Deep Well Dewatering - Saint Gobain Glass Factory

Permanent dewatering solution to the rising groundwater issues at a glass manufacturing facility within a Groundwater Protection Zone

Objective

Saint Gobain Glass (SGGUK) contacted Stuart Wells looking for a permanent solution to the rising groundwater issues at their glass manufacturing facility. The facility’s location within a Groundwater Protection Zone would require careful coordination with the local Environmental Agency (EA) to ensure both long-term groundwater engineering and the groundwater environment protection were reached.

Overview

Saint Gobain Glass required a permanent solution to rising groundwater issues at its glass manufacturing facility. Stuart Wells applied for all the necessary permissions with the Environment Agency and designed a permanent dewatering system.

This consisted of a series of 6no x 50m deep abstraction wells around the furnace perimeter to control the groundwater level in the Sherwood Sandstone. The abstracted groundwater was transferred via a pipeline to a series of 31 no recharge wells located on the site boundary and injected back into the Sherwood Sandstone aquifer.

Solution

The project involved the submission and approval of an initial Groundwater Investigation Consent (GIC) to conduct a pumping test. This provided crucial data to finalise the design which included permanent abstraction wells with the abstracted groundwater transferred to recharge wells at the site boundary, where it was reinjected back into the same aquifer.

Pumping Test

The pumping test involved reinjecting all abstracted groundwater back into the aquifer using recharge wells. The test highlighted issues with recharging and the conceptual model was altered to accommodate more recharge wells than initial envisaged.

Ahead of the Groundwater Investigation Consent (GIC) application a Water Features Survey to evaluate the impact of the proposed abstraction (dewatering) on the surrounding water environment; sensitive water receptors and abstractions was undertaken by Stuart Wells. The pumping test was undertaken to GIC conditions and involved the installation of 2no abstraction well and 8no recharge wells, all located and designed to enable reuse in any subsequent permanent dewatering system. Groundwater levels were observed in existing site monitoring wells, together with all identified environmental assists; prior and during the pump test phase.

Pump Testing consisted of the following scope

Permanent Dewatering Design & EA Groundwater Transfer Licence Application

Data and information generated from the pumping test was used to model a permanent dewatering and recharge design to comply with both groundwater engineering requirements, in terms of required drawdown, contingency wells to allow for long-term maintenance and environmental objectives and constraints.

The achievable recharge flow rates observed during the pumping test and subsequent modelling identified the need for more recharge wells than initially envisaged, together with additional ongoing monitoring requirements. In October 2020, Stuart Wells mobilised 2no rotary drilling rigs to site and drilled, installed and developed installed all remaining abstraction and recharge wells over a 6-week period.

Abstraction Well Detail

Recharge Well Detail

415V Caprari submersible borehole pumps c/w level probes were installed within each abstraction well on 2.1/2” steel riser. In turn these connected to a 110mm PE collection main that linked to a 225mm PE recharge main with individual take-offs at recharge well locations.

All wells were housed within manhole chambers with cablings buried and contained within ducting. The pumps were controlled by 2no 4-way variable speed drive pump control panels, that in turn where connected to site mains power supply.

Groundwater levels were monitored using pressure transducer dataloggers and abstraction flow rates recorded by MAG flowmeters. All monitoring data was managed to enable remote monitoring, establishment of an alarm arrangement, all powered by solar panel set up at individual location.