DN 19-21 DREDGING NOTICE
U.S. ARMY CORPS OF ENGINEERS
ST. PAUL DISTRICT
NOTICE DATE: June 21st, 2019 DREDGING CATEGORY: Emergency
MEETING DATE: June 24th, 2019 MEETING TIME: 11:00 AM
BOAT REQUIREMENT: see below MEETING LOCATION: see attachment
DREDGE CUT NAME: McMillan Island RIVER MILE: 618.1 – 618.6
Frequency: 49% Avg. Quantity/Job: 36,643 yd3
Date Last Dredged: October 19th, 2018 Avg. Quantity/Year: 17,948 yd3
Date Surveyed: June 17th, 2019
Water Surface Elevation: 613.8
Low Control Pool Elevation: 609.8
Net Difference: +4.0
5 Day River Forecast: steady decline
Recommended Channel Width: 500 feet
Recommended Dredging Depth: 12 feet
Estimated Quantity: 48,618 yd3
Type of Dredge: Government Hydraulic
Proposed Dredging Date: June 22nd, 2019
Estimated Duration: 6 Dredging Days
Justification for Dredging: The navigation channel is closed between the 9.0’ and 10.5’ contours on a recommended bend of 500’. When the water gets down to flat pool.
MATERIAL PLACEMENT DATA
Proposed Placement Site: Thalweg Placement
Site Characteristics: The placement method for this dredging event will be in-water, within the thalweg. Two placement matrices have been laid out which the dredge Goetz will reference throughout the dredging operation. A web meeting was held with partners on 20 June to discuss various alternatives, discussion continued into 21 June and it was determined that this was the best alternative given the circumstances. The placement matrices have capacity for ~85K cy of material. Preliminary hydraulic analysis reveals that this material is likely to be re-suspended and become part of the overall bedload, though a very minute portion of the overall bedload. Because of this, we anticipate that this action will not impact flood stages. With that said, we will monitor the location via channel surveys and analyze conditions over time. If we determine that the material is not re-suspending, we will relocate the material to a suitable location.
An OSIT meeting will be held on Monday, 24 June at 1100 hrs to observe dredging practices at McMillan Island, see attachment for meeting location. Please notify a Channel Maintenance Coordinator via cell phone at 651-272-6633 if you plan on participating so that they can coordinate boat transportation.
If you have any other questions concerning this project please call a Dredging Manager at (651) 290-5155.