of the garden.
  • Consider using a pretreatment chamber. A pretreatment chamber functions like a filter, capturing floatables like leaves, trash, seeds, and sediment to ensure rain gardens are able to properly receive water and dry between storms
Rain garden mid-construction, with a retaining wall and intact curb
Location
  • Rain gardens should be sited where they will capture runoff from a sizeable contributing drainage area that would otherwise make it into a priority water resource.
  • They should treat stormwater that isn't already routed to a stormwater pond or other installation for stormwater management.
  • They should be strategically located on properties where they will quickly fill during storms and quickly drain between storms.
  • They need to be located where they won't interfere with utility lines. Utility companies have minimum cover requirements over lines that may not be met following rain garden excavation. While some utilities like cable lines can be moved or lowered for a relatively low expense, others like gas and electrical lines can be cost-prohibitive to relocate when they conflict with the proposed rain garden location.
  • If a rain garden is installed in an area where the road routinely floods over the curbs, water will flow into the rain garden over the sides and cause erosion. It will also result in deeper water than intended, which will take longer to drain out.
  • If a rain garden receives water from a large neighborhood with non-natural runoff sources like irrigation systems or sump pump discharge, the rain garden may never have the chance to drain completely.
Rain garden pretreatment chamber

Installation

  • Curb-cut rain gardens are one of the few conservation practices where landowners volunteer to use their property to treat runoff from other properties. The landowner volunteering contributes relatively little to the problem and benefits relatively little from the solution. They also commonly assume maintenance responsibility for 10 years. For these reasons, local government should consider covering 100% of the construction costs.
  • Avoid equipment traffic within the garden.
  • Check soil infiltration rates. If they are under the design specification, loosen soil throughout the
  • garden with a four-foot auger.
  • Plant gardens in the spring and early summer, not in the fall.
  • Lay no more than three inches of mulch.
  • If possible, consider leaving the curb intact until the plants are established and then complete the curb-cut. Minimally, when installing a curb-cut rain garden as a retrofit, leave the curb intact until the basin is completed. This ensures the basin is stable and ready to receive runoff as soon as the curb-cut and apron are installed.
  • Install informative temporary signage during construction and permanent signage upon project completion that explains the value and function of the rain garden.
Ideal rain garden

Maintenance

This is a list of suggestions that can be provided to a homeowner after installation:

  • Get your neighborhood involved! If your neighborhood has several rain gardens, try to schedule a periodic neighborhood cleanup day.
  • Mulch will break down and should be refreshed every couple years.
  • Stay on top of weeding. Err on the side of pulling too much.
  • Homeowners should not be afraid to experiment with the plants in their rain garden. Try using native plants to encourage pollinator presence!
  • Pretreatment chambers should be cleaned out after each rain event. This should take no more than a few minutes.
  • Remove excess leaves in the fall. Having a few leaves is great for catching sediment and creating critter habitat, but too many leaves will create mats and slow down water infiltration.
  • Regularly remove sediment that makes it past the pretreatment chamber.
Community rain garden cleanup in Anoka county

Follow-Up

  • The sponsoring local government should connect annually with homeowners to remind them of maintenance needs, expectations, and flexibility.
  • Make sure homeowners know who to call if they experience problems.
  • Consider providing a maintenance program to help with plant replenishment or other incentive to keep gardens well maintained.
  • After the 10-year life of the garden, consider a refresh. Hire professionals to remove all plants, mulch, and accumulated sediment and debris, and power wash the retaining wall and pretreatment chamber. Then, add new mulch and replant, salvaging mature plants whenever possible. This relatively inexpensive investment can buy another 10 years of function.

When done right, rain gardens are an effective and beautiful method for combating pollution in lakes and streams, replenishing groundwater, and creating pollinator habitat. However, not every property or every homeowner is ideally suited to have a rain garden. While professionals at ACD can assess whether or not a property is a viable candidate, only the homeowner can decide if they are up to the task of maintaining a rain garden.

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What in the World is a Rain Garden?

  Rain gardens have popped up like weeds throughout the Twin Cities over the last decade to mitigate stormwater pollution in lakes, rivers, and streams. Despite their prevalence, the function and purpose of these little curbside gardens remain a mystery for many folks.

Downspout rain garden

Rain Garden Benefits:

Cities are very dirty. When it rains, stormwater picks up everything from feces to the motor oil that your neighbors spilled on their driveway. Many older neighborhoods were developed without stormwater treatment, so pollutant-laden runoff from roads, houses, driveways, and parking lots makes its way directly into rivers, lakes, and streams. Stormwater doesn't end up in a wastewater treatment facility or septic system like the water that drains out of your bathtub.

When functioning correctly, rain gardens protect natural water bodies from polluted stormwater, reduce flooding, recharge groundwater, and provide habitat for local pollinators. Rain gardens can be built to any size or shape to fit into the landscape of old neighborhoods where space is limited. They are relatively inexpensive to design and construct and can be maintained by homeowners who agree to take on that responsibility.

To treat all of the water in a neighborhood, it may be necessary to pepper the neighborhood with many small rain gardens, or put in a few larger gardens depending on available space and landowner interest. A well-functioning rain garden will dry out within 48 hours after a rain event, which keeps the plants healthy and prevents creation of mosquito habitat.

  Rain Garden Types:

There are two basic types of rain gardens, those built to treat water exiting a gutter downspout, and those built to treat road runoff. The first type, called a downspout rain garden, can easily be installed by a homeowner. This type of rain garden can prevent flooding around downspouts and allow rainwater to recharge groundwater.

The second type is called a curb-cut rain garden because an opening is cut into a roadside curb to allow water to flow off the road into the rain garden. When the rain garden has filled to the brim, the stormwater flowing along the curb will pass by and flow into the storm drain as it did prior to installing the rain garden. Curb-cut rain gardens are much larger, more complex, and should be designed and installed by professionals. Curb-cut rain gardens are more cost-effective because they only treat water that would definitely have made it into the stormwater system. For this reason, they are the only type of rain garden for which Anoka Conservation District currently provides assistance.

While traditional curb-cut rain gardens are built with the expectation that water will drain through the soil, some rain gardens are built in conditions that don't allow for water to drain quickly enough. In this scenario, an underdrain would be installed below the rain garden. The underdrain re-directs excess water from the rain garden into the street's stormwater drain to prevent the rain garden from flooding.

Thriving curb-cut rain garden that easily drains within 48 hours
Failed rain garden that does not drain between storms

Rain Garden Pitfalls:

Unfortunately, some rain gardens don't work as intended. Due to poor planning, faulty design, shoddy construction, or a lack of maintenance, some rain gardens fail to properly fill or drain. When done right, rain gardens are an effective and aesthetically pleasing method for combating pollution in lakes and streams, replenishing groundwater, and creating pollinator habitat. However, not every property or every homeowner is ideally suited to have a rain garden. While professionals at ACD can assess whether or not a property is a viable candidate, only the homeowner can decide if they are up to the task of maintaining a rain garden.
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