MATRIX DIFFUSION IN GROUNDWATER PLUMES - … 3... · Project Organization NIRAS A/S •Henrik Engdal Steffensen •Charlotte Riis •Anders G. Christensen GSI ENVIRONMENTAL, US •Charles

MATRIX DIFFUSION IN GROUNDWATER PLUMES

Anders G. Christensen, NIRAS A/S

ATV Vintermøde 2015

Project Organization

NIRAS A/S •Henrik Engdal Steffensen •Charlotte Riis •Anders G. Christensen

GSI ENVIRONMENTAL, US

•Charles Newell •David Adamson •Shahla Farhat

The Capital Region of Denmark •Mads Terkelsen •Peder Johansen

The Municipality Gladsaxe •Claus Frydenlund

ATV Vintermøde 2015 10-03-2015

What is matrix diffusion

• Matrix diffusion is a term used to describe transport of contaminants

• Storage & release from low k-layers

• Underestimation of the source life time

• Matrix diffusion is typical not integrated into groundwater models


Effects of Matrix Diffusion

Initial

Release

Loading

Stage

Back

Diffusion

Stage C

B

A


Loading history

Newell & Sale 2011


Results of 15 years Pump & Treat

Discharge 20 g/day

MODFLOW


Project Objective

The overall objective of this project is to investigate the influence of matrix diffusion at 3 sites

on risk, on selection of remediation technique for source and plume on estimating clean-up criteria


Project activities

√ Phase 1. Kick-off meeting and final scoping of activities: finished

√ Phase 2. Collection of field data and evaluation: finished

℗ Phase 3. Modelling and evaluation of transport processes in the plumes: in progress

© Phase 4. Development of paradigm/framework for future projects and final report: after phase 3

We will here look at data from one site where depth specific sampling using the GeoProbe system has been used (MiHPT-logs, soil coring, groundwater sampling and detailed subsampling at the cm-scale)


Location Nørgaardsvej Plume

Cross section


Geological cross section site A

Groundwater flow direction

Clay Till

Sand

Sand

Clay Till

Clay/silt

GVS

sekundært

magasin

GVS

primært

magasin

P&T and Airsparging has been in operation for more than 10 years, but this reevaluation of the contamination has shown DNAPL also in the deeper secondary aquifer

P&T and IAS


Factory

South North

Sand

Clay/Clay till

Clay till

Top soil

Sand

Initial Conceptual Site Model & High Resolution Characterization Profiles

DN

AP

L?


MI1

02

MI1

01

MI1

03

GVS

primært

magasin

Kraftig jord- og grundvandsforurening

Svag jord- og grundvandsforurening

GVS

sekundært

magasin


Results MI101 Source area (DNAPL)

17

16

15

Sand

Clay, silty

Clay, silty

Sand

Sand, with silt

Sand

Tetrachlorethylen (mg/kg DW) 10 102 103 104 105 106

Sample analysed

40

.00

0

2.3

00

1.5

00

Ele

vati

on

(m

)

Cor. HPT Pressure (kPa) 100 200 400 600

DNAPL


San

d

Cla

y, s

ilty

Cla

y, s

and

y Sa

nd

Results MI102 Near Source (-DNAPL)

Corr. HPT Pressure (kPa) 50 100 150 200

Tetrachlorethylen (mg/kg DW) 0 10 20 30 40 50

XSD (µVx105)

Ele

vati

on

(m

)

18

17

16

EC


Results MI103 Plume (-DNAPL)

Tetrachlorethylen (mg/kg DW) 0 2 4 6 8 10 12

Cor. HPT Pressure (kPa) 100 200 400 600

19

16

17

18

Ele

vati

on

(m

)

XSD Max (µVx105) 1 2 3 4

PID Max (µVx105) 1 2 3


Lessons Learned

• Continuous core sampling for detailed geological

description is necessary (Sonic Drill, Dual Tube, Single steel

tube sampling)

• Important to measure hydraulic pressure (HPT) through

the whole profile two distinguish low-K and high-K zones.

• High vertical resolution = high number of soil analysis in

order to “deconstruct” the loading history over time.

• MiHPT enables detailed correlation between

contamination and the hydrostratigraphy


• A very localized conceptual model are needed and will

complement the more overall site conceptual model.

Phase 3 and 4

• To calculate the back diffusion from low-k layers to transmissive zones (aquifers) based on the results from phase 2.

• Risk assessment • Evaluation of further remedial actions, • Calculation of clean up criteria

Practical challenge to set up a model which can handle • Contaminant transport in groundwater aquifers • Back diffusion • Vertical advective transport


Remediation scenarios Preliminary modelling results

Factory

South North

Sand

Clay/Clay till

Clay till

Top soil

Sand



Possible scenarios: - Clean up the sand only

(P&T)

- Also reduce mass stored in the low-K zones (clay) by 90%

16-03-2015

Run 5: No DNAPL, Sand Completely Remediated, Clay Remediated 90% T = 50 years

Run 3: No DNAPL, Sand Completely Remediated, Clay Unremediated T = 0.01 day

Run 3: No DNAPL, Sand Completely Remediated, Clay Unremediated T = 50 years

Remediation scenarios Preliminary modelling results

ATV Vintermøde 2015


Documents

MATRIX DIFFUSION IN GROUNDWATER PLUMES - … 3... · Project Organization NIRAS A/S •Henrik Engdal Steffensen •Charlotte Riis •Anders G. Christensen GSI ENVIRONMENTAL, US •Charles