Investigate Assess and Implement Water Quality Monitoring Solutions at Marine Corps Air Ground Compact Center (MCAGCC) Twentynine Palms California

Albert Pollack; Jody Lipps; Gregory Headington; Battelle Memorial Institute Environmental Restoration Department
2008-04-01
US Army Corp of Engineers; Marine Corps Air Ground Combat Center Plessie Ellitt Natural Resources/Environmental Affairs

During this study several water quality/monitoring issues were addressed at MCAGCC. They included: (1) identify, procure, install, and evaluate drinking water sampling stations for potable water quality monitoring at various locations in the MCAGCC distribution system; (2) conduct an industrial wastewater monitoring program to implement an Industrial Pretreatment Monitoring Program; (3) establish and evaluate a passive, storm water sampler in the storm water collection system at MCAGCC; and (4) review, recommend and evaluate dust control/road stabilization agents on training/range access roads at MCAGCC to determine their effectiveness to mitigate dust.

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The views, opinions, and/or findings contained in this report are those of the authors and should not be construed as an official Department of the Army position, policy, or decision, unless so designated by other documentation.

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Section 6.0: INVESTIGATION OF DUST/EROSION CONTROL OPTIONS FOR TRAINING/RANGE ACCESS ROADS

The unpaved roads at MCAGCC are a major source of particulate air pollution at the installation. The EPA indicates that “unpaved roads produce almost five times as much particulate matter as construction activities or wind erosion” (Gesford and Anderson, 2006).  At MCAGCC, the combination of the sandy indigenous soil, very low soil moisture, and military vehicle traffic result in dust issues. Dust control is recognized by MCAGCC and is typically addressed by watering the unimproved roads with potable or non-potable water. However, the continued use of trucks to haul and spray the water is costly in terms of fuel usage, manpower, and impacts the limited water resources at the Base.

To address this ongoing issue, a work element to review, recommend, and evaluate up to two options for dust control/road stabilization on MCAGCC’s training/range access roads was included in this task. Successful dust control would also reduce soil erosion and storm water runoff with heavy soil loadings.

6.1 Dust/Erosion Control Options

Several options exist for the control of dust on MCAGCC’s training/range access roads. Operational changes such as limiting traffic, reducing vehicle speed, or controlling vehicle weights can reduce dust generation. However, these are not viable options as they would severely impact the training mission at MCAGCC. Paving the roads is possible for small sections in sensitive areas and has been done at MCAGCC on a limited basis.  However, the specifications (8 to 10 inches of concrete) for roads suitable for heavy, tracked vehicles results in an extremely expensive dust control option.  The use of water to control dust is a standard approach for desert environments and is currently being employed on a large scale at MCAGCC. However, this technique is a short-term control due to rapid evaporation rates in the desert and typically has to be done on a daily basis. As a result, ongoing costs are incurred for a substantial manpower force and the necessary tanker equipment when using this approach. The use of water for dust control will likely continue at MCAGGC. However, alternatives which are longer lasting and more cost effective than daily water applications would be beneficial at MCAGCC.

6.2 Available Dust Control Agents

Several types of dust control options are currently in use on civilian roads (Gesford and Anderson, 2006).  Some commonly used materials are presented.

6.2.1 Calcium and Magnesium Chloride Solutions. Calcium and magnesium chloride solutions have been used for dust control because they can reduce water evaporation by a factor of 3.4 to 3.1, respectively, and they begin to absorb moisture from the atmosphere at 29% and 32% relative humidity, respectively. These are well suited for use in more temperate areas with elevated humidity but are not suitable for desert environments such as those found at MCAGCC. Additionally, chloride solutions may pose a concern for environmental impacts, especially during runoff from storm events.

6.2.2 Brines. Brines are typically a byproduct of gas production wells. Primarily chloride based, they offer the same hydroscopic properties as other salt solutions in that they draw moisture from the atmosphere and thereby bind dust particles. However, they are generally expensive, can be contaminated with oils, heavy metals, or other materials, and require extensive quality control before being used.

6.2.3 Lignin Derivatives. Lignins are a byproduct of the paper industry and their sticky nature is what binds and controls dust particles. However, it is generally acidic, foul smelling when spread, and sticks to vehicles. Lignins can be slippery when wet and brittle when dry and although they have been used for dust control, they are not commonly used.

6.2.4 Asphalt Emulsions. A combination of asphalt, water, and an emulsifier allows for the application of asphalt in a liquid form to roads. As the water evaporates, the asphalt is left behind. The asphalt essentially glues the soil particles together and with repeated use can form a hard crust. It is not well suited for extremely hot environments because the material can return to a semi-liquefied state that aggressively sticks to vehicles as they are driven over the treated surface.

