Contaminated Site Audit, Proposed Residential Redevelopment, City of Belmont, Swan Coastal Plain, Western Australia
 
Land previously used for residential purposes and limited commercial operations has been cleared, and is proposed for High rise residential redevelopment.

A Contaminated Site Audit (CSA) was undertaken on behalf of the proponent to support an application for rezoning at an increased residential density. 

Former houses have been demolished.  Investigation works have identified the presence of  organo-chlorine/phosphate (OCP) pesticides in soils around the former housing pads above applicable guidelines for  residential development. 

The demolition and removal of boundary fences has resulted in isolated occurrences of asbestos on the soil surface. Shallow groundwater adjacen to the Swan River has been impacted by OCPs above applicable guidelines for  irrigation and the marine environment, applicable to the adjacent estuarine River Swan.

Current investigations will determine the extent of this impact.

A stage 3 Site Management Plan is currently being formulated for the removal of surface impacted soils and replacement with clean fill, including removal of isolated asbestos. 

Stuart Jeffries
Hydrosolutions Pty Ltd

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Audit 13

NATIONAL RIVERS AUTHORITY UK (now ENVIRONMENTAL PROTECTION AGENCY):
National Groundwater Protection Policy- Determination of Groundwater Protection Zones, 750 Public Water Supply sources, throughout England and Wales.

Groundwater protection zones (GPZ’s) were developed for 750 public water supply groundwater sources as
part of the National Groundwater Protection Policy for England & Wales.  A consistent methodology was
developed for each source.  A data request proforma was used to obtain hydrogeological data from regional water  authorities.  The quality of data was evaluated and a decision made on the most appropriate method to delineate the GPZs. Like sources/locations were grouped where possible.

Analytical methods were used initially to provide a simple check on the catchment & time of travel zones
using recharge estimates. The analytical result was adopted for sources with poor data quality.  GPZ for
sources with intermediate data quality were determined using the USEPA computerised analytical model
WHPA (“Well Head Protection Area”) using backward particle back-tracking methods.

Sources with ‘good’ data were analysed using the numerical finite difference model FLOWPATH (WHI).  A hydrogeological conceptual model was developed & agreed, which was represented as a numerical flow domain.  The following isochrone & catchment zones were defined:

• The 50-day (inner) protection zone (biological  & sanitary protection)
• The 400-day (outer) protection zone (response zone in the event of a contaminant release to the aquifer
• Total catchment zone: Steady state based on recharge estimates.

A standardised report was produced for each group of sources, including:

• All data & evaluations
• Analytical determinations
• Numerical model & source codes/files
• Time of travel & total catchment maps as Geographical Information System (GIS) files

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro19

PIONEER CONCRETE
Mineral landbank development with low-level restoration, Lincolnshire, England

Options to extract aggregate and restore the site were reviewed for a sand and gravel lens above liassic clay.

No constraints on dewatering by conventional means were identified.  The dewatering scheme included the recirculation of abstracted water via two settlement ponds, to permit mixing and the regulation of  groundwater quality.

Options for the low-level restoration of the site were examined.  The use of in-situ materials was identified to be the most cost-effective option compared to construction of a bentonite slurry wall as a permanent groundwater exclusion structure.  Long-term incidental rainfall and likely seepage rates were identified using numerical modelling. An assessment of settlement potential due to dewatering was also undetraken

Recommendations were made for internal and external drainage structures to be incoporated into the design.  

A geotechnical appraisal of the suitability of on-site clays to form the exclusion structure was undertaken.

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro18

RESOLUTE SAMANTHA
Additional groundwater resources for Bulla Bulling Minesite, near Coolgardie, Goldfields, Western Australia

A groundwater exploration program was undertaken to establish additional process and potable water supplies to meet minesite capacity expansion.

Existing prospects were reviewed.  Four additional production bores were established to access groundwater resources within a concealed palaeochannel sequence identified via goephysical survey at three locations chosen to minimise bore interference.  A fifth bore was established at a nearby abandoned borefield.  All bores were test pumped to estblished hydraulic parameters aand sustainable yield. 

Recommendations were made for sustainable yield and borefield operations.

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro17

PEAK HILL RESOURCES LTD
Development of additional groundwater resources for minesite, Meekatharra, Goldfields, Western Australia

A groundwater exploratory program was undertaken to establish additional process and potable water supplies for the minesite.

