Master planning St Philip’s Marsh: Bristol's King's Cross?

On Tuesday 26th February 2019, Hydrock hosted its latest thought leadership event: St Philip’s Marsh – Bristol’s King’s Cross?

St Philip’s Marsh, an inner industrial area of Bristol, is one of the city’s few remaining major opportunities for redevelopment and regeneration. With numerous issues to overcome, including multiple landowners, ground contamination from historic heavy industry, and the bounding River Avon and Feeder Canal making St Philip’s Marsh almost an island, kick starting development is complex.

A regeneration opportunity faces the city which by area is five times that of London’s King’s Cross, hailed as one of the UK’s best master planning successes.

Hydrock's approach

Bristol City Council has commissioned an official master plan which is due for delivery later in 2019.

In the interim, and with St Philip’s Marsh gaining traction, Hydrock invited representatives from Bristol's built environment community to consider how an aspirational master plan could look.

Hydrock’s experience delivering opportunity and constraint reports for clients presented an opportunity to conduct a speculative analysis of the key engineering constraints of the site. We analysed the geotechnical, flood risk, air quality, noise, utility and transportation constraints and illustrated the results to start the conversation.

These constraints were presented to some of Bristol’s best planners, master planners, agents and architects in a bid to generate a theoretical master plan for St Philip's Marsh.

The output was then presented to a live audience of 170 people including Colin Molton, Director of Growth and Regeneration and Zoe Wilcox, Director of Development for Bristol City Council.

Let's start with the background: The engineering constraints of St Philip's Marsh.

Flood risk

Bounded by waterways, St Philip’s Marsh is subject to both river and tidal flooding: A one in 200 year flood event would significantly affect almost half of the site, and primarily waterfront development - the most desirable location for residential. Without the provision of flood defences, individual developments would need to be raised.

Geotechnical

Following extensive industrial use, St Philip’s Marsh remains heavily contaminated in parts requiring remediation prior to new development.

Similarly, made ground, silt deposits and clay have created a layer of relatively soft ground approximately 6 metres deep. Harder Redcliffe sandstone sits below this at c.17m below ground, enabling deep-piled foundations for taller buildings. Data regarding unexploded ordinance is limited following the destruction of the data storage facility during a bomb raid in the second world war.

Transportation

The island nature of St Philip’s Marsh creates a limited number of access routes on and off the site. At present, no bus routes operate due to height restrictions on roads connecting the site with existing transport infrastructure. To the adjacent North West is Temple Meads, a significant rail hub, which provides no active service onto the site. There is little cycle infrastructure, however there is a greenway to the south of the site along the River Avon, and in part a single cycleway along Feeder Road leaving, but not returning to, the city.

Utilities

There is sufficient utilities capacity at this time (gas, water, electric and communications). However, there are a number of significant assets on the site that present as constraints. This includes the primary substation to the east of the site, adjacent to St Philips Causeway. It is unlikely the substation would be relocated due to cost constraints. There are buried HV oil cables running from the north east of the site to the south of the site, however these are located in the highway and should have minimal impact on private development.

Noise

Acoustic levels largely follow the transport infrastructure and the impacts typically microclimatic. The main rail line into and out of Temple Meads presents a noise impact and vibration risk to those sites immediately adjacent to the line. Similarly, the Causeway to the east and A4 Bath Rd to the south present potential noise impact during the day. Beyond the transport network, the nightclub Motion can provide a significant noise impact when weekend 'day raves' are held during the summer.

Air Quality

Air quality issues also follow the transport network. Busy junctions, such as those connecting to the Causeway and at the Totterdown Bridge to the south of the site, regularly see queueing traffic with idling engines producing large amounts of airborne pollution. Diesel trains exiting Temple Meads emit significant diesel fumes and braking trains on the way into the station emit brake dust. Whilst of lower volume, brake dust is notably more harmful to human health.