Engineer Hired by City Says Municipal Plans for Legacy Park Design ‘May Not Pencil Out’

• Public Turnout Is Low at First Session Exploring Site Options for Major Endeavor

BY BILL KOENEKER

An engineering consultant, who is doing the design work for Legacy Park, told a sparsely attended joint meeting of the city council and the planning commission last week that the ultimate plans for the wastewater and stormwater projects may not work out to the extent municipal officials hoped for.

“It may not pencil out,” said RMC Engineering consultant Steve Clary, who said the constraints because of the size of the 15-acre parcel coupled with the requirements for stormwater use may not allow for seasonal storage of wastewater.

The discussion had focused on how after the park is set up for storage for processing for the stormwater treatment facility how much land would be left over for storage of wastewater during the rainy season when little landscape irrigation is needed and groundwater levels are already high.

Clary said it would be difficult to obtain the needed seasonal storage capacity of treated water for reuse in the dry summer months.

“We would need a pretty large parcel of land, and it wouldn’t be cheap. We don’t have the financial ability. We are not doing that,” said the consultant, who also explained about the problems of using reclaimed water for firefighting. Clary also was emphatic in explaining how stormwater and wastewater would not be commingled.

Because the city is a lot further along on its plans for stormwater treatment, the discussion about the improvements to the park centered on the various ways that system would or could operate including using a permanent water feature for aesthetic reasons.

Clary was openly frank in discussing the engineering problems connected with developing the park, including deed restrictions, groundwater levels, restrictions placed on the property because of grant money utilized to acquire the site and other constraints.

A good deal of time was spent discussing how and what kind of system could be set up to capture the stormwater runoff for processing in the plant. How much is processed per day. What would be the size and dimension of a storage pond or basin based on numerous criteria.

Some council members and commissioners were keenly interested in how often the clean water system would be able to comply with state mandated discharge requirements.

Clary explained that compliance especially 100 percent is actually not required and can be very expensive. He said many government entities make a trade off-possibly attempting to reach 75 percent compliance or in some instances even 98 percent compliance. “It makes a difference on trade-offs. Compliance of the last two percent requires twice the [detention] basin [size],” he added.

An alternative to a detention basin is what is called a subsurface flow wetland. There is no open water and the wetlands are engineered using a gravel trench with bulrushes and others plants to create the wetlands. The gravel allows more water and soil interaction and provides ten times the treatment capacity as a conventional wetland, according to Clary. The subsurface wetland is also a natural treatment system and because there is no open water creates no opportunities for mosquito breeding.

During public comment, Terry Lucoff wanted to know if the dispersal of water meant discharging into the creek. Clary said there is no direct discharge. That the plan calls for dispersion through the soil. The exception is during the height of the storm season when there is more water than the system can handle.

John Mazza asked if the need for wastewater disposal would overshadow the recreational aspects of the park. “Are we creating a park with public funds for higher [building] density?” he queried.

Clary said the current thinking is that treated wastewater flows may go back to the leachfields of commercial users for dispersal. “We never intended to collect wastewater from homes and go back to the house’s leachfield,” he added.

It was David Resnick who pointed out that the use of additional acres for subsurface wellands are not amenable for wastewater dispersal.

Yes, agreed the consultants. Every acre used for subsurface wetlands cannot be used for wastewater dispersal. That creates another engineering challenge and leads to the limited ability to store enough treated wastewater for later reuse.

Resnick also wanted to know how important is the proposed Linear Park to the current plans for Legacy Park. He was told it was not part of the forum for the consultants. However, City Manager Jim Thorsen said it would ultimately be a part of the plans.

Local development consultant Don Schmitz wanted to know if there were any plans to take water out of the creek or lagoon and clean it and return it to its source. He was told there was no such plan.

After about two hours, the meeting was turned over to landscapers from the engineering company who talked about the look of the park and what amenities could be included also given the deed restrictions and other constraints.