6.2.5 Resins, Enzymes, Oils. Many manufacturing byproducts have been used in attempts to control dust. These include vegetable oils, soybean soapstocks, and sugar beet extracts. In most cases, as long as the material has binding, persistent characteristics, it can be spread and used to hold dust in place. The use of these byproducts is typically done on a site-specific approach and close to where the material is being generated so as to reduce shipping costs.

6.2.6 Specialized Dust Control Agents. The need for specific dust control/road stabilizing agents has resulted in a dust control industry. As opposed to the use of manufacturing byproducts simply to use them and forgo disposal costs, these agents are specifically formulated for specific soils, environmental conditions, and vehicle type use. They may still be manufacturing byproducts, but they receive higher quality control and may contain additives that enhance their dust control capabilities. They can be synthetic organic fluids, polymer and copolymer emulsions, or combinations of both and provide either simple dust control or aggressively stabilized the soils to the point of where a hard road surface is formed. These materials are typically more expensive than simple brines, asphalt emulsions, and oils but they are generally better suited for specific applications.

With the desert conditions at MCAGCC and the use of heavy, tracked and wheeled vehicles, it was determined that the commercially available specialized dust control agents would be investigated during this task.

6.3 Selecting Dust Control Agents to Evaluate

An internet search for dust control agents that had been used specifically for military applications (roads, airfields, tank trails, etc.) and/or mining haul roads were targeted during the searches. Two manufacturers were identified that provide dust control agents for heavy-vehicle road use. They are Midwest Industries Supply, Inc. (www.midwestind.com) and Soilworks, LLC (www.soilworks.com). These manufacturers specifically stated that their products would withstand military vehicle traffic in a desert environment.

Midwest Industries Supply, Inc. provides two materials that appeared to be appropriate for use on MCAGCC roads.  These products are Soil-Sement® and EnviroKleen®.

Soil-Sement® is a polymeric material that when applied, binds the soil together. As a soil stabilizer it forms a hard road surface that essentially no longer has dust associated with it. When properly applied, it forms a road base that reportedly can support both rubber tired and tracked military vehicles. The material is shipped as a concentrate that is added to water and then applied to the road surface. This material has been approved for use by several State of California Regulatory Agencies and reportedly does not pose any environmental hazard for its use. A quote received in May 2005 indicated that Soil-Sement®, with a topical application rate of 1 gallon concentrate per 35 ft2 of surface area, would be appropriate for a heavy traffic area. Cost, at that time, for delivery and application was quoted at $3.90 per gallon.

A second product offered by Midwest Industries Supply, Inc. for dust control is EnviroKleen®.  This synthetic material does not stabilize soil by forming a hard crust but persistently binds the soil particles together so that dust cannot be generated. A topical application rate of 1 gallon per 25 ft2 of surface area was recommended for severe traffic conditions with distressed soil types. Cost for delivery and application (in May 2005) was $5.90 per gallon. Reportedly, EnviroKleen® has no toxic properties and is suitable for use in most environments.

Soilworks, LLC offers similar types of materials in their Soiltac® and Durasoil® products. Soiltac® is a vinyl copolymer concentrate that, when mixed with water, forms an emulsion that is applied to the road bed. Upon curing, a hard road surface is produced which is similar in appearance to a concrete road surface. Representatives at Soilworks, LLC did not recommend the use of this material for tracked military vehicles unless a very hard road bed was first established below the treated soil.  This was required to support the stabilized soil or otherwise the treated surface would crack under the cutting action of the tracked vehicles. This type of surface was recommended for heavy, tired vehicles. A May 2005 quote for Soiltac® was $8.00 per gallon and did not include delivery costs or its application. Application rates depend on the nature of the soil and type of vehicle traffic. For heavy vehicle traffic the Soiltac® content in solution is generally approximately 0.04 gallons per square foot.  The Material Safety Data Sheet (MSDS) for Soiltac® did not indicate any hazards associated with its use.

A second product offered by Soilworks, LLC is Durasoil®.  This synthetic organic dust control agent does not form a hard surface but, just as EnviroKleen®, it persists on the soil and binds the dust particles so that they cannot become airborne. This material was recommended for both tired and tracked vehicle traffic. Durasoil® is applied as the concentrate is received from the manufacturer. It is topically sprayed onto the road with minimal or no road preparation. For unpaved tank trail dust control an application rate of 0.05 gallons per square foot is recommended. A May 2005 quote provided by Soilworks, LLC was $4.75 per gallon of Durasoil® and did not include delivery charges or its application. The MSDS for Durasoil® did not indicate any hazardous nature for this material.

