Tuesday, March 26, 2013


Work began Sunday, March 23, on the east end
of the Island ferry dock. Ramp in foreground was removed
for access to footings beneath.  This ramp was used more
than any of the other landing points since
installation in 2000.
Detroit Harbor, Washington Island -

Dredging around island ferry docks was nearly complete as of this past Sunday, March 23.  Work immediately shifted from removal of bottom material to the repair of the docks themselves.

The original foundations for these piers were wooden cribs, protected by driven, wooden piles.  The first work was completed around 1931, when Captain Bill Jepson moved his ferry operation from the shipyard at the eastern end of the harbor to the former Ole Christianson boatyard site.  Slowly, those docks were expanded upon and repaired over time.  During the 1960s, interlocking sheets of steel were driven outside the wooden structure.  This provided a tight and lasting perimeter for the wooden pier, encompassing all of the rock and fines that filled the interior.  Concrete was added later to the margins, both below and above dock surface, caulking holes that appeared from time to time from settlling.  This capped the material that lay beneath the dock and provided a cleaner, more durable surface.  It was thought at the time each work phase was completed, that stability would be brought to that portion of the pier for decades to come.

View from end of island pier looking west, shows pier
 under construction with A-frame pile driver / dredge
moored to left.  This is the same basic shape as the pier today.
To the north (right) is the Standard Oil dock.
A guess as to the date: 1931

But as will happen with fluctuating water levels, the finest materials wash and settle, and if there is a chance of escaping outside the sheeting, they will.  Voids can open up beneath the concrete and blacktop, and yet for appearances it still looks like one, solid dock.  Large voids within the dock are what occurred in two locations where the interlocking sheets of steel years ago weren't driven deeply enough into the bottom.  Then, lower water levels coupled with aggressive wash from the ferry propellers when backed in stern-first created openings at the foot of those sheets.  This became most pronounced where the ferries back in frequently with props toward the pier, at the east end and south side ramps.

[Last August in order to examine those voids, Hoyt Purinton dove with a video camera and filmed the underwater structure.   He discovered dozens of smallmouth bass resting within the shade of those mini-underwater caves.  You can see several minutes of his underwater footage - and lots of bass - by going to the Ferry Line's website  wisferry.com     and there will be a tab along the top to take you to the Facebook page.  Hoyt is working with that video so that it will load more easily.   Patience, please!]

Step one in repair was removal of the 20 x 20 steel ramp from its foundations at the end of the dock, so that a hammer could break up the concrete cap.  Like a dentist drilling into a decayed tooth, large voids were exposed, and the result was nearly as painful to see as the trip to the dentist can be under such circumstances.   The exposed cavities beneath the concrete were larger than anticipated, and the scope of work quickly expanded.  (Thinking root canal, I was...)

Added to our current navigational problems with water depth is the fact that these adjustable ramps have been at their lowest possible settings most of this past year.  The steel and concrete foundation "floor" prevented them from going lower.  But low water also presents the perfect opportunity to fix the pier and to lower the ramp.

A horizontal beam called a whaler ties all of the sheets together in a straight line, and such a beam was installed on the inside face of the sheeting.  The lowest practical point a whaler can be attached to sheets is just above the lake level, where cutting and welding and fitting can be managed.  Now that the water level is down, this whaler can be lowered to accommodate the new lake level.  The H-beam whaler and the 1-1/8" steel rods that tie it in place are fastened to a pile driven vertically into the pier and later covered up with fill.  This whole arrangement can be installed to accommodate the new lake levels.  (Some day, this installation may be beneath the lake if water levels rise.  But we'll deal with that if and when it happens.)

Rich Ellefson inspects and pulls pieces of broken concrete
from one of the two deepest voids on either side of the ramp box.
Daylight can be seen, down five feet and to his left.
This project may sound fairly easy and straight forward, but there are many steps, each with a great deal of handwork:  cutting concrete; cutting steel, welding and grinding,  besides use of heavy equipment to break up and lift concrete and rock.

The two deepest voids, on each side of the ramp box, had to be dug by hand, one piece of rock or concrete at a time.  Those large boulders seen piled on the dock in the top photo were set aside by Mike Kahr from recent dredge spoils.  They'll be packed into the voids to anchor the base of the sheets from inside the pier.  To that mass will then be added smaller pieces of broken, jagged rock.  Concrete with steel reinforcement will cap the rough rock.

This project is expected to take several more weeks, during which time the bay and harbor ice may begin to soften.  (Night time temperatures are still lower 20s, and we've barely been above 35 for the daytime temperature.)  Its a good bet ice will still be around, in and near our route during that time, so the Potato Dock remains the landing of choice.

Excavator breaker was used to open up concrete
foundation (about 10 inches thick) and create trenches for tie-backs
to the new deadman, the pile driven at left.
Besides extensive dock work is the pair of engines and gears waiting on the deck of the Eyrarbakki for installation, back on the island after major overhaul.

There has been no shortage of winter work.  Keeping our heads (and keels) above water has not been easy.

-  Dick Purinton


Richard Purinton said...

A reader asks: What are the intended repairs to close the gaps at the foot of the sheets?

Essentially it will involve driving new and longer sheets outside of the existing sheets, then fastening them to the overall dock structure, so that ice or other forces won't separate the two faces over time.

Pulling the original steel sheeting out and starting over would be unnecessary work and mean that the entire end of the dock would be temporarily exposed. Our solution, devised by our contractor Kahr, keeps the basic dock intact while allowing us to shore up the short sheets. - DP

Richard Purinton said...

Terrific explanation of what it takes to repair this vitally important dock. When the water level drops and the sheet steel is not driven deep enough do you have to have more sheets driven into the bedrock to avoid future wash out? Thanks. Eric

Tony Woodruff said...

Your recent blogs have been interesting. The work on the Island ferry dock appears challenging, and the continued dredging a (necessary) nuisance (We enjoyed meeting and chatting with Mike Kahr at Findlay's last weekend). The Thordarson/Rock Is. book will be a great read; unique history there! Thanks for the photos and notes on the various vessels. - - Tony & Grace