MOUNTAINSIDE – When Lake Surprise was dredged a decade ago, the last thing anyone wanted, was for sediment to clog the 24-acre lake again—or at least any time soon.
So as part of an effort to slow down the forces of nature in Union County’s Watchung Reservation, the county launched a major project late last year targeting the ravines where rain water rushes down to the lake.
“We spent $1.3 million taking sediment out of Lake Surprise. We didn’t want to be back doing it anytime soon,” said Alfred Faella, who heads the county’s parks department. Most of the funding for the dredging in 2000 came from the state as part of the compensation to the county for the parkland required to complete Route 78.
Lake Surprise was created in the mid-1800s through the damming of the Blue Brook. The lake served as a reservoir to ensure sufficient water power to a mill downstream, west of the lake.
Nestled between the First and Second Watchung Mountain ranges, more than 1,000 acres of hilly terrain drain into the lake, which also marks the boundary line between Mountainside and Summit. When heavy rains roll through the region, the water run-off from some of the steeper slopes carries the well-worn soil down to the lake.
So the county brought in engineering consultants to identify the most serious locations where sediment was washing down to the lake and design measures to slow or stop those erosive forces, Faella said. There are now rock-lined channels at five different locations along the lake.
“Because of the slopes involved, you need to armor these ravines to prevent them from being torn up,” Faella said.
In some cases, rip rap rock was set in place, while in others, gabions or layers of rock wired together in a cage, were used. Unlike the gabions seen along interstate highways in falling rock zones that are shaped like hay bales, these gabions were designed more like mattresses, shallow, but very wide.
“The idea is that the water, which is throttling down through there after a major rain, will run across the stone and not drag more silt down to the lake,” Faella said, noting that this past summer witnessed some incredibly heavy storms that actually shifted the stone in some places, further evidence of just how strong a force stormwater runoff can be in the reservation.
Hikers who frequent the lake area may be a bit stunned when they first see the new rock channels, said Freeholder Bette Jane Kowalski, who serves as the liaison to the parks.
“We don’t necessarily like the look of all that rock, but over time the rock will get filled in with leaves and sediment. Grasses and plants will begin to grow in them and they will start to look more natural,” Kowalski said.
The $777,385 year-long stormwater management project also included building a manure storage shed up at the Watchung Stables.
In the past, rain and snow would pass through the soiled stable straw that was full of horse urine and waste, producing what came to be known as “manure tea,” which would wash down to the lake. High in nitrogen and phosphorous, the “tea” accelerated the growth of aquatic weeds.
Now the straw is protected by a pavilion until it is hauled away, Faella said.
SLOWING DOWN MOTHER NATURE…on the banks of Lake Surprise in Union County’s Watchung Reservation. Located between the First and Second Watchung Mountain ranges, the 24-acre man-made lake was dredged in 2000. However, heavy rains will carry soil down to the lake, causing it to eventually fill in. To slow down that process, five ravines were lined with stone this year as part of a project to protect the lake.
Located between the First and Second Watchung Mountain ranges, the 24-acre man-made lake was dredged in 2000. However, heavy rains will carry soil down to the lake, causing it to eventually fill in. To slow down that process, five ravines were lined with stone this year as part of a project to protect the lake.
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