Following discussions with the POC, it was indicated that Soil-Sement® had been used at MCAGCC, so its ability to control dust was already determined. It was recommended that the Soilworks, LLC products be evaluated so that the Base could expand their understanding of available dust control agents for use at MCAGCC. Both Soiltac® and Durasoil® would be tested during the evaluation. Product information and the MSDS sheets for both of these amendments are provided in Appendix D-1.

6.4 Test and Evaluation Plan

The test and evaluation of the two dust control agents would be conducted at two locations at MCAGCC. The first site was a heavily traveled tank trail located above the paved road from Del Valle to the Small Arms Ranges on Rifle Range Road. This road has both tired wheel and tracked vehicle activity and is a main entry way from Mainside to the Range Complex at MCAGCC. The road surface is an aggregate base of compacted gravel and native soil. Visual observations indicated that large plumes of dust were being generated on this road as military vehicles left the concrete tank trail and traveled over the dirt road.  This site was called the Tank Trail Test Site.

Conversations with the technical representative at Soilworks, LLC resulted in the decision to use only Durasoil® at this test site. The existing road bed was compacted but without additional road preparations it was not expected to provide a firm enough subsurface for tracked vehicles such as the Light-Armored Vehicles (LAVs) and tank traffic. Using Soiltac® for this application would have resulted in the tracked vehicles breaking through the cured material and that would compromise the integrity of the amendment.

At the Tank Trail Test Site, two 300-ft plots would be treated with Durasoil® for the entire width of the road bed, 24 ft. No road preparations would be performed before the dust control agent was applied to the road. Two application rates (12 ft2 per gallon and 24 ft2 per gallon) would be made to the soil to determine what rate provides adequate dust control.

The second test site was located at the Combined Arms Military Operations in Urban Terrain (CAMOUT) facility.  This road has only tired vehicles traveling over it.  A total of ~900 linear feet of road surface would be treated at the CAMOUT. Two 300 ft sections would be prepared for application of Soiltac® and one 300 ft section of road would have an application of Durasoil®. The entire width of the road, 20 ft, would be treated. For the Soiltac® to work properly, the road bed would be graded to remove any thick layers of loose soil. For the Durasoil®, no road preparation was required.  Utilizing this approach, it would be possible to determine if both amendments are suitable for tired traffic and also determine how well they tolerate the desert environment.

Soil characterization would be done to qualify the nature of the soil and provide information on the best application rates.

6.5 Soil Characterization and Monitoring Activities

Soil samples were collected at both test sites and submitted for particle size and compaction strength analysis. Ten pounds of soil were collected from each of the two test sites. This soil was shipped to CTL Engineering, Inc., in Columbus, Ohio, for analysis. Both soils were submitted for grain size analysis with hydrometer, Atterberg limits, specific gravity, and pH. A second sample (weighing 50 pounds) was collected from the CAMOUT site and submitted to CTL Engineering for a Modified Proctor Test (ASTM D1557) so that maximum dry density of the soil could be determined for compaction calculations. This information is required by the manufacturer to determine the proper application rate for the Soiltac® amendment at the CAMOUT. The Tank Trail test site soil was classified as sand and gravel with traces of silt and clay.  While the CAMOUT test site soil was classified as sandy with traces of gravel and silt. In both cases, soil moisture was < 2% which is extremely dry. Data from these tests are provided in Appendix D-2.

To quantify the performance of the dust control amendments, three measurements were needed. Those were: particle measurements in ambient air, wind speed, and a vehicle counter. The particle counter used was a Thermo Electron Corporation Model pDR-1000 passive air sampler. This instrument provides real time particulate measurements ranging from 0.001 milligrams per cubic meter (mg/m3) to 400 mg/m3. This handheld instrument would allow us to compare the dust being generated by vehicles as they drove from the untreated to the treated road surfaces. A handheld anemometer was used to determine the wind speed when particulate samples were being collected. The handheld unit was an EXTECH Instrument, Mini Thermo Anemometer, Model #45158.  This instrument permitted the real time measurement of wind speed as particulate measurements were made. Finally, two, TRAFx Research Ltd. Magnetic Vehicle Counters were procured to allow the unattended counting of the number of vehicles that traveled over the treated roads.

