Multi-layer methodology for the assessment & remediation of a site with a complicated

use history

Dr Fouad AboTechnical Leader – Contamination Assessment &

Remediation Technologies GHD Pty Ltd

VI International Seminar on Remediation & Redevelopment of Contaminated Sites, Sao Paolo, 27 – 28 Oct 08

Outline• The site history

• Why anecdotal can be frustrating• Covering “all angles” as an auditor• This is not your standard SH

• Cultural heritage and military history search• Geophysical study and Validation• Sampling & analysis• Results• Using the soil characteristic• Groundwater and Regulatory Guidelines• Aesthetic and asbestos• Conclusions

Site History• The site is >200ha• The site uses are not consistent throughout:

• Some areas of the site were used as an air base during WW2 (1938/45).

• They were used as a military training ground.• Planes were disassembled on the site after the war.• It has a timber treatment plant (1960/80).• Some areas were used as a fuel storage.• The site has few hangars.• It has a sheep dip.• It has an incinerator.

…Continued.. Site History• It has even a former Carn-boon home stead that was demolished

and dumped in situ!• It has few animal carcasses.• Allegedly an As based herbicides/insecticides drums were dumped

on site!!• It was and continues to be sued as a sheep grazing field.• One of the hangar is used by the “B24 Liberators Memorial

Restoration Fund”. • It has heritage issues with the Hangars that are full of asbestos• Is that enough!!!

There is more …

Archaeological & Heritage SearchArchaeological and Cultural Heritage Survey provided detailed assessment of the

archaeological and cultural heritage of the site.

There are evidences of > 40,000 years of Aboriginal presence in Victoria, and it is an offence to damage or destroy such places.

• One Aboriginal site (the Kulin association of 5 groups) is located on the alluvial terrace adjoining the bank of the Werribee River.

• One Non-Aboriginal Historical Archaeological site known as the ‘Carn-boon Homestead’ is listed on the Inventory at Heritage Victoria.

Military Site History Search

The Review of World War II Era Military Activity at Werribee Fields provided background information regarding the previous military land use and other historically significant sites at Werribee Fields.

The Military archives showed that an area of the site (about 45 ha) was used for RAAF training area. Photo below shows the numerous planes stationed at the site.

There were records that planes were diss-assembled at the site after WW2, this was confirmed through metal debris discovered at the area, possible UXO!!

Hence, the need for Geophysical study, where a number of technics were used.

WW2 Photo for the RAAF area of the site

Geophysical Investigation The Sub Surface Survey Report provided information on potential

Underground Storage Tanks (USTs), munitions burials, the extent of ferrous and non-ferrous debris and the presence of unexploded ordnances.

The surveys of the perennial dam and central portion of site have failed to identify any evidence of illicit dumping, including possible CCA drums.

The Enterra report did not identify any areas of UXO, ammunition, armaments Or burial locations .

Validation of Geophysical Findings

A number of methods were used to confirm the findings:Test pits;Long trenches;Random selection and systematic counting; andDefine area based on “hits” and sieving of soil.

Findings

Site History & Contamination Potential

• Inorganics (primarily As, Cr, Pb, Cu, Zn);• BTEX and TPHs;• OPPs and OCPs;• Chlorinated Hydrocarbons and Solvents;• PAHs and Cresol;• E.coli/pathogens; • nutrients; • PCBs; and• Aesthetic.

Selection of Analytes List

• Analytes comprised BTEX; TPHs; PAHs; speciated phenols; chlorinated hydrocarbons; OCPs; OPPs; PCBs; Inorganics including: antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, tinand zinc; pathogen, cresol, NH4, and NO3.

• Asbestos.

Sampling and Analysis

• The Australian Standard AS 4482.1 provides recommendation on sampling density. For an 86 ha site a minimum of 946 sampling locations (excluding targeted locations) is required for site characterisation.

• This mounted to high cost and there was need to rationalise without affecting the outcome.

• At the end enough samples were collected with a focus on balance between targeted, systematic, and random sampling.

