Results of Lead Mobility Study: Sporting Clays Range At the Travis Family Shooting Facility Peaceful Valley Boy Scout Ranch Elbert County, CO by J. Robert Clark, Ph.D. August 23, 2007 7778 Lewis Street Arvada, CO 80005 303-420-6646 Executive Summary A study was conducted at the Sporting Clays Range on the Peaceful Valley Boy Scout Ranch to ascertain the mobility of lead, the potential for lead to migrate off the range in running water, and the potential for lead contamination of groundwater. Lead, in the form of lead shot, is present in certain areas in the top layer of soil at the Sporting Clays Range because lead shot has been used, and is intended to be used in the future, in shotgun loads for sport shooting. In conducting this study, surficial soil and sediment samples were collected at: Shot impact areas at four shooting stations on the Sporting Clays Range ("Impact Zones"); Four ecologically equivalent uncontaminated areas ("Background Sites"); The mouth of the dry wash that drains the Sporting Clays Range. At each of these locations, samples were collected at the surface and at a depth of eight to fourteen inches below the surface. The surface samples show the amount of lead that has built up on the surface; the samples collected below the surface provide an indication of whether lead is migrating in solution down into the soil and potentially contaminating groundwater over time. During the course of the sampling, observations were made of the characteristics of the soil, geomorphologic features, and vegetation that might influence the interpretation of the data. There are two possible mechanisms by which this lead could be dispersed around or off the Sporting Clays Range: mechanical transport of lead shot due to running water, and dispersion of lead dissolved in water. Some small amount of lead shot will be dispersed by running water, but because lead is relatively heavy and settles to the bottom of running water quickly, this lead would be easily prevented from moving downstream with a small containment dam. Transport of lead dissolved in water is not viable at the Sporting Clays Range, because lead is highly insoluble in the soils or subsoils present at the Peaceful Valley Boy Scout Ranch. Accordingly, there is very little potential for lead from the Sporting Clays Range to infiltrate and contaminate groundwater. Testing and soil management practices are recommended to confirm this conclusion and protect against the minor risk of lead migration in the future. All the data from the Sporting Clays Range confirm a general statement that the EPA makes on one of their web pages: "What happens to lead when it is released to the environment? When released to land, lead binds to soils and does not migrate to groundwater. In water, it binds to sediments." (http://www.epa.gov/safewater/contaminants/dw_contamfs/lead.html) Recommendations Summary Lead data from the samples collected in the Impact Zones were compared to data from the comparable Background Sites around the range. At three of the sites, no differences were found in lead content between the soils at the surface in Impact Zones and Background Sites. This is due to limited use of the Sporting Clays Range to date. However, future use at shooting stations for flying targets may eventually result in accumulation of lead shot requiring mitigation or management. If the Sporting Clays Range is used for only ten events per year, as requested in the Special Use Permit application, then the soil in the Impact Zones should be tested on a two-year basis using EPA Method 6010B. Should this test yield a value above the Colorado Department of Public Health and Environment limit of 400 mg/kg, then the Toxicity Characteristic Leaching Procedure (TCLP; EPA method 1311) should be used to ensure that dissolved lead is not migrating into groundwater or off the range (1)*. (* A number in parentheses indicates the number of the reference listed under References) A high lead concentration was found in the surface sample in the Impact Zone for the running rabbit target (Sporting Clays Station 5). This shooting station is unique at the Sporting Clays Range because it is the only station where targets are located on or near the ground. It was expected that this shooting station would have a buildup of lead pellets because the rolling targets are shot at in a relatively narrow area, unlike the other stations at the Sporting Clays Range where targets are shot in flight, and the pellets fall over a broad area. Lead in this Impact Zone should be tested every two years using both EPA methods 6010B and 1311 (TCLP). Annually that slope should be treated with pulverized limestone and phosphate fertilizer to insure the immobility of lead (2, 3). Grass should be maintained on that hillside, but nitrogen fertilizer should NOT be used. For the purpose of convenience, all