SALT REMEDIATION: BEST PRACTICES FROM THE OIL PATCH

Transcription

1 SALT REMEDIATION: BEST PRACTICES FROM THE OIL PATCH TRB Committee ADC60 Summer Workshop SAIC Energy, Environment and Infrastructure Eric Schmidley, PG July 2013 NATIONAL SECURITY ENERGY & ENVIRONMENT HEALTH CYBERSECURITY

2 SAIC Eric B. Schmidley, PG Program Manager & Senior Hydrogeologist 26 Years Experience Site Characterization & Remediation Professional Geologist Pennsylvania & Delaware Office Lead SAIC Exton PA Environmental Consultant to PennDOT - 12 Years

3 SAIC Company Profile CAPACITY 45 offices 44,000 Staff (SAIC) 2,280 Staff (SEE&I) CAPABILITIES Full-Services A / E / DesignBuild SM Pennsylvania Department of Transportation Oklahoma Department of Transportation Oklahoma Turnpike Commission RECOGNITION 40+ Design Awards in the past 5 years 90+ LEED Projects SAIC SOON TO BE leidos

4 Best Practices From the Oil Patch Technology applications and lessons learned from brine remediation in the oil patch have direct application and value for characterization and remediation of deicer brines at state DOT facilities Technologies are not new Technologies are not expensive Source (Soil) characterization & remediation Protecting future surface water and groundwater quality 4

5 Salt Remediation Strategy Salt Remediation Strategy: SOIL: Remove the lingering source of salt through soil excavation, or sometimes amendment, to protect future water quality GROUNDWATER: Get out of the way of impacted water natural attenuation flush out Remove receptors ahead of flushing: Drill new well(s) convert to public water buy property 5

6 Best Practice Methodology HELP THE RIGHT METHOD..the first time Hydrogeologic setting Electromagnetic (EM) survey Limited soil excavation Purposeful sampling/analysis RESULTS IN Compressed time frame Reduced costs Stakeholder compliance 6

7 Salt and Brine Primer Electrically neutral, ionic compound Chloride salts Na +, K +, Mg + most prevalent and very soluble Sodium and chlorine ubiquitous in rock forming minerals, 6 th and 20 th most abundant elements Worlds oceans up to 500 millions years old.plenty of time to dissolve rock 3-5% TDS: Na + = 1%; Cl - = 2% Sea water gets recombined into rock via sediment burial Mississippi River Delta Marcellus marine clays Ancient evaporation basins Sabkahs 7

8 Salt and Brine Primer Brine: An aqueous solution with 3.5% total dissolved solids (TDS) Primarily salt; halite or sodium chloride 80% of TDS Dissociated metals/inorganic ions. Brines are trapped seawater further mineralized by rock& produced during drilling and production 8

9 Environmental Health Why Do We Care About Salt? No federal and few state cleanup levels for soil. Pennsylvania (PADEP) does not have a soil standard been directed to attain 1,500 mg/kg Kansas (KDHE) cleanup level for soils: 1,000 mg/kg New Mexico (NMEMNRD) land farming regulation: 500 mg/kg if GW ft bg; 1,000 mg/kg if GW > 100 ft bg Goals for surface water and groundwater secondary guidance levels only: 250 mg/l chlorides The economic and social benefits of salt management for road deicing far out way the short term side effects until the side effects become acute 9

10 Environmental Health Too much salt in: Soil root osmosis stops.chloride toxicity plants wilt and die healthy plant growth <0.2% soil salt Surface water critters will die electrolyte imbalance.gill function harmed/shut down Groundwater develops salty taste from dissociated Cl - and Na + on taste buds. Sodium leads to high blood pressure (1,500 2,300 mg/day) Groundwater electrolyte forms corrosion rates increase significantly metal like Fe +2 oxidizes to Fe +3 while O 2 is reduced rust 10

11 Salt Behavior Rainfall creates brines.denser than fresh water..mobilizes salt to surface water and into soils to groundwater. Wetting front dissolved Na + and Cl -.moves through soil, Na+ dislodges other cations (Al, K, Mg) off clays..promotes clay swelling, lowering permeability..slope failure. Cl - moves with wetting front on to groundwater, or As the soil begins to dry, dissolved Cl - and Na + exceed pore water solubility and snap back together.. precipitate out of solution as salt crystals in soil pores. Another rain event partially dissolves the soil pore salt.moves deeper into soil..cycling between dissolution and reprecipitation NaCl Solubility in Water: 359 g/l 11

12 The Brine Release Hello, your friendly neighborhood DOT, how may we help you? Hello, Mr. Consultant, we need your HELP! My home is across the street from your salt stockpile and my water tastes funny, my water heater rusted out and my grass never grows. Take two aspirin and call my attorney in the morning!! I m suing! Even though modern salt practices are sound, spills can happen, new roads can focus runoff and salt can linger in soils beneath old stockpiles for years to decades before problem presents itself at a receptor 12

13 Hydrogeologic Setting - HELP What is the BIG Picture hydrogeologic setting of the salt release? Must know to understand potential flow paths, end-point receptors and characterization tools: Develop from existing background information Where was salt handled historically Topography and storm water flow paths Soil profile thickness and relation to bedrock Surface water discharge Groundwater wells (drinking, agricultural, industrial) 13