Geology & Soil• The region is formed by a succession of geological events, starting about 65

M years ago with the earth movement in the Cainozoic Era. the site is situated on Quaternary Age ‘Deutgam Silt’, which overlies the Quaternary Age Newer Volcanics Formation, predominantly comprising dark to light grey olivine basalt.

• The soil is red-brown silt characterised by a hard-setting loamy surface soil, with a paler subsurface (A2) horizon, abruptly overlying reddish-brown clayey subsoil. The surface soils are poorly structured and have high fine sand and silt. According to the ASC System these soils are Chromosols with a clear textural B horizon where the major part of the upper 0.2 m of the B2 horizon is not sodic and not strongly acid.

Groundwater• The Newer Volcanics and Brighton Group Formations are the two

primary aquifer systems in the vicinity of the site. Groundwater flow is toward the Werribee River and Port Phillip Bay, located approximately 900 m to the east and 7 km to the south east of the site respectively.

• Groundwater was encountered at depths ranging from approximately8.1 to 9.5 metres during the groundwater investigation program, and stabilised at depths of between 6.818 and 9.362 metres in the completed monitoring wells.

Results • Statistical, sensitivity analysis, and comparisons of data provided

confidence on the reliability of the results.• Groundwater with some elevated background inorganic levels.• High levels of As in the CCA treatment plant. • Health and ecological impact were not identified.• Soil results were generally within acceptable levels for residential land

use scenario, however, there was some high level inorganics such as Pb, Zn, As, Mn, & Ni.

• So TCLP & ASLP tests were conducted:

• “leachable % was low.• Difference between

TCLP & ASLP was high:

0.60.1

18030

TCLP: 4.9ASLP: 6.5

630Mn

--

<0.005<0.005

TCLP: 4.9ASLP: 6.5

60Ni

4.94.2

190160

TCLP: 4.9ASLP: 6.5

77As

13.30.3

10,000190

TCLP: 4.9ASLP: 6.5

1500Zn

0.260.1

4911

TCLP: 4.9ASLP: 6.5

370Pb

% Leachable

Leachable Conc (µg/L)

Procedure & pHSoil Conc. (mg/kg)Contaminant

Table 1: Summary of results from leachability tests

Soil Characteristic and Results

• Knowing your soil always helps assessing the risk that contaminants may pose.

• In this instant the soil is of high % clay and loam, the clay isdeveloped over volcanics (basalt), hence expected to be of high CEC/high contaminants assimilation capacity.

• So using the soil characteristics to explain the dynamics/kinetics of the soil chemical process was used to assess the contaminant risk mitigation.

• It was also important to assess the contaminants potential mobility by ‘comparing” the widely used TCLP and ASLP tests result.

What about the Plant Analysis

• Where high level of contaminants was found (i.e. timber treatment plant), plant analysis was used as an other mean of assessing contamination risk.

• This has provided some important info as part of the multi layerevidence for an audit.

GW Quality Outcome • Some of the Zn, Se, Pb, Cu, Ni levels detected exceeded mostly

the MoE, so we needed to find the reason.• The scenario was: look at the site history, geology,

hydrogeology, beneficial uses in accordance with the SEPP, soil type, contaminants nature, corresponding levels in soil.

• Concluded that these levels are naturally occurring, hence high background levels.

• This was presented to EPA andaccepted.

Aesthetic and Asbestos

• The Land SEPP raises the aesthetic issue as part of the audit requirement. There is no criteria and could be subjective.

• So in a site like this, there are few metal debris from previoususes esp. the planes disassembly.

• The auditor needed to be satisfied that adequate assessment is carried out, this was done by: random and judgemental soil excavation (so not only based on geophysics); soil sieving; counting of objects found per area.

• Asbestos was not a big issue as it was found on limited areas and removed then soil validated.

CCA timber treatment

Conclusions

• For such a complicated site, it was important to integrate a number of approaches in an innovative way to reach an outcome that satisfy all stakeholders and future users.

• So a combination of science, logic, experience, consultation, and common sense was crucial.

• It is important to challenge existing conventional way of doing things and to share the lessons learned.

Thank You