Impact Zones should be tested on the same schedule. Eventually lead shot may be carried down to the mouth of the dry wash in sufficient quantity to make it necessary to contain the transport of lead pellets in the sediment. Sediment samples should be collected and tested for lead by EPA method 6010B at the mouth of the wash every two years. In addition, a small containment dam will eventually need to be built just below the mouth of the wash. Lead shot has a very high density compared to most silicate minerals that comprise the bulk of stream sediments, and the ponding effect of the low containment dam will cause lead pellets to settle out at the top end of the pond. Once the runoff has drained away, the lead pellet detritus will remain trapped in the sediment at that point, preventing further mobility downstream. Author's Qualifications J. Robert Clark has a Ph.D. in Geology from the Colorado School of Mines. He has thirty-seven years experience working in a variety of areas in geology and geochemistry. He has worked in government and private industry. Among his specialties are geochemical method development and application of new geochemical technologies to geological problems. He has numerous publications, six patents, and has been an invited or keynote speaker at a number of scientific conferences. His experience in environmental work includes wilderness study projects where impact from natural and human sources of pollution had to be evaluated. He was involved at the ground level in the planning of the National Water Quality Assessment Program (NAWQA), and he administered the NAWQA projects in the Kentucky River Basin and the Illinois River Basin. His work has involved evaluating sources and mobility of lead pollution in a variety of areas. The author's Professional/Technical Record can be downloaded at: http://www.enzymeleach.com/~bobclark/Clark_JR_Full_PTR.pdf Contents Page Executive Summary ……………………………………………… 2 Recommendations Summary ……………………………………. 2 The Authors Credentials ………………………………………… 3 Abbreviations and Layman's Explanations ..……………………. 5 Introduction ..……………………………………………………. 6 Study Area Description …………………………………………. 7 Procedures and Methods .……………………………………….. 7 Results, Observations and Interpretations ..…………………….. 12 Acid Digestion Results …..………………………………. 12 Impact Zone Accumulation of Lead ……………… 12 Geochemical Mobility of Lead …………………… 14 Mechanical Mobility of Lead …………………….. 14 Water-Extractable Lead …………………………………… 14 Soil pH Data ………………………………………………. 15 Discussion .………………………………………………………. 15 References ………………………………………………………... 17 Figures and Tables Page Figure 1. Sample site locations relative to the Sporting Clays Range …..…………………………………… 9 Table 1a. Sample Site Descriptions ………………………. 10 Table 1b. Sample Descriptions ..………………………….. 11 Table 2. Analytical Data …………………………………... 13 Abbreviations and Layman's Explanations Pb – Chemical symbol for lead. Detritus (noun) and detrital (adj.) – Relating to particles, either minerals or lead shot, that are carried in the sediment load of running water. Geochemical processes – These are natural chemical processes that occur in the earth. Hydromorphic transport – The process of moving metals, dissolved minerals, or colloids in flowing water. ICP-MS – Inductively Coupled Plasma/Mass Spectrometry uses an argon plasma (which is as hot as the sun) to ionize trace elements in a test solution. The trace element ions are then measured in a mass spectrometer, which sorts the elements by their atomic mass and charge. Solubility – the maximum equilibrium concentration of a substance in an aqueous solution. Introduction Peaceful Valley Boy Scout Ranch, which is located in Elbert County, CO, set up and began to operate the Sporting Clays Range in May, 2006. The Sporting Clays Range was an addition to the Travis Family Shooting Facility in the southwestern part of the Peaceful Valley Ranch. The Sporting Clays Range has been used intermittently since that time. In August, 2007 a lead mobility study was undertaken at the Sporting Clays Range. The study was designed to: Examine the current status of lead accumulation on the ground in shot impact areas. Test for evidence of solid lead shot and shot fragments being carried down an intermittent stream to the ranch property boundary. Evaluate the potential for water-soluble forms of lead being transported hydromorphically away from the range or down into the groundwater. Samples were collected in the area of the Sporting Clays Range in a manner intended to test these three points. Based on observations and data produced in the course of this study, interpretations and recommendations are discussed in this report. These interpretations are based on existing scientific knowledge of the geochemical behavior of lead. Metallic lead is so insoluble in pure water that a solubility reference is not readily