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Ecowrappin'
SHALLOW & McNAB -THE MARL LAKES
Tuesday, July 25, 2006
Shallow Lake, as its name implies, is a shallow water body encompassing some 900 acres of open waters, marshland and swamp. Perhaps was is the more accurate and operative word, for Shallow Lake has partially, if not completely, dried up during the summer months for nearly a century. Shallow Lake is situated 13 kilometres northwest of the city of Owen Sound in the County of Grey. On the northern extremity of its shores lies the village namesake of Shallow Lake.There is little doubt that Shallow Lake was once a pristine wetland, part of a complex of other wetlands and shallow lakes, all located within a few kilometres of each other. But Shallow Lake, and the 520-acre McNab Lake situated about 5 kilometres to the north, contained bottom substrates comprised of a natural material called marl. Late in the nineteenth century and early into the twentieth century marl was the primary component used in the making of cement. The Canada Cement Company built a cement plant on the northerly shoreline of Shallow Lake and ran a railroad spur northward to McNab Lake. The natural outlets of both lakes were blasted through the limestone bedrock to facilitate the drainage that would allow for the effective mining of marl from their respective lakebeds.
By 1915 the process for extracting lime from limestone rock had been perfected and the use of marl in large-scale Portland cement production was abandoned, as were the operations at Shallow and McNab Lakes. For the next 50 years both lakes lay in a badly degraded state. In the 1960's the Sauble Valley Conservation Authority, since amalgamated with the North Grey Region Conservation Authority into the Grey Sauble C.A.; attempted to restore both lakes to some semblance of their former glory. The Sauble Valley Conservation Authority had acquired the lands around McNab Lake and most of the lands associated with Shallow Lake through the 1950 to early 1970 decades. The water levels of McNab Lake were successfully restored via a small concrete weir that was anchored into the blasted limestone channel that had previously drained the lake.
A concrete and timber structure was also placed in the channel at the outlet of Shallow Lake, but success in restoring a consistent hydrological regime in this case met with very limited success. The removal of the shallower deposits of marl in Shallow Lake had exposed fissured limestone bedrock in several places. Without the watertight layer of marl, water flowed into these fissures and away through underground aquifers. Even with the annual inputs from Davidson and Cashore Creeks from the south, and the Francis and McNab Lake watersheds from the north, large expanses of Shallow Lake dried up each summer. The Sauble Valley C. A. made several attempts, including the redistribution of remnant marl deposits and the use of imported clay and concrete, to block points of water loss into the lake bottom. A wall was even built around the largest fissure or sinkhole. These attempts were largely unsuccessful and Shallow Lake continues to dry out to a great extent during most summers.
For several decades, ownership and leasehold issues and arrangements associated with the old cement plant and associated property could not be resolved so that renewed restoration attempts at Shallow Lake might be undertaken under a clear land title. Then, in 2003, the modern successor of the Canada Cement Company, Canada Lefarge, dropped its claims to the site. This was a major step forward in a direction that could eventually lead to the restoration of this significant wetland resource to a year-round aquatic habitat. There has been a resurgence of interest among local conservationists and resource agencies in this regard.
Much has recently been made about finally taking ownership of this key property at Shallow Lake---and rightfully so. Concurrent claims that the wetland has now been restored to full aquatic function and vitality through this land acquisition are, however, completely false. Most of this water body will continue to go dry every year, just as it has for nearly a century. It will take considerable in the way of motivated, dedicated and decisive efforts---all behind quality engineering in concert with substantial financial input--- to restore Shallow Lake to some degree of its original aquatic functions and biological values. Hopefully, Ducks Unlimited Canada will be prepared to bring these necessary attributes to the restoration table, just as it did nearly twenty years ago when it replaced the old, leaky weir in the outlet of McNab Lake with a modern concrete and steel water management and conveyance structure. After all, for much of nearly 70 years as the leader in wetland conservation, this is what Ducks Unlimited Canada has done best.
I was born on the Bruce Peninsula on July 20, 1951 and raised on a farm just south of the village of Lionís Head, which is located about halfway up the peninsula on the Georgian Bay shoreline. I graduated from Georgian College of Applied Arts and Technology in Barrie in 1973 as a Resources Engineering Technologist. I was hired by Ducks Unlimited Canada (DUC) in April of 1975 as the first DUC employee in Ontario. Throughout almost 29 years I was involved with the implementation of more than 500 wetland projects and project complexes in southwestern and south central Ontario. Some of these habitat projects included important waterfowl and migratory bird habitat along the eastern shoreline of Lake St. Clair. Just three weeks short of completing 29 years with DUC, I accepted an early retirement opportunity effective March 31, 2004.
