BMP for Lead <strong>at</strong> Outdoor <strong>Shooting</strong> Rangesowners/oper<strong>at</strong>ors to develop a BMP programth<strong>at</strong> contains elements discussed l<strong>at</strong>er in thismanual. Contact <strong>the</strong> NRA <strong>and</strong> NSSF foradditional guidance m<strong>at</strong>erials available on leadmanagement practices.By implementing appropri<strong>at</strong>e lead management<strong>at</strong> outdoor shooting ranges, range owners <strong>and</strong>oper<strong>at</strong>ors can reduce <strong>the</strong> environmental <strong>and</strong>health risks associ<strong>at</strong>ed with lead deposition,meet legal requirements <strong>and</strong> realize quantifiablebenefits.1.1 Lead Contamin<strong>at</strong>ion’s Impacton Human Health <strong>and</strong>EnvironmentExposure RoutesHistorically, <strong>the</strong> three major sources for humanexposure to lead are lead-based paint, lead indust <strong>and</strong> soil <strong>and</strong> lead in drinking w<strong>at</strong>er.Typically, human exposure occurs throughingestion, which is <strong>the</strong> consumption of lead orlead-contamin<strong>at</strong>ed m<strong>at</strong>erials, or by inhal<strong>at</strong>ion.The main human exposure to lead associ<strong>at</strong>edwith shooting ranges is through leadcontamin<strong>at</strong>edsoil. However, o<strong>the</strong>r p<strong>at</strong>hways arediscussed below, along with lead’s detrimentaleffects on humans <strong>and</strong> animals.Lead can be introduced into <strong>the</strong> environment <strong>at</strong>shooting ranges in one or more of <strong>the</strong> followingways. Each of <strong>the</strong>se p<strong>at</strong>hways is site-specific<strong>and</strong> may or may not occur <strong>at</strong> each individualrange:• Lead oxidizes when exposed to air <strong>and</strong>dissolves when exposed to acidic w<strong>at</strong>er orsoil.• Lead bullets, bullet particles, or dissolvedlead can be moved by storm w<strong>at</strong>er runoff.• Dissolved lead can migr<strong>at</strong>e through soils togroundw<strong>at</strong>er.Lead oxidizes when exposed to air <strong>and</strong>dissolves when exposed to acidic w<strong>at</strong>er or soilWhen lead is exposed to acidic w<strong>at</strong>er <strong>and</strong>/orsoil, it breaks down by we<strong>at</strong>hering into leadoxides, carbon<strong>at</strong>es, <strong>and</strong> o<strong>the</strong>r solublecompounds. With each rainfall, <strong>the</strong>secompounds may be dissolved, <strong>and</strong> <strong>the</strong> lead maymove in solution in <strong>the</strong> storm runoff w<strong>at</strong>ers.Decreases in w<strong>at</strong>er acidity (i.e., increases in itspH) will cause dissolved lead to precipit<strong>at</strong>e out ofsolution. Lead concentr<strong>at</strong>ions in solution arereduced by this precipit<strong>at</strong>ion. At pHs above 7.5,very little lead remains in solution. Increasedtime of contact between lead <strong>and</strong> acidic w<strong>at</strong>ergenerally results in an increase in <strong>the</strong> amount ofdissolved lead in <strong>the</strong> storm runoff w<strong>at</strong>er. The fivefactors which most influence <strong>the</strong> dissolving oflead in w<strong>at</strong>er are summarized below:Annual Precipit<strong>at</strong>ion R<strong>at</strong>e - The higher <strong>the</strong>annual precipit<strong>at</strong>ion r<strong>at</strong>e, <strong>the</strong> faster <strong>the</strong> leadwe<strong>at</strong>hers. Also, during prolonged rains, <strong>the</strong>contact time between w<strong>at</strong>er <strong>and</strong> lead isincreased. In general, <strong>the</strong> higher <strong>the</strong>precipit<strong>at</strong>ion r<strong>at</strong>e, <strong>the</strong> higher <strong>the</strong> potential risk oflead migr<strong>at</strong>ion off-site in solution.pH of Rain <strong>and</strong> Surface W<strong>at</strong>er - The acidity of<strong>the</strong> rainw<strong>at</strong>er decreases as basic (alkaline)minerals in <strong>the</strong> soil are dissolved. If sufficientminerals such as calcium, magnesium, <strong>and</strong> ironare present in local soils, <strong>the</strong>n <strong>the</strong> lead mayquickly precipit<strong>at</strong>e out of solution entirely as<strong>the</strong>se o<strong>the</strong>r minerals are dissolved. The pH ofshallow surface w<strong>at</strong>er is an indic<strong>at</strong>or of <strong>the</strong>presence or absence of basic minerals in <strong>the</strong>local soil <strong>and</strong> in gravel within <strong>the</strong> stream bedsthrough which <strong>the</strong> w<strong>at</strong>er has moved. The w<strong>at</strong>erin deeper streams <strong>and</strong> lakes is more likely to becomposed of acidic rainw<strong>at</strong>er th<strong>at</strong> is notneutralized.Contact Time - The contact time betweenacidic surface w<strong>at</strong>er <strong>and</strong> lead is a factor in <strong>the</strong>amount of lead th<strong>at</strong> is dissolved. For example,lead shot deposited directly into a lake has alonger contact time <strong>the</strong>n lead shot deposited inupl<strong>and</strong> areas.Soil Cover - Organic m<strong>at</strong>erial will absorb lead<strong>and</strong> remove it from a w<strong>at</strong>er solution. The thicker<strong>the</strong> organic leaf <strong>and</strong> pe<strong>at</strong> cover on <strong>the</strong> soil, <strong>the</strong>lower <strong>the</strong> lead content in solution in w<strong>at</strong>er leaving<strong>the</strong> shot area. Organic m<strong>at</strong>erial has a strong<strong>Chapter</strong> I - Page I-2
BMP for Lead <strong>at</strong> Outdoor <strong>Shooting</strong> Rangesability to extract lead out of solution in w<strong>at</strong>er.pH of Groundw<strong>at</strong>er - During periods of norainfall, <strong>the</strong> w<strong>at</strong>er flowing within most streamscomes from groundw<strong>at</strong>er discharging into <strong>the</strong>stream channel. Therefore, <strong>the</strong> acidity of <strong>the</strong>groundw<strong>at</strong>er affects <strong>the</strong> acidity of <strong>the</strong> surfacew<strong>at</strong>er, <strong>and</strong> hence, affects <strong>the</strong> solubility of anylead particles carried into <strong>the</strong> stream duringstorm runoff.Lead bullets, bullet particles or dissolved leadcan be moved by storm w<strong>at</strong>er runoffThe ability of w<strong>at</strong>er to transport lead is influencedby two factors: velocity of <strong>the</strong> w<strong>at</strong>er <strong>and</strong> weightor size of <strong>the</strong> lead fragment. W<strong>at</strong>er’s capacity tocarry small particles is proportional to <strong>the</strong> squareof <strong>the</strong> w<strong>at</strong>er’s velocity. Clear w<strong>at</strong>er moving <strong>at</strong> avelocity of 100 feet per minute can carry a leadparticle 10,000 times heavier than w<strong>at</strong>er moving<strong>at</strong> a velocity of 10 feet per minute. Muddy w<strong>at</strong>ercan carry even larger particles. The five factorsth<strong>at</strong> most influence velocity of runoff aredescribed below:Rainfall Intensity - The gre<strong>at</strong>er <strong>the</strong> volume ofrainfall during a short period of time, <strong>the</strong> faster<strong>the</strong> velocity cre<strong>at</strong>ed to carry <strong>the</strong> rainfall off-site.The higher <strong>the</strong> annual rainfall, <strong>the</strong> gre<strong>at</strong>er <strong>the</strong>number of periods of heavy rainfall.Topographic Slope - Generally, <strong>the</strong> steeper <strong>the</strong>topographic slope, <strong>the</strong> faster <strong>the</strong> velocity ofstormw<strong>at</strong>er runoff.Soil Type - More rainfall will soak into s<strong>and</strong>ysoils <strong>the</strong>n into clay soils. Hence, for a givenrainfall intensity, <strong>the</strong> volume of runoff will begre<strong>at</strong>er from areas underlain by clays or o<strong>the</strong>rlow permeable