6.6 Study and Site Preparations

Prior to conducting the dust control applications, estimates of the amount of Soiltac® and Durasoil® needed were made.  In order to treat approximately 9,600 ft2 of soil at a heavy rate and light rate, a total of 550 gallons of Soiltac® was needed. For the treatment of 18,000 ft2 of road surface at rates ranging from 10 to 30 ft2 per gallon, a total of 1,075 gallons of Durasoil® was required. These materials were ordered from Soilworks, LLC and delivered to MCAGCC.

The two test sites were marked with signage to indicate that a dust control study was in progress.  Dig permits were applied for and received before the sign posts were installed.

Because of the need for road preparation before Soiltac®  could be applied, a purchased service agreement was established with a local contractor to: (1) grade approximately 500 yards of existing road bed; (2) establish a 6 in loose surface into which the Soiltac® would be mixed; (3) provide a water truck with spray bar for applying an emulsion of Soiltac®/water to the road; (4) provide a tiller to incorporate the Soiltac® into the top 6 inches of soil; (5) provide a pneumatic roller to compact the treated soil; and (6) provide a top coating of Soiltac® to the compacted soil. No road preparation was required for the Durasoil® application.  The only equipment for its application was a trash pump and fire hose.

Conversations with representatives from Soilworks, LLC resulted in their decision to provide on-site technical support during the dust control agent applications at no cost to MCAGCC.

6.7 Field Notes during Dust Suppressant and Soil Stabilizer Applications

The following is a summary of field notes associated with the application of Durasoil® and Soiltac® soil amendments at the MCAGCC test sites.

6.7.1 Preparations for Durasoil® Application, 23 April 2007 Field Notes. Field support staff measured and marked off 200 running yards of the gravel roadway that military tracked vehicles and large trucks use to access the training ranges. The roads’ width measures approximately 24 ft and has raised shoulders on each side.  This run of road was referred to as the Tank Trail during this demonstration. After completing this task, staff returned to the Field Office and inventoried the products that were purchased for our demonstration from Soilworks, LLC. Available for application was:

  • 4 each – 275 gallon totes of Durasoil®
  • 2 each – 275 gallon totes of Soiltac®

A representative from Soilworks, LLC was on site to assist with the application of the materials and indicated that the totes actually have a capacity of approximately 290 gallons. Staff returned to Tank Trail with two 4 × 4 wooden posts and water for digging post holes for posting the study site. One sign post also provided a place to secure the vehicle counter which records changes in magnetic field and permits documenting the number of vehicles using the test plots. The 4 × 4 posts were installed, study signs were attached, and the lockable counter box was installed.

Durasoil® was scheduled for application to the Tank Trail plots in the morning with a trash pump and fire nozzle.

6.7.2 CAMOUT Inspection and Durasoil® Application at Tank Trail, 24 April 2007 Field Notes. The second test site at the CAMOUT installation where three plots will be constructed in native material was inspected. The subcontractor, McMurrays Grading and Engineering, was already preparing the road surface for the applications.

The road preparation was initiated by grading off the loose material down to the solid base. At this site, two plots for Soiltac® application were to be done, one with a heavy application rate and one with a light application rate.  This was done to evaluate how each holds up to the vehicle traffic and would make it possible to determine the most cost-effective application rate for these types of soils. A third plot, treated with Durasoil®, was to be constructed between the two Soiltac® plots, which would allow an area for the water trucks, grader and compactor to turnaround during the construction. The Durasoil® plot measured 20´ X 300´ (600 square feet).

We discussed with the grading contractor the lack of a soil disc for mixing and spoke to Soilworks, LLC about using the grader blade for mixing the product.  Soilworks agreed that it should be acceptable as long as thorough mixing takes place. It was decided that product application would be performed on April 25, 2007. The grading subcontractor continued with preparation of the CAMOUT roadway.

Staff then returned to Field Trailer and proceeded with the Durasoil® application. Application activities were started on the Tank Trail at 1200 hours.  Equipment used included:

  • pick-up truck
  • utility trailer to carry product totes
  • trash pump
  • 2 inch hose and fire nozzle.

Application rates were heavy (12.5 ft2 per gallon) on Plot #1 and light (24.5 ft2 per gallon) on Plot #2.

