Characterizing Contaminant and Water Fluxes in … Contaminant and Water Fluxes in Fractured Rock Systems ... FRPFM packer or inflating fluid ... Selection of Sorbents and Resident

Characterizing Contaminant and Water Fluxes in Fractured Rock Systems

GQ 2013

Kirk Hatfield University of Florida

April 25, 2013

ESTCP Project ER0831

Project Technical Objectives

The objective of this ESTCP project is to demonstrate and validate the fractured rock passive flux meter (FRPFM) as an innovative closed-hole technology. Specific project objectives are:

1. Demonstrate and validate an innovative technology for the

direct in situ measurement of cumulative water and contaminant fluxes in fractured media

2. Formulate and demonstrate methodologies for interpreting contaminant discharge from point-wise measurements of cumulative contaminant flux in fractured rock

Technology Description

Unfractured Bedrock

Ground Surface

Water Table

Fracture planes and flow directions

FRPFM packer or inflating fluid

FRPFM impermeable flexible liner and attached sorbent layer

Flow through matrix blocks

Unfractured Bedrock

Ground Surface

Water Table

Fracture planes and flow directions

FRPFM packer or inflating fluid

FRPFM impermeable flexible liner and attached sorbent layer

Flow through matrix blocks

Packer minimizes vertical cross-flow between fractures

FRPFM Packer Design

Technology Description

● The FRPFM is essentially an inflatable packer or impermeable flexible liner that holds a reactive permeable fabric against the wall of the borehole and to any water-filled fractures intersected by the borehole.

● Reactive fabrics capture target contaminants and release non-toxic resident tracers (e.g., visible dyes and branch alcohols).

● Tracer loss is proportional to ambient fracture flow.

● Leached visible tracers reveal location and orientation of active fractures and flow direction.

● Contaminant mass captured is proportional to ambient contaminant flux.

Inflatable Packers

Nominal 4-inch

Diameter Borehole

Inflatable Core with mesh 5 mm Sorbent (AC Felt 2.5 mm) K =0.08 m/d

Sock with visual tracer

Air line to packers Air line to core

Inflatable Shield-Packer

FRPFM Shield

Air line to shield-packer

Accelerometer

FRPFM Prototype with Shield

Dimensions Borehole ID = 3.8 in (9.652 cm) Nominal 4 in borehole Un-Inflated Dimensions Shield packer OD = 3.5 in Shield OD = 3.5 in Packer OD = 3.3 in Core OD = 3.2 in (with sorbent and sock) Note: When inflated all dimensions match borehole ID

Selection of Sorbents and Resident Tracers Suite of Non-toxic Branched Alcohols

Batch Tracer Sorption Isotherms on Felt 1300

Laboratory Fracture Simulator

Fracture Dimensions: • Horizontal • Aperture = 500 μm • Width = 26 cm • Length = 53 cm • Conductivity ~0.7 cm/s

Borehole: • Diameter 10.16 cm

Flow Convergence: • Maximum = 1.76

Flow Front

Up Gradient

Left

Right

Back Down Gradient

Visual Tracer Reveals Fracture Location and Orientation and Flow Direction

Front Up Gradient

Back Down Gradient Left Right

• 0.5 mm fracture aperture • Q = 1.5 ml/min, q = 2500 cm/day • Duration 1 day •Visual fracture zone (max) aperture 4 mm •Visual fracture zone length along circumfrance147 mm

4 mm

Visual indication of flowing fracture

FRPFM Performance in the Laboratory

Visible Tracer Elution Patterns

Dyed fabric

AC-felt

metal mesh

Water

Tracer Front Streamlines

0

40

80

120

0 40 80 120

CumulativeContaminantFlux

Measured Flux [ mg/cm2 ]

True Flux [ mg/cm2 ]

Cumulative Contaminant Flux

0

2000

4000

6000

8000

0 2000 4000 6000 8000

Cumulative WaterFlux

True Flux [ cm ]

FRPFM Performance

Measured Flux [ cm ]

Cumulative Water Flux

Large Aquifer Box (High contrast flow zones)

Flow

Screened Wells (4-inch diameter PVC)

Alternating Sand and Gravel Layers

Box Dimensions (length x width x height)

2.0 x 0.5 x 1.3 m

Visual Indication of Flow

FRPFM Results in Aquifer Box

NAWC Site (West Trenton, NJ)

NAWC Site (West Trenton, NJ)

Site Description Former Naval Air Warfare Center (NAWC), West Trenton, NJ

(High flow zones will be used to facilitate remediation)

• Former jet engine testing facility • TCE, DCE, and VC • Pump and Treat Operations

• Site is well characterized • Bedded fractured Mudstones • High to low bulk conductivity • Exposed Outcrop

• Can leverage project ER1555

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

10 100 1,000 10,000 100,000 1,000,000 10,000,000

TCE (ppb)

Dep

th B

LS (f

t)

PumpedSamples

CoreSamples

A

B

C

D

E

F

Figure 11. Bulk concentration of TCE from samples of rock core taken from 68BR as a function of depth are shown in comparison to the concentrations of TCE from water samples collected from the 6 monitoring intervals in 68BR (A, B, C, D, E, F). (Shapiro SERDP Project ER-1555: Annual Report 2008)

NAWC Site: Well 68-BR TCE concentrations

FRPFM tests to date all in Zone D

Fracture Rock Passive Flux Meter (FRPFM)

Shield Packer

Accelerometer Weight

Stainless Steel Shield

NAWC Site (West Trenton, NJ)

Figure 7. Location of selected monitoring boreholes at the former Naval Air Warfare Center, West Trenton, NJ. (Shapiro SERDP Project ER-1555: Annual Report 2008)

FRPFM test well 68BR

Groundwater Flow Direction

Pumping well 15BR

NAWC Site: Borehole BR-68 target depth 95 ft-bgs

Bottom

0 090 180 270 0

20

Black and White picture of the traces Traces with

Centroids

Yields: •Flow Direction

Black and White picture of the traces

Traces with Fitted Sine Functions

Yields Trace: •Depth •Dip •Orientation

Histograms of Fracture Depth, Dip, Orientation and Centroid angles

Depth Dip Orientation Centroid Angles

Borehole Dilution (BHD) Probe

Top Packer

Bottom Packer

Flow Return Line

Variable Speed Submersible Pump

BHD Probe is assembled so that the interrogation zone (1 m) matches that of FRPFM

0 4 891

92

93

94

95

960 20 40 60 80

Specific Discharge (cm/day) D

epth

Bel

ow G

roun

d Su

rfac

e (ft

)

Mass Flux (ug/cm2/day)

TCE DCE

Specific Discharge PRE-BHD

POST-BHD

Comparisons with Independent Field Measurements

FRPFM BHD USGS

q (cm/d) 2.6 2.9 (2.2-3.6)

TCE Cf mg/l 5.5 6.9 (4-9.8) 10.8

DCE Cf mg/l 2.7 1.7 (1.7-1.7) 3.1

Top

Bottom

Project Team

University of Florida: Michael Annable, Harald Klammler, Mark Newman, Jaehyun Cho, Bidhya Yadav, and Ozlem Acar University of Guelph: Beth Parker, John Cherry, Pete Pehme, Patryk Quinn, Ryan Kroeker, and Bassel Nemer

Questions?