residents’ meeting - water supply arsenic levels in ...€¦ · 1. background information on: i....
TRANSCRIPT
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Residents’ Meeting - Water Supply
Arsenic levels in Groundwater
May 2018
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1. Background information on:i. arsenic in groundwaterii. Identifying the issue
2. Sampling results to identify: i. affected areasii. likely source of arsenic
3. Water supply options for residents
This presentation covers:
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Introduction1. Residents’ and Hawke’s Bay agency
responsibilities2. The issue3. International/ national context4. Groundwater sampling results5. Options for residents
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1. Agency responsibilitiesi. HB Regional Council
Natural resource knowledge and management
ii. HB District Health BoardWe want everyone in the region to be healthy
iii. Napier City Council and/or Hastings District Council
To provide facilities and services
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www.horizons.govt.nz/HRC/media/Media/Water/Guidelines-for-well-owners.pdf?ext=.pdf
District Health Board
City Council
Well siting
Regional Council
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1. Agency responsibilities
Facilities and ServicesEnvironmental Health Officers
Natural Resource Knowledge & Management
Groundwater ScientistsResource Use Officers
Health ServicesDrinking Water AssessorsHealth Protection Officers
DWGCJoint Working Group
City/ District Council
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1. Rural resident involvement
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2. The issue – a private bore: 3 separate locations
i.e. arsenic concentration = 500 µg/LMaximum Acceptable Value (MAV) =10 µg/L(based on long-term exposure)
500 µg/L
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2. The issue – a private bore
Arsenic concentration = 500 µg/LMaximum Acceptable Value (MAV) =10 µg/LLethal dose is approx. 70,000 µg
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3. New Zealand context1. Arsenic >MAV in groundwater is found:
i. Canterburyii. Marlboroughiii. Manawatuiv. Bay of Plentyv. Waikato
2. Natural arsenic may be associated with:1. Geothermal activity2. Volcanic geology3. Reducing conditions (very low oxygen)4. Peat and carbon-rich material
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3. New Zealand context1. Arsenic >MAV in groundwater is found:
i. Canterburyii. Marlboroughiii. Manawatuiv. Bay of Plentyv. Waikato
2. Natural arsenic may be associated with:1. Geothermal activity2. Volcanic geology3. Reducing conditions (very low oxygen)4. Peat and carbon-rich material
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3. New Zealand context1. Arsenic >MAV in groundwater is found:
i. Canterburyii. Marlboroughiii. Manawatuiv. Bay of Plentyv. Waikato
2. Natural arsenic may be associated with:1. Geothermal activity2. Volcanic geology3. Reducing conditions (very low oxygen)4. Peat and carbon-rich material
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3. Worldwide context
USA natural sources > 1,000
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3. Worldwide context
USA natural sources > 1,000
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3. In Hawke’s Bay – Breckenridge 2017
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3. Hawke’s Bay – Breckenridge 2017
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3. Hawke’s Bay – Breckenridge 2017
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3. Private bore – Poraiti Hill, 2018
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3. Poraiti Hill – potential sources
Information presented to residents 19 April:
• No contaminated sites identified from HAIL database
• No known land use activities that might be a source
• Possibly a natural source, mobilised by groundwater conditions
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4. Sampling plan – 19 April 2018
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4. Sampling results
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4. Sampling results
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4. Sampling results
-180
-140
-100
-60
-20
20
60
100
140
180
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Redo
x Po
tent
ial (
mV)
Arsenic Concentration (mg/L)
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4. Sampling results
-180
-140
-100
-60
-20
20
60
100
140
180
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Redo
x Po
tent
ial (
mV)
Arsenic Concentration (mg/L)
-180
-140
-100
-60
-20
20
60
100
140
180
0.00 0.02 0.04 0.06 0.08 0.10
Redo
x Po
tent
ial (
mV)
Arsenic Concentration (mg/L)
MAV
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4. Sampling results• Arsenic exceedances in more than one
bore• No particular area affected – the issue is
not uniform. • No evidence of a contamination plume• Arsenic is strongly associated with anoxic
groundwater• Highly likely to be a natural source of
arsenic
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Resident’s involvement
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Agency responsibilities
Facilities and ServicesEnvironmental Health Officers
Natural Resource Knowledge & Management
Groundwater ScientistsResource Use Officers
Health ServicesDrinking Water AssessorsHealth Protection Officers
DWGCJoint Working Group
City/ District Council
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5. The role of HBRC• Sampling is completed in Poraiti Hill area • Our role is now to ensure all households
are informed, including advice to test groundwater supplies for arsenic
• Regional investigation and information to domestic groundwater (self-supply) users
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5. Options for owners of affected bores1. Arsenic greater than 10 mcg/L is not potable2. Point of use treatment3. Alternative suppli
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5. Options for owners of affected bores3. Alternative supplies:
• Rainwater collection?• Community groundwater supply?• Reticulated supply?• Other options?
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5. Options for owners of affected bores1. Suggestion for residents to consider
preference for:a) household solutions, orb) community solution
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Summary1. Although not all bores are affected, arsenic
exceedances may occur in groundwater throughout aquifer systems
2. Highly likely to be a natural source, associated with anoxic groundwater
3. HBRC will inform all residents, including advice to test groundwater supplies
4. Options and alternatives for residents to consider – with support from Agencies