Storm Water Redesign Improves Scottish Coast

Discussion of engineering projects, especially between engineers, often moves swiftly from “why” to “how.” A project’s raison d’être can be overlooked in favour of analysing how the outcome was achieved. As engineers finish one project and move to the next, the opportunity to reflect on the legacy of work recently completed can be limited.

However, reaction to a project in Campbeltown, Scotland, brings the “why” into sharp focus. Campbeltown is a port on the Kintyre peninsula in western Scotland. Historically, during periods of heavy rainfall, storm water flows affected the quality of the town’s coastal waters.

As a result, Scottish Water has undertaken an environmental project to reduce the frequency of storm water discharges. Although the community may not have recognized the complexity of the engineering challenge, people seem clear about the project’s benefits. The palpable sense of appreciation may even elicit a moment of reflection from those involved in the project, including the Black & Veatch design and build team responsible for the fifth and final phase.

Community blogs are usually frank. One such blog, For Argyll.com, which had been vocal about the environmental challenges, reported, “The project now completed is helping to protect the environment in Campbeltown Loch by reducing the frequency of discharges of wastewater in storm conditions. It has also substantially reduced the risk of flooding to properties.”

Similarly, The Kintyre Forum noted, “Scottish Water has welcomed praise from community representatives in Campbeltown following the completion of our massive environmental improvement project in the area.”

During an event to mark the project’s completion, Mary Turner, a local farmer and ex-community councillor, observed, “I think the project has been a great success. The local community is very grateful to Scottish Water for the investment they’ve made and for their efforts with community relations during the work.” According to Councillor Rory Colville, “[Campbeltown Loch] is the cleanest it’s been for centuries.”

REDESIGN REDUCES LAND REQUIREMENTS

Black & Veatch’s contribution encompassed enhancements to both Campbeltown’s Wastewater Treatment Works (WwTW) and sewerage network.

“Our approach was characterized by a number of improvements beyond the design as specified in the tender. Collectively, these improvements achieved capital and operational efficiencies,” said Charlie Bull, Black & Veatch Contracts Manager. “We reused existing assets in an innovative manner and reduced the number and size of new structures. We also reduced the footprint of the new works and minimised the impact of difficult ground conditions.”

The WwTW capacity needed to be increased. The specified design required upgrading a temporary supplementary treatment stream. But instead, improved treatment was provided by a new, more reliable solution using elements of the existing stream. Instead of the large sand filters in the original design, Black & Veatch chose less visually obtrusive disc filters. This eased planning issues. In addition, the change brings the operational benefits of lower pumping requirements and easier maintenance.

The amount of new services and equipment required was reduced where possible. For example, the separate motor control centers for the storm and supplementary treatment facilities were combined into a single unit. The revised layout allowed the desludge and washwater pumps to share a common pumping station, further reducing land take and cost.

The project required a new stormwater treatment facility. The tender design layout was improved by replacing the flume and weirs with a simpler pipe control and overflow system. This combined the inlet chamber, flow control channel, outlet and overflow chambers in a single efficient structure.

Adopting a mixer arrangement to clean the storm tank eliminated the need for a separate storm sludge system. The new arrangement also removed the need for rock excavation to accommodate the sludge hopper and pipework. Relocating the storm tank and revising the overall layout reduced the project’s land take by approximately one-third and reduced the landscaping, site roads and earthworks required.

A COMMUNITY BENEFIT

The way the scheme has been delivered drew praise from Scottish Water Project Manager Eddie Burns: “Our contractors have done an excellent job. They met all target dates agreed with the Scottish Environment Protection Agency, worked to a very high standard and were quick to respond to any issues raised by stakeholders, including our customers.”

“Our contractors have done an excellent job. They met all target dates agreed with the Scottish Environment Protection Agency, worked to a very high standard and were quick to respond to any issues raised by stakeholders, including our customers.”

Further evidence of the manner in which the project was delivered comes from success in the Considerate Constructors Scheme (CCS). Sites participating in the CCS are assessed for compliance against eight categories in a code of practice that addresses the effects the site may have on the environment, the workplace and the general public. Campbeltown won a Silver Award in 2011, and in 2012 won a Gold Award and the title “Most Considerate Site, Runner-up.”

The response of Scottish Water’s customers to Campbeltown raises a bigger point. Although such projects are driven by environmental regulation, it is possible to forget that they are not being undertaken for the regulator. As the reaction demonstrates, the benefits are felt by local communities.

SUBJECT MATTER EXPERT

Charlie Bull: BullC@bv.com

This article has been republished with permission by Black & Veatch. 

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About Malcolm Hallsworth, Black & Veatch

Topics: Black & Veatch.

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