Exploratory bores were drilled around the existing main borefield completd within the Bangemall metsediments.  One bore provided a short-term yield of 220kL/d, although interference effects will limit
long-term yield.  Borefield supplies are also limited by the volumetric capacity of the existing pipeline
servicing the mining operation.

A second exploratory program was undertaken around the ‘Spehrs’ borefield completed within the folded mine sequence.  Minor additional water supplies were obtained from bores completed within the exposed hanging wall sequence; numerous bores had been drilled with highly variable results.  The geological structure was reviewed; successful bores intercepted a chert sequence locally absent through folding and faulting.

Two additional bores were completed, providing an additional 463kL/d.  The additional water resource obtained from the overall program was in excess of the net target requirements for the minesite.

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro16

COMMONWEALTH DEPARTMENT OF DEFENCE
Environmental Restoration Plan, Naval Communication Station Harold E Holt,
Northwest Cape, near Exmouth, Western Australia

Contamination had arisen at the Naval Communication Station due to historical waste disposal, chemical applications, industrial activities and chemical spillages since the base was commissioned in 1966.  The base extends to four areas in excess of 15km2.

The main contaminated materials included:

-Mixed domestic and industrial wastes
-Discharges of bunker fuel & diesel
-Organo-chlorine herbicides/pesticides
-Polychlorinated biphenyls (PCBs)
-Garnet from maintenance operations
-Asbestos building wastes
-Metals leached from below ground
 structures

The remedial scheme involved the removal by excavation of contaminated materials present above environmental guidelines followed by restoration with virgin fill. The contaminated soils were either to be bioremediated & replaced (for hydrocarbon impacted soils), or for more intractable materials for disposal
to a class IV (low-level) waste landfill, the first to be designed & commissioned in WA.

Numerical modelling was undertaken to assess the risk to groundwater, including the stygofauna, and to the marine environment from possible failure of the landfill liner. 

Removal of contaminated material was validated.  Each excavated area was to be re-instated with topsoil and re-seeded with native vegetation.  An aftercare period of five years was specified.

An on-going groundwater monitoring program within the underlying karst limestone and superficial deposits was put in-place to verify that the intent of the remedial program was met.

Stuart Jeffries
Hydrosolutions Pty Ltd

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SiteRem4

Public Water Utility, Gatehampton, England
Resource investigation of a 22ML/d Public Water Supply bore affected by phenols

The potential to realise the licensed yield at a major chalk groundwater Public Water Supply (PWS) affected by phenolic contamination was undertaken.  A desk study examined the history of contamination: phenol & other organic and organo-chlorine (OC) contaminants were periodically present in raw water obtained from bores within the PWS, restricting the operation and yield of the source. Two potential upgradient sources for the phenol were identified; a former town-gas works, and a former wood mill using OC preservatives.

A site investigation program included on and off site soil bores to obtain unsaturated zone cores: interstitial fluids were removed via centrifuge for analysis.  Off-site groundwater monitoring bores were constructed throughout the dry-river valley adjacent to the source.

A major test pumping program was undertaken over two weeks at the PWS maximum licensed abstraction rate of 22 ML/d, with discharge being directed into an adjacent perched water course.

Low-level non-chlorinated phenols were analysed on one occasion at commencement of the test, with other organic contaminants including phthalate esters identified periodically.  However a nearby satellite bore was found to contain high concentrations of phenols.  It was concluded from the phenol speciation that contaminants were present from the former gas works operations, although regional numerical groundwater modeling results indicated that the lateral extent of the contaminant plume was strongly influenced by large-scale abstraction up and down gradient with the river valley.

Overall, the existing combined abstractions were beneficial in promoting natural attenuation of the
residual urban contaminants.  It was concluded that the licensed yield could be obtained safely, provided an on-going monitoring program was in place.