soils than from permeable s<strong>and</strong>ysoil.Velocity - Velocity tends to decrease as streamwidth increases. Merging streams, eddycurrents, <strong>and</strong> curves in streams are o<strong>the</strong>r factorsth<strong>at</strong> may reduce <strong>the</strong> velocity. Generally, <strong>the</strong>shorter <strong>the</strong> distance from <strong>the</strong> lead deposit to <strong>the</strong>property line, <strong>the</strong> more likely it is th<strong>at</strong> <strong>the</strong> leadfragments in suspension will be transported offsite.Veget<strong>at</strong>ive Cover <strong>and</strong> Man-made Structures -Structures such as dams <strong>and</strong> dikes reduce <strong>the</strong>w<strong>at</strong>er’s velocity <strong>and</strong> gre<strong>at</strong>ly reduce <strong>the</strong> size <strong>and</strong>weight of <strong>the</strong> lead particles <strong>the</strong> w<strong>at</strong>er can carry.Since lead particles are heavy compared to <strong>the</strong>o<strong>the</strong>r suspended particles of similar size, <strong>the</strong>yare more likely to be deposited under <strong>the</strong>influence of anything th<strong>at</strong> reduces velocity of <strong>the</strong>storm runoff. Grass <strong>and</strong> o<strong>the</strong>r veget<strong>at</strong>ionreduce runoff velocity <strong>and</strong> act as a filter toremove suspended solids from <strong>the</strong> w<strong>at</strong>er.Dissolved lead can migr<strong>at</strong>e through soils togroundw<strong>at</strong>erAcidic rainw<strong>at</strong>er may dissolve we<strong>at</strong>hered leadcompounds. A portion of <strong>the</strong> lead may betransported in solution in groundw<strong>at</strong>er bene<strong>at</strong>hl<strong>and</strong> surfaces. Groundw<strong>at</strong>er may transport leadin solution from <strong>the</strong> higher topographic areas to<strong>the</strong> lower areas such as valleys, where it isdischarged <strong>and</strong> becomes part of <strong>the</strong> surfacew<strong>at</strong>er flow. If <strong>the</strong> w<strong>at</strong>er flowing undergroundpasses through rocks containing calcium,magnesium, iron, or o<strong>the</strong>r minerals more soluble<strong>the</strong>n lead, or through minerals th<strong>at</strong> raise <strong>the</strong> pHof <strong>the</strong> w<strong>at</strong>er, <strong>the</strong>n <strong>the</strong> lead in solution may bereplaced (removed) from <strong>the</strong> solution by <strong>the</strong>seo<strong>the</strong>r metals. However, if <strong>the</strong> soil is a cleansilica s<strong>and</strong> <strong>and</strong> gravel, fractured granite, orsimilar type m<strong>at</strong>erial, <strong>the</strong>n <strong>the</strong> lead may movelong distances in solution. The factors mostlikely to affect <strong>the</strong> amount of lead carried by <strong>the</strong>groundw<strong>at</strong>er in solution are discussed below:Annual Precipit<strong>at</strong>ion - Generally, highprecipit<strong>at</strong>ion r<strong>at</strong>es result in heavy dew, morefrequent rainfall, numerous streams, shallowdepth to groundw<strong>at</strong>er, shorter distance of travel,<strong>and</strong> more rapid r<strong>at</strong>es of groundw<strong>at</strong>er flow. Also,<strong>the</strong> gre<strong>at</strong>er volumes of rainfall over geologic timeprobably have reduced <strong>the</strong> amount of calcium<strong>and</strong> o<strong>the</strong>r soluble basic minerals th<strong>at</strong> could raise<strong>the</strong> w<strong>at</strong>er pH <strong>and</strong> cause lead to precipit<strong>at</strong>e(settle) out of solution from <strong>the</strong> groundw<strong>at</strong>er.Soil Types - Clays have a high ionic leadbonding capacity <strong>and</strong> more surface area towhich <strong>the</strong> lead can bond. Also, groundw<strong>at</strong>ermovement in clay is very slow, which increases<strong>the</strong> contact time for lead to bond to <strong>the</strong> clay.<strong>Chapter</strong> I - Page I-3