Evaluation of Water Quality Impacts from Dust Suppressants

By David Reisman; Karen Irwin; Rodney Langston; Jo Crumbaker; Fred Hall; William Kemner; Dr. Ed Beighley
2011-11-07
Clark County DAQEM; Maricopa County DAQEM; QSEM Solutions; San Diego State University; U.S. Environmental Protection Agency

Objectives

  • Determine the water quality impacts of each dust suppressant in a simulated real world environment
  • Focus on products typically used in the desert Southwest
  • Focus on construction activity, as opposed to road or pile surface stability

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Table: Suppressants Selected for Study

Soil Selection Criteria

  • No visible contamination
  • Native land, no farming/industrial history
  • Normal soil range of metals
    • 6010 test for metals
    • 7471 test for Mercury

Soils Selected

  • Clark County AQMD and Maricopa County AQD recommended sample locations
    • Based on soil maps of each county
    • Maps classify soils by texture and dust-emitting potential
  • One Gallon Samples – 5 per county
  • Bulk Samples (five cubic yards) – 1 per county

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Map: Sampling Locations in Clark County

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Map: Sampling Locations in Maricopa County 

Soil Samples

  • One gallon samples taken by hand
    • Evaluate sensitivity of select water quality parameters to soil chemistry differences
  • Bulk samples taken by excavators
    • Pre-tests for metals contamination
    • Shipped to SDSU-SERL in super sacks

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Photo: One Gallon Samples

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Photo: Job Site/Heavy Equipment

Soil Processing

  • Sizeable rocks and debris removed
  • Performed sand, silt, and clay analysis
  • Thorough mixing at laboratory
  • Chain of custody procedures followed

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Graph and Table: Particle Size Distributions for Bulk Soils 

Test Protocol

  • Control Plots Treated with Reverse Osmosis Water Only
  • Surface Leaching (Runoff to Surface Waters)
    • Simulated rainfall (0.7, 1.3, and 2.4 inches/hour)
    • Simulated heating
    • Tested for general chemicals of concern
    • Tested for aquatic toxicity (fish, algae, and invertebrates)
  • Column Migration (Potential to Reach Groundwater – Subsurface Leaching)
    • Migration rate
    • Tested for general chemicals of concern

Sample Preparation

  • One of two reapplication/soil disturbance scenarios
    • A. Soil surface raked daily and product applied each day
    • B. Soil surface raked daily and product applied on days 1, 3, and 5
    • For synthetic products, B scenario was higher initial application and no reapplication
  • Duration for both scenarios is consecutive 5-day period following initial application
    • Each of 5 days, soil raked in alternating directions
    • Reapplication rates same as original application

Rainfall Events

  • 0.7 inches per hour for 150 minutes
  • 1.3 inches per hour for 80 minutes
  • 2.4 inches per hour for 43 minutes

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Photo: Runoff Collection from Test Tray 

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Photo: Runoff Collection/Soil Test Tray

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Schematic: Soil Bed Layout

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Photo: Tilting Bed SDSU-SERL

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Photo: Rain Heads SDSU-SERL

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Photo: Plan View of Tilting Soil Bed

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Schematic: Vertical Leaching Experiment

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Photo: Preparing Migration Test Cylinders

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Photo: Typical AZ (Left) and NV (Right) Soil Columns

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Table: Products Tested

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Table: Experimental Parameters

 

Analytical for Runoff and Leachate

  • Ph
  • Electrical Conductivity
  • TSS
  • TDS
  • DO
  • TOC
  • Nitrate and Nitrite
  • Total Phosphorous
  • Aquatic Toxicity (Runoff only)

Qualitative Analysis of Test Results

  • Surface Leaching Tests
    • All six products met study DQOs for pH, TDS, TOC, DO, and Nitrate
    • Most significant effect – High TSS in runoff from soils treated with Durasoil and EnviroKleen
    • AZ soil runoff typically had higher conductivity, TDS, TOC, nitrate, nitrite, and phosphate
    • NV soil runoff had higher pH and TSS
    • DO similar for both soils
  • Vertical Migration Tests
    • Water migration through a 12­inch column of soil
    • Average results by product for eight of nine parameters meet DQOs
    • TSS results varied but typically not a concern for groundwater quality
  • Pilot Tests
    • Evaluated soil/water/product mixtures
    • TDS for Enviro Roadmoisture 2.5 and Durasoil samples significantly higher than control samples – Not observed in runoff tests

Aquatic Toxicity Tests

  • Runoff samples for toxicity collected as part of SDSU’s surface leaching tests
  • Toxicity tests conducted by EPA Region 9 Lab
    • Fish (flathead minnow) – acute tests
    • Algae – chronic tests
    • Invertebrate (Daphnia Magna) – acute tests
  • Control samples based on RO water only

Aquatic Toxicity Testing

  • Fish Tests
    • No toxicity to fish observed in any runoff sample
  • Algae tests
    • No toxicity to algae observed in any runoff sample
    • Test may underestimate impact due to fine filtration of samples to remove sediments required by test protocol
  • Invertebrate Tests – Daphnia magna
    • For 4 surfactants, majority of samples showed no toxic effect relative to control samples
    • Adverse physical effect on daphnids for Envirokleen and Durasoil samples compared to control (Daphnids trapped on surface not able to re-enter water column).
    • Additional tests with smaller invertebrate (Ceriodaphnia Dubia) conducted on product samples of Envirokleen and Durasoil did not show physical entrapment effect.
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