Sand & Gravel Extraction Methods

Deepwater Dredging

• Deepwater dredging is also known as wet-pit mining. Wet-pit mining requires an active stream and either a hydraulic excavator or dragline to remove the sand and gravel from beneath the water table. In contrast, dry-pit mining tends to occur in streams where the water is low, yet still flows during the wetter months and during floods. Regulations against both of these methods are in place, including the use of untouched "buffer zones" that will allow the channel to flow freely and not disturb the vegetation around it.

In-stream Sandbar and Gravel Bar Skimming

• The preferred method of in-stream mining for sand and gravel is bar skimming. This method allows for sandbars and gravel bars to be "shaved" or "skimmed" of their topsoil down to the water level. By doing so, the necessary aggregates are removed without much harm to the surrounding channels or linked environs. As with other forms of mining for sand and gravel, leaving enough space for future shifts or floods in the channel is necessary.

Extraction Methods from Floodplains

• Because sand and gravel are in the same regulation area as limestone, granite, clay and sandstone, sand and gravel are also often mined in open pits on floodplains. As with stream mining, open pits are not to be dug in the water channel, nor where the water usually is in wet months if the water level lowers. If a pit is dug, it must follow the same guidelines in regard to buffer zones and travel areas.

Negative Impacts and Reclamation

• Some negative impacts of improper sand and gravel extraction include headcutting and bed degradation, accelerated bank erosion, damages to bridges and other utilities on the eroding banks, sedimentation, destruction of aquatic habitats and loss of fish. In regard to improper pit mining, the pit can become a serious drain on the route of the water. Regulations exist to moderate these environmental hazards while allowing for the mining to continue. Part of the regulation regards reclamation of the mining sites: lessening pit walls, replacing topsoil and reseeding grasses. This includes in-channel operations.