Halifax Watershed Studies: Sandy Lake and Preston Area for...
Transcript of Halifax Watershed Studies: Sandy Lake and Preston Area for...
Client logo
Halifax Watershed Studies:Sandy Lake and Preston Areafor theRegional Watersheds Advisory Board
AECOM
Timothy Bachiu M.Sc., P.Geo.
September 10, 2014
Client logo
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
Client logo
Sandy LakeStudy Area
September 10, 2014
Client logo
Sandy LakeExisting Conditions
September 10, 2014
Client logo
Sandy LakePotential Development
September 10, 2014
Client logo September 10, 2014
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
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
50.00
May-05 May-06 May-07 May-08 May-09 May-10 May-11 May-12 May-13 May-14
Tota
l Pho
spho
rus
(ug/
L)
HRM samples AECOM Samples Phosphorus Average Phosphorus Median
Eutrophic
Mesotrophic
Oligotrophic
Water Quality Objective: 18 µg/L
Client logo September 10, 2014
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
Client logo September 10, 2014
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
Client logo
Sandy LakeConstraints Map
September 10, 2014
Client logo
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
Client logo
Break for Questions regarding Sandy Lake
September 10, 2014
Client logo
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
Client logo
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
Client logo
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)
Client logo
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)
Client logo
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)
Client logo
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
Client logo
Preston Residential Well Survey
September 10, 2014
Montague Gold Mines
East Preston
Lawrencetown/Mineville
Client logo
Arsenic in Groundwater
September 10, 2014
Client logo
Preston residential well results summary
September 10, 2014
0
10
20
30
40
50
60
70
80
90
100
% of Residences with yield issues
% of residences with As > 10 ug/L or total coliforms present
0
10
20
30
40
50
60
70
80
90
100
Perc
enta
ge o
f Res
iden
ts S
urve
yed
% of residences without treatment systems and havetotal coliforms present% of residences without treatment systems and havehigh arsenic concentrations
Perc
enta
ge o
f Res
iden
ts S
urve
yed
Client logo
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