Chapter I: Environmental and Regulatory Concerns at the Shooting ...

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BMP for Lead at Outdoor Shooting Rangesowners/operators to develop a BMP programthat contains elements discussed later in thismanual. Contact the NRA and NSSF foradditional guidance materials available on leadmanagement practices.By implementing appropriate lead managementat outdoor shooting ranges, range owners andoperators can reduce the environmental andhealth risks associated with lead deposition,meet legal requirements and realize quantifiablebenefits.1.1 Lead Contamination’s Impacton Human Health andEnvironmentExposure RoutesHistorically, the three major sources for humanexposure to lead are lead-based paint, lead indust and soil and lead in drinking water.Typically, human exposure occurs throughingestion, which is the consumption of lead orlead-contaminated materials, or by inhalation.The main human exposure to lead associatedwith shooting ranges is through leadcontaminatedsoil. However, other pathways arediscussed below, along with lead’s detrimentaleffects on humans and animals.Lead can be introduced into the environment atshooting ranges in one or more of the followingways. Each of these pathways is site-specificand may or may not occur at each individualrange:• Lead oxidizes when exposed to air anddissolves when exposed to acidic water orsoil.• Lead bullets, bullet particles, or dissolvedlead can be moved by storm water runoff.• Dissolved lead can migrate through soils togroundwater.Lead oxidizes when exposed to air anddissolves when exposed to acidic water or soilWhen lead is exposed to acidic water and/orsoil, it breaks down by weathering into leadoxides, carbonates, and other solublecompounds. With each rainfall, thesecompounds may be dissolved, and the lead maymove in solution in the storm runoff waters.Decreases in water acidity (i.e., increases in itspH) will cause dissolved lead to precipitate out ofsolution. Lead concentrations in solution arereduced by this precipitation. At pHs above 7.5,very little lead remains in solution. Increasedtime of contact between lead and acidic watergenerally results in an increase in the amount ofdissolved lead in the storm runoff water. The fivefactors which most influence the dissolving oflead in water are summarized below:Annual Precipitation Rate - The higher theannual precipitation rate, the faster the leadweathers. Also, during prolonged rains, thecontact time between water and lead isincreased. In general, the higher theprecipitation rate, the higher the potential risk oflead migration off-site in solution.pH of Rain and Surface Water - The acidity ofthe rainwater decreases as basic (alkaline)minerals in the soil are dissolved. If sufficientminerals such as calcium, magnesium, and ironare present in local soils, then the lead mayquickly precipitate out of solution entirely asthese other minerals are dissolved. The pH ofshallow surface water is an indicator of thepresence or absence of basic minerals in thelocal soil and in gravel within the stream bedsthrough which the water has moved. The waterin deeper streams and lakes is more likely to becomposed of acidic rainwater that is notneutralized.Contact Time - The contact time betweenacidic surface water and lead is a factor in theamount of lead that is dissolved. For example,lead shot deposited directly into a lake has alonger contact time then lead shot deposited inupland areas.Soil Cover - Organic material will absorb leadand remove it from a water solution. The thickerthe organic leaf and peat cover on the soil, thelower the lead content in solution in water leavingthe shot area. Organic material has a strongChapter I - Page I-2
BMP for Lead at Outdoor Shooting Rangesability to extract lead out of solution in water.pH of Groundwater - During periods of norainfall, the water flowing within most streamscomes from groundwater discharging into thestream channel. Therefore, the acidity of thegroundwater affects the acidity of the surfacewater, and hence, affects the solubility of anylead particles carried into the stream duringstorm runoff.Lead bullets, bullet particles or dissolved leadcan be moved by storm water runoffThe ability of water to transport lead is influencedby two factors: velocity of the water and weightor size of the lead fragment. Water’s capacity tocarry small particles is proportional to the squareof the water’s velocity. Clear water moving at avelocity of 100 feet per minute can carry a leadparticle 10,000 times heavier than water movingat a velocity of 10 feet per minute. Muddy watercan carry even larger particles. The five factorsthat most influence velocity of runoff aredescribed below:Rainfall Intensity - The greater the volume ofrainfall during a short period of time, the fasterthe velocity created to carry the rainfall off-site.The higher the annual rainfall, the greater thenumber of periods of heavy rainfall.Topographic Slope - Generally, the steeper thetopographic slope, the faster the velocity ofstormwater runoff.Soil Type - More rainfall will soak into sandysoils then into clay soils. Hence, for a givenrainfall intensity, the volume of runoff will begreater from areas underlain by clays or otherlow permeable soils than from permeable sandysoil.Velocity - Velocity tends to decrease as streamwidth increases. Merging streams, eddycurrents, and curves in streams are other factorsthat may reduce the velocity. Generally, theshorter the distance from the lead deposit to theproperty line, the more likely it is that the leadfragments in suspension will be transported offsite.Vegetative Cover and Man-made Structures -Structures such as dams and dikes reduce thewater’s velocity and greatly reduce the size andweight of the lead particles the water can carry.Since lead particles are heavy compared to theother suspended particles of similar size, theyare more likely to be deposited under theinfluence of anything that reduces velocity of thestorm runoff. Grass and other vegetationreduce runoff velocity and act as a filter toremove suspended solids from the water.Dissolved lead can migrate through soils togroundwaterAcidic rainwater may dissolve weathered leadcompounds. A portion of the lead may betransported in solution in groundwater beneathland surfaces. Groundwater may transport leadin solution from the higher topographic areas tothe lower areas such as valleys, where it isdischarged and becomes part of the surfacewater flow. If the water flowing undergroundpasses through rocks containing calcium,magnesium, iron, or other minerals more solublethen lead, or through minerals that raise the pHof the water, then the lead in solution may bereplaced (removed) from the solution by theseother metals. However, if the soil is a cleansilica sand and gravel, fractured granite, orsimilar type material, then the lead may movelong distances in solution. The factors mostlikely to affect the amount of lead carried by thegroundwater in solution are discussed below:Annual Precipitation - Generally, highprecipitation rates result in heavy dew, morefrequent rainfall, numerous streams, shallowdepth to groundwater, shorter distance of travel,and more rapid rates of groundwater flow. Also,the greater volumes of rainfall over geologic timeprobably have reduced the amount of calciumand other soluble basic minerals that could raisethe water pH and cause lead to precipitate(settle) out of solution from the groundwater.Soil Types - Clays have a high ionic leadbonding capacity and more surface area towhich the lead can bond. Also, groundwatermovement in clay is very slow, which increasesthe contact time for lead to bond to the clay.Chapter I - Page I-3
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Chapter I: Environmental and Regulatory Concerns at the Shooting ...

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