Groundwater Contamination at Shooting Ranges: Managing the Risk

LESSER KNOWN SOURCES OF GROUNDWATER CONTAMINATION

 Heavy metals from shooting ranges pose environmental risks. Learn how lead, antimony and arsenic from ammunition cause groundwater contamination and best management practices to mitigate the threat.

Shooting ranges have long been recognised as a potential source of environmental and groundwater contamination due to the build-up of lead in the soil from shooting activities. The extent of this contamination depends on the type of shooting activity.

Key Contaminants and Their Fate

The main contaminants of concern are heavy metals, particularly lead and nickel, which are used in ammunition manufacturing. Traditional ammunition is primarily composed of lead, making up about 97% in shot and 90% in rifle bullets. Once in the environment, bullets are subject to weathering, which can form secondary minerals. These minerals may become soluble, releasing lead and other co-contaminants into the soil. Soil properties affect how bullets weather and the overall availability of contaminants.

Despite lead generally being immobile—forming poorly soluble compounds that bind to soil, with few reported cases of groundwater contamination—other metals in traditional ammunition pose a greater threat. In addition to lead, traditional ammunition typically contains small amounts of other heavy metals, including antimony, arsenic, cadmium, copper, and zinc. Arsenic and antimony are distinct because they can form mobile oxyanions in alkaline conditions. Due to their high mobility and toxicity, the potential migration of arsenic and antimony into groundwater used for domestic water, can pose a risk to human health.

Sources of Contamination and Environmental Impact

Elevated lead concentrations are mainly reported in the bullet impact berms (backstops) and shot fall zones.

• Rifle and Pistol Shooting: Bullets accumulate in natural barriers. As bullets pass through sandy backstops, physical abrasion occurs, causing an immediate release of lead and other metals. This abrasion creates a fine lead powder that is quickly converted to lead-bearing minerals, which may pose a risk to groundwater. The contamination from rifle ranges is often considered manageable because of the limited area of pollution and the treatability of sandy soil.
• Shotgun Shooting (Skeet, Trap, Clay): With shotgun ranges, ammunition is dispersed across a wide area, and contamination can extend beyond 10 hectares. In this scenario, shot weathering is the main way metals are released into the soil.

Over the long term, ammunition decomposes in the environment due to weathering. Numerous studies have investigated the risk of soil and groundwater contamination beneath shooting ranges and the resulting toxicity in the receiving environment. This creates a viable environmental risk and consideration should be given to mitigation measures through best management practices.

Best Management Practices (BMPs)

Containing both bullets and bullet fragments is crucial for lowering the risk of environmental and effectively, groundwater contamination. BMPs focus on trapping and containing the actual bullet. Containment device options include:

• Earthen Berms and Backstops
• Sand Traps
• Steel Traps
• Lamella or Rubber Granule Traps
• Shock Absorbing Concrete

The most critical BMP for managing lead during range operation is lead reclamation. The removal and recycling of bullets from range soils can significantly reduce the contaminant burden, as well as the environmental and human health risk. Implementing a regular reclamation program helps limit the need for expensive remedial action later. The simplest and most low-cost management alternative, especially at smaller ranges, is the manual raking and/or sifting of bullet fragments from the soil. These activities should be concentrated at the surface layer and performed on a regular basis, such as weekly. Once collected, the lead must be taken to a recycler or reused. It is important to note that caution should be exercised during mechanical lead removal, as it may result in the abrasion of lead fragments and the enrichment of metals in the soil

Read more about groundwater contamination:

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