LICO visits the Holland Marsh
Nov. 5, 2013, Ontario – Members of the Land Improvement Contractors of Ontario (LICO) learned the ins and outs of the Holland Marsh Drainage System Canal Improvement Project this past July.
The bus tour was held July 15 and hosted by Frank Jonkman, drainage superintendent for Bradford-West Gwillimbury. Frank started with a history of the Holland Marsh, explaining how the 28 kilometres of canals and dykes were first built around the perimeter of the marsh in the 1920s to allow for the reclaiming of 3,000 hectares of marshlands for farming and to protect the area from flooding from the surrounding watershed. In 1954, the heavy rains of Hurricane Hazel breached the dykes and flooded the entire area to a depth of up to 10 metres. Following the flooding, a major cleanout was completed and the dykes were rebuilt and raised.
Over the next 50 years, the system steadily deteriorated. The canal filled in and was only providing protection for a 25-year return storm. The dykes, which were built of the high organic spoil taken from the canals, subsided as much as one meter, leaving the road on top very rough. Finally, with little separation between the canal and the road, many accidents and several drownings occurred as cars drove into the canal.
A cleanout was proposed to address these problems, as well as to enhance the habitat for the fish, animals and plants living in and next to the canal. Starting with the engineers’ report in 2003, it has become the largest project under the Drainage Act at an estimated cost of $26 million, with assessments made to 9,000 landowners on 25,000 hectares of land in the watershed.
Attendees were able to see how the canal was deepened but also relocated to leave a wide buffer area between it and the road. The cross-section had a shallow bench on one side (littoral shelf) to allow for the establishment of aquatic plants and animal life. Gravel beds, root masses and tree trunks were included for fish habitat and spawning. The new roadbed was made of excavated materials from Toronto construction sites to reduce the subsidence problems. The canal or road or both were moved and separated to provide better protection for vehicular traffic.
Jonkman also explained a creative approach to the tethering process. Because of the unknowns for both the engineers and the contractors as to what the cleanout costs would be, the estimates in the report were set very high. Rather than go to tender with these unknowns, it was decided to complete a pilot project involving 650 meters of canal. Four contractors were hired to each clean out a short section on a time and materials basis. It turned out that the construction difficulties were fewer than anticipated. With this experience, these contractors were able to submit bids 75 percent less than the engineer’s estimates, saving several million dollars. Furthermore, the project will be completed three years ahead of schedule.