The Little Forest Legacy Site (LFLS) is a legacy, low-level radioactive waste disposal facility located at Lucas Heights in eastern NSW, Australia. The site was operated by the Australian Atomic Energy Commission between 1960 and 1968. Landfilling of wastes was to a maximum depth of three (3) metres into clay and shale material of the Hawkesbury Sandstone Formation.
Monitoring of radionuclide containment at LFLS has been ongoing since the emplacement of waste. In recent decades the level of characterisation at LFLS has intensified to develop a more comprehensive understanding of the site geology, hydrogeology and hydro-geochemistry. This additional work is being undertaken to support detailed plans for site management.
Recent site characterisation activity has included coring and geological logging, a range of geophysical surveys, monthly monitoring of groundwater and surface water quality and various laboratory analyses. Groundwater levels have also been recorded every 15 to 30 minutes since mid-2007 at twenty-three (23) locations about the site.
This paper reports the results of our preliminary analysis of the comprehensive groundwater level monitoring data at the LFLS. This includes an analysis of the data with the episodic master recession (EMR) tool recently published by USGS. The EMR program provides a largely automated workflow to estimate groundwater recharge as a function of individual groundwater recharge events. When coupled with historical and/or synthetic rainfall time-series data the output of the tool can also be used to support simple but rapid simulation of past and/or future site groundwater levels.
The data analysis techniques trialled in this study will be of interest to most hydrogeologists routinely involved in site characterisation studies. Our estimates of groundwater recharge rates into the clays and shales of the Hawkesbury Sandstone Formation at the LFLS may also be of interest to many practitioners working in the Sydney Basin.