Keeping a good pace
Published 10:26 pm Wednesday, September 5, 2018
Dredge continues to keep schedule moving forward
If dredging progress is any indication, the Shell Rock River Watershed District’s clock is running a bit fast.
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Watershed District Administrator Andy Henschel said as of Wednesday, the district has dredged 196,000 cubic yards of sediment — this is a third of the total goal for phase one, JF Brennan surveyor Ryan Sands said. Sands said the project is ahead of schedule.
Phase one broke Edgewater Bay down into six areas, of which the dredge has completed area six and will finish area five within the next three weeks, Henschel said. The areas start at the southwest corner and move up and east.
“Everything’s been going really well,” Henschel said.
The city’s aeration system was removed for the dredging and the district is working with the city to have it replaced, Henschel said.
Dredge operator Wesley Groth, one of the five-member team from Brennan conducting dredging operations for Edgewater Bay, said of his 14 years of experience dredging, Albert Lea’s project is one of the easier ones due to lower lake traffic and respectful boaters.
The tentative schedule has the district completing area four in November of this year. Henschel said the last day the dredge is on the lake will depend on when the ice arrives for the winter.
Since dredging began, Henschel said the district has made an adjustment to ensure the district hits its intended sweet spot of 617,000 cubic yards for phase one. Between the last bathymetric map, or map of the lake bottom, completed in 2009 — the one the Shell Rock River Watershed District and the Minnesota Department of Natural Resources used to discuss how much sediment could be removed — and the one done by Brennan prior to dredging, Henschel estimated there were roughly 60,000 to 70,000 additional cubic yards of sediment deposited in Edgewater Bay.
To accommodate that additional sediment, the project shifts up three inches. According to Henschel, Brennan has a three-inch overage allowance below the target depth. Because of that extra sediment and the need to fit all that is dredged into the confined disposal facility, the previous target depth has become the new overage depth.
Henschel said the district monitors water quality at the confined disposal facility on a daily basis. He said wind has a greater effect than rain on sediment settling at the CDF.
Earlier in the week, the district is able to discharge more water back into the lake because sediment pumped into the CDF from the previous week has had a chance to settle and allow water to be skimmed off the top to return. On Mondays, Tuesdays and Wednesdays, the rate of return is around 7,000 gallons per minute, while on Thursdays and Fridays the rate is closer to 1,300 gallons per minute.
Henschel said the district is looking ahead to phase two of the dredging process, which it hopes to bid out in October.