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro15

AGROCHEMICAL MANUFACTURER, Kwinana, Western Australia
Review of deep waste injection operation

An agrochemical manufacturing site has been in operation in Kwinana since the 1960’s.  Former waste disposal practices involved the disposal of waste oils, intermediates and wash down from reaction vessels into shallow unlined pits, which resulted in the contamination of unconfined groundwater by salt-water/ brine, diesel, toluene and organo-chlorine pesticide residues and contaminant bi-products, including 2,4-Dichlorophenoxyacetic Acid (2,4-D) and 2,4,5-Trichlorophenoxyacetyic Acid (2,4,5-T).  2,4-D and 2,4,5-T were mixed together in approximate 50:50 ratio to form the defoliant ‘Agent Orange’ during the Vietnam War.  The former manufacturing process for 2,4,5-T may introduce trace amounts of the dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which, if present, is highly toxic to humans.

Following a review of waste disposal options, a license was granted in 1984 for the disposal of effluent by deep waste injection (DWI) to the Cockleshell Gully Formation.  A deep cased bore was constructed to a depth of 1457mBGL, and perforated over the designated injection horizon.

A review was undertaken to assess the historical DWI operations, in line with more stringent requirements in the United States of America (USA) and proposed changes restricting or preventing similar operations within Western Australia.  The hydrogeology of the receiving environment was reviewed: saline groundwater is confined by thick overlying Cadda Formation.  No significant mineral resources were identified.  The area is relatively stable seismically.  Re-modelling of solute movement under an increased injection rate was undertaken, which indicated that the waste would be contained within the injection
horizon for the foreseeable future. It was concluded that the DWI operation was being operated within applicable regulatory requirements.

Recommendations were made for a program of  integrity testing in line with proposed US underground injection control (UIC) guidelines.

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro14

CONTAMINATED SITE AUDIT 
Former Fuel Bunkering Terminal, Fremantle, Swan Coastal Plain, Western Australia
 
A Contaminated Sites Audit (CSA) was undertaken on behalf of the site owner, of a former marine bunker fuel and diesel storage terminal.  The Site had been leased since 1921 to various oil companies, who had operated a storage terminal for marine fuels in large capacity above ground storage tanks (ASTs), storing light diesel and bunkering oils.  As a condition of the lease, the site was to be returned to the owner in a condition suitable for residential development.   

The former site operator undertook demolition works during 2005. Investigation and remedial works occurred  between January and October 2005.

The audit reviewed completed reports for the Stage 1 Preliminary Site Investigation (PSI), Stage 2 Detailed Site Investigation (DSI), Stage 3 Site Management Plan (SMP) and Stage 4 Remediation, Validation anjdf On-going Monitoring (RVoM) work undertaken by the former operator. Investigation works included soil and groundwater monitoring bores.

Hydrocarbon contaminated soils above applicable guidelines for residential development were
identified at various locations at former tank footprints, pipeline corridors and Anpress unit. 
Groundwater was impacted by Phase Separated Hydrocarbons (PSH) and dissolved phase hydrocarbons present in both on-site and offsite bores.

A Site Management Plan involved the removal of impacted soils above guideline levels to
depths in excess of 2mBGL for off-site disposal and replacement with clean fill. Unsuccessful
attempts were made to recover PSH from the water table.  A long term management plan via
Monitored Natural Attenuation (MNA) was proposed.

Due to identified shortcomings in the remedial works undertaken, the site was  classified as
‘Contaminated – Remediation required’.

Stuart Jeffries
Hydrosolutions Pty Ltd

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(Audit 12)

CHLOR-ALKALI MANUFACTURER, Kwinana, Swan Coastal Plain, Western Australia
Groundwater investigation

An investigation of groundwater quality was undertaken at a chlor-alkali manufacturing plant, which produces chlorine gas, sodium hydroxide and hydrogen from brine by electrolysis.  The manufacturing process involves solid salt dissolved in heated water to form a hot brine. Leakage of brine through the dissolver had lead to a a salt plume within the fresh underlying groundwater within the Safety Bay Sand superficial aquifer.

A geophysical survey using the Em34 was undertaken to produce electomagnetic resistivity profiles of the operational site. These data were used to infer potential points of leakage to groundwater.

A groundwater monitoring network was established to determine the hydrogeological conditions
and groundwater quality in 3-dimensions.

The rate of movement and salt flux was estimated.

It was concluded that the low migration rates would promote natural attenuation of the salt
by advective dispersion in the absence of any downgradient users.

Recommendations were made for an ongoing monitoring program.

Stuart Jeffries
Hydrosolutions Pty Ltd

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Hydro13