Post on 17-Jul-2020
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Halifax Watershed Studies:Sandy Lake and Preston Areafor theRegional Watersheds Advisory Board
AECOM
Timothy Bachiu M.Sc., P.Geo.
September 10, 2014
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Two Watershed Study Areas• Sandy Lake
– 24 hectares– Sub-watershed of the Sackville River
• Preston Area– 66 hectares– Two watersheds
• Salmon River• Partridge River
– Rural Dartmouth– Little
development anticipated
– Groundwater used for potable water in several communities
September 10, 2014
Bedford AreaDevelopment plans
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Sandy LakeStudy Area
September 10, 2014
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Sandy LakeExisting Conditions
September 10, 2014
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Sandy LakePotential Development
September 10, 2014
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Sandy Lake - Objectives
• What are the existing lake water quality conditions?– Historical data and three sampling events– Set Water Quality Objectives based on historical and recent data
• What are the potential impacts of future development on lake water quality?– Lakeshore Capacity Model– 3 scenarios of development
• What areas are suitable/not-suitable for development?– Constraints map
Client logo September 10, 2014
Sandy Lake – Existing water quality conditions
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May-05 May-06 May-07 May-08 May-09 May-10 May-11 May-12 May-13 May-14
Tota
l Pho
spho
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(ug/
L)
HRM samples AECOM Samples Phosphorus Average Phosphorus Median
Eutrophic
Mesotrophic
Oligotrophic
Water Quality Objective: 18 µg/L
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Sandy Lake – Lakeshore Capacity Model
• Phosphorus load modeling– Land Use map– Phosphorus export for each land use type
• Phosphorus flux + hydraulic budget = average concentration
• Model Uncertainty
• Four scenarios– Modeling Scenario 1: Existing Conditions; – Modeling Scenario 2: Future Developments; – Modeling Scenario 3: Future Developments plus; and– Modeling Scenario 4: Future Developments (Scenario 3) with
Advanced Stormwater Management
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Sandy Lake – Lakeshore Capacity Model
Scenario Sandy LakePredicted Phosphorus (µg/L)
Marsh LakePredicted
Phosphorus (µg/L)
Scenario 1: Existing Conditions 12 11
Scenario 2: Planned Developments 16 15
Scenario 3: Planned Developments + removal of Uplands WWTF and Septic Systems near Sandy Lake
15 14
Scenario 4: Future Developments (Scenario 3) with Advanced Stormwater Management
13 12
Recommended Water Quality Objective 18 15.5
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Sandy LakeConstraints Map
September 10, 2014
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Sandy Lake Summary
• Increasing total phosphorus concentrations
• Future development will impact water quality
• Mitigation measures– Septic and WWTF to
municipal waste water– Advanced stormwater
management
September 10, 2014
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Break for Questions regarding Sandy Lake
September 10, 2014
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Preston Study Area• Little Salmon River
• Lake Major• Long Lake• Tributaries to Major• Cole Harbour
• Partridge River• Winder Lake• Eagle Lake• Frog Lake• Lawrencetown Lake
• Protected Areas• Lake Major PWA• Waverley Game Sanctuary• Waverley Salmon River Long
Lake Wilderness Area
• Additional Sampling
Major
Long
Eagle
Surface Water Sample
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Objectives
• What are the conditions of the surface water?– Historical data and
sampling completed.
• Are there groundwater issues in areas that rely on groundwater?– Residential well survey
September 10, 2014
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Water Quality DataSampled
bySampling Program
Sampling Period
Sampling Locations
HRMWinder Lake
TreatmentPlant
2006 - 2011 Winder Lake
HalifaxWater
Lake MajorProtected
Water Area2009 - 2013
Lake MajorLong Lake
AECOM This Study
2013 - 2014
3 sampling events
Long LakeLake MajorEagle LakePartridge
River
2014
2 sampling events
Frog LakeGammon
LakeRobinson
LakeNelson Lake
September 10, 2014
(2013-2014)
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Salmon River Watershed
• Lake Major total phosphorus• Inputs to Lake Major: 8 to
17 µg/L • Lake Major: 2 to 7 µg/L • Oligotrophic
• Long Lake TP• 2 to 34 µg/L• Mesotrophic
September 10, 2014
(2013-2014)
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Partridge River Watershed• Winder Lake (n=17)
• Total Phosphorus: 100 to 300 µg/L (median 100 µg/L) Eutrophic
• Eagle Lake (n=3)• Total Phosphorus: 15, 27,
20 µg/L Mesotrophic/Eutrophic
• Frog Lake (n=2)• Total Phosphorus: 23, 33
µg/L Eutrophic
• Partridge River Outlet (n=3)• 15, 15, 21 µg/L
Mesotrophic
September 10, 2014
(2013-2014)
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Additional Lake Sampling
• Nelson Lake– May 2014: 24 µg/L– July 2014: 16 µg/L
• Robinson Lake– May 2014: 22 µg/L– July 2014: 18 µg/L
• Gammon Lake– May 2014: 21 µg/L– July 2014: 16 µg/L
September 10, 2014
Nelson Lake
Robinson Lake
GammonLake
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Preston Residential Well Survey
September 10, 2014
Montague Gold Mines
East Preston
Lawrencetown/Mineville
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Arsenic in Groundwater
September 10, 2014
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Preston residential well results summary
September 10, 2014
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% of Residences with yield issues
% of residences with As > 10 ug/L or total coliforms present
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Perc
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% of residences without treatment systems and havetotal coliforms present% of residences without treatment systems and havehigh arsenic concentrations
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Preston Area Summary• Lake Major water
quality is good
• North Preston WWTP is impacting Eagle Lake and Frog Lake – Both lakes may be
eutrophic
• Groundwater Quality– Arsenic in Montague and
Mineville/Lawrencetown– Bacteria in dug wells in
PrestonSeptember 10, 2014
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Thank You
Timothy.Bachiu@aecom.com