New Jersey Scuba Diving

Using Concrete Rubble To Create Artificial Reef Habitat

Each year, millions of tons of concrete and steel debris are dumped into landfills in our state. This material is generated from the continuous demolition of aging buildings, bridges, roadways and piers. Now, the artificial reef program can use much of this material in a useful way to create marine fish habitat.

Chunks of concrete make ideal reef material. Concrete is dense enough so there is little problem with movement during storms and as it slowly ages it simply breaks down into sand and lime, two natural constituents of the ocean. A pile of concrete on the ocean bottom is a cheap imitation of a natural rock outcropping. providing a firm substrate for mussels and barnacles and all kinds of hiding places for sea bass. tog and lobster.

Acceptable demolition debris includes concrete, brick, stone, glass, and heavy gauge steel. Unacceptable are materials of low density, such as corrugated sheet metal, aluminum arid plaster. The debris must be free of floatables - wood, plastic, and containers. Fine particulate matter, which would include gravel, soil, and granulated concrete, cannot exceed five percent of the load by volume. As far as the fish are concerned, the bigger the pieces the better.

Rubble is transported to the reef site on large barges capable of carrying 3,000 to 5.000 tons of material. For slabs and boulder-sized chunks, deck barges are used; bulldozers push the material overboard. For smaller-sized chunks, less than a cubic yard. hopper or pocket barges which have a half-dozen or more hoppers, each with a trap-door bottom, are utilized. Once on the reef site, the doors are opened and piles of rubble drop straight to the ocean floor.

The strategy of making reefs with concrete rubble is to pile it up on top of itself. Because of its density, scattered pieces of concrete quickly subside and disappear into the sand bottom. Piling relies on the bottom layer providing a stable foundation and results in more structure jutting up above the bottom. To accomplish this, several barge loads of material are dropped at the same location.

From A Guide to Fishing & Diving New Jersey's Artificial Reefs
New Jersey Department of Environmental Protection, 1989