RAINWATER HARVESTING

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RAINWATER HARVESTING

• DOES IT HAVE A FUTURE?

S E WIELEBSKI MSc (Dist) CEnv PEng FCIOB FBEng
MSPE ACIArb FRSA DIVISIONAL DEVELOPMENT DIRECTOR
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RAINWATER HARVESTINGDOES IT HAVE A FUTURE?

• A few thoughts to set the scene
• A little bit of history
• A review of RWH from a Developers perspective
• Flood Water Management Act 2010/CfSHs
  implications
• Potential impact on new home owners
• Decision time

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RAINWATER HARVESTING

• A few questions to get you thinking about the
  wider picture
• Is it just a fad or an effective means of
  responding to the climate change agenda?
• Does it make an effective contribution in terms
  of flood risk mitigation?
• Is it affordable?
• Consider the present Governments approach to new
  guidance and regulation, i.e. one in one out with
  any new requirement being cost neutral to
  industry, therefore
• Given the (additional) capex cost of RWH what do
  we say has to give way to pay for it?
• Wider implications arising from the FWMA 2010
• Impact on the zero carbon agenda

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RAINWATER HARVESTINGUK WATER COMPANIES

• Based on Water Company statutory leakage returns
  to Ofwat
• If Water Companies reduced their leakage by 1 it
  would..
• Provide sufficient potable water to serve.
• 160,000 new homes

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A FEW MORE WaSC FACTS

• Water Companies little if any investment in new
  infrastructure since privatisation in urban
  areas, several reservoirs decommissioned and sold
  for residential development
• 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
• Current combined infrastructure charge -
  600/dwelling (before the recession this provided
  WaSCs with an annual income of around 100
  million)
• Pollution from agriculture is degrading water
  resources so severely that some have had to be
  decommissioned

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RAINWATER HARVESTING

• Does it make an effective contribution in terms
  of flood risk mitigation?
• In short, no because
• The Environment Agency do not recognise it as an
  effective means of surface water run-off volume
  control, which means..
• Tank full conditions must be allowed for,
  therefore no corresponding reduction in SW
  infrastructure cost

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RAINWATER HARVESTING

• Is it affordable?
• Miller Homes experience - 2500 to 3000/dwelling
  in terms of additional cost (excluding soil
  disposal cost)
• Note - there is little difference in cost even if
  we consider communal RWH systems
• At a plotting density of 17 dwellings/acre (PPS3)
  ave 46,750/acre in terms of compensating land
  value but..
• This cost has to complete with others arising
  from an increasing regulatory burden
• So what do we do without to pay for it?

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REGULATORY BURDEN IMPACT ON LAND VALUES
Price for 1.00 acre with residential OPP 631,000 DCLG Statistics Feb 2011 (table 563) (Excludes London land prices)
Less cost of CfSH Level 5 (595,000) Based on actual costs incurred/acre
36,000
Less cost of RWH (46,750) Cost/acre
-10,750 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
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SECONDARY ISSUES

• Variable rainfall intensities across the UK SE
  lower rainfall
• Additional energy costs not factored into the
  regulated energy use of a new home issue with
  carbon compliance (zero carbon strategy)
• Outcome of NHBC Foundation research RWH
  additional carbon emissions therefore, not truly
  sustainable
• Installation in contaminated ground impact on a
  approved remediation strategy not fully
  considered and/or appreciated.
• CDM Regulations Health and Safety

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IMPACT ON REMEDIATION

• 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)
• 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
• Typical soil disposal costs for a 2000 litre
  tank-
• Inert soil c145
• Non-hazardous soil c720 (nominally elevated
  contaminants)
• Hazardous soils c1440

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RWH TANKS ABOVE GROUND

• A real issue for a number of planning authorities
• Reduces garden amenity space and therefore is a
  sales disincentive
• Tanks susceptible freezing
• In winter conditions some would advocate emptying
  the tank and decommissioning the pump to prevent
  frost damage

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DESIGN IMPLICATIONS

• Competition for space with SuDS in particular
  soakaways/infiltration cells/swales
• Landscaping position and type will be affected
• Limit of approach to foundations needs careful
  consideration - must not adversely affect
  foundation construction/cost
• 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
• Communal systems easements for distribution
  pipe-work

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WHAT COULD THIS MEAN FOR A PURCHASER?
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HEALTH SAFETY ISSUES

• We can deal with the water quality side of things
  biocides etc but
• How do we future proof plumbing installations
  against RWH being de-commissioned and a return to
  the use of potable water?
• 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)
• As a designer, what are my legal obligations
  under CDM Regulations?
• As a designer, do I have legal responsibility for
  latent issues arising from uncontrolled
  modifications to a RWH system? DIY implications

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ADDITIONAL CONSIDERATIONS

• Limited rainfall - longer detention times
  increased degradation in water quality greater
  propensity for compromised public health
• Back-up required from potable water supply
  waste of resource and energy
• Regular maintenance required to maintain
  efficiency and effectiveness
• Additional house-holder cost routine and annual
  maintenance therefore sales disincentive
• Geotechnical considerations increasing reliance
  on SuDS infiltration latent changes in
  groundwater regime mitigation of floatation
  effects may have to become routine

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DECISION TIME

• Principle of RWH accepted
• Engineering principle work from the whole to
  the part not the reverse
• Surface water management start at the macro
  level, design the most effective solutions
  following the SUDS train management concept
• RWH should be the very last resort
• 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?

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RAINWATER HARVESTING

• From a developers perspective it is not cost
  effective
• When considered alongside other legislative
  changes that will be introduced by Government
  under the FWMA 2010 RWH low on the agenda
• 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?
• Duty of care implications

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RAINWATER HARVESTINGPEER REVIEW CONCLUSIONS

• ROI is unfavourable given the high installation
  costs and current relatively low price of mains
  water DCLG Report BD 2833 December 2010
• High capex cost, running cost, and carbon
  footprint do not meet the test of sustainable
  construction NHBC/BRE Foundation Research 2010
• SuDS Standards will replace CfSHs SUR 1 category
  from April 2012
• Take due cognisance of the unintended
  consequences HBF 2010/2011

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Thank you for listening.Questions?