RAINWATER HARVESTING
DOES IT HAVE A FUTURE?
S E WIELEBSKI MSc (Dist) CEnv PEng FCIOB FBEng MSPE ACIArb FRSA
DIVISIONAL DEVELOPMENT DIRECTOR
RAINWATER HARVESTING
DOES IT HAVE A FUTURE?
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A few thoughts to set the scene
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A little bit of history
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A review of RWH from a Developers perspective
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Flood & Water Management Act 2010/CfSH’s implications
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Potential impact on new home owners
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Decision time
RAINWATER HARVESTING
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A few questions to get you thinking about the wider picture:
1. Is it just a fad or an effective means of responding to the climate
change agenda?
2. Does it make an effective contribution in terms of flood risk
mitigation?
3. Is it affordable?
4. Consider the present Government’s approach to new guidance
and regulation, i.e. one in one out with any new requirement
being cost neutral to industry, therefore……
5. Given the (additional) capex cost of RWH what do we say has to
give way to pay for it?
6. Wider implications arising from the FWMA 2010
7. Impact on the zero carbon agenda
RAINWATER HARVESTING
UK WATER COMPANIES
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Based on Water Company statutory leakage returns to Ofwat
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If Water Companies reduced their leakage by 1% it would…..
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Provide sufficient potable water to serve…….
• 160,000 new homes
A FEW MORE WaSC FACTS
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Water Companies – little if any investment in new infrastructure
since privatisation; in urban areas, several reservoirs
decommissioned and sold for residential development
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House-builders have contributed circa £1.25 billion in
infrastructure charges since WIA 1991; rationale – additional
water supply and sewerage infrastructure provision to meet the
needs of a plan-led planning system
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Current combined infrastructure charge - £600/dwelling (before
the recession this provided WaSC’s with an annual income of
around £100 million)
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Pollution from agriculture is degrading water resources so
severely that some have had to be decommissioned
RAINWATER HARVESTING
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Does it make an effective contribution in terms of flood risk
mitigation?
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In short, no because………
1. The Environment Agency do not recognise it as an effective
means of surface water run-off volume control, which means…..
2. Tank full conditions must be allowed for, therefore no
corresponding reduction in SW infrastructure cost
RAINWATER HARVESTING
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Is it affordable?
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Miller Homes experience - £2500 to £3000/dwelling in terms of
additional cost (excluding soil disposal cost)
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Note - there is little difference in cost even if we consider communal
RWH systems
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At a plotting density of 17 dwellings/acre (PPS3) = ave £46,750/acre in
terms of compensating land value but……..
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This cost has to complete with others arising from an increasing
regulatory burden
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So what do we do without to pay for it?
REGULATORY BURDEN – IMPACT ON
LAND VALUES
Price for 1.00 acre with residential
OPP
Less cost of CfSH – Level 5
£631,000
DCLG Statistics Feb 2011 (table 563)
(Excludes London land prices)
(£595,000)
Based on actual costs incurred/acre
+£36,000
Less cost of RWH
(£46,750)
-£10,750
Cost/acre
NEGATIVE LAND VALUE
Less cost of FWMA 2010
?
Could be in excess of £3500/dwelling
Less cost of CIL
?
Could be £3000/dwelling
Less cost of Afford Housing
?
Significant
Less cost of Lifetime Homes
?
Still to be decided
Less cost of Merton Rule
?
Renewable energy
SECONDARY ISSUES
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Variable rainfall intensities across the UK – SE lower rainfall
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Additional energy costs not factored into the regulated energy use of
a new home – issue with carbon compliance (zero carbon strategy)
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Outcome of NHBC Foundation research: RWH = additional carbon
emissions therefore, not truly sustainable
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Installation in contaminated ground – impact on a approved
remediation strategy not fully considered and/or appreciated.
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CDM Regulations & Health and Safety
IMPACT ON REMEDIATION
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80% of approved remediation schemes for contaminated land rely
on inert cap and cover systems – most sustainable & cost effective
approach (relict contaminants allowed to remain in-situ)
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The installation of underground RWH storage tanks:• re-introduces the pollutant linkage
• results in more contaminated soil arisings having to be
disposed of to licensed landfill – contrary to current
Government landfill disposal policy.
• increases the cost of remediation
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Typical soil disposal costs for a 2000 litre tank:• Inert soil – c£145
• Non-hazardous soil – c£720 (nominally elevated contaminants)
• Hazardous soils – c£1440
RWH TANKS ABOVE GROUND
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A real issue for a number of planning authorities
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Reduces garden amenity space and therefore is a sales disincentive
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Tanks susceptible freezing
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In winter conditions some would advocate emptying the tank and
decommissioning the pump to prevent frost damage
DESIGN IMPLICATIONS
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Competition for space with SuDS – in particular
soakaways/infiltration cells/swales
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Landscaping – position and type will be affected
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Limit of approach to foundations needs careful consideration - must
not adversely affect foundation construction/cost
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Location of RWH tanks both above and below ground with be
affected by the introduction of the forthcoming Mandatory Build
Standards (MBS) for adoptable sewers. With effect from the 1st
October 2011, this will include all domestic drainage (in gardens)
serving two or more dwellings
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Communal systems – easements for distribution pipe-work
WHAT COULD THIS MEAN FOR A
PURCHASER?
HEALTH & SAFETY ISSUES
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We can deal with the water quality side of things – biocides etc
but…
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How do we future proof plumbing installations against RWH being
de-commissioned and a return to the use of potable water?
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On a similar note how do we stop ‘tampering’ with the system
thereby increasing the risk of cross contamination? (Recent
incident in Anglian Water, E-Coli infections)
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As a designer, what are my legal obligations under CDM
Regulations?
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As a designer, do I have legal responsibility for latent issues arising
from uncontrolled modifications to a RWH system? DIY implications
ADDITIONAL CONSIDERATIONS
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Limited rainfall - longer detention times – increased
degradation in water quality – greater propensity for
compromised public health
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Back-up required from potable water supply – waste of
resource and energy
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Regular maintenance required to maintain efficiency and
effectiveness
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Additional house-holder cost – routine and annual maintenance
– therefore sales disincentive
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Geotechnical considerations – increasing reliance on SuDS
infiltration – latent changes in groundwater regime – mitigation
of floatation effects may have to become routine
DECISION TIME
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Principle of RWH – accepted
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Engineering principle – work from the whole to the part not the
reverse
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Surface water management – start at the ‘macro’ level, design
the most effective solutions following the SUDS train
management concept
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RWH should be the very last resort
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A message for Water Companies – Part G current water usage
125litres/person/day, why continue to base water demand for
new supplies on 150 litres/person/day + an allowance for
leakage?
RAINWATER HARVESTING
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From a developers perspective – it is not cost effective
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When considered alongside other legislative changes that will be
introduced by Government under the FWMA 2010 – RWH low on
the agenda
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From a personal perspective, as a designer I have serious
concerns about the longer-term implications – currently no
control over what home-owners can do with their plumbing
systems. What are my liabilities under CDM?
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Duty of care implications
RAINWATER HARVESTING
PEER REVIEW CONCLUSIONS
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“ROI is unfavourable given the high installation costs and
current relatively low price of mains water” – DCLG Report
BD 2833 December 2010
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High capex cost, running cost, and carbon footprint do not
meet the test of sustainable construction – NHBC/BRE
Foundation Research 2010
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SuDS Standards will replace CfSH’s SUR 1 category from
April 2012
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Take due cognisance of the unintended consequences – HBF
2010/2011
Thank you for listening
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Questions?