Lecture 4: Contaminated Site Characterization

Transcription

1 ENGI 7718 Environmental Geotechniques ENGI 9621 Soil Remediation Engineering Lecture 4: Contaminated Site Characterization Spring 2011 Faculty of Engineering & Applied Science 1 1

2 4.1 Introduction Site characterization a systematic investigation aimed at obtaining appropriate and adequate data in order to define the type and extent of contamination as well as to assess the fate and transport of contaminants under various scenarios (1) Information required for site characterization Geologic data Hydro-geologic data Contamination data 2

3 (2) Questions to be answered by site characterization Nature and extent of contamination where is it? What is future migration and control where is it going? What are receptors and their risk what harm will it do? What are technical options for remediation how do we fix it? 3

4 (3) General methodology for site characterization Source: Sharma and Reddy, Geoenvironental Engineering,

5 4.2 Preliminary and exploratory site assessment (1) Phase I: Preliminary site assessment to collect and review available or published site-specific or regional data involves two tasks: literature review and site visit (a) Literature review site use and history site permits water well logs and records aerial photos other sources site personnel interviews geological maps and reports topographic maps soil survey maps 5

6 Effective actions: Action I Get a topo map understand geographic setting, topography, nearby water bodies Action II Get background geologic data through consulting ground-water atlas of Canada getting reports on geology, hydrology, meteorology checking for reports from province and national geological surveys Action III Investigate regional geology and hydrogeology help to understand site geology and hydrology understand effects on contaminant movement 6

7 (b) Site visit observe/record all potential important surface site features + collect surface water and nearsurface soils Where were chemicals handled or disposed? What site structures or activities are potential sources? What chemicals are and were handled? Prevention of costly mistakes such as multi-aquifer wells 7

8 (2) Phase II: Exploratory site investigation to confirm findings in the preliminary assessment to obtain preliminary site-specific data to facilitate design of a detailed site investigation program a written work plan for phase III sampling and testing procedures sampling locations and frequency QA/QC plan health and safety (H&S) plan schedule cost assessment 8

9 H&S plan Source: US EPA, Emergency response program,

10 Health and Safety Levels Source: Rast, Environmental Remediation Estimating Methods, 1997 More information about H&S plan, visit /health_and_safety/by_topic/assets/pdf/howtoimplement_ohs.pdf 10

11 4.3 Detailed site investigation Phase III : detailed site investigation a comprehensive field and laboratory test program, along with S&H and QA/QC plans Methods of obtaining soil and rock data Direct methods Geophysical methods Drive methods 11

12 Direct methods near surface soil sampling bucket augers; spiral or ram s horn auger Source: Sharma and Reddy, Geoenvironental Engineering,

13 Direct methods soil sampling by solid-stem auger drilling Drilling stop at the desired depth augers remove from the borehole a sampler is attached to the end of the drill put the entire string back to the borehole a sample is taken from the bottom flight by Only for sampling from soil, not applicable to saturated zones Power-driven solid-stem augers: (a) solidflight auger; (b) relationship of surface cuttings and subsurface Source: Sharma and Reddy, Geoenvironental Engineering,

14 Direct methods soil sampling by hollow-stem auger drilling Drilling a center rod (with a pilot bit and plug) is lowered inside the auger till the sampling position is reached the center rod/bit/plug are removed soil sampler is applied Applicable to soil/uppermost level of groundwater sampling Typical components of a hollow-stem auger: a hollow pipe with a continuous ramp of upward-spiraling flight welded around them Source: Sharma and Reddy, Geoenvironental Engineering,

15 solid-stem (left) and hollow-stem (right) augur flights Source: DeJong & Boulanger, 2010 a hollow-stem augur in action 15

16 Direct methods popular samplers Thin-walled tube samplers Source: Sharma and Reddy, Geoenvironental Engineering, 2004 A split-spoon sampler 16

