The cost of capturing rainwater from the courthouse parking lot will be higher than expected. An engineer’s estimate of $6,831 was quite a bit lower than Crawford Excavating’s bid of $15,264.
Cook County Soil and Water Conservation District Director Rebecca Wiinanen and Conservation Technician Tristan Beaster discussed the cost at a Soil & Water board meeting Thursday, September 3, 2009.
The cost estimates were done before the engineering work was done, Beaster told the board. “…It’s a pretty beefy project,” he said.
“It’s almost asking the impossible of the engineer to come up with an accurate cost estimate,” said Wiinanen.
Designed to prevent oils, salt, and sediment from entering the city storm sewer and Lake Superior, the garden will extend across the courthouse lawn from the southeast corner of the parking lot to the south end of the set of flagpoles. It will leave room for public gatherings around the poles, however.
A rain garden works especially well during large rainstorms when pollutants would otherwise be carried over the top of a regular grass lawn, Wiinanen said. Maintenance of a rain garden, however, is higher than maintenance of a regular lawn, according to Beaster.
To create a rain garden, a basin is excavated and lined with drain tile. Underground pipes disperse water outside the borders of the rain garden as well. At the courthouse, 1,400 plants (costing a total of $4,200) will be planted over layers of aggregate, soil, and mulch. The plants will have deep roots and be able to handle salts and other pollutants.
The project does not have to be done, Soil & Water Supervisor David Berglund stated. He asked if a 10-foot strip of tall grass would bring the same benefit as a rain garden. According to Beaster, tall grass might not allow pollutants to settle and could invite invasive species.
Most of the city’s storm water goes directly into the lake, Wiinanen said. As the town grows, new ways to keep pollutants out of the lake will be needed. A demonstration project like this will allow the public to learn about rain gardens, Supervisor Jim Hall said.
“It’s kind of a top-of-theline rain garden, and it needs to be because it’s in a public place,” said Wiinanen. It will be able to process up to an inch of rain within 24 hours. Wiinanen said the first quarter to half inch of runoff carries the most pollution.
In the future, Supervisor Don Goodell said, they need to obtain better cost estimates before spending a lot of staff time on projects like this. Newer grants offer funding for design engineering first, separate from funding for implementation, Wiinanen said, so these types of surprises shouldn’t happen again.
Wiinanen commended the board for asking if this was a good use of public funds. Seventy-five percent of the project, including some local staff time, will be paid for by a Lake Superior Coastal Program grant. Theother 25% will be matched by the county in the form of staff time and volunteer labor. Obtaining funds through the Coastal Grant Program is not a perfect method, Wiinanen said, but it’s the best way the state has to get projects like this done.
If it’s this expensive, asked Supervisor Joan Farnham, could a homeowner afford one? An individual property owner would install a much smaller rain garden, Beaster answered. These kinds of questions should be debated before having the staff apply for these grants, Supervisor Roger Hartle said.
After the Soil & Water board voted to go ahead with the project, Tristan Beaster brought it to the county board for its approval September 8.
Commissioner Bruce Martinson asked if the rain garden could be expanded to prevent roof runoff from entering the city storm sewer. Maintenance Director Brian Silence said the garden would have to be much bigger to handle that much water. The courthouse parking lot is a bit under 20,000 square feet, and the rain garden will be about 1,000 square feet.
With Lake Superior Coastal Program funding, Beaster is conducting a study on storm water management in Grand Marais. Wiinanen hopes the study could determine how much rain garden and other treatment such as impervious surface would be needed to treat runoff naturally before it enters Lake Superior.
“I think we have to look at the public benefit here,” Commissioner Jim Johnson said regarding the cost of the project. He said Extension Director Diane Booth has told him people come all the time to see the new rain garden behind the 4-H building.
The board voted unanimously (with Commissioner Bob Fenwick absent) to approve the change in cost for the rain garden. The county’s 25% share is $3,816, and the money needed beyond staff time and volunteer labor will be taken from the fund balance. Wiinanen believes the cash amount needed from the county will be less than $1,000.
Another demonstration site is planned for the lawn in front of the Grand Marais Library. That project will cost $13,159, well over the $7,859 estimate. Only two bids were received for each project, Wiinanen said. “It’s a reasonable bid,” Wiinanen said of the courthouse bid from Crawford Excavating, although the county board has not yet approved it.
Soil & Water Supervisor Goodell mentioned that some Twin Cities communities are installing grid chambers in their storm sewers to prevent oils from entering area lakes.
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