Role of groundwater gradients and external sinks:
— Local groundwater gradients associated with the OCP (acting as a groundwater combined sink east of the TSF) and the inferred groundwater divide along the northeast-southwest trending topographic ridge are expected to control the direction of seepage migration, eastward toward the pit in areas hydraulically connected to it.
5.2
Field investigations
The field investigations described in the following subsections are intended to improve understanding of seepage pathways, groundwater surface water interaction, and subsurface conditions in the vicinity of the UMG TSF, and to support validation and refinement of the conceptual and numerical groundwater models.
5.2.1
Watercourses reconnaissance
Watercourse reconnaissance will be undertaken along Paddy Creek and Spring Creek and their confluences with Turner Creek to support the following seepage assessments by providing site specific observations of surface water conditions and their interaction with the groundwater system. The investigation is intended to ground‑truth the current hydrogeological conceptualisation and to inform interpretation of modelling outcomes.
The reconnaissance will include the following key elements:
— Visually assess watercourse conditions during both wet and dry seasons.
— Evaluate the degree of interaction between surface water and groundwater, including evidence of gaining or losing reaches. — Confirm the current conceptual understanding that both creeks are intermittent, flowing during the wet season and remaining dry or largely dry during the dry season.
— Identify locations where surface water is present and actively flowing.
— Record observable flow paths, wetted extents, and any zones of persistent flow or ponding.
— Develop a visual estimate of relative flow magnitude, and apparent discharge.
— Confirm absence of surface flow or presence of isolated pools.
— Identify any locations where groundwater discharge may persist beyond the wet season.
Reconnaissance to be conducted over seasons to capture inter‑annual variability and seasonal contrasts, and its findings documented in a technical memorandum. A reconnaissance plan will be developed prior to undertaken the field campaign.
5.2.2
Geological mapping
Detailed geological mapping will be undertaken to improve the definition of subsurface conditions relevant to the following UMG TSF seepage assessments. The mapping program will focus on verifying key geological contacts, stratigraphic units, and structural features that influence groundwater flow and seepage pathways.
The geological mapping will specifically aim to:
— Identify and map the contact between the Paleozoic bedrock and the Razorback Beds, with particular attention to the spatial continuity and geometry of this interface within and adjacent to the proposed TSF footprint. — Confirm the presence, thickness, and define lateral continuity of stratigraphic layers conceptualised as hydrostratigraphic units within the Razorback Beds, including upper and basal sandstone layers and claystone interval.
Project No PS213278 Mount Morgan Mine - Upper Mundic Gully TSF Seepage Management Plan Heritage Minerals
WSP May 2026 Page 21
Powered by FlippingBook