available. When metallic lead is exposed to air and humidity, a microscopically thin, highly-insoluble layer of lead oxide forms on its surface (4). In outdoor shooting range berms, weathering lead commonly precipitates as minerals of lead oxide, lead carbonate, or lead phosphate (2, 3, 5, 6). All of these mineral phases are insoluble in water at pH values that are not too acidic or too alkaline (7, 8, 9). Lead also does not dissolve in some mineral acids, such as sulfuric acid and hydrochloric acid, due to the formation of insoluble minerals on the surface of the metal (7, 8, 9, 10, 11). However, lead forms soluble complexes with the anions of some organic acids, such as acetic acid (vinegar) and citric acid (10, 11). The presence of a small amount of an organic acid and a low (acidic) pH can significantly affect the solubility of lead. For instance, the public has been warned not to eat acidic foods, such as tomato sauces, off of pewter plates (pewter being a lead-tin alloy). Organic acids (such as humic acids produced by the decay of organic matter) are found in many soils in concentrations that would affect soil pH, and in turn affect the potential chemical mobility of lead in those soils. As a general guide, the U.S. Environmental Protection Agency lists the ideal soil pH range for a shooting range berm as 6.5 to 8.5 (3). However, microbial activity that causes soil organic matter to decay also generates substantial amounts of carbon dioxide in the soil. The elevated CO2 in turn causes insoluble lead carbonates to precipitate in the soil (2). Also, phosphorus released by decaying organic matter in the soil can cause extremely insoluble lead phosphate to form. Insoluble lead minerals have been observed to form in soils where the pH is as low as 4.8, immobilizing the lead (2). Considering the low annual precipitation and the generally neutral to slightly alkaline pH of the soils in the eastern plains of Colorado (12), lead would be expected to be geochemically immobile. The pine forest over much of the Peaceful Valley Boy Scout Ranch would tend to make the soils slightly acidic. This study was conducted in part to test the mobility of lead on the Sporting Clays Range under the prevailing conditions. Study Area Description The Sporting Clays Range is located in the southwestern corner of the Peaceful Valley Boy Scout Ranch. The range is located in Section 23, T. 10 S., R. 64 W., bounded by UTM coordinates 540600 to 542000 Easting and 4335000 to 4336000 Northing. That part of the ranch is a dissected upland underlain by weathering-resistant, medium-to-coarse-grained sandstones and conglomerates of the Dawson Arkose and Castle Rock Conglomerate, which are of Tertiary age. This sandstone is comprised mostly of detrital grains of quartz and orthoclase, a potassium-rich feldspar. The mineralogy of the sandstone is reflected in the soil minerals on the range and in the sediments of the dry wash draining the range and the sediments in Kiowa Creek. This part of the upland is truncated on the west by the alluvial plain of Kiowa Creek, a high- order, intermittent, north-south oriented drainage that is a tributary to the South Platte River approximately forty miles downstream. A sharply incised, second-order, intermittent stream (herein referred to as the "wash") drains the area of the Sporting Clays Range into Kiowa Creek. This wash only flows during runoff caused by large rains or heavy snow melt. The sides of the main channel of the wash are very steep. Three of the sporting clays stations are on a side channel of the wash, which has gentler slopes along the sides. The upland above the wash is a rolling surface with substantially more gentle slopes. Soils in the study area reflect the mineralogy of the underlying sandstone. Varying amounts of organic matter and silt in the soil causes distinct color variations from one site to the next. On south-facing slopes, the soils are generally lighter in color, due to less organic matter in the soil, and the soils on the north facing slopes are typically darker in color. Vegetation varies considerably in the area of the Sporting Clays Range. Canyon walls and steeper slopes often have pines with brush and grass undergrowth. If the slope is north-facing, then the stand of trees is often more closely spaced. Grass meadows are found in some areas on the upland and on some of the more gentle slopes. Prior land use in the area of the Sporting Clays Range has probably involved cattle ranching. While sampling, some old cattle manure was observed in two locations. There is no evidence of cultivation. Two groomed foot trails cross the area, and there are two dirt roads in the range. There is no history of mining or other mineral extraction activities on the ranch. Historical records do indicate some limited coal mining in Elbert County, but this would not have any impact on the