Investigations

This section contains summaries of reports on drinking water
quality incidents and investigations.

Report on drinking water quality incident at:
Dores Water Treatment Works in December 2007

Scottish Water Executive Summary

Scottish Water Solutions (SWS) as part of the Q&S3 programme of works has to address the disinfection (DW13) driver for Dores Water Treatment Works, located 5 miles south west of Inverness on the shore of Loch Ness. The solution approved by Scottish Water (SW) to address the driver is to construct a new water pipeline from the Inverness WTW to the Dores existing water distribution network. This work comprised the construction of a Water Pumping Station (WPS), 100m3 Clear Water Tank, (CWT) and 4km of 110mm OD HPPE water pipeline.

Alfred McAlpine as Partners in SWS were contracted to undertake the work. They sub contracted the Civils Engineering Element to a local contactor, MacLean - Ardgay, the Mechanical/Electrical elements to Nomenco, and the Telemetry/Radio Link to ID Systems based in Glasgow.

As part of the commissioning process the new infrastructure had to be disinfected in accordance with Scottish Water's Hygiene Code of Practice and Distribution Operation and Maintenance Strategy (DOMS). To undertake this efficiently both McAlpine and MacLean - Ardgay contracted this work to EPSCO, a specialist disinfection contractor.

On Tues 4th Dec, 2007 the disinfection of the pipeline/pumping station and CWT commenced. Wed 5th Dec Water is drawn from Inverness CWT for disinfecting. During this process SW Customer Operations witness petrol driven pumps, without drip trays, and a gerry can beside open excavation. This was immediately brought to the contractor's attention and drip trays were installed and the gerry can removed. Disinfection was completed and samples taken. Mon 10th Dec McAlpine request pipeline be installed to allow pumps to be tested. Request was approved by SWS Ops and Comms Liaison Engineer without checking with SW Customer Operations. SW Ops Coordination Manager advised SWS Ops and Comms Liaison Engineer of Drip tray and gerry can incident. SWS Ops and Comms Liaison Engineer arranges bacteriological and Hydrocarbon samples to be taken for possible contamination. A section of pipeline was also removed to maintain air gap between new infrastructure and the live system. In addition to this McAlpine's reviewed their access certificate and found that it had expired. Tue 11th Dec SW Senior Scientist raised Near Miss event relating to non-compliance with DOMS procedures. Wed 12th Dec McAlpine undertake an investigation of the Near Miss.

Actions arising from the incident include the instigation of a DOMS audit procedure for contractors working on live sites, retraining in DOMS procedures of SWS staff involved in incident and raising awareness of access permit procedures.

DWQR Assessment on the incident

During 5th December 2007 work connected with improvements at Dores WTW, undertaken on behalf of Scottish Water by subcontractors, resulted in a "near-miss" when a pump without appropriate spill protection and a "gerry can" of petrol were discovered beside an open trench containing a section of newly-laid water main. Both occurrences were in breach of Scottish Waters Distribution and Operation and Maintenance Strategy (DOMS) procedures.

In an associated incident on 10 December 2007 a section of pipe was connected between two hydrants at Inverness WTW the result of which was to increase the risk of contamination of the drinking water supply with water being used to commission the new pipeline.

In both "near-miss" instances a failure to properly comply with SW's procedures was a significant factor in the chain of events leading to the "near-miss". Once the "near-miss" had been recognised, DWQR is satisfied that Scottish Water took appropriate steps to protect drinking water supplies.

For the period covering these two "near-miss" events the access certificate issued by Scottish Water to the subcontractors was out-of-date. This occurrence has been attributed to (i) a failure of communication between Scottish Water, Scottish Water Solutions (Scottish Water's delivery partner) and the subcontractor resulting from (ii) staff changes. A similar situation occurred during an incident at Glenconvinth WTW in November 2005. At that time Scottish Water undertook to act on their (Scottish Water's) report's recommendations including recommendation 8 dealing with organograms for the works being undertaken. DWQR is satisfied that Scottish Water have acted on the recommendations made in the 2005 Incident Report but the rigour applied at Dores/Inverness in December 2007 in respect of Glenconvinth recommendation 8 was not satisfactory. Scottish Water and their delivery partners must ensure that appropriate hand-over procedures are in place during personnel changes and that such procedures ensure that all requirements set out in Scottish Water policies, procedures and contracts are adequately adhered to.