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Thursday July 31, 2014




Explore the project

Portland Harbor is being dredged to bring the shipping channel to a uniform depth of 35 feet. Use the buttons on the right to explore some features of the project.

Demolition

Five granite tabletops exposed near the 35 foot mark were destroyed using a series of controlled blasts. The circles represent the blast radii.

Lobster Removal

By state law, lobsters and other sea life must be removed before a dredging operation. As of February 25, crews had captured 998 lobsters, 30,899 green crabs, 23,360 sand crabs, 460 Jonah crabs and four snow crabs. The total removal cost is $90,000.

Trap Barricade

A barricade using 300 traps has been placed at the mouth of Portland Harbor, stretching from the eastern end of the breakwater at Spring Point to the eastern tip of Fort Gorges and continuing on to Fish Point.

Dredging

The yellow area represents points where dredging is occurring. Most of the work is concentrated on the sides of the channel where sediment has either built up or collapsed.

Contract Cost

$9,200,000

Sediment to be Removed

708,000 yd3

Rock Removed

1,550 yd3

Lobster Removal Cost

$90,000

Cost per Lobster

$90.18

Crews have also removed:
30,899 green crabs
23,360 sand crabs
460 Jonah crabs
4 snow crabs

Recaptured Lobsters

2

Finish Date

3/25/14

Dump Distance

7.1 mi

Measured from Cape Elizabeth

Boom Size

125 ft

Dredge Bucket Size

54 yd3

Equivalent to:
1,134 bushels
486 wheelbarrows
18 heaping pickup trucks loads
3.6 large dumptrucks

Work Cycle

24/7

The crew works around the clock in twelve hour shifts

Maximum Sea Height

6-8 ft

If sea height outside Casco Bay reaches this limit, work must stop

Dredge Power Output

1,600 eKW

Uses two synchronized Caterpillar C27 tier 4 diesel generators

Dredge Weight

1,500 tons

The dredge measures 185 feet long by 65 feet wide.

Dredging the harbor

The U.S. Army Corps of Engineers this winter is dredging the shipping channel in Portland Harbor, a $9.2 million project that will remove as much as 700,000 cubic yards of sediment and assure depths of 35 feet at mean low tide. The contractor, Cashman Dredging of Quincy, Mass., is using two clam shell dredges. It has also used explosives to remove 1,500 cubic yards of rock ledge. The sediment and rock is being loaded into four dump scows, which are then towed to a disposal area more than 7 miles offshore.

SOURCE: Portland Harbor Authority, staff research, news reports
INTERACTIVE: T.E.D. Andrick
Portland Press Herald

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