Victoria’s Lifeline-Hwy 5 Sink Hole

For the past many years, a stretch of Highway 5 just east of downtown Victoria has been sinking every year.  That stretch is located between the HEI wetland marshy pond and the marshy wetland behind the Victoria Fire Station.  The highway sinking is noticeable every spring after the snow and ice have disappeared.  And every year, MnDOT (it’s a state trunk highway) comes in with equipment and men and repaves the stretch of road over the Sink Hole area.  But during this Summer of 2012, Highway 5 was repaired, and the hope is that it will never sink again!  Ken Slama, Project Engineer with MnDOT, was very helpful in answering questions and providing information.

This spring — June 2012 —  asphalt was ground off, not reusable, and hauled to a pit in Shakopee.  Contractor on the job was S.M. Hentges.

The excavation was approximately 700 feet long and had depth ranging from 1 foot to 8.8 feet. 

It seemed like a larger-than-life sandbox that was supplied with major pieces of equipment “toys.”

What was hauled in to replace the poor road soil?  The surcharge material is sand and clay.  After the surcharging was done, the material was replaced with geofoam blocks.  These are essentially Styrofoam blocks with structural capacity to replace the material with a lighter load.  This will alleviate the sink hole.

The surcharge consisted of 3,000 cubic yards of sand and it was estimated to need 55  days to do its work — to accelerate the sinking so it shouldn’t happen again in the future.  MnDOT monitored the surcharge as time progressed.

MnDOT piled sand on city property next door, on the hill behind the Victoria Fire Station.

I took this photo back in 2006 from the top of the Victoria Fire Station/Water Treatment Plant, and it shows the stretch of highway in the Sink Hole area.

Stieger Lake Lane was the detour used to get into downtown Victoria.

The engineer said that more excavations will take place after removal of the forthcoming surcharge.

By the way, I learned at the end of the summer, that the hay was to be used for the spreading of grass seed on the steep ditch slopes which were being constructed on each side of the “new” road.

In August the surcharge was replaced with geofoam blocks which are essentially Styrofoam blocks with structural capacity to replace the material with a lighter load.

The surcharged weighed down the sink hole area for 49 days.  During that time, it appeared that people weren’t working on the project but, in fact, the surcharge was working.

The geofoam blocks will placed neatly along the entire section of the Sink Hole.  At the same time, the surcharge continued to be removed.

While the geofoam blocks were being laid, the rest of the highway next to the Sink Hole and east all the way to Highway 41 in Chanhassen received improvements and turn lanes.

Approximately 1,900 geofoam blocks were hauled in and placed across that stretch of Highway 5.  I took this photo from the parking lot at Dr. Baker’s Dental Office.  That’s HEI on the right with the red roof.

Sometime between now and then, the Old Ski Factory, which has gone from Nature’s Bounty to Digger’s Arctic Cat, is now sporting a new water sport business.

Each geofoam block weighs about six pounds and measures 4 feet by 4 feet by 4 feet.

It appears that the blocks were hauled six at a time.

I found it very interesting to see a highway constructed in this manner.

You can see men in the excavated area, playing with the blocks — I mean, placing the blocks.

It certainly was a good summer for getting work done.

This is the intersection of 78th Street —where traffic was detoured — directly adjacent to the east end of the Sink Hole, where Stieger Lake Lane and 78th Street meet.  See Dr. Baker’s office in the background.

Geofoam blocks were also used in Trunk Highway 241 in St. Michael, MN, in 2006.  Currently Maryland Avenue Bridge over I-35E is using geofoam, according to Mr. Slama of MnDOT.

According to Mr. Slama, geofoam is used to essentially reduce the load that the organics need to support. 

By removing the heavier traditional fill (about 120 pounds per cubic foot) and replacing with geofoam (about 2 to 3 pounds per cubic foot), the load is reduced to the point that the organics no longer need to consolidate and can support the loads without deforming.

The effectiveness of the geofoam is increased when used in conjunction with a surcharge.  With a surcharge, the organics are pre-consolidated with a heavier load than what they traditionally have had to support.  The amount of work that went into this highway correction was just amazing.

When the surcharge is removed and the road core is  filled with geofoam, the organic material is seeing a net reduction in load, and therefore should not consolidate further.

Are there warranties?  Said Mr. Slama, “The warranty generally comes from the manufacturer that the contractor obtains the blocks from.  There is no warranty for the installation.”  See the truckload.

The geofoam blocks, he said, can be expected to keep the sink hole from sinking for the life of the road.

Six inches of sand were laid below the geofoam blocks, while a 4-inch cement cap was placed on top of the foam to distribute traffic loads, followed by 2.6 feet of sand, 8” of Class 5, and 7” of bituminous.

Asphalt helped return the road to “normal.”

Huge gravel trucks continued to haul away the tons of surcharge as work continued over the geofoam.

After the road was beautiful and black, a large backhoe lifted all the concrete Jersey Barriers from the bottom of the back slope of the road that went down to meet the swamp — and dirtied up the road.

The Jersey Barriers kept runoff from the roadway from running into the wetland.  Because the area was so marshy, there was no way to get a silt fence installed there as is normally done on projects.

Here a backhoe is spreading black soil on the slope, soil that will support green grass.

Various pieces of equipment were used to till and prepare the black dirt for seed.

This is called a hydro-seeder because it premixes in the tank — seed, mulch, and water — and sprays it on the slopes.  Because it’s all mixed together, it tends to create a blanket that sticks to the soil and provides moisture for the seed to germinate quickly.  There’s probably also fertilizer mixed with it to give it a quick start.  (Thank you, Allan Orsen, P.E., for knowing some of these things.)

Before the mixture was sprayed on the slopes, some hand work was needed to get rid of the lumps.

The ceremonial Ribbon Cutting was held on Wednesday, August 29th.  In June the Gazette had asked Mr. Slama, MnDOT’s project manager, when the road would be navigable.  He had replied, “Construction will be complete August 30th, 2012, and open to traffic August 31st, 2012.”  That’s exactly how it came to be.  That’s (l-r) Jim Sanborn (Waconia City Councilmember), Mayor Mary Thun of Victoria, and Tom Furlong (Chanhassen Mayor).  

The road is done!  If you look carefully, you can see that the slopes are seeded and sprayed.

Mayor Mary Thun, who ably and admirably led the community through the Summer of 2012, thanked everyone for their work and cooperation in helping Victoria successfully navigate the closures of Hwy 5, which is the lifeline of the City of Victoria.  Many of the people that the Mayor thanked were on hand for the Ribbon cutting — including Victoria city staff, councilmembers, city committees, groups, businesses, MnDOT, the mayors and leaders of area cities, county commissioners, state officials, engineers, and contractors.  Above, Carver County Commissioner  Randy Maluchnik addresses the crowd.

It was stated by many that the City of Victoria should be credited with creating a model of communication and cooperation that should be written and used by other communities when faced with such huge disruption.

The End

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