The Tank Trail required no road preparation for the application of Durasoil®.  The neat liquid was applied by pumping product directly onto the test plots and slowly moving the truck/trailer up the roadway. One operator slowly drove the truck as the second operator ran the pump and hose. Two passes were made across the heavy application plot, which were finished at 1305 hours.  There was approximately 575 gallons of Durasoil® applied to Plot #1. Plot #2 was treated in the same manner as Plot #1, except at a 50% lower application rate. The application started at 1347 hours and was completed at 1405 hours. Following this application, staff returned to the Field Office, cleaned the equipment thoroughly with water, and finalized planning/loading of materials for the CAMOUT test area applications.

The Tank Trail test site was immediately opened for all military vehicle use by MCAGCC.

6.7.3 Soiltac® Application at CAMOUT Test Site, 25 April 2007 Field Notes. After arriving at the CAMOUT test site, preparations were made to apply the Soiltac® soil stabilizer and the Durasoil® dust suppressor. At 0800 hours, 135 gallons of Soiltac® concentrate were added into a truck containing 3,565 gallons of water. The water truck was driven around the site for mixing. At 0830 hours, this mixture was applied with a spray bar at a coverage rate of 35 ft2 per gallon of solution and integrated into the soil at the furthest most plot from the road split. A Cat 140 H grader followed the water truck and blended the Soiltac® into the soil with the grader blade. The water truck and grader alternated applying product and mixing it to the roadway plot.  At 0906 hours the water truck was empty and the grader continued working the road surface to obtain even mixing. At 0933 hours grading/mixing was completed and compaction of the amended soil was begun with a Caterpillar CS-563E vibratory roller.

At 1010 hours, preparations began for applying a heavy application rate of Soiltac® at a rate of 15 ft2 per gallon. The Soiltac® dilutions were done by lifting the Soiltac® tote over the manhole opening of the water truck, then it was gravity fed into the water tank via the valve on the bottom of the tote. The totes were graduated on the sides making it was easy to meter in the required amount of soil stabilizer.  For this application, 320 gallons of Soiltac® were added to the water tank which already contained 3,500 gallons of water. The addition of Soiltac® to the water was completed at 1035 hours, at which time the water truck was driven along an adjacent dirt road for thorough mixing.

At 1040 hours the Soiltac®/water mixing was complete and the application to Plot #2 was begun. The grader moved some loose material back onto the roadway prior to liquid application so that there was about a 6-inch bed of soil for the Soiltac® to be integrated into. At 1114 hours the Soiltac® application at Plot #2 was completed. Immediately after the solution of Soiltac® was emptied from the water truck, a thorough cleaning of the tank and all plumbing that had been exposed to the mixture was conducted. This is extremely important, as the Soiltac® solution hardens over time and will plug any piping/spray bars that are not thoroughly cleaned. The water truck was rinsed with 2 to 3 tanks of clean water to remove all of the Soiltac® from the tank and its plumbing. At 1143 hours the mixing/grading of the soil was complete and soil compaction was started. Soil compaction of the two test plots was done by 1225 hours. This completed the need for the heavy equipment.  During this effort, the following equipment was used:

  • 1 – Caterpillar CS 563E soil compactor
  • 1 – Caterpillar TH 560B telehandler
  • 2 – 4,000 gallon water trucks
  • 1 – Caterpillar 140H motor grader
  • 2 – Pick-up trucks to transport product

The staff returned to the Field Office where two Soiltac® totes, each containing 50 gallons of Soiltac® concentrate, were loaded onto a 16-ft utility trailer. Water was added to both totes to bring the final volume in each to 250 to 260 gallons. These solutions were to be applied to the Soiltac® test plots at the CAMOUT as the final top coat required to complete the application process. Because of the small volume, the top coat was applied with the trash pump and sprayed onto the test plots.

6.7.4 Soiltac® Top Coating and Durasoil® Application at CAMOUT, 26 April 2007 Field Notes. At 0820 hours, staff arrived at the CAMOUT test site to make the final topical application of Soiltac® to the two test plots.  The plots that were treated the day before had already set well enough that it was possible to drive over them with the pickup truck and trailer as the topical application was made. Some fugitive sand had blown onto the treated roadway overnight, but this did not compromise performing the topical application. The top coating of Plot #1 was initiated at 0835 hours with the trash pump and hose/nozzle and was finished at 0855 hours. The top coating of Plot #2 was started at 0900 hours. For this plot, which had an appreciable slope, the top coat was started at the bottom of the hill which helped with the coverage. A lighter application was made as the top coat was advanced up the hill as some of the Soiltac® ran down the grade and eventually soaked into the treated surface. All of the top coat applications were completed at 0915 hours. This concluded the Soiltac® application process.

