CULTEC chamber system helps city of Rochester handle nuisance water.
Minnesota is rich in water resources, but in the city of Rochester, water was causing problems.
A drainage area leading to a ditch along a roadway in the city’s rural Crystal Spring neighborhood drains approximately 9 acres of woods and yards. A Decorah Edge spring coming from a nearby oak savanna hillside contributed to the wet conditions, which caused problems for a local property owner. Approximately 3 to 5 gallons of water per minute flow through a culvert leading to the ditch, and the amount of water increases after precipitation events.
In 2015, the city graded the ditch bottom, which provided only temporary relief, as the entire ditch section had very low grade of less than 1 percent. This past fall, the city looked for a creative solution instead of trying to regrade hundreds and potentially thousands of feet of ditch bottom and trying to reset private driveway culverts.
Ryan Thesing, a stormwater compliance specialist with the city of Rochester, took the lead on the project. Ryan and co-worker Mike Kraszewski researched infiltration alternatives, since the area had underlying sandy soils. Their goal was to get the water to infiltrate at the upper end of the ditch, potentially solving the water problems for the homeowner and the remaining neighbors downstream.
“The city is familiar with nuisance water in many rural and historic areas of town. The returning water here meant that we needed a different solution,” Thesing says. “Typically, in a situation like this, the city could install a few hundred feet of precast drainage pipe for the whole neighborhood. This normally results in an assessment project and cost to the homeowners, which can be expensive and not always what the adjoining property owners want. The underlying soil at this location is sand, so we were able to test and determine whether an infiltration system would be adequate. This kept the excavation localized to one property, working within the right-of-way and saved the city and homeowners from a larger, more expensive project.”
His team reached out to Royal Enterprises, a local water control and utility infrastructure product supplier, for recommendations. Keeping in mind that the city was searching for a cost-effective solution that could be implemented throughout Rochester, water resource engineer Josh O’Neill recommended CULTEC Recharger 330XL stormwater management chambers.
“We’ve worked with CULTEC’s products for many years, mostly on large commercial developments,” says O’Neill. “Contractors appreciate that they can get nearly a whole project’s worth of materials delivered on one truckload, and that they can maneuver the chambers in the trench without the use of heavy equipment. The ease of installation was very appealing to the Public Works department. They did not want to compound the eyesore caused by the wet condition by impacting the homeowner’s property or work outside the ROW with the use of heavy equipment. We suggested the Recharger 330XLHD because it can store a lot of water in a small area and can be hand-carried into place. The chambers will allow the water to infiltrate within the footprint of the existing ditch while providing a more aesthetically pleasing and suitable underground alternative.”
The chambers are 30 1/2 inches high and 8 1/2 feet long; each unit is able to handle 390 gallons of water without stone. The midsized chambers were able to maximize storage capability on site while managing the stormwater by spreading the water over a larger infiltration area of the ditch.
The Public Works team excavated the ditch to 54 feet long, 5 feet wide and 4 feet deep. After the excavation was complete, a nonwoven geotextile was placed at the bottom and along the sides of the trench. Six inches of clean rock was laid down as a stable base for the chambers. A total of five Recharger chambers were interlocked end to end in the retrofitted trench, which now provides approximately 541 cubic feet of water storage. An inspection port was installed so the Rochester Water Resources staff can periodically check to make sure the system is working properly and has not become clogged with silt or leaves.
The chambers were surrounded in embedment stone (1- to 2-inch-diameter washed, crushed stone) consisting of a 1-foot stone border from the chamber sidewall to an elevation of 6 inches above the chamber crown. A layer of geotextile was placed above the stone for the length of the trench, covering the entire chamber system and preventing soil intrusion into the stone. The ditch was then filled in to final grade with washed rock to promote infiltration over the entire ditch section.
A review of the site shortly after completion showed that the chambers are infiltrating properly and as expected, draining water from the spring and any precipitation events. Checking the inspection port located on the third chamber shows that the fall’s precipitation didn’t fill the system, and water had only reached about the first 5 to 10 linear feet of the system.
All parties involved, from the homeowner to the Rochester Water Resources Department, were pleased with the installation of the CULTEC chambers. The homeowner now has better conditions in front of his property, and the city has an additional option for handling similar nuisance water issues where local geology allows.
“The continued success of the Crystal Spring project gives us a benchmark best practice moving forward where the right soils and topography are present,” Thesing says. “We could certainly utilize infiltration chamber systems on similar projects in the future.”