study area. There is no potential for lead mineral occurrences in Elbert County, and no known natural source of concentrated lead could affect the results of this study. Procedures and Methods The Peaceful Valley Boy Scout Ranch commissioned a study to determine if there is significant potential for lead being dispersed off the area of the Sporting Clays Range. On August 2, 2007 the site was visited, and the area to be evaluated was inspected looking for geological or environmental variables that might be important factors in the study. Samples were collected with the following criteria in mind. Impact Zones were selected as the primary sampling sites for evaluating lead buildup in the surface layer of soil, and for testing for any evidence of lead migrating down in the soil profile. Impact Zones were identified by the plastic shotgun wads and the broken clay birds on the ground. The portion of these Impact Zones farthest from the shooting stations would likely have the highest levels of lead pellets, and these were chosen as sites to collect soil samples. Background Sites were selected to match slope and soil conditions as closely as possible with those at each of the Impact Zones. These were used to contrast with the Impact Zones, looking for evidence of significant differences in lead levels. These soil sample sites were selected in the bottom of the wash, on south-facing slopes, on north-facing slopes, and on the rolling upland above the wash. A stream sediment site was selected at the mouth of the wash to ascertain if any lead shot had as yet been carried by runoff down to that point. Stream sediment samples were also collected in Kiowa Creek, upstream from and downstream from the confluence with the dry wash. Comparing these two sites would show any influence that the Sporting Clays Range had on the sediment in Kiowa Creek. A sample location map is provided in Figure 1. At each Impact Zone and Background Site two samples were collected. A composite surface sample consisted of soil material from the top one inch of the soil profile. This upper layer would have the greatest chance of showing contamination from spent lead pellets, which would be on or slightly under the surface of the soil. In the Impact Zones, these samples would give an idea about how much lead has accumulated at the Sporting Clays Range. A second soil sample collected at a depth of eight to fourteen inches below the surface was used to determine whether or not there is any evidence that lead is migrating downward in the soil. Even if no evidence was found of vertical migration of lead in the soil, these deeper samples would provide a baseline of data for future monitoring. Descriptions of the sample sites are given in Table 1a, and the sample descriptions are given in Table 1b. A Global Positioning System (GPS) reading was taken at each sample site with a Garmin 12 XL GPS unit. A description was recorded for each sample, and the sample material was sealed in a 50 mL high-density polyethylene centrifuge tube. A picture was taken at each of the Impact Zones, showing the location relative to the shooting stand. Other pictures were taken to document the topography, vegetation, and soil variations. The samples were sent by Federal Express to Skyline Assayers & Laboratory in Tucson, Arizona. At the laboratory a split of each sample was set aside, and soil pH was measured on that portion in order to determine if chemical conditions in the soil might be conducive to the formation of water-soluble (and geochemically mobile) lead complexes. Water from the pH tests was used to determine "water-extractable lead" for each sample. These determinations were made by ICP-MS. The bulk of the sample material was then treated to one of two sample preparation procedures. Since lead shot would be unevenly distributed in the surface soil samples and sediments, they were pulverized to homogenize any lead contamination in the sample. Thus any aliquots weighed out for analysis would have the same lead content. Quartz cleaner sand was run through the pulverizing mill between samples to remove any lead smeared on the hardened surfaces in the mill. ? Figure 1. Sample locations on and near the Sporting Clays Range, Peaceful Valley Scout Ranch. Table 1a. Sample Site Descriptions. (Site numbers not in this sequence are being used in other aspects of studies on the Travis Family Shooting Facility at the Peaceful Valley Scout Ranch.) Site #: UTM Easting UTM Northing Type of Site Topography Vegetation 1 540865 4335681 Sporting Clays Station 1 – soil Bottom of dry wash Sparse grass and weeds 2 541065 4335541 Sporting Clays Station 4 – soil South-facing slope Pines with grass and brush undergrowth 3 541135 4335666 Sporting Clays Station 5 – soil North-facing slope Mowed grassy slope, shaded by a pine. 4 541372 4335603 Sporting Clays Station 8 – soil Upland