Table 5.13 (continued) Entry-level Maximal and Residual risk assessment assessment and precommissioning residual (operational) simplified risk assessment assessment become zone or aquitard collapse or – Preventive artesian water quality and levels in consolidation measures Backfill wells other aquifers • Where real-time adaptive • that intersect Restrict injection and management is required, • Pump the target recovery rates • use feedback control selection aquifer and are Construct piezometers to • systems (to change and poorly give early detection of pumping rates or shut placement completed or leakage down pumps) and have telemetered messaging multiple • As per systems • completions, precommissioning where the rate residual risk assessment, of vertical with refined seals flow is likely identification of on wells to adversely artesian wells – that are impact water poorly completed wells quality in the – d to target storage bursting pressure – monitoring at Monitoring Estimate or • critical control measure points seasonal or Monitor subsidence if • annual warranted by injection and geotechnical evaluation recovery and head volumes s Perform pumping test and Monitor control system • • down-hole flow metering to to detect potential evaluate transmissivity and hydraulic storage coefficient for the failure, for example target aquifer at the injection burst aquitard – well, and to predict fate of excessive leakage – recharged water in the aquifer subsidence Monitor observation well in – • the overlying aquifer excessive – adjacent to the injection well, preferential flow and in the target aquifer, at a lack of flushing – small radius. This will provide early warning of artesian conditions in other wells, potential for subsidence or aquitard failure Also monitor heads in well at • margin of attenuation zone (if a different well) to verify projected head changes in aquifer Implement groundwater- level • monitoring as early as possible before commissioning, to generate background data As per maximal • risk assessment, plus
Table 5.13 (continued) Entry-level assessment and simplified assessment Maximal and precommissioning residual risk assessment Residual risk assessment (operational) Preventive measures • Pump selection and placement • seals on wells that are to become artesian • Backfill wells that intersect the target aquifer and are poorly completed or have multiple completions, where the rate of vertical flow is likely to adversely impact water quality in the target storage zone or water quality and levels in other aquifers • Restrict injection and recovery rates • Construct piezometers to give early detection of leakage • As per precommissioning residual risk assessment, with refined identification of – artesian wells – poorly completed wells – bursting pressure – aquitard collapse or consolidation • Where real-time adaptive management is required, use feedback control systems (to change pumping rates or shut down pumps) and telemetered messaging systems Monitoring • Estimate or measure seasonal or annual injection and recovery volumes • Perform pumping test and down-hole flow metering to evaluate transmissivity and storage coefficient for the target aquifer at the injection well, and to predict fate of recharged water in the aquifer • Monitor observation well in the overlying aquifer adjacent to the injection well, and in the target aquifer, at a small radius. This will provide early warning of artesian conditions in other wells, potential for subsidence or aquitard failure • Also monitor heads in well at margin of attenuation zone (if a different well) to verify projected head changes in aquifer • Implement groundwater- level monitoring as early as possible before commissioning, to generate background data • As per maximal risk assessment, plus monitoring at critical control points • Monitor subsidence if warranted by geotechnical evaluation and head • Monitor control system to detect potential hydraulic failure, for example – burst aquitard – excessive leakage – subsidence – excessive preferential flow – lack of flushing d s
water-recycling-guidelines-mar-24.docx