At 1008 hours the application of the Durasoil® at the CAMOUT was started. A total of 280 gallons of Durasoil® was sprayed onto the 300´ X 20´ section of roadway, which was between the two Soiltac® plots. The application of the Durasoil® took ten minutes to accomplish and was complete at 1018 hours.

The CAMOUT test site was barricaded so that no vehicular traffic could use the roadbed until the Soiltac® had time to cure. The manufacturer recommended a minimum of 72 hours for the curing process. It was also indicated, the longer the better, as moisture has to be drawn from the soil for the Soiltac® to harden. The desert environment is ideal for using Soiltac®, as the typically dry conditions are conducive to rapid curing.  Soiltac® should not be applied if rain is predicted.  Battelle spoke with the site coordinator about leaving that section of treated roadway closed until at least Monday, April 30, 2007, and this was agreed upon.

This concluded the application of the Durasoil® and Soiltac® at both study sites. During the application of Durasoil® and Soiltac®, digital videos were taken of the activities and these are provided in Appendix D-4.

6.8 Monitoring Results at the Test Sites

In order to quantitatively evaluate the performance of the soil amendments at the two test sites a monitoring program was conducted from April 30, 2007, until June 28, 2007.  Vehicle counting was performed automatically at each test site.  Particulate measurements were made manually to determine if the amendments did reduce dust levels as vehicles passed over the treated areas. Wind speed was recorded since it has a direct bearing on the amount of dust coming off the roads and the distance it is transported from the road. Field notes associated with the observations made at the Tank Trail and the CAMOUT test site are provided in Appendix D-3.

6.8.1 Tank Trail Site Monitoring. Tank Trail site monitoring began on April 30, 2007, immediately after the Durasoil® was applied to the test area. Particulate counts were made during the monitoring program as tanks, LAVs, Humvees, dump trucks, 7-ton military trucks, water trucks, and pickup trucks traveled over the road surface.  A summary of the dust emissions at the Tank Trail test site is shown in Figure 21. Comparatively, dust emissions from vehicular traffic on the untreated road bed were anywhere from 6.6 to 153 times greater than that from the road surface treated with Durasoil®. Wind speeds ranged from 1.4 miles per hour (mph) to 15 mph and they generated a noticeable dust plume from the untreated road that carried particulates several hundred yards down wind of the road bed. Essentially no dust plume was observed for the same vehicles as they traveled over the treated road.

During the 8-week monitoring period, 14,033 vehicles were recorded by the automatic vehicle counter as having traveled over the Tank Trail test site. By the end of the monitoring period wind-blown sand was being deposited on the treated road surface and this was starting to compromise Durasoil’s® ability to control the generation of dust particulates (Figure 22). Even though Duraosil® remained in place and vehicle traffic had no other effect than to work the amendment deeper into the road bed (approximately the top 6 to 8 inches had evidence of Durasoil®), the new sand migrating onto the road bed was beginning to overwhelm the coating capability of the single application of Durasoil®. Conversations with the manufacturer indicated that under these heavy-use and fugitive sand conditions, a second topical application of Durasoil® was recommended.  However, this was not done during the testing.

By the conclusion of the monitoring period the Durasoil® continued to have a positive effect on controlling dust emissions from the Tank Trail test site. However, it was becoming evident that to reduce particulate levels to < 0.10 mg/m3, a maintenance application of Durasoil® would soon be required. Even though dust emissions were controlled by the Durasoil®, it was noted that the typical “washboard” effect was starting to become apparent at this test site. It was not as severe as on remote, unimproved tank trails that do not have any formal road base but slight rippling of the road surface was noted.

6.8.2 CAMOUT Test Site Monitoring. The same monitoring was conducted at the CAMOUT test site. Vehicle traffic on the CAMOUT road was different from the tank trail in as much as no tracked vehicles used this road. All vehicles were tired and included: heavy water trucks, cement trucks, pickup trucks, 18-wheeled vehicles transporting construction materials, dump trucks, and passenger vehicles.

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Figure 21.  Tank Trail Dust Emission Comparison

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Figure 22.  Durasoil® Treated Tank Trail at Conclusion of Monitoring Period

The CAMOUT test site was treated with both Durasoil® and Soiltac®. The Durasoil® performed in a similar manner as at the Tank Trail with the soil remaining loose and dust particles being bound onto the larger soil particles. Soiltac®, being a soil stabilizer, essentially generated a hard road surface that was similar in appearance to a concrete road bed. Essentially no dust came off the Soiltac® treated surface, other than wind-blown sand that had landed on the road and was disturbed by the traffic.