Scattered pines with grass and brush 5 541547 4335636 Background Site – soil Upland Grassy area between scattered pines 6 541215 4335750 Background Site – soil South-facing slope Pines with some brush undergrowth 7 541037 4335693 Background Site – soil North-facing slope Pines with grass and brush undergrowth 8 540627 4335747 Dry wash – sediment Edge of Kiowa Creek floodplain Sparse grass under pines 11 540505 4336320 Background Site – soil Edge of Kiowa Creek floodplain Grassy area between scattered pines 12 540211 4336809 Kiowa Creek – sediment Downstream from dry wash Sparse grass 13 540489 4334232 Kiowa Creek – sediment Upstream from dry wash Sparse grass Site #: Site Description 1 Pellet fall zone is in alluvial bed of dry wash. Site is at far edge of debris field of clay birds and spent wads. 2 Pellet impact zone on south facing hillside. Site is in area of broken clay birds, spent wads, and shot damaged plants. 3 Site is in middle of very intense impact zone for the "running rabbit" target; abundant lead pellets visible in a very restricted area. 4 Pellet fall zone for an aerial clay bird. Site is at far edge of debris field of clay birds and spent wads. 5 Background site that has a similar situation to site 4. 6 Background site that has a similar situation to site 2. 7 Background site on same north-facing slope as site 3. It is in a small grassy area surrounded on three sides by trees. 8 At point where dry wash crosses boundary of Kiowa Creek floodplain; braided channel when the stream is flowing. 11 Background site at the edge of the Kiowa Creek floodplain; about 600 meters north of site 8. 12 Alluvial sediment site in dry bed of Kiowa Creek downstream (north) of confluence of the dry wash with Kiowa Creek. 13 Alluvial sediment site in dry bed of Kiowa Creek upstream (south) of confluence of the dry wash with Kiowa Creek. Table 1b. Sample Descriptions. Site #/ Sample: Depth Sample Description 1 – Surface soil Top 1" of soil Very coarse to fine sand on top of low stream terrace; abundant quartz and orthoclase; dry. 1 – Deep soil 12" to 14" Very coarse to fine sand; abundant quartz and orthoclase; damp – darker color due to moisture. 2 – Surface soil Top 1" of soil Medium gray, course to fine sand mixed with fine, dark organic matter – A-horizon soil; dry. 2 – Deep soil 10" to 12" Dark gray, poorly sorted course to fine sand and silt – A-horizon soil; dry. 3 – Surface soil Top 1" of soil Very dark gray, medium sand to silt; rich in organic matter and visible lead pellets; A-horizon. 3 – Deep soil 12" to 14" Very dark gray, medium sand to silt; rich in organic matter – A-horizon soil; slightly moist. 4 – Surface soil Top 1" of soil Medium gray, medium-grained sand to silt; rich in organic matter – A- horizon; dry. 4 – Deep soil 11" to 12" Mottled medium to light gray, medium-grained sand to silt – B-horizon; dry. 5 – Surface soil Top 1" of soil Compact, grayish-light brown, medium to very fine sand and silt – A- horizon; dry. 5 – Deep soil 10" to 12" Compact, grayish-light brown, medium to very fine sand and silt – A-horizon; dry. 6 – Surface soil Top 1" of soil Medium to light gray, coarse sand to silt – A-horizon; decaying pine needles; dry. 6 – Deep soil 10" to 12" Dark-gray to grayish-brown, coarse sand to silt – A-horizon; dry. 7 – Surface soil Top 1" of soil Very dark gray, coarse sand to silt, rich in organic matter – A-horizon; slightly damp. 7 – Deep soil 10" to 12" Medium tan, very coarse sand to silt, with no organic matter – B-horizon; moist. 8 – Surface sediment . Top 1" of soil Light grayish-tan, very coarse to fine sand; abundant quartz and orthoclase; alluvial sediment; no organic matter; damp. 8 – Deep sediment . 8" to 10" Light grayish-tan, very coarse to fine sand; abundant quartz and orthoclase; alluvial sediment; no organic matter; very damp. Collected one inch above base of channel scour in the profile. 11 – Surface soil Top 1" of soil Dark grayish-brown, medium sand to silt – A-horizon; slightly moist. 11 – Deep soil 8" to 10" Dark grayish-brown, medium sand to silt – A-horizon; slightly moist. 12 – Sediment . 0" to 8" Light grayish-brown, very coarse to fine sand; abundant quartz and orthoclase; alluvial sediment. 