Groundwater Risk Assessment Model (GRAM): Groundwater Risk Assessment Model for Wellfield Protection

Abstract

A groundwater risk assessment was carried out for 30 potable water supply systems under a framework of protecting drinking water quality across South Australia. A semi-quantitative Groundwater Risk Assessment Model (GRAM) was developed based on a "multi-barrier" approach using likelihood of release, contaminant pathway and consequence equation. Groundwater vulnerability and well integrity have been incorporated to the pathway component of the risk equation. The land use of the study basins varies from protected water reserves to heavily stocked grazing lands. Based on the risk assessment, 15 systems were considered as low risk, four as medium and 11 systems as at high risk. The GRAM risk levels were comparable with indicator bacteria-total coliform-detection. Most high risk systems were the result of poor well construction and casing corrosion rather than the land use. We carried out risk management actions, including changes to well designs and well operational practices, design to increase time of residence and setting the production zone below identified low permeable zones to provide additional barriers to contaminants. The highlight of the risk management element is the well integrity testing using down hole geophysical methods and camera views of the casing condition.

Engineering and environmental remediation scenarios due to leakage from the Gulf War oil spill using 3-D numerical contaminant modellings

“…The data and our interpretations have been sourced from consultant reports by SMEC (2014). The ultimate aim of the numerical groundwater modelling is to assess risk and potential remediation scenarios to allow an informed decision to be made on the preferred scenario (Somaratne et al 2013;. Further to the preliminary assessment of the scenarios, the model may be used for optimisation using the results of future pilot field trials.…”

Groundwater Engineering in an Environmentally Sensitive Urban Area: Assessment, Landuse Change/Infrastructure Impacts and Mitigation Measures

“…Some of these impacts are tangible and can be measured, while others are intangible and difficult to assess [9]. Planning and control policies, if effective and enforced, can be very influential in controlling the extent and rate of groundwater degradation.…”

“…Numerical modeling is obviously the preferred choice for the spatial and temporal groundwater assessment role in investigating the effects of climate and human interventions in groundwater head fluctuations [8]. The model can predict the future behaviour of the phenomena and its uncertainty [9,10].…”

Review of Risk Status of Groundwater Supply Wells by Tracing the Source of Coliform Contamination

“…In drinking water sources, the presence of faecal bacteria is considered a health hazard, as they may indicate the presence of human viruses, or parasites Giardia or Cryptosporidia [1]. In a groundwater risk assessment study [2] using a multi-barrier analysis approach, risk levels for town water supply wells compare favorably with respect to coliform detection. Out of 144 town water supply wells in South Australia, 142 wells recorded detection of coliform ranging from 1% of frequency in low risk confined aquifers to 87% frequency of detection in a high risk unconfined aquifer in karst limestone.…”

“…Aquifer pathways from hazard to receptor may exist due to the hydrogeological setting in a particular area, including soil and strata types, depth to groundwater and type of well construction and maintenance. This study builds on the development of a groundwater risk assessment model (GRAM) [2] and involves identifying the sub-type of coliform indicator bacteria present in the water sources ranging from low risk to high risk wells. The sub-typing of bacterial strains recovered from water supply wells constructed in different climate and geologic settings with different maintenance history is a valuable tool for identification of contamination sources and pathways.…”