Preventing future flooding at Valley Green Park is a priority for city officials, but it also comes with a hefty price tag.
The Jordan City Council was informed Monday night that adding Valley Green Park to the city’s proposed flood control improvements would nearly double the estimated costs. Incorporating a Valley Green levee and ditch bypass would add $4.9 million to the proposed $6.56 million project that would improve levees in other low-lying areas of town, according to the city’s engineer, Mike Waltman of Bolton & Menk.
The estimated costs were outlined in an updated flood control feasibility study presented to the council. The council was given a draft report in December, but the updated study includes ways to mitigate flooding in Valley Green Park.
Instead of detailing bridge improvements and diversion efforts, which engineers found to be relatively ineffective and cost-prohibitive, the report outlines four segments of levee improvement and construction projects that mitigate runoff flooding, as opposed to the May flooding in Valley Green Park caused by an ice jam.
Runoff flooding is caused by an intense rate of flow, while ice jam-related flooding is much less predictable and characterized by a sudden increase in water volume, Waltman said. In addition to being the focus of the study, runoff flooding also dictates floodplain limits and flood insurance rates.
“I think what’s on everyone’s mind right now is the flood event we just had in March, whereas a lot of the other stuff I’m talking about is really related to runoff flooding which is not really the same,” Waltman said.
The report outlines remedies for four segments in need of flood control.
In the first segment, between Varner Street and Highway 282, engineers recommended building a 100-foot steel flood wall six feet above the ground and three feet above the water level. The improvements would make the existing levee meet Federal Emergency Management Agency’s certification, which would remove nearby property owners’ requirement to purchase flood insurance. Improvements to this segment would require some partial and complete land acquisition.
Councilman Jeremy Goebel was concerned that the benefits of a certified levee would would not be worth the loss of usable land for many residents.
“The way you described phase one, those homes there, they’re going to hate this,” Goebel said. “You’re effectively taking their entire backyard and building a hill and a giant sheet metal wall.”
The second segment, between Highways 282 and 169, would add a smaller steel wall that would only rise three feet from the ground, due to the fact that an earthen levee already exists in the area. Improvements to this segment would require some partial land acquisition.
The third segment, between Highway 169 and Syndicate Street, would require no land acquisition. Engineers suggest expanding the existing levee and constructing a stormwater pond in the area. Waltman said the stormwater pond would address internal runoff water, largely attributed to rainfall, from within the city.
“Rather than build an enormous pump that pumps storm water out, they would build a pond to temporarily store that water,” Waltman said. “That enables us to have much smaller pumps, which are the biggest piece of the cost equation.”
Waltman said the large stormwater pond would be dry 99 percent of the time and could be used for other things.
The fourth segment would address runoff flooding in Valley Green Park. The primary contributors to flooding in this area, Waltman said, are Sand Creek and water flow from two large box culverts that discharge water from underneath Highway 169 into a ditch that goes through Valley Green.
“The flooding that’s by Valley Green is actually as much as anything caused by the water that comes out of that culvert system,” Waltman said. “If we were to build just a straight levee across Valley Green to berm off Sand Creek, we’d still have to do something with that water that is coming through those box culverts into that ditch section.”
Engineers recommend the city build an earthen levee along Sand Creek at the north end of Valley Green and mitigate the culvert water flooding with a ditch bypass along the east side of Valley Green. The ditch bypass would discharge the water in Sand Creek farther downstream. The option to build the ditch bypass is estimated to cost $600,000. In order to address rainfall inside Valley Green Park, the report recommends widening the existing ditch and installing pumps to remove internal runoff over the levee into Sand Creek.
If improvements were implemented to all four segments, Waltman said, 115 properties would be removed from the flood hazard area. Fifty properties that pay $48,551 in annual flood insurance premiums would be removed by improvements to segment one. Sixty properties that pay $66,155 million in annual premiums would be removed by improvements to segment two. Four properties would be removed after improvements to segment three and Valley Green Park, which is defined as one property, would be removed if improvements were made to segment four.
Altogether, the improvements would save property owners $114,706 in annual premiums at current rates, which the report projects will increase 8 percent annually on average.
“Maybe that gets turned into funding for the project in a way because if they’re paying that, they’re shelling that out one way or another, there is probably a benefit there,” Waltman said.
The cost of the project could be covered by a mix of funding, including special assessments, general tax increases and Department of Natural Resources hazard mitigation funding.
DNR funds would cover a large amount and come from a competitive program that requires a 50 percent local match, capped at $2.4 million for Jordan. Waltman said the DNR program typically distributes no more than $2 million per community project annually, so he suggests breaking the project into multiple phases with costs of $1 to 2 million per phase.
“If we structure this project into phases that make sense to implement in some given order, on that cost-share basis they may give you that $1 million, $1.5 million, maybe up to $2 million in any given year,” he said.
The report outlined a suggested phasing program. The first phase, estimated to cost $2.1, would include design costs for the first three levee segments and acquisition of property for the first segment.
“The acquisitions of property that we’re estimating are the biggest chunk of that, it’s about $1.7 million just in terms of acquisition,” Waltman said.
The second phase, the construction of levee segment one, would cost an estimated $1.2 million. The $1.4 million third phase would build the storm water pond and levee. The $854,600 fourth phase would build levee segment two. Phases five and six, together totaling $4.5 million, would be the construction of the Valley Green Park levee and bypass ditch.
The city council is expected to make a decision early next month on whether or not to direct city staff to begin pursuing the project.