13 – Sediment 0" to 8" Medium grayish-brown, medium to fine sand and silt; very little orthoclase; alluvial sediment. Deeper soil samples were sieved for the minus-80-mesh fraction to concentrate the portion of the sample material with the most surface area per unit weight. When transported hydromorphically, heavy metals like lead will be adsorbed or precipitated onto mineral surfaces in soil or sediment. Thus, smaller size fractions of soil are more sensitive indicators of hydromorphic heavy metal transport. Each prepared sample was digested using a hot mixture of concentrated nitric acid and perchloric acid. This procedure is very effective for dissolving metallic lead, lead oxides, and lead minerals. It will also completely dissolve oxide coatings due to weathering and will digest much of the weathering rinds on mineral grains in soil. Any organic matter in the sample is totally digested. This digestion will leach lead from silicate minerals such as sericite and orthoclase feldspar. However, lead from silicate minerals is part of the natural background in the area, and is not related to the environmental problem being studied. Hydrofluoric acid was not included in the process, because lead fluoride could have precipitated in samples with high lead concentrations, erroneously reducing the lead values. Sulfuric acid should not be used to digest lead samples, since lead sulfate is insoluble. Lead determinations in the sample solutions were made by ICP-MS. Results, Observations and Interpretations 1.) Acid Digestion Data: a.) Impact Zone Accumulation of Lead – Acid digestion data for lead in the Sporting Clays Range samples and background samples are summarized in Table 2. Sample Sites 1, 2, and 4 are typical of nearly all the shooting stations on the Sporting Clays Range, in that the targets are shot as they sail through the air. In these cases the lead pellets fall to the ground over a broad area, making it very difficult to find visible lead pellets on the ground. Samples at these sites were literally skimmed off the top one inch of the soil near the back edges of the impact zones in an attempt to accentuate the lead values. Lead concentrations in the surface samples at the shooting stations fall in the same range as the values from the surface samples at the background sites. Therefore, it is very difficult to measure lead accumulation in the soil at nearly all the Impact Zones above natural geochemical background. The one exception is the "running rabbit" target at shooting station 5; i.e. Site 3. These targets roll down a hillside about twenty-five yards in front of the shooting stand. Most of the shots impact an area that is approximately eight yards wide by fifteen yards long. With each shooter firing ten rounds into the center of that area, there is visible accumulation of lead pellets on the surface and in the top one inch of the soil. The surface soil sample taken from the center of the impact zone had visible pellets, and it was measured to contain 3.4% lead, suggesting that regular management of lead at this station is necessary. However, this is such a small impact area that management can be easily accomplished by annually applying pulverized limestone and phosphate. This buffers the soil pH, and it provides abundant carbonate and phosphate to guarantee the precipitation of any lead that might possibly go into solution, preventing its chemical mobility. Table 2. Analytical data for soil and sediment samples from the Sporting Clays Range at the Peaceful Valley Scout Ranch. Total lead analyses of lead concentrations are given in micrograms/gram (parts per million, PPM). Water-extractable lead concentrations are given in nanograms/gram (parts per billion, PPB) Sample: Site: total Pb in soil/sediment (ppm) Water-extractable Pb in soil/sediment (ppb) Soil pH Surface Soil – Site01 Sporting Clays Station 1 3.78 1.8 6.9 Surface Soil – Site02 Sporting Clays Station 4 11.90 4.5 6.3 Surface Soil – Site03 Sporting Clays Station 5 33,800.00 121.0 7.1 Surface Soil – Site04 Sporting Clays Station 8 11.70 12.3 5.9 Surface Soil – Site05 Background 9.52 11.1 6.8 Surface Soil – Site06 Background 6.19 11.7 5.9 Surface Soil – Site07 Background 21.60 16.2 6.5 Surface Soil – Site11 Background 15.50 13.6 7.0 Deep Soil – Site01 Sporting Clays Station 1 28.20 11.2 6.5 Deep Soil – Site02 Sporting Clays Station 4 12.90 9.2 6.4 Deep Soil – Site03 Sporting Clays Station 5 15.00 6.1 6.6 Deep Soil – Site04 Sporting Clays Station 8 8.60 5.5 6.1 Deep Soil – Site05 Background 16.40 10.2 6.6 Deep Soil – Site06 Background 11.10 13.2 6.2 Deep Soil – Site07 Background 15.70 17.4 5.1 Deep Soil – Site11 Background 20.40 11.1 6.4 Surface Sediment – Site08 Alluvial sediment at mouth of wash 3.30 2.9 7.4 Deep Sediment – Site08 Alluvial sediment at mouth of wash 717.00 2.0 6.4 Stream Sediment – Site12 Kiowa Creek sediment below range 3.04 8.4 6.6 Stream Sediment – Site13 Kiowa Creek sediment above range 6.93 6.5 7.1 b.) Geochemical Mobility of Lead – As stated above, deeper soil samples were collected to test for the vertical migration of lead in the soil at the shooting stations. These samples were processed to accentuate the effects of any hydromorphic geochemical transport of lead downward. There is no difference in the lead content between the deeper soil samples collected in the Impact Zones and samples collected at Background Sites. Even at Site 3 (i.e. the running rabbit), where the lead concentration at the surface is much greater than the deeper soil, there is no indication