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Project Focus: Newport retail development requires sewer makeover

A landmark new retail development in Newport city centre needed a redesigned sewer system to serve it, built against tight timescales

Work underway at the Friars Walk site in Newport. The complex will open in NovemberWork underway at the Friars Walk site in Newport. The complex will open in November

Drivers

- Friars Walk is a 390,000 sq ft retail development which will regenerate Newport and create 1200 jobs

- Two major sewers crossed the site which needed to be replaced with one

- Strict timetable meant sewer relocation work coincided with steel erection work

by Simon Thomas, Managing Director, Asset International

The new Friars Walk retail development in the heart of Newport city centre is the lynchpin of the Newport 2020 development plan, a masterplan of citywide schemes and projects which will invest £2BN in this economically deprived region over the next twenty years, in order to deliver a more prosperous and vibrant city.

In partnership with Newport City Council, in 2012 Queensberry Real Estate secured planning consent for a new 390,000 sq ft shopping centre to be constructed in the heart of the city centre, in between the River Usk and Newport’s existing main retail zone. The Friars Walk development is set to open in November 2015 and will provide a department store, five major retail units, a cinema, food quarter, bus station and a 350-space car park.

The Friars Walk scheme has been on the drawing board for some time, however, construction work only commenced in early 2014. The site was initially cleared of buildings and structures with a number of controlled explosions, principally of the nine-storey Capitol car park. The demolition of buildings in John Frost Square marked the first phase of the Friars Walk development, and paved the way for principal contractors Bowmer & Kirkland to move in.

The site of the new Friars Walk development has a long and tangled history which impacted on the groundworks programme. Up until the early nineteenth century, the site was occupied by terraced buildings, a corporation yard, and the remains of a refectory and friary. The original friary walls are located in the north of the site, which influenced the development’s name. The site’s riverside location also means that several Wharfs have historically been located adjacent to the eastern site boundary. In the seventies and eighties the site was progressively redeveloped to comprise a bus station, two multi-storey car parks, retail premises, an engineering works, a number of warehouses and an electricity depot. The result was not only an unattractive blight on the city landscape above ground, but also a subterranean infrastructure nightmare that needed to be addressed before the clean modern architectural lines of Friars Walk could start to take shape.

One of the major early considerations was the fact that two major sewers, each five metres deep, crossed the site, which needed to be replaced with one new sewer during the construction programme. The sewers ran directly across what was soon to be the main retail mall. However, such was the strict project timetable that the relocation of the sewers needed to be done at the same time as the commencement of the steel erection programme which formed the frame of the development. Necessity meant that early on the sewer work took priority, meaning that the erection of the retail area had to be phased around the sewer relocation works.

As well as meeting the stringent project time constraints, groundworks contractor Churngold required a sewer diversion pipeline that would not only be able to divert the existing sewer system around the area, but also to accommodate the sewerage from the Friars Walk development itself. Churngold knew the site’s requirements could be met by water management firm Asset International, whose large diameter plastic Weholite pipes could be utilised to create a new sewer system, under the Friars Walk site.

To deliver Churngold’s requirements Asset manufactured a twin 750mm sewer pipeline with an integral dry weather flow channel, as well as numerous complex flow control chambers. The pipes were delivered to site in six metre lengths.

The use of a twin pipeline means that there is always a redundant pipe, so if there is a problem with one of the pipelines, there is always a standby.

The design engineer also opted to implement a combined sewer system, which mixes the storm and the foul water, all of which is piped to the sewage treatment works for cleansing. This is not particularly common in new developments, but the advanced age of the existing Newport city sewerage system meant that it was required in this instance.

Each pipe is also fitted with a dry weather flow channel, which concentrates the flow into a narrower channel and keeps water and solids moving by increasing flow velocity, even during dry spells. This limits the risk of contamination and effectively self-cleanses. During periods of high rainfall, the full capacity of the pipe can be used to keep flow moving - something that was necessary on the Friars Walk site due to the area’s high water table.

A particularly relevant additional factor in the decision to procure Weholite pipes was the speed of installation that Asset International could deliver, thanks to their method of working which involves delivering factory built, pre-fabricated pipes to site in large segments, meaning that little on-site assembly and installation time was required. This is a must-have requirement in a city centre environment where space is tight and deliveries were restricted. Furthermore, once installed Weholite pipes are service ready immediately, unlike alternative materials such as concrete where days of dry time need to be factored into project timelines.

Another additional benefit brought to the project is the fact that the Friars Walk site is just a few miles down the road from Asset’s Newport factory. This meant that not only did the financial investment remain local, but carbon emissions in the transportation process were kept to a minimum as the pipes were shipped just a short distance between factory and site.

Speaking about the project Darren Williams, Asset International Technical Engineer commented: “We are highly experienced in working in challenging site environments, particularly exigent city centre locations, where space and time are at an absolute premium.

“In fact, our Weholite products are perfect for such environments, as not only are they pre-fabricated off site, but they can be delivered and installed in a matter of hours if required. The process is unbelievably quick in comparison to alternative methods.”

Topic: Sewer Networks
Tags: construction , sewers , plastic pipes

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