
The photo on the left was taken last week. It is a photo of a contractor’s backhoe on the frozen wetland in the Purgatory Creek Recreation Area. This is the “before” photo.
The photo on the right, also taken last week, is the same backhoe several hours later, not too long after the ice gave way and it sank into four feet of very cold water and muck. This is the “after” photo. You can click on both photos to see them in a larger size and greater detail.
Yes, a backhoe plunging through the ice on a cold February day is interesting, but you might also be interested to learn about why that backhoe was out on that ice to begin with.
We have recently contracted with a private construction company to install a new boardwalk/pier at the Purgatory Creek Recreation Area. The boardwalk will extend about 45 feet out over the water and be approximately 3.5 feet above the water. This boardwalk was part of the original design concept for the park and when complete it will have benches and tables for park users sit upon and enjoy the sights and sounds of the park and pond area. The construction plan is to have the pier built and open to the public by mid-May.
In order to build the boardwalk, pier anchors must be installed to support the weight of the wood beams and decking. This isn’t your typical lake home style boardwalk and the soils below the water are best described as “pure muck”. Due to the poor weight bearing capabilities a foundation system called Helical Piers is being used. This is best described as a large screw that is twisted into the soil using 3.5 inch diameter pipe extensions until the screw head is embedded in firm enough soil to bear the weight of the boardwalk and people.
This type of foundation system has been around over 90 years, but with the advent of hydraulic power heads the uses have increased dramatically. For example the lighting fixtures within the
In order to install these anchors, the contractor needed to use a machine capable of drilling the helical screws to the projected depth of 60 feet or greater. The pond ice thickness was checked and found be 18 to 20 inches of good clear ice. The water depth where the boardwalk is being installed is about 4 feet deep. There are a total of 14 vertical piers to support the boardwalk and 10 of these needed to be installed through the ice. The machine that the contractor used weighs around 26,000 pounds and everything went fine last Thursday until the installation of the 10th pier. Then the ice started to give way at the rear of the machine and the operator immediately started to move the backhoe for shore. Unfortunately he didn’t quite make it and the backhoe slowly settled to the bottom. The crew called in help and after a couple of hours was able to get the machine out of the water.
Fortunately, there were no injuries, no damage to the machine or its engine and there was no leakage of fuel or fluids into the pond. The contractor finished up the installation on Friday by finishing the 10th pier from shore as well as the four remaining dry land anchors. The next phase is to install the beams, decking and safety railing in March/April. You can enjoy this new park feature later this spring.
Note: I had help on this post from our Parks & Natural Resources Manager Stu Fox with the photos and the information about the project. Thanks Stu!















