September 2003

Aggregate Provides Natural Alternative

Natural water intake systems offer environmental and cost benefits to users, sales opportunities to producers.

By Mark Vergallito

A barge loaded with aggregate from Lafarge prepares to unload through the bottom into a 280- x 260- x 14-ft. excavation in the lake bottom.

Municipalities and industrial and power-generation facilities located near the Great Lakes or other large water bodies typically use lake bed intake systems to obtain fresh water. However, traditional systems can kill fish entrapped in open-crib structures and are susceptible to clogging by organisms. As an alternative, natural intake macro-filtration systems constructed of gravel and sand provide environmental and economic benefits to water users and present a potentially significant aggregate market.
Traditional water intake systems may require use of chlorine treatment. The natural aggregate alternative does not, thereby reducing the potential for lake contamination. Beyond that, the natural aggregate macro-filtration system provides water that is filtered to the point that turbidity levels generally meet drinking water requirements. This reduces the need for a high level of filtering once the water is harvested.
Using all natural materials that mimic the natural lake bottom also prevents deterioration of the local ecosystem. Fish are not drawn in with the water. In addition, water-based organisms, such as zebra mussels, are not able to clog up the intake, eliminating significant repair costs and downtime.

Market potential
Working with consulting engineers Prien and Newhof, Lafarge North America’s Great Lakes Division supplied a high quality traditional product for two natural water intake systems in Lake Michigan in southwest Michigan. One system involved the municipal water intake for Grand Haven, Mich.; the other system supplied industrial water to a power-generating firm in South Haven, Mich. The projects called for the intake filtration system to resemble the natural lake bottom of Lake Michigan. Lafarge materials, including natural washed gravel (MI-DOT 17A) and sand (2NS), were used as part of a filtration media for the systems.
Each project required 30,000 tons of the 17A gravel and 8,000 tons of 2NS sand. Geology of Lafarge’s product — impervious granite — was a perfect fit for the project. This material was chosen over limestone because it is more durable and does not have a “softening” effect on drawn water. Using these materials, the system should have an indefinite life span.
Engineering plans afforded only a narrow window of product delivery because silt movement into the 280-ft.-long, 260-ft.-wide, 14-ft.-deep lake bottom excavation could jeopardize successful completion of the operation. The Lafarge Great Lakes Division team, led by Dave Sheldon, sales and marketing, and Reg Gardiner, production manager, worked closely with construction contractor Great Lakes Dock & Materials and the intermediate dock managed by Stoneco to meet the tight production and delivery schedule. Gravel and sand was delivered to the offshore site in barges equipped with bottom off-loading capabilities.
Through this project, Lafarge North America’s Great Lakes Division benefited from the use of a traditional aggregate product in a new way. Typically, Lafarge’s sand and gravel pits contain 60 percent gravel and 40 percent sand. Sand is cheaper to manufacture and has greater demand, generally resulting in a significant inventory of gravel. Some of the larger material is sold for landscaping, while smaller material is used in home development and building. This project, and others like it that may develop, provide a market for the intermediate size material. This allows Lafarge to better manage inventory.
In the Great Lakes region alone there is an average of one natural water intake project a year, according to Prein and Newhof. Although the total number of water intake projects, including open systems, is not readily known, several avenues exist to pursue increased aggregate sales to this market. Prospects include municipalities revamping water intakes with traditional open cribs, municipalities seeking a way to pre-filter raw water to reduce mechanical filtration costs, power generating firms with water intake systems, and even aggregate operations that use large quantities of water.
The two projects highlighted here required 60,000 tons of natural washed gravel and 16,000 tons of sand. At current average selling prices, a single project can generate nearly $1 million in gross revenue. Increased sales revenue and improved inventory management and pit optimization are some of the benefits aggregate producers can achieve while providing a natural alternative for lake-bottom water intake systems.

Mark Vergallito is environmental health and safety manager for Lafarge North America, Great Lakes Division. The company’s involvement in construction of two natural water intake systems received a gold award in the National Stone, Sand and Gravel Association’s 2002 Capstone competition recognizing innovative marketing and market development.