PRESENTS:

Best Practices for NAPL Mobility Core Collection in Sediment A Systematic Approach to Maximize Sample Integrity

AGENDATrends in NAPL Mobility Testing

Why Now?

Framework for Core Collection

Target Interval

Conclusion

2

Trends in NAPL Mobility Testing

Trend 1 – Increased Sophistication in Testing

Niemet, M. R., Gentry, J. L., Bruno, M., Berggren, D. R., & Tsiamis, C. D. (2015). Gowanus Canal Superfund Site. I: NAPL Mobility Testing of MGP-Impacted Sediments. Journal of Hazardous, Toxic, and Radioactive Waste, 19(1). doi:10.1061/(asce)hz.2153-5515.0000251

▪ Advantages: Economical, quantitative, short-duration, regulatory acceptance

▪ Disadvantages: Air is permeating fluid, excessive force

Early – Mid 2000’s - Centrifugation at 1000x gravity for 1 hour, after Brady and Kunkle Method

▪ Advantages: Water is permeating fluid, gradients or flux similar to site conditions

▪ Disadvantages: Can be expensive and time consuming for lower permeability sediments

Current Trend – Rigid/flexible-walled permeameter

Brady M.M., L.A. Kunkel, A screening Method for Determining Free Product Mobility, Petroleum Hydrocarbons and Organic Chemicals in Groundwater: prevention, Assessment and Remediation Conference, 2005

Centrifuge MethodRigid Walled

Permeameter Method

0

10

20

30

40

50

60

70

0 1000 2000 3000 4000

Ave

rage

% In

itia

l Po

re V

olu

me

TarGOST Response (% RE)

Linear Fitting – NAPL Saturation vs TarGOST

Response

10% LCL

75% UCL

25% UCL

Fitted LineR2 = 0.79

90% UCL

Trend 2 – Increased Evaluation by Practitioners

▪ Mobility potential from discrete sample applied to a less surgical removal

Early

▪ Multiple lines of evidence to assess the site significance of mobility test results

▪ Correlating discrete test results to other parameters (multiple lines of evidence)

Current Trend

Trend 3 – Increased Consideration By Regulatory Agency

▪ Intrusive remedial decisions based on NAPL presence alone

Early

▪ Intrusive remedial decisions for potentially mobile NAPL

▪ Less intrusive remedial decisions for non-mobile NAPL

Current Trend

Why Think About Collection Methods Now?

Why Now?

8

Increased sophistication and reliance on results

Accuracy of test results is dependent on representativeness of sample

Technical challenges related to core integrity and target sample interval

Collection of an “undisturbed” core in sediment may not be practical using traditional methods

Critical to maximize and document sample integrity procedures

Framework for NAPL Mobility Core Collection

Initial NAPL Distribution

Goal: Establish lateral and vertical distribution of NAPL

Coring Method: Disturbed sample is acceptable to maximize core recovery.

Advancement Method: Continuous sampling of entire sediment interval and noting potential NAPL presence

NAPL Mobility Core

Goal: Understand NAPL mobility potential

Coring Method: Undisturbed core

Advancement Method: Typically discrete at NAPL-bearing interval

Framework for NAPL Mobility Core Collection

3

Traditional Methods

2

Low Disturbance Methods

1

In Modified Operations

Thin-walled Sampling

Direct Push Direct Push

Vibracore Vibracore

Sonic Sonic

Increased Potential for Disturbance

Thin-walled Sampling

13

Traditional “Gold” Standard for Undisturbed Core

Draw Backs:

▪ Not recommended for coarse sand, gravel, or larger size soil particles, cemented, or very hard soils

▪ Recovery in soft silt

Potential Resolutions:

▪ Modify with Piston Sampler

http://www.damascopenna.com.br/en/GridPortfolio/shelby/

Attempts

Attempt 1: Hydraulic

advancement

Attempt 2: Automatic drop

hammer

Attempt 3: Traditional percussion

Approach

Largest diameter possible

Use most versatile machine available

http://www.geoprobe.com/probingtimes

Direct Push

Increased Potential for Disturbance

Vibracore

Attempts

Attempt 1: Use push core

techniques

Attempt 2: Pause vibratory motor

at interval

Attempt 3: Use vibratory motor

throughout

Approach

Largest diameter possibleTapered tube/cutting shoe

Increased Potential for Disturbance

Sonic

Attempts

Attempt 1: Hydraulic

advancement

Attempt 2: Automatic drop

hammer

Attempt 3: Traditional

Sonic

Approach

Use rigid core barrel linerUse most versatile machine available

Increased Potential for Disturbance

ASTMD6169 – vibratory/sonic may be required to obtain intact samples in cohesionless sediments

Keys to Success

Work Plan Flexibility

Driller Versatility

Time

Target Interval

Target Interval

19

Lacks Field Visual Confirmation

Identify Uncertainty

- Recovery of original core

- Sediment Elevation

Incorporate Safety Factor

When possible, increase target interval to address uncertainty

13-14 ft.

Conclusion

20

Increased sophistication and reliance on results

Representativeness of the sample is paramount

Following a systematic framework can help maximize and document sample integrity procedures

Increased likelihood of regulatory/stakeholder acceptance or results

Lead to selection of the most appropriate remedy

QUESTIONS AND REVIEW

Thank you!Marcus D. Byker, PE – marcus.byker@obg.com

Recovery Improvement

General practice: ~70-80% = Acceptable

23

Approach Punch/PushVibratory-

DrivenSonic

Thin-walled (Shelby Tube)

Split-Spoon

Direct Push

Reduce the core penetration and extraction rate

✓ ✓ ✓ ✓ ✓ ✓

Reduce core barrel length

✓ ✓ ✓ ✓

Increase core barrel length

✓ ✓ ✓

Increase or decrease sample diameter

✓ ✓ ✓ ✓ ✓ ✓

Incorporating or modifying core catcher

✓ ✓ ✓ ✓

Incorporate Piston

✓ ✓ ✓ ✓ ✓