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The Hopwood Park motorway service area (MSA) is situated at Junction 2, on the M42, where the A441 crosses the motorway.
Fig 1: Location of Hopwood Motorway service area(click to enlarge)
The MSA comprises an amenity building surrounded by car parking, coach parking and a dedicated HGV park with a centrally located fuel filling area. The MSA is enclosed in a series of planted banks and falls northwards to the Hopwood Stream which flows eventually to the River Arrow.
The site comprises 34 hectares of which 9 hectares is the MSA and 25 hectares a wildlife reserve. A stormwater ditch draining
the adjacent A441 divides the MSA into 2 sub-catchments,
the HGV Park and the remainder of the MSA.
The concept of the management train has been used at Hopwood Park MSA with a variety of SuDS components in series to improve the flow and quality of runoff in stages prior to release into the local watercourse.
Each part of the site collects runoff in a different way but
treats the 10mm ‘first flush’
in stone treatment trenches where possible, a conventional grit
/ oil separator to the coach park and fuel filling area with roof water directly
to a feature pond from the amenity building.
Fig 1: Spillage basin newly constructed
Fig 2: Constructed wetland
Fig 3: Feature pond receiving roof water
All balancing ponds discharge through flow controls to the stilling area and clean water flows into the Hopwood stream at a ‘greenfield’ rate of runoff.
Areas considered to pose a pollution risk to the environment
have used the ‘management train’ concept in full to ensure good
water quality and to deal with unforeseen spillage events.
The HGV park and the fuel filling area, coach park and service yard pose a serious pollution risk and have an extended management train.
The car park and amenity building roof water were considered
less likely to cause pollution and therefore have progressively shorter treatment
systems although the concept is applied generally to provide insurance against
unforeseen spillage events.
The MSA was designed to meet a 1 in 25 storm return period and greenfield runoff rate of 5L / sec / hectare.
Runoff from the HGV park is directed to a tributary of the Hopwood Stream via the Wildlife Reserve to enhance a pre-existing wetland and help sustain base flow in the watercourse.
Open wetland systems are protected by pretreatment features including filter strips, treatment trenches or separators to reduce pollution or silt loading and prevent catastrophic damage in the event of spillage.
Wetland basins are lined completely where designed to treat
runoff or partially where a retention volume is required in the pond feature.
The design of Hopwood Park MSA was undertaken before the publication of the CIRIA design manuals and followed guidance from the Environment Agency and a review of stormwater management manuals from the USA. Construction was completed in 1999.
The site has been monitored since construction to evaluate performance and costs.
Benefit: Control of volumes and flows on site with discharge to the Hopwood Stream at greenfield runoff rates.
Benefit: SuDS techniques used in series; the management train, ensures acceptable clean water enters the natural drainage system.
Benefit: Protected wetland features to manage runoff provide a visual and wildlife resource for the site.
Benefit: The cost of drainage maintenance has been reduced,
by using the Landscape Contractor to manage the site.
Benefit: The series of ponds, wetlands and low flow channels behind the Amenity building now form a SuDS walk for visitors with information boards to explain the Sustainable Drainage approach to managing rainfall on development sites.
Benefit: The SuDS features are robust and withstand damage and
lack of maintenance without failure.
The information on Hopwood Park MSA M42 is provided by Robert Bray Associates, who, in association with Baxter Glayster Consulting Ltd – Consulting Engineers, designed the Sustainable Drainage System and have been responsible for arranging the management and monitoring of the site. The Client for the site was Welcome Break.