Ardesier Port

Project Overview

Dewatering of coastal sands for an energy transition facility on the Moray Firth

Objective

The development of an Energy Transition Facility in the Moray Firth, involved the construction of a 1150m quay that required dewatering of tidal flat and raised marine sand deposits to enable the placement and fixing of 45m long tie-rods between the quay and anchor diaphragm wall.

With early engagement Stuart Wells developed a dewatering strategy, with the undertaking of pumping tests that lead to the design and the successful operation of a combined vacuum wellpoint and deep well dewatering system.

Scope of Works

A. Conceptual Modelling, Pumping Test & Dewatering Design

With the construction being undertaken adjacent to the Moray Firth, dewatering of tidal flat and raised marine sand deposits was required. Dewatering reduced and maintained the tidal groundwater level to below the bulk excavation level enabling construction of capping beams along the anchor diaphragm wall.

Prior to the main works, a pumping test was undertaken to generate data for the dewatering design and required licenses and permissions from Scottish Environment Protection Agency (SEPA). Alongside the pumping test a trial dewatering operation was undertaken in conjunction with a construction trial of a sheet-piled excavation with exterior micro-grouting.

B. Dewatering Design & Operation

Construction work was undertaken in 5no zones (S1 to S5) and progress in sequence, with over-lapping dig zones from S1 (East) to S5 (West). The dewatering objective was to enable bulk excavation and tie rod installation works to be undertaken in dry and stable conditions, which required a groundwater drawdown to 8.7 m BGL in Areas S1, S2, S3 & S4 and 10.7 m BGL in S5.

Solution

Stuart Wells carried out conceptual modelling and pumping tests to inform the dewatering design. In combination the internal deep well dewatering and external anchor wall wellpoint dewatering systems allowed the anchor wall works to be undertaken in dry and stable conditions