Plymouth City Council

Background to specification
The A386 Tavistock Road Improvements (Park & Ride) Plymouth, a £14m project designed and commissioned by Plymouth City Council, would include a purpose-built terminus equipped with real-time displays of bus arrivals and departures.

For contractors South West Highways Ltd, the project was its largest contract since privatisation. Plymouth City Council specified drainage requirements to Highways Agency and environmental specifications, and Tubosider attenuation systems were proposed to reduce risk of flooding and erosion of the nearby water courses.

Supervising engineer John Coleman of Plymouth City Council and contractor’s site manager Chris Veal were invited to Tubosider’s factory in St Helens to see our manufacturing in progress.

Key criteria
The specification required the construction of a stormwater retention tank with almost 1000 m³ storage volume. The scheme arrived at by Tubosider provides a 985m³ storage volume in 1.8m diameter pipes of 3mm galvanised steel with Trenchcoat coating.

The Trenchcoat coating, a protective process which can be applied by Tubosider to any tank or pipe which requires it, meets Highways Agency Standard BD12/01 for HA loading and aggressive environmental conditions and providing a minimum design life of 120 years.

Solution & benefits
The footprint for the attenuation system in the car park consists of six legs of 63.5m length and a manifold either end with access shafts & ladders. Inside the tank is a Mosbaek flow regulator also supplied and fitted by Tubosider at the outlet to regulate the flow to 30 litres/second.

“This 18 month project has been our most important to date, so we needed to be sure that there would be no delays and that any teething troubles were resolved quickly and smoothly,” says South West Highways’ Chris Veal.

“We have been very impressed with the all-round support we had from Tubosider, which included the recommendation of a specialist installer for their system soon after it was ordered. We look forward to being able to maintain that relationship on further projects.”