Depleted Uranium (DU)

DU ammunition is used by all U.S. services and is found in the following U.S. munitions.

Ranges that deploy DU rounds must obtain a license from the Nuclear Regulatory Commission (NRC) prior to firing. The license gives the base permission to fire DU rounds.

In terms of UXO clearance DU is relatively harmless unless ingested or absorbed into bloodstream through open cuts. DU emits alpha, beta and gamma radiation. The radiation dose rate from a DU projectile is about .2 milliRoentgen per hour (millRoentgen is a measurement of exposure to gamma radiation). Bare DU would have to be directly handled over 150 hours continuously before the person would suffer any adverse effects. This external hazard would be significantly reduced if gloves were worn to attenuate the dose radiation.

DU also poses an inhalation hazard to the UXO or EOD worker because of the potential for DU dust. The hazard is related more to the toxicity of the dust than its radioactivity. Having proper respiratory protection should be enough to protect the immediate worker from the hazard.

• Non magnetic
• Extremely heavy (about 50% more dense than lead)
• Jet black lumps or dust (may have a greenish tinge) that eventually turn green.
• Honeycomb like texture
• Spark when struck with a metallic object (like a pick or shovel)

In many cases it may not be possible to identify DU areas with a visual inspection and normal radiographic instruments are not sensitive enough to detect DU in ordnance. If UXO work is conducted in an area where DU is suspected of being fired it is usually customary for one team member to wear a Thermoluminescent Dosimeter that is designed to indicate when the radiographic exposure level exceeds a set threshold. It is also recommended that urine tests be conducted if the person is exposed on a regular basis just for precautionary measures.

UXOInfo.com provides this information for background and information purposes only - UXO personnel should consult professional medical help for specific safety instructions or precautions.

Small Arms Lead Contamination

Small arms firing ranges are essential to weapons training and the mission of the military. However, range use often produces soil contaminated with metals from spent bullets. This contamination can create environmental and occupational health problems during range operation and maintenance, as well as during redesign, reuse, and remediation of the range. However, proper management of ranges should alleviate these problems.

Lead is the primary soil contaminant of concern at these ranges. Antimony, a hardening agent in bullets, and copper and zinc, the primary components in shell casings and jackets, can also contribute to soil contamination. Bullets are often fragmented and pulverized upon impact with backstops, berms, or bullet traps located at the range. The normal operation of a range can produce lead concentrations of several percent (one percent = ten thousand parts per million) in soils located behind and adjacent to targets and impact berms. Elevated levels of lead have also been found in vegetation growing near impact berms. Care must be taken to protect human health and the environment from lead's potential harmful effects. Antimony, copper, and zinc should be considered as secondary contaminants of potential concern when developing a list of contaminants targeted for analysis and/or cleanup.

Lead is a naturally occurring, grayish soft metal, found in the Earth's crust. Human activities such as mining, manufacturing, and the burning of refined fossil fuels have concentrated the amount of lead in certain areas of the environment. Harmful exposures to lead can occur from inhalation of lead dust or fumes, and ingestion of lead contaminated food and water. Lead can accumulate in human, animal, and plant tissue and can cause chronic health effects. Lead contamination in soils at firing range sites can be transported via the following mechanisms:

• Airborne Particulate Lead - Very small lead particles can become airborne if wind, foot traffic, or maintenance activities disturb contaminated soil. Airborne particles smaller than 10 microns can be inhaled, and fine particles smaller than 250 microns in diameter can be incidentally ingested. Soil particles smaller than 100 to 200 microns are likely to be ingested because fine particles adhere to skin while larger particles are easily brushed off. Intake of lead through inhalation is usually small.
• Storm Water Runoff and Erosion - Storm water runoff has the potential to erode and transport contaminated soil and lead particles away from the normal confines of a firing range. Rainfall intensity, ground slope, soil type, and obstructions such as vegetation and fabricated structures will influence the potential transport of lead away from the range. Once the contaminated soil is transported beyond the firing range's boundary, additional environmental impact (e.g., bioaccumulation or bioconcentration) and human exposure could occur.
• Dissolved Lead in Groundwater/Surface Water - At a neutral pH, lead is relatively insoluble. As water becomes more acidic (decreasing pH), lead solubility tends to increase. When storm water (normally slightly acidic) comes in contact with lead contaminated soil, the lead can be dissolved into the water and transported to nearby groundwater or surface water. If sufficient lead is mobilized, environmental receptors can be affected and risk to human health could occur if these sources are used for drinking water. When groundwater is more than 10 feet below ground surface, it is generally not affected by leaching of lead from soil. However, some regulatory agencies consider dissolved concentrations of lead above 15 micrograms per liter (parts per billion) a potential health concern (Reference: Appendix A: National Primary Drinking Water Standards, Action Level for Lead, 1997.)

As with most metals, lead, antimony, copper, and zinc tend to adhere to soil grains and organic material and remain "fixed" in shallow soils.

Small Arm Ranges - Lead Remediation Approaches

The remediation of lead contaminated soils at firing ranges, either as part of maintenance or site closure activities, does not differ significantly from any other soil remediation project. However, development of remediation goals will depend upon whether the proposed action is maintenance at an active firing range or remediation supporting a potential change of land use. Firing range remediation activities involve soil characterization/remediation, and waste treatment and disposal.

