Download Subgroup - Site characterisation

Working document for the REMTEC subgroup Site
Characterisation
Group composition and stakeholders
DTU Environment: Ida Damgaard, Camilla Christiansen, Julie Chambon, Mette
Broholm, Charlotte Scheutz, (Poul Bjerg)
GEUS: Bertel Nilsson, Knud Erik Klint, Carsten Suhr, Jacob Bælum
Orbicon: Nina Tuxen
1. OVERALL OBJECTIVE
In order to plan and design the remediation of a contaminated site a good
characterisation of the site and contamination is needed. As some of the processes
enhanced by the remediation technology may occur naturally, detailed knowledge of
contaminant distribution and naturally occurring processes are needed in order to set
the background for evaluating the effect of the remediation.
The site characterisation will be carried out as an integrated study of geology,
hydrogeology and contaminant distribution. The integrated study will lead to a better
understanding of the contaminant distribution and naturally occurring processes
taking place at the site. The investigation will create a robust basis for the following
remediation.
2. GEOLOGY
Objectives
The objective is to develop a standard site characterisation methodology that includes
till, fracture and sandlense classification in a simple standard diagram.
Activities
1-2 excavations to 5m depth in stepwise profiles (1.5m high) and 1-1.5m wide
horizontal plans. Methods used: till classification, fracture classification, fracture
measurements techniques. Development of conceptual 3-D fracture network model
and statistical properties of fractures and sand inclusions. The characterisation follows
procedures outlined in Klint (2008).
Objectives
Statistical analysis of sandlense distribution and practical approaches.
Activities
An area nearby the contaminated site will be used for geoprobe drillings on an area
with dimensions 50m x 50m. About 25-30 geoprobe wells will be established to
depths of about 10-15m (bottom of the contaminated zone?). All the fully cored
sediment profiles are described in terms of sand/clay relation + redox state. The
spatial distribution of the embedded sandlenses will be analysed by the geostatistical
software (TPROGS).
Furthermore surveyings of vertical clayey till profiles in nearby gravel pits will be
carried out.
Objectives
Investigations at several sites to see if the method is working (Seeland or not too far).
Activities
The statistical sand/clay distribution obtained in the geoprobe study site will be
compared with other geological till settings in the same region to obtain characteristic
(unique) quantitative numbers of clay/sand distribution.
3. HYDROGEOLOGY
Objectives
Hydrogeological characterisation of fractured sites.
Activities
A suite of hydraulic test methods will be undertaken using grain size distribution,
matrix permeability determined on small plugs, slug tests in wells, pump tests and
tracer tests to characterize the hydraulic properties above and below the redox
transition at the contaminated site.
4. CONTAMINATION, BACTERIA AND PROCESSES
Objectives
The objective of the plume characterisation is to draw a detailed picture of the
contaminant, bacteria, redoxcondition and organic carbon source distribution between
sandlenses, fractures and the matrix, to identify the naturally occurring processes in
the system. The investigations will be carried out at three different scales (site scale,
source scale and core scale) to get a detailed background picture before a remediation
is started. The microbial community involved in dechlorination of the chlorinated
solvents is indeed an important factor for the description of our site.
Activities
Site scale: Available field site data will be collected and analysed. If necessary more
data will be collected (e.g. more boreholes will be made, extraction of groundwater
samples, soil samples etc.).
Source scale: The vertical distribution of the contaminant in the source area will be
described using detailed soil sampling and Membrane Interface Probe (MIP). This
will be carried out at several locations in the source area to picture the horizontal
distribution as well. Boreholes will also be installed in the source area to be able to
extract groundwater samples and to measure the hydraulic gradient.
Core scale: Core samples will be collected from the ground surface and down through
the contaminated area. The geological composition of the cores will be described and
detailed profile soil sampling will be carried out to picture the contaminant
distribution and ongoing natural processes in sandlenses/fractures and the clayey till
matrix. Both the general phylogenetic markers and more specific functional markers
involved in dechlorination are important. It is suggested to make microbial
community analysis prior as well as subsequent to any treatment event. To investigate
the possibility for bacteria to move into the clayey till matrix geologic thin sectioning
will be made to picture pore sizes. Furthermore, we intend to apply molecular
microbial analysis on a micro scale characterization based on the geologic thin
sectioning of the sediment pore structure.
Some of the parameters that will be measured to be able to understand the processes at
the field site are:
 Chlorinated solvents and their degradation products.
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Redox conditions (both dissolved and bound compounds (speciation of FeII and
FeIII on the sediment)) and carbon source availability (organic carbon and fatty
acids).
Isotope fractionation for stable carbon and chlorine isotopes.
Microbiology: DGGE profiles based on 16S rRNA will be used as the
characterization of the general microbial community; A quantitative measure of
Dehalococcoides spp. based on 16S rRNA genes specific to Dehalococcoides as
well as a quantitative measure of tceA-, vcrA-, and bvcA genes will provide a
characterization of the community of the specific degraders.