Evaluation of Water Quality Impacts from Dust Suppressants (TPD0811029)

Topics of Discussion

n  Selection of Suppressants to be tested

n  Selection of soil types

n  Precautions taken to ensure defensible results

n  Development of specific Test Procedures

n  Evaluation of Results

n  Reporting

Objectives

n  Determine the water quality impacts of each dust suppressant in a simulated real world environment

n  Focus on products typically used in the desert Southwest

n  Focus on construction activity, as opposed to road or pile surface stability

Suppressants Selected for Study

Soil Selection Criteria

n  No visible contamination

n  Native land, no farming/industrial history

n  Normal soil range of metals

n  6010 test for metals

n  7471 test for Mercury

Soils Selected

n  Clark County AQMD and Maricopa County AQD recommended sample locations

n  Based on soil maps of each county

n  Maps classify soils by texture and dust-emitting potential

n  One-Gallon Samples –5 per county

n  Bulk Samples (five cubic yards) – 1 per county

Sampling Locations in Clark County

Sampling Locations in Maricopa County

Soil Samples

n  One gallon samples taken by hand

n  Evaluate sensitivity of select water quality parameters to soil chemistry differences

n  Bulk samples – taken by excavators

n  Pre-tests for metals contamination

n  Shipped to SDSU-SERL in super sacks

Test Protocol

n  Control Plots Treated with Reverse Osmosis Water Only

n  Surface Leaching (Runoff to Surface Waters)

n  Simulated rainfall (0.7, 1.3, and 2.4 inches/hour)

n  Simulated heating

n  Tested for general chemicals of concern

n  Tested for aquatic toxicity (fish, algae, and invertebrates)

n  Column Migration (Potential to Reach Groundwater – Subsurface Leaching)

n  Migration rate

n  Tested for general chemicals of concern

Sample Preparation

n  One of two reapplication/soil disturbance scenarios

n  A-Soil surface raked daily and product applied each day

n  B-Soil surface raked daily and product applied on days 1, 3, and 5

n  For synthetic products,  B scenario was higher initial application and no reapplication

n  Duration for both scenarios is consecutive 5-day period following initial application

n  Each of 5-days, soil raked in alternating directions

n  Reapplication rates same as original application

Rainfall Events

n  0.7 inches per hour for 150 minutes

n  1.3 inches per hour for 80 minutes

n  2.4 inches per hour for 43 minutes

Soil Bed Layout

Products Tested

Experimental Parameters

Analytical for Runoff and Leachate

n   Ph

n   Electrical Conductivity

n   TSS

n   TDS

n   DO

n   TOC

n   Nitrate and Nitrite

n   Total Phosphorous

n   Aquatic Toxicity (Runoff only)

Qualitative Analysis of Test Results

n  Surface Leaching Tests

n  All six products met study DQOs for pH, TDS, TOC, DO, and Nitrate

n  Most significant effect – High TSS in runoff from soils treated with Durasoil and EnviroKleen

n  AZ soil runoff typically had higher conductivity, TDS, TOC, nitrate, nitrite, and phosphate

n  NV soil runoff had higher pH and TSS

n  DO similar for both soils

n  Vertical Migration Tests

n  Water migration through a 12-inch column of soil

n  Average results by product for eight of nine parameters meet DQOs

n  TSS results varied but typically not a concern for groundwater quality

n  Pilot Tests

n  Evaluated soil/water/product mixtures

n TDS for Enviro Roadmoisture 2.5 and Durasoil samples significantly higher than control samples – Not observed in runoff tests

Aquatic Toxicity Tests

n   Runoff samples for toxicity collected as part of SDSU’s surface leaching tests

n   Toxicity tests conducted by EPA Region 9 Lab

n  Fish (flathead minnow) – acute tests

n  Algae – chronic tests

n  Invertebrate (Daphnia Magna) – acute tests

n   Control samples based on RO-water only

n  Fish Tests

n  No toxicity to fish observed in any runoff sample

n  Algae tests

n  No toxicity to algae observed in any runoff sample

n  Test may underestimate impact due to fine filtration of samples to remove sediments required by test protocol

n  Invertebrate Tests – Daphnia magna

n  For 4 surfactants, majority of samples showed no toxic effect relative to control samples

n  Adverse physical effect on daphnids for Envirokleen and Durasoil samples compared to control (Daphnids trapped on surface not able to re-enter water column).

n  Additional tests with smaller invertebrate (Ceriodaphnia Dubia) conducted on product samples of Envirokleen and Durasoil did not show physical entrapment effect.

http://www.epa.gov/region09/air/dust/Dust Suppressants-sept2008.pdf