17 Direct methods Installing piezometers and monitoring wells by wet rotary drilling Drilling boreholes drilling fluid is pumped down hollow rotary drill rods the fluid circulates back to surface by moving up the annular space between drill rods and borehole wall stabilization of the borehole wall installation of the piezometer/monitoring wall If the circulation medium is air instead of water air rotary drilling Source: Sharma and Reddy, Geoenvironental Engineering, 2004 Direct mud rotary circulation system 17

18 Source: DeJong & Boulanger, 2010 This image shows a rotary wash boring set-up. The drilling "mud," a mixture of water and bentonite, is circulated through the tank in the left-foreground of the photo. The mud is pumped down the drill stem to the hole bottom, where it picks up soil cuttings and carries them to the surface and into the tank. The mud also serves to support the borehole walls. 18

19 Direct methods we should also know Logging Field testing Surveying Borehole abandonment Laboratory testing Geophysical methods Borehole geophysical methods a probe into the borehole using a cable transmit signals to surface instruments generate logs or charts Surface geophysical methods no requirement of boreholes conduct electric/seismic/electromagnetic surveys as well as the use of ground penetrating radar 19

20 Geophysical methods Electrical resistivity Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration,

21 Geophysical methods Seismic reflection Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration,

22 Geophysical methods Electromagnetic Induction Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration,

23 Geophysical methods Ground penetrating radar Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration,

24 Drive methods e.g. cone penetrometer technology CPT a method of providing realtime data for use in characterizing the subsurface, as opposed to older methods of analyzing subsurface conditions in the laboratory It consists of a steel cone that is hydraulically pushed into the ground at up to 40,000 pounds of pressure Sensors on the tip of the cone collect data 24

25 4.3.2 Methods of obtaining hydrogeologic data Direct methods Piezometers and monitoring wells Water-level measurement In-situ hydraulic conductivity test Packer test Slug test Pumping test Drive methods 25

26 Piezometers Structure of a piezometer Installing Piezometers with a Manual Slide Hammer Source: Shanahan, Waste Containment and Remediation Technology,

27 Monitoring wells -- Structure Source: Shanahan, Waste Containment and Remediation Technology,

28 Monitoring wells -- Development Source: Shanahan, Waste Containment and Remediation Technology,

29 Source: Shanahan, Waste Containment and Remediation Technology,

30 Well development by surge block Source: Shanahan, Waste Containment and Remediation Technology,

31 Source: Shanahan, Waste Containment and Remediation Technology,

32 A developed well with a cover Source: Shanahan, Waste Containment and Remediation Technology,

33 Water-level measurement Source: Shanahan, Waste Containment and Remediation Technology,

34 In-situ hydraulic conductivity test Source: Eijkelkamp, Agrisearch Equipment, 2010 ( (b) (a) (a) Applying a bailer a portion of the water is removed from the bore hole after which measurement can commence The rise rate of the groundwater is determined by using a measuring tape with a float and a stopwatch (b) The determination of the saturated water permeability using the Guelph permeameter. 34

35 Packer test (a) The schematic of a packer test apparatus (b) Field packer test Sources: Groundwater data collection, USGS Illinois Water Science Center Searchable Publications Database, 2010, (Left) Cutting Edge Drilling, 2010, (Right) 35

36 Slug test Source: Butler, et al., Analysis of slug tests in formations of high hydraulic conductivity, Ground Water, v. 41, no. 5, ,

37 Pumping test Single well pumping test Source: Sharma and Reddy, Geoenvironental Engineering,

38 4.3.3 Methods of obtaining contaminant data Contaminant in soil analyze the samples from soil sampler Contaminant in water analyze the samples from piezometers and/or monitoring wells Contaminant in soil vapor analyze the samples from soil gas sampler 38

39 Soil gas sampler Source: Environmental Support Technologies, Inc.,

40 Potential character of soil gas contamination Source: Cohen and Mercer, DNAPL site evaluation,