STERLING – The park district is gathering information so it can weigh its options for dealing with the algae-infested Thomas Park pond.
The park district budgeted $5,000 this fiscal year to investigate what can and can't be done. Wendler Engineering, the Dixon-based firm that has worked on several projects at the Westwood Sports Complex, was hired to do some preliminary work with the pond.
"Initially, we looked things like depth, what needed to be removed, permitting, and who will be involved in the process," Sterling Park District Executive Director Larry Schuldt said.
The pond, built in 1975 over about 1.33 acres, once had 6 feet of water. Runoff from land to the north, mainly farmland, has created a silt deposit problem. That and drought have left the pond with less than 1 foot of water in most places, spurring the algae growth.
Schuldt said the pond's sediment will be tested soon. A plan will be sent to the Army Corps of Engineers, which automatically triggers EPA notification. What is in the water also factors into what can be done with about 7,400 cubic feet of material that would have to be dealt with, if the pond was dredged.
"We would need an area the size of two football fields, if we were to store it on-site," Schuldt said.
The cost estimate for dredging the pond is $150,000, but transporting the material would push the total over the $200,000 mark. That makes sediment testing a key component.
"We have to test the material to see if we can leave it in an area of the park," Schuldt said. "If there are contaminants and we have to take it somewhere else, the cost goes up considerably."
Schuldt said the park district will get numbers on filling in the pond and replacing it with grass, but it's likely that dredging will be the only feasible option.
The pond situation is also the responsibility of the city, because it also is used as a stormwater retention pond. The city and park district say they won't know how the cost will be divided until all of the information is available.
The pond slows down the stormwater flow, making it less likely that the ultimate destination, Elkhorn Creek, is not flooded during periods of heavy rain.
The water can rise in the pond first before draining to an outlet pipe that moves it to a ditch along Lynn Boulevard, before making its way to the creek.
Sterling City Manager Scott Shumard said the pond plays a key role in drainage.
"The farther west you go, it would make a big difference," Shumard said. "In front of Kroger, there's a paved ditch that winds adjacent to several neighborhoods, so it slows down what can go into the creek and potentially flood those areas."
In fact, the Lynn Boulevard bike path plan calls for eventually building three more ponds along that stretch between the park and Sixth Avenue.
"The ponds would be for bike path scenery, and could also be used as city retention ponds," Shumard said.
The city would absorb all of the cost for those ponds, he said.
Schuldt hopes to have all of the information he needs to make a decision about the pond sometime this fall.
"We should be able to make presentations in late fall or early winter to the council and park board," he said. "If we make the decision to dredge, it would be done next summer sometime."
Concerns about the pond have largely been about aesthetics, Schuldt said. However, a couple of weeks ago, the Whiteside County Health Department responded to a call from a resident concerned about mosquito-borne diseases. After looking at the pond, the health department concluded that the pond scum doesn't draw the type of mosquito that carries West Nile virus and other such diseases.
"This isn't the type of environment where the culex mosquito typically lays its eggs," said Gene Johnston, Whiteside County Health Department environmental director. "They are more likely to lay eggs in containers, tires, and empty pools – where there is no current or habitat."
Johnston said the banks of the pond could, however, be a fertile breeding ground for the basic floodwater mosquito.
"That variety is a nuisance, but it doesn't spread disease."