The particulate measurement data from the CAMOUT are depicted in Figure 23. The treated road at the CAMOUT was opened for vehicular use on May 15, 2007. Pairs of data were not collected during every sampling event because of limited vehicle traffic.

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Figure 23.  CAMOUT Test Area Dust Emission Comparison

When data were compared for treated and untreated soil traffic, the untreated road had from 24 to 92 times the particulate emissions than that being generated from the treated road. At no time was a particulate reading of >0.64 mg/m3 recorded for the treated soil. This level of particulate emission is not evident to the naked eye. The Durasoil® and Soiltac® at the CAMOUT test site did not allow for the generation of dust during vehicular traffic.

Over the course of the monitoring period at the CAMOUT test site, a total of 2,680 vehicles were indicated by the vehicle counter. Once again, only tired vehicles used this test road. Some small potting of the Soiltac® road surface was observed but for the most part those imperfections were present when the road bed was initially compacted after the soil stabilizer was applied. At the end of the monitoring period there was no evidence that the Soiltac® treated soil had been degraded through vehicle traffic (Figure 24).

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Figure 24.  CAMOUT Test Site at Conclusion of Monitoring Period

Additionally, there was no evidence of any “washboarding effects” on the stabilized road bed, which is very evident on the untreated roads leading to the CAMOUT. Visually, the Durasoil® treated section at the CAMOUT test site was performing well (Figure 24, Dark Soil Between Soiltac® Treated Areas) at dust suppression until the end of the monitoring period.  Because of the lighter traffic load at this site, the dark Durasoil® treated soil was still evident and had not been affected as much by windblown sand.

Generally at the CAMOUT test site, the Durasoil® and Soiltac® were performing as specified by the manufacturer with dust suppression and road stabilization being maintained after 8-weeks of vehicle use. There was no evidence for a need for a topical application of either amendment at this location at the end of the monitoring period.

6.9 Durasoil® and Soiltac® Application Rates at MCAGCC

Durasoil® was applied at application rates of 12.5 ft2/gal (heavy) and 24 ft2/gal (light) at the Tank Trail test site. Because the two application sites were in contact with each other it was observed during monitoring that the Durasoil® migrated back and forth between the two application points and eventually generated an application rate of ~18 ft2/gallon over the central portion of the test area. There was no visible difference noted between the two application rates. It is therefore recommended that for soil types and vehicle traffic such as those seen at the Tank Trail test area, an application rate of ~18 ft2/gallon of Durasoil® should be suitable for dust suppression at MCAGCC.  It should also be expected that subsequent topical applications of Durasoil® to control blowing sand that migrates onto a treated road surface will be required.

Soiltac® was applied at 13 ft2/gallon (heavy) and 26 ft2/gallon (light) at the CAMOUT test site. The two application rates were separated by the Durasoil® test plot and therefore were independent and no migration of amendment occurred. In both cases, the treated soil remained intact and showed no signs of degradation after seven weeks of use. Therefore, for soil conditions and vehicle use similar to the CAMOUT test site, the lower application rate of 26 ft2/gallon of concentrate seems to be appropriate for soil stabilization at MCAGCC.

6.10 Cost for Dust Control with Durasoil® and Soiltac® Versus Daily Water Applications

It is difficult to extrapolate from the limited test sites to a large-scale dust control project. However, to provide some indication of amendment costs versus the conventional approach of watering roads for dust control it is assumed that a ¼ mile road would be treated and maintained. The costs for the several hundred yards of road treated during this study have been extrapolated to ¼ mile and the quoted costs for dust control by daily watering have been calculated from a proposal for 11 miles of road maintenance.

The costs for dust control using Durasoil® would include the cost of the amendment and the labor to apply the dust suppressant. There are no road preparation costs for Durasoil® and since the material is sprayed directly from shipping totes, no spray truck are required. The General Services Administration (GSA) cost for a Durasoil® is $5.50 per gallon, when purchased in a 275 gallon tote. At an application rate of 18 ft2/gallon, 1,760 gallons of Durasoil® would be required to treat ¼ mile of road. The cost of the Durasoil® would be $9,680. Based upon the labor required to apply the Duraosil® during this study, it is estimated that it would require 8-man hours to apply Durasoil® to a ¼ mile stretch of road. At a labor rate of $100/hour, the labor for the 8 man-hours would be $800. The cost for treating a ¼ mile stretch with Durasoil® would be approximately $10,400 and would reportedly provide dust suppression for up to nine months.  Any secondary topical maintenance applications would cost essentially the same.

