Providing North West England with environmental infrastructure will cost £29bn over the next 20 years and a further £8bn to provide it for the 460,000 new homes planned, according to an Environment Agency study.
The work looked at the cost of infrastructure needed to meet the North West Regional Spatial Strategy and is the second of a series of studies for each region, following earlier work on the South East Plan.
A key aim is to inform the location of new development and it says that there are significant water and wastewater uncertainties if growth levels are pursued beyond 2015.
"New growth can be achieved without harming the environment, but early investment and careful planning is critical," said Agency head of sustainable communities Julie Foley.
The report says urgent action is needed to improve delivery of environmental infrastructure if growth aspirations are to be realised.
It calls for tougher limits on flood risk areas and improved co-ordination.
It says it is easier to assess flood risks on brownfield sites as they can be assessed in relation to known flood zones, but flood risks from sewers need to be added. But it warns that infiltration-type sustainable drainage is harder to achieve on brownfield sites which are contaminated as it may increase pollution from leachates and provide pathways into the ecosystem.
Higher density developments also present challenges with higher volumes of run off, but additional off-site attenuation can be more cost-effective and sustainable in such cases.
The report looks at further development of its model and says it should allow scenarios other than growth including worst case, business as usual and climate change adaptation.
