Jack Lanigan, BASF, Ecology Services Department
Introduction and History
BASF Corporation and its predecessor companies have owned Fighting Island since 1918. The southern three-quarters of the island was divided into three settling beds. The beds serve as the final disposition for alkaline by-products predominantly from the manufacture of soda ash and other lime-based products. The beds were in service between 1924 and 1982. The beds hold approximately 20 million cubic meters (706 million cubic feet) of material.
The alkaline by-products consist mostly of calcium chloride, sodium chloride, coke ashes, un-reacted limestone, and limestone impurities such as silica, alumina, and metallic oxides. These by-products were pumped in slurry form to Fighting Island where they were allowed to dry and decant. The grain size typically is in the silt to fine silt range.
Beginning in the mid-1970s and continuing today, BASF actively encourages re-vegetation on Fighting Island. The early efforts targeted increasing the stability of the perimeter containment dikes. The re-vegetation goals expanded steadily to include reducing dust problems, increasing wildlife habitat, controlling runoff, and enhancing the physical appearance.
Many factors contribute to discourage vegetative growth in these materials. The factors include: high pH, high moisture content, general absence of organic components, high concentrations of salts, and the very smooth ground surface. The smooth surface promotes transport by wind and discourages resident time for seeds to root. The high moisture content along with the materials' fine grain size combine to inhibit any kind of large-scale tilling.
BASF's primary methods for increasing vegetative cover fall into six categories. A discussion for each method follows.
Reduce the water content of surficial deposits to promote plant growth: Assessments by the Ontario Ministry of Environment beginning in 1982 concluded that the high moisture content significantly inhibited plant growth. BASF reduced the soil's moisture content by building and excavating channels through the beds. These channels enhance drainage on all the beds and carry excess water to the decant channels.
Build wind breaks at strategic locations to catch dust, seeds, and blowing soil: BASF brought in thousand of bails of hay and straw to build approximately 9.6 km (six miles) of wind breaks that catch dust and seeds. As the wind breaks decay, they provide good organic base matter for plant growth. Additionally, several thousand stick and mulch plots on the beds act as small isolated wind breaks.
Transplant trees and scrubs to develop deeper root and soil zones: Since the mid-1980s, BASF planted approximately 45,000 trees and seedlings on Fighting Island. Early survival rates were marginal, but several species do very well. These species include poplars, Russian Olives, and cottonwood. BASF purchased most seedlings and saplings from the Seedling Nursery Stock Program through the ERCA. Recently, BASF transplants a significant number of trees and scrubs from the northern marsh area on Fighting Island to the settling beds.
Acquire and apply yard wastes from local communities to increase organic content: BASF acquired and maintains an Organic Soils Conditioning Permit to apply leaves on the Island. Beginning in the early 1990s, BASF began accepting leaves from the Town of La Salle free of charge. The leaves are spread inside the perimeter dikes and are allowed to decay for a few years. BASF then seeds the decayed leaves with grasses. Branches are placed in humps across the beds where they act as small wind breaks and seed areas. The branches also help increase the organic content of surface soils.
Acquire and apply organic biosolids (if available) also to increase organic content organic: BASF worked with several local groups to increase the fertility of the lime beds through the application of bio-solids (wastewater treatment plant sludge). In 1981 and 1982, BASF participated in a pilot scale project using bio-solids from the City of Detroit. The sludge was blended with the spoils at various percentages to find the optimum mix ratio, and test plots were planted with a variety of vegetation. Although the pilot project was declared an overall success, the project was discontinued because of elevated concentrations of metals in the sludge and perceived political complications. Two additional opportunities arose in the 1990s to apply bio-solids from the Windsor Wastewater Treatment Plant to Fighting Island. These initiatives, in cooperation with the Fighting Island Development Group (a.k.a. Dean Construction Company), also were unsuccessful primarily due to budget concerns in Windsor's City Council.
Encourage use of the island by waterfowl: Waterfowl, especially gulls, are moving onto Fighting Island in ever increasing numbers. The contribution of bio-solids from this source has been an unexpected benefit to increasing organic content of the spoils. Since realistic estimates of the gull population began in 1991, their number has increased by over 230% (currently estimated at over 350,000 individuals). While it may be difficult to demonstrate that BASF encourages gulls to live on Fighting Island, BASF in fact discourages them from congregating on its other river front properties, most notably on the North Works.
Effectiveness and Further Steps
Overall vegetative cover on the southern three-quarters of the island increased from less than 40% in 1987 to nearly 80% in 1997. The fruits of these rehabilitation efforts include decreased runoff of alkaline waters into the Detroit River, decreased incidents of dust rising from the lime beds that once caused problem for local residents, increased habitat for resident and migratory birds, and a more aesthetically pleasing appearance for residents on both sides of the Detroit River.