New plan calls for 'armoring' Robin Hood Dam
As published on page one of the September 23, 2011 edition of The Keene Sentinel, and online.
The city may not drain Robin Hood Pond after all.
Instead of replacing Robin Hood Dam, the almost 120-year-old earthen dam that creates the pond in a park on the eastern side of Keene, officials now say they can reinforce the structure -- a solution that should cause less disruption in the park.
The $721,400 price tag on the new plan is also lower than the alternative, according to officials.
While the initial estimate for replacing the dam was $630,000, that number was revised to $980,000, City Engineer James J. Donison told the City Council's finance, organization and personnel committee Thursday evening.
The estimate went up because of the rising price of concrete and other construction materials, Donison said.
The city has already raised $1.1 million through bond sales to pay for the work, officials said.
The new plan is to "armor" the dam, leaving the old dam in place but adding a layer of specially designed concrete bricks to the outside to prevent erosion.
If the City Council approves the plan, work is expected to start in May 2012 and run through November that year, Donison said.
The parks and recreation department will schedule recreational programs that usually happen in Robin Hood Park in the spring and summer to other parks, Donison said, and there will be a way for people to get onto the walking trails.
The work may require the level of water in the pond be lowered a few feet during construction, Donison said, and the playground below the dam would be off-limits for the summer, but the tennis court might stay open.
Since 2008, Keene officials have been faced with state requirements that said the dam isn't big or strong enough to protect the people who live downstream in the case of a serious flood.
In November, city staff presented a plan to completely replace the dam, a project that would require emptying the pond and also raising the height of the dam.
Residents responded that draining the pond would be bad for the animals that live in the water as well as the people who live around it, including concerns that the empty pond would smell.
The replacement dam would have been larger than the one now in place -- a foot higher and with a larger outlet pipe through which more water could flow during heavy rains.
The armoring approach takes a different attitude to lots of water: It will be allowed to flow over the top of the dam in the event of a flood. This is what happened during the 2005 flood, when water flowed into the park below, Donison said. Armoring will make that safer by preventing erosion that could cause the overtopped dam to break and send a wall of water toward downstream residences.
State dam officials were not familiar with the idea of armoring a dam in this way, Donison said, so they initially rejected the idea before changing their minds.
The new plan will leave the dam looking pretty much the same, officials said.
The bricks that would be added to the outside have holes in them through which grass grows, creating a green hillside, according to engineers.
Because the armoring plan leaves the outflow pipe at its current size, it also saves the city the headache of having to enlarge the pipes the water flows through after it leaves the dam and winds its way through town.
One of those downstream culverts runs beneath the garage of a Woodland Avenue residence.
Kelly Roe, who lives in that house, told the finance committee Thursday there was a reason city officials were able to come up with an alternate plan.
"It was because of the people pushing back," she said.
The finance committee unanimously recommended the plan, and the proposal will go before the City Council on Oct. 6.
tagged with: city government, dam removal, Keene N.H., Robin Hood Park
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