Clean-up Goals for Lead

In July of 1994, the EPA issued "Revised Interim Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities." This memorandum provides "screening levels" to be used as a tool to define a level of lead contamination above which there may be enough concern to warrant further site-specific study. The guidance encourages the risk manager to select, on a site-specific basis, the most appropriate combination of remedial measures, from intervention to abatement, needed to address lead exposure threats. The memorandum, which is directed toward protection of children and assumes residential future land use, sets a screening level in soils of 400 mg/kg, below which no corrective action is recommended, and a screening level in soils of 5,000 mg/kg, above which corrective action is recommended. Concentrations falling between these screening levels could warrant corrective action depending upon the results of site-specific risk evaluations. Additionally, site-specific risk assessment may lead to a finding of "no further action."

Remediation goals should be developed to be protective of receptors consistent with planned future land use. Examples of receptors and future land use include: continued operation as firing range, commercial redevelopment of the site, and residential reuse. In any case the age of the potential people effected must be factored into the remediation goals.

Disposal/Treatment Options for Lead Contaminated Soils

Off-range Disposal

Physical Separation

These processes use techniques designed to separate particles based on particle size and/or density. Sifting is one method that can significantly reduce the quantity of soil that may require off-site disposal, stabilization, or further treatment by acid leaching.

Stabilization/Solidification

Stabilization and solidification is another treatment/disposal option for soil contaminated with lead in excess of the hazardous waste threshold. This technology involves adding ingredients to contaminated soils that coat the soil grains and/or fill inter-granular pore spaces, permanently sealing off the lead contamination from the environment. This technology immobilizes contaminants in the soil and results in a solid or granular material.

Soil Washing

A soil washing process has been successfully used to reduce lead concentrations in soils to background levels at a U.S. Army Superfund site. The Army had previously burned scrap ammunition, powder and buried shell casings at the site, resulting in total lead concentrations in soil as high as 86,000 parts per million. After sifting the soil and separating the munitions particles from the sand and gravel, the soil was washed in an aqueous acid solution to dissolve and remove the lead from the sand and gravel. Although the process was speedy and cost effective, the spent acid solution required treatment and disposal as a hazardous waste.

Frost Effects on Buried UXO

Buried objects have been known to move or migrate towards the surface during freezing and thawing cycles. This phenomenon is often referred to as frost heave. At most sites, it is recommended that UXO clearance be performed at least to the local frost line. In cases where it is not feasible or practicable to clear UXO to the frost line, surveys and ordnance sweeps should be conducted on a regular basis as part of the post site maintenance.

Corrosivity of UXO

Deteriorated UXO can present serious explosive hazards. As UXO casings degrade under certain environmental conditions, their fillers, propellants, and other constituents may leach into the surrounding soils and break down creating a highly explosive environment. The synergistic effects of commingled explosives can create compounds of unknown sensitivity, potentially greater than the individual sensitivities of the original chemicals. In addition, deteriorated explosive compounds may also pose greater explosive risks than when in pristine condition.

Many munitions made prior to the 1950s relied on unstable explosive fillers, initiating explosives, and bursting charges that are very susceptible to deterioration. Several environmental factors can affect the corrosion rate of UXO containment casings and explosive constituents, including soil characteristics. The soil characteristics that affect the likelihood and rate of UXO corrosion include: soil moisture, soil type, soil pH, buffering capacity, resistivity, electrochemical (redox) potential, moisture, including precipitation, high soil moisture, and the presence of groundwater. Soils with a low water content (i.e., below 20 percent) are slightly corrosive on UXO casings, while dry soils are neutral and soils with periodic groundwater inundation are moderately corrosive. The texture and structure of soil affect its corrosivity. Cohesive soils, those with a high percentage of clay and silt material, are much less corrosive than sandy soils. Soils with high organic carbon content, such as swamps, peat, fens, or marshes, as well as soils that are severely polluted with fuel ash, slag coal, or wastewater, tend to be highly corrosive. The pH level also affects soil corrosivity. Normal soils with pH levels between 5 and 8 do not contribute to corrosivity. In fact, soils with pH above 5 may form a calcium carbonate coating on buried metals, protecting them from extensive corrosion. However, highly acidic soils, such as those with a pH below 4, tend to be highly corrosive.

Buffering capacity, the measure of the soil's ability to withstand extreme changes in pH levels, also affects the corrosion potential. Soils with a high buffering capacity can maintain pH levels even under changing conditions, thereby potentially inhibiting corrosive conditions. However, soils with a low buffering capacity that are subject to acid rain or industrial pollutants may fluctuate in pH levels and promote corrosivity. Another factor affecting the corrosive potential of soils is resistivity, or electrical conductivity, which is dependent on moisture content and is produced by the action of soil moisture on minerals. At high resistivity levels (greater than 20,000 ohm/cm) there is no significant impact on corrosion; however, corrosion can be extreme at very low resistivity levels (below 1,000 ohm/cm). High electrochemical potential can also contribute significantly to UXO casing corrosion. The electrochemical or "redox" potential is the ability of the soil to reduce or oxidize UXO casings (the oxidation-reduction potential). Aerated soils have the necessary oxygen to oxidize metals as well as certain anaerobic bacteria that can create an oxidizing environment.

Although the soil characteristics influence the likelihood of corrosion, in general UXO deterioration depends on the integrity of the UXO casing.

DoD is currently conducting studies aimed to determine whether undamaged UXO casings corrode when left on ranges and, if so, how long it takes until the explosives might be released into the surrounding environment. Preliminary observations at one site indicate that under specific conditions, the environmental impact from undamaged UXO could be minimal. This research is still in its early stages, but understanding how munitions can be less environmentally destructive is an important part of reducing their future environmental impacts.