whatsoever of the higher lead concentration at the surface being carried down into the soil. In fact, the lead content in the deeper soil at Site 3 is essentially identical to the value at the background site 100 meters to the west; i.e. Site 7, where there has been no shooting activity. In summary, no evidence was found of lead migrating by hydromorphic geochemical processes downward in the soil. The most likely location for evidence of geochemical migration is at Site 3, and none was found. Therefore, it is highly improbable that lead will be chemically transported into groundwater or off the range, and the suggested management practices would prevent even this small risk. c.) Mechanical Mobility of Lead – Lead pellets can be transported as a solid by flowing water. Denser and coarser mineral grains are dragged along the bottom of the stream by friction with the running water. This is referred to as the bed load of a stream. Due to its high density, metallic lead behaves in a stream or river like a heavy mineral such as gold. Heavy minerals (and lead pellets) concentrate where a high energy current first slows down. They settle to the bottom first, and lighter material settles over them. Lead analyses of sediment in the bed of the wash, at the point where it reaches the flood plain of Kiowa Creek, are shown in Table 2. Site 8 is located in the dry wash at a point where it exits the draw and crosses onto the floodplain of Kiowa Creek. It is two hundred yards downstream from Sporting Clays Station 1, where lead pellets fall onto the bed of the dry wash. A surface sample taken in the center of the channel at Site 8 had a lead concentration comparable to background. However, the deeper sediment sample, collected at the bottom of a channel scour, contains 717 parts per million lead, the amount of lead (0.0842g) equivalent to one No. 8 lead shot pellet being present in the sample. This is evidence that intermittent runoff in the wash is beginning to push lead pellets that fall onto the bed of the dry wash down the channel. However, at present this does not constitute a hazard. Lead analyses of sediment samples from the bed of Kiowa Creek show that there is no appreciable difference between the sediment upstream from the shooting facility and sediment downstream. In fact, analyses of both of these samples produced lead results that are quite low. There is no evidence that lead from the Sporting Clays Range is impacting Kiowa Creek. 2.) Water Extractable Lead: Lead that can be extracted from a soil by soaking the soil in de-ionized water occurs in two forms; 1) soluble complexes of lead formed with humic acids, and 2) colloidal-sized lead dust that could be formed by impacting lead against a hard surface. Colloidal particles are so small that they can stay suspended in a liquid. (Milk is an example.) Water-extractable lead in these soils and sediments are given in Table 2. Natural soils commonly have water-extractable lead values between five and forty parts-per-billion ("ppb" or nanograms/gram). In some natural soils, water-extractable lead has been observed above one hundred ppb. Extractable lead is quite low in all the soil and sediment samples, except for the surface soil at the running rabbit station, Site 3. The value for Site 3, although ten-times higher than the rest of the samples, would not translate into an appreciable rate of transport of lead. It is not reflected in the deeper soil sample at Site 3. This relatively small amount of extractable lead in the surface layer would be mitigated with the simple steps that have already been described for Site 3. Data for water-extractable lead confirm the conclusion that lead is not being mobilized in solution through geochemical processes on the Sporting Clays Range. 3.) Soil pH Data: Soil pH measurements for these soil samples mostly fall into a slightly acid to slightly alkaline range (Table 2). These readings are a little more acidic than are normal for the semi-arid high plains of Western North America. This is probably related to the number of pine trees covering the study area. For instance, at every sample site where pine trees surrounded the site, the soil pH is 6.5 or lower. At Sites 4 and 6, where a thin mat of pine needles lay on the surface, the soil pH is 5.9. In a slightly acid to slightly alkaline soil, a lead ion in solution in water passing through that soil will quickly precipitate as lead carbonate or lead oxide on a mineral grain surface in the soil (2, 3). These precipitates are extremely insoluble (2, 3, 5), rendering lead chemically immobile. The U.S. Environmental Protection Agency lists the ideal soil pH range for a shooting range berm as 6.5 to 8.5 (3). Two of the Impact Zones have values as much as 0.6 pH units below that ideal range. However, insoluble lead carbonate and lead phosphate have been observed to form in