14 Electromagnetic (EM) Survey - HELP All earth materials have a natural level of electrical conductance, clays more than silica sands Flooding earth materials with dissolved Na + and Cl - electrolyte solution artificially raises that electrical conductivity of the earth material Electromagnetic (EM) geophysical instrumentation VERY SENSITIVE to even subtle changes in conductivity GPS coupled with EM provides for VERY ACCURATE mapping of conductivity changes spatially Hand held instrument generates oscillating EM energy which penetrates the ground and induces secondary EM fields in regions of elevated electrical conductivity and metal 14

15 Electromagnetic (EM) Survey - HELP Receiver Transmitter Secondary Magnetic Field Primary Magnetic Field Eddy Current Eddy current magnitude a function of the material conductance Metal objects briefly magnetize

16 Electromagnetic (EM) Survey - HELP Geonics lead the way with EM instrument development and refinement induction systems.walk and measure EM31-MK2 3.7 m intercoil space 3-6 m depth resolution Metal detection EM , 20, 40 m intercoil space 60 m depth resolution 2 personnel EM38 MK2 2 receiver coils: 0.5 m & 1.0 m m, vert. or horiz. Dipole mode Wide range of temperatures: -40 to 120 F 16

17 Electromagnetic (EM) Survey - HELP Relationship of Soil Chlorides to EM Response North Dakota Pennsylvania 17

18 EM Survey Application Bird Tracks Fixed traverse in open space to avoid overlap Meandering path in limited access Electromagnetic (EM) Survey - HELP 18

19 Electromagnetic (EM) Survey - HELP EM38/31 Survey - Meandering Path Traverse Central Pennsylvania EM m EM31 6 m 19

20 Electromagnetic (EM) Survey - HELP EM38-MK2 0.5 m intercoil data (0.75 m) EM38-MK2 1.0 m intercoil data (1.5 m) 20

21 Electromagnetic (EM) Survey - HELP EM38-MK2 Magnetic Susceptibility Anomalies disappear, consistent with pore water electrolyte induced conductance not a metal object. Anomaly remains, consistent with a metal object: steel pipe & metal debris. 21

22 Electromagnetic (EM) Survey - HELP EM34-3 Depth Profiling at Progressive Intercoil Spacing 22

23 EM Data Guided Surgical Soil Removal Limited Soil Excavation - HELP Go straight from EM Survey to soil excavation.yes Looking for relative contrast: Background typically 5-15 ms/m, although site-specific Threshold for impact to groundwater: 15 to 50 ms/m Use GPS coordinates from edge of anomaly to map out excavation, no interpolation between sparse soil samples Use EM response from various dipole orientations to guide depth of excavation Dig & stage, or load & go 23

24 EM Data Guided Surgical Soil Removal Limited Soil Excavation - HELP 24

25 EM Data Guided Surgical Soil Removal Limited Soil Excavation - HELP Progressively screen soils for specific conductance via soildeionized water slurries: 1:3 SC s < us/cm Meters and colorimetric test kits capable of screening for chlorides off a tailgate (low ppm resolution). 0-3,000 ppm mg/l Fast-turn 24-hr lab samples 25

26 Purposeful Sampling - HELP To Characterization Sample, or Not To Characterization Sample? In most cases, can go straight from EM survey to soil excavation If brine spill small and/or new If brine spill old, but soil profile relatively thin (< 15 ft) If brine spill large, old and/or soil profile thick, may want to consider bounding the depth by conventional soil sampling, direct-push EC probe just how leachable is the salt?...before you dig If a characterization report or a remedial action plan required, regulator might need ground truthing of EM data, before implementing remedy 26

27 Purposeful Sampling - HELP Post-Excavation Soil Quality Documentation Pennsylvania s Act 2: Why? Not really a tool.yet Maybe systematic random sampling grid with total chlorides and leachable (SPLP) chlorides...de facto attainment demonstration of SHS soil-to-groundwater pathway SPLP.synthetic precipitation leaching procedure demonstrate that soils cannot leach chlorides above groundwater/surface water standard (250 mg/l) But a failure at the lab scale does not necessarily mean an exceedance at the field scale.be careful..dilution Monitoring well and use of the Act 2 SHS Equivalency option Better yet, Saturated Paste Analysis 27

28 Purposeful Sampling - HELP Post-Excavation Soil Quality Documentation Saturated Paste Analysis: USDA Handbook No. 60 Saturate 250 gm soils in deionized water for 18 hrs, then vacuum extract and analyze Conventional analysis for: ph Metals (Na, Ca, Mg) Chloride Electrical Conductivity (EC) Total soluble salts (TSS) Cation Exchange Capacity Sodium Adsorption Ration (SAR) Exchangeable Sodium Percentage (ESP) 28

29 Purposeful Sampling - HELP Post-Excavation Soil Quality Documentation Saturated Paste Analysis: USDA Handbook No. 60 Provides very accurate assessment of leachable chlorides EC directly proportional to TSS, or leachable salts and a thoroughly researched assessment of soil salinity: EC < 4 mmhos/cm = healthy, arable soils, no potential for groundwater impairment Saturated paste chloride correlation to total chloride varies, likely as a function of the less accurate total chloride measurement South Dakota soils SP Cl < 15% of T Cl Pennsylvania soils SP Cl > 50% of T Cl 29

30 Purposeful Sampling - HELP EM vs. Total Chloride vs. Leachable Chloride: How do they stack up? #1: Source Removed #2: Future Water Quality Protected 30