The costs for soil stabilization using Soiltac® would be higher than dust control with Durasoil® because of the road surface preparations, incorporation of the amendment into the soil, and the compaction requirements. At an application rate of 26 ft2/gallon, approximately 910 gallons of Soiltac® concentrate would be required. The GSA cost for Soiltac® in 275 gallon totes is $7.00/gallon. Therefore, the Soiltac® cost for ¼ mile of road would be ~$6,370.  The cost for road preparation for 24,000 ft2 was $12,000.  Therefore, the cost of treating ¼ mile with Soiltac® would be approximately $18,370.

Conversations with MCAGCC staff indicated that quotes were received from contractors to perform dust control for 11 miles of unimproved road by spraying the entire length of the road twice daily with water and grading the road one time each month. The proposed cost for this service, which included the vehicles, grading equipment, water trucks, and operators of the equipment was $700K for nine months and a second bid was for $550K for an eight month period. At these rates, the cost per ¼ mile of dust control via daily watering would be in the range of $15,000 for a nine month period. Additionally, if the only available water is potable water, then its use for dust control appears to be an inappropriate use of this limited resource.

Based upon the recommended application rates, the observed costs for amendment applications, and an estimate for long-term dust control via daily watering, it appears that dust suppression with Durasoil® may be a viable alternative to daily watering for dust control at MCAGCC.

6.11 Summary

A commercially available dust suppressant (Durasoil®) and soil stabilizer (Soiltac®) were tested at two locations at MCAGCC. The two test sites were: (1) a Tank Trail with heavy vehicle traffic of military tracked vehicles and military/civilian vehicles equipped with tires; and (2) at a CAMOUT Road used only by vehicles equipped with tires 

Durasoil® is suitable for either tracked or tired vehicles and it was applied at high and low application rates on both roads at MCAGCC. Soiltac® is not designed for tracked vehicles and was applied at two application rates.

Following soil characterization at both test sites, the amendments were applied according to manufacturer recommendations. Durasoil® was sprayed as a concentrate onto the road with no road preparations required. The treated road was opened to traffic immediately after the dust suppressant was applied. Soiltac® was diluted in water, and applied with a water truck and spray bar after the road surface had been graded. The Soiltac® was thoroughly mixed into the upper 6 inches of soil and then compacted to form a hard road surface. Following a final dress coating, the Soiltac® treated soil was allowed to cure for 19 days before traffic was diverted onto the road surface.

The monitoring of particulate emissions from the treated and untreated road surfaces was conducted over an eight week period. Data indicate that dust emissions from vehicular traffic on the untreated road bed were anywhere from 6.6 to 153 times greater than from the road surface treated with Durasoil®.  Similarly, data were collected at the Soiltac® test area and the untreated road generated from 24 to 92 times the particulate emissions than that being generated from the treated road. In both cases, the amendments substantially reduced dust emissions when compared to no dust control.

It was determined that the lower application rates that were used for both Durasoil® and Soiltac® were suitable for use at MCAGCC for the locations tested. An application rate of 18 ft2/gallon of Durasoil® concentrate provided dust control over an eight week period and the only degradation was attributed to wind-blown sand that was migrating onto the treated surface and subsequently diluting the amendments dust control capabilities. A light topical application of Durasoil® would have addressed this situation. A Soiltac® application rate of 26 ft2/gallon of concentrate (which would be diluted in water at a ratio of 135 gallons of Soiltac® added into ~3,500 gallons of water) was suitable to treat a road surface that had been properly prepared. This application rate generated a durable, hard surface that did not fail under the weight of cement trucks, water trucks, and 18-wheeled tractor trailers.

The estimated costs associated with applying these amendments were calculated and compared with daily watering and monthly grading. For ¼ mile stretches of road, daily watering and monthly grading would cost approximately $15,000 for a nine month period. The cost of a Durasoil® application for ¼ mile and with a reported lifetime of nine months would be approximately $10,400. To treat ¼ mile with Soiltac® would cost approximately $18,370. Based upon these cost estimates it appears that commercially available dust suppressants and soil stabilizers may be cost competitive with daily watering efforts.

The commercially available dust suppressant and soil stabilizer that were tested at MCAGCC appear to have performed as advertised. When applied as recommended by the manufacturer, they substantially reduced particulate emissions from military and commercial vehicle traffic over unimproved roads and appear to offer an alternative to daily watering activities currently being used at MCAGCC.

It is recommended that these alternatives be considered before continuing to use the limited water resources for dust control at MCAGCC.

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