soils with pH values as low as 4.8 (2). In summary, there is no evidence that soluble lead complexes are forming in the slightly more acidic soils on the Sporting Clays Range, as is indicated by the water-extractable lead values. Where the soil pH is below 6.5, treating the Impact zone with pulverized limestone to buffer the pH and with phosphate fertilizer will insure that lead is immobilized (1, 2, 3). Discussion The Sporting Clays Range is only a little over a year old, and it has been used so little that at most shooting stations it is difficult to detect accumulation of lead above background on the surface of the soil. No significant differences were found in lead content between the soils at the surface at three of the Impact Zones and the Background Sites. No evidence was found of geochemical mobility of lead on the Sporting Clays Range. Instead, the data show that lead is immobile. Where lead accumulation was found in the Impact Zone at Site 3, it is not migrating downward in the soil profile, and water-extractable lead is not at a level that would indicate significant mobility. Therefore, the evidence indicates that lead is not migrating downward and contaminating groundwater. Although the soil pH is slightly more acidic at some of the sample sites than the ideal pH range for shooting ranges (3), the soil pH is still within a range where naturally occurring carbon dioxide and phosphate in the soil would immobilize lead as insoluble minerals. This immobilization effect can be enhanced in the Impact Zones by spreading pulverized limestone and phosphate on the soil. Limestone will buffer the pH of the soil, and both the limestone and phosphorus would provide mineral anions to the soil to insure the precipitation of any lead that might possibly go into solution. Because lead pellets behave like heavy minerals in a drainage, the rate of movement down the dry wash will be slow. A sample from the bottom of a sediment scour in the channel of the dry wash contained the lead concentration equivalent to one No. 8 bird shot pellet. Although lead pellets will be carried down the drainage channel in larger numbers over time, their high density makes it very easy to contain them by reducing the velocity of the runoff at some point in the lower part of the wash. This could be done with a small containment dam. The location of the Sporting Clays Range in a canyon and the surrounding topography generally dispel any concern that lead pellets from the range could fall into Kiowa Creek. Supporting this observation, no evidence was found of lead contamination in the Kiowa Creek sediment samples. Therefore, there is no evidence that lead from the Sporting Clays Range has impacted Kiowa Creek. In summary, all the data from the Sporting Clays Range confirm a general statement that the EPA makes on one of their web pages: "What happens to lead when it is released to the environment? When released to land, lead binds to soils and does not migrate to groundwater. In water, it binds to sediments." (http://www.epa.gov/safewater/contaminants/dw_contamfs/lead.html) References Colorado Department of Public Health and Environment, 2005, Corrective Action at Outdoor Shooting Ranges Guidance Document. Hazardous Materials and Waste Management Division, January, 12 p. Ma, L.Q., Hardison, D.W., Harris, W.G., Cao, X., Zhou, Q., 2007, Effects of Soil Property and Soil Amendment on Weathering of Abraded Metallic Pb in Shooting Ranges. Water, Air, and Soil Pollution; 178:297-307. U.S. Environmental Protection Agency, 2005, Best Management Practices for Lead at Outdoor Shooting Ranges. EPA-902-B-01-001. Region 2. June. 103 p. Hampel, C.A. (ed.), 1968, Encyclopedia of the Chemical Elements. Reinhold, New York, 849 p. Cao, Xinde, Ma,, Lena Q., Chen, Ming, Hardison, Jr., Donald W., and Harris, Willie G., 2003, Weathering of Lead Bullets and Their Environmental Effects at Outdoor Shooting Ranges. Journal of Environmental Quality 32, pp. 526-534.Chemical Rubber Company, 1988, Handbook of Chemistry and Physics. CRC Press, Cleveland, OH. U.S. Environmental Protection Agency, 2003, TRW Recommendations for Performing Human Health Risk Analysis on Small Arms Shooting Ranges. OSWER #9285.7-37, March. Krauskopf, Konrad B., 1967, Introduction to Geochemistry. McGraw-Hill, 721 p. Goldschmidt, V.M., 1958, Geochemistry. Oxford University Press, Oxford, pp. 398-408. Hurlbut, C.S., 1966, Dana's Manual of Mineralogy. John Wiley and Sons, New York, 609 p. Chemical Rubber Company, 1988, Handbook of Chemistry and Physics. CRC Press, Cleveland, OH. Wedepohl, K.H., 1978, Handbook of Geochemistry. Springer, Berlin, Vol. II/5, Section 82, C1-M3. Larsen, L.S., Baber, T.G., Wesswick, E.L., McCoy, D.E., and Harman, J.B., 1966, Soil Survey of Elbert County, Colorado, Eastern Part. U.S. Dept. of Agriculture, Soil conversation Service: Series 1960, No. 31, pp. 76.