Transcript Bloomington`s Water Supply - Mahomet Aquifer Consortium

Bloomington’s Water Supply:
System Overview and Planning
by: Rick Twait,
Superintendent of Water Purification
City of Bloomington
Mahomet Aquifer Consortium
Meeting No. 56 October 22, 2007
Urban-Rural Growth, 1950-2000
McLean County, Illinois
120000
Urban (Bloomington/Normal)
100000
Rural (All other Areas)
Population
80000
60000
40000
20000
0
1940
1950
1960
1970
1980
Year
Source: U.S Census of Population, 1950-2000
McLean County Regional Planning Commission
1990
2000
2010
Bloomington, Illinois
Water Rates per 100 Cubic Feet
3.20
WaterRate
(Dollars/100 cubic Feet)
3.00
2.80
2.60
2.40
2.20
2.00
RatePer100Ft3 InsideCity
1.80
First 2,300
Next 11,700
Next 486,000
Over 500,000
Cubic Feet Purchased per Month
Bloomington, Illinois
Water Utility
• 77,000+ Customers
• 75,000 City Residents
• 2,200+ Customers from Villages and Public
Water Districts
• 11,400,000 Gallons Average Daily Pumpage
• Approximately 80% Residential Consumption
• BNWRD Discharges ~20 mgd
Bloomington’s Two Water Supply Reservoirs
Lake Bloomington
Constructed in 1929
Raised 5 feet in 1954
635 surface acres
8,760 acre-ft storage
69.5 sq.mi. drainage area
70:1 drainage to surface area ratio
Evergreen Lake
Constructed in 1971
Raised 5 feet in 1995
900 surface acres
15,480 acre-ft storage
41.1 sq.mi. drainage area
29:1 drainage to surface area ratio
Lake Bloomington and Evergreen Lake Stage-Volume Curves:
Hanson Engineers, 1999 data
725
720
Elevation (ft above msl)*
715
710
705
Evergreen Lake
Lake Bloomington
700
695
690
685
680
675
0
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000110001200013000140001500016000
Cumulative Volume (acre-feet)
Bloomington, Illinois
High Service Pumpage
High Service Pumpage
(million gallons per day)
25
20
15
10
5
0
1980
1985
1990
1995
Year
Average for Month
2000
2005
Bloomington, Illinois
High Service Pumpage
High Service Pumpage
(million gallons per day)
25
20
15
10
5
0
1980
1985
1990
1995
Year
Average for Month
12 Month Running Average
2000
2005
Bloomington, Illinois
High Service Pumpage
25
High Service Pumpage
(million gallons per day)
20
15
10
5
0
1980
1985
1990
1995
Year
Average for Month
12 Month Running Average
Maximum Day for Month
2000
2005
Dry Spells to Droughts
 In
Detecting Drought Conditions in Illinois
Changnon (1987): Described
Meterological, Agricultural, Hydrological,
and Economic Drought Conditions
 US Drought Monitor (website): Describes
conditions in terms from abnormally dry to
exceptional drought, agricultural and/or
hydrologic
Dry Spells to Droughts

In Drought Response Plan, City of Bloomington,
Illinois Water Department, Wittman (2006)
proposed a practical definition of drought for
municipal water systems as:
“A reduction in precipitation or aquifer recharge
that affects the ability of the public water system
to meet the demands of the customers or
causes regulatory or aesthetic reductions in
water quality.”
Types of Municipal Water
Shortages
Supply Shortages Can be Caused by:
 Drought
 Demand
 Quality:
• Health (Regulatory)
• Aesthetic
Types of Municipal Water
Shortages (cont’d)
Treatment Shortages Can be Caused by
Inadequate:



Treatment Capacity
Transmission Capacity
Storage Capacity
To Meet Demands
Elevation (ft above msl)
725
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
720
715
710
705
700
89
90
91
92
93
94
95
Year
96
97
98
99
00
Precipitation (in)
Lake Bloomington Water Levels and Precipitation
Bluegreen Algal Filament
Heterocyst
400x
400x
1988-89 Drought
 Water

Problems
Extremely Low Reservoir Levels
• Concerns about Getting Water to Pump Intakes

Extremely High Demands:
• Decreased Treatment Efficiency
• Plant Operated at Peak Capacity

Low Water Quality
• Taste and Odor Episodes Frequent and Severe
1988-89 Drought
 Operational

Responses
Water Restrictions
• Lawn Watering
• Water Served in Restaurants by Request

Taste and Odor
• KMnO4
• CuSO4
• PAC

Purchase Floating Pumps
1988-89 Drought

Planning/Supply Responses







F&W Long Term Water Study
Initiate Watershed Protection Program
Raise Evergreen Lake Spillway by 5 Feet
Build and Obtain Permit for Mackinaw River Pumping
Pool
Raised Water Rates
Installed GAC Caps on Filters
Begin Planning and Investigation of Groundwater
Source
1988-89 Drought
 Planning/Supply



Responses (continued)
Expand Treatment Plant Capacity at Lake
Bloomington
Construction of 2 MG Elevated Tank
Construction of Additional Transmission Main
from Lake Bloomington to Town
01/14/98
01/14/97
01/14/96
01/14/95
01/14/94
01/14/93
01/14/92
01/14/91
01/14/90
01/14/89
01/14/88
01/14/87
01/14/86
01/14/85
01/14/84
01/14/83
NO3-N (mg/L)
Bloomington, Illinois Finished Water Nitrate Levels
35
30
25
20
15
10
5
0
Raising Spillway Elevation of Evergreen Lake Increased Capacity by 36%
Lake Bloomington and Evergreen Lake Stage-Volume Curves:
Hanson Engineers, 1999 data
725
720
Elevation (ft above msl)*
715
710
705
Evergreen Lake
Lake Bloomington
700
695
690
685
680
675
0
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000110001200013000140001500016000
Cumulative Volume (acre-feet)
Additional Watershed Area Due to
Mackinaw River Pumping Pool
Drought of 2005
 Demand

Hit Plant Capacity
Cool Period Limited Duration of Extreme
Demand
 Extra
Capacity of Evergreen Lake
Extended Days of Available Supply
 Higher Reservoir Levels, GAC Caps, and
Destratifiers Resulted in Fewer T&O
Issues (initially)
Drought of 2005
 Pumping
Pool: From late December 2005
through April 2006: 364 million gallons
pumped (over a month’s supply at average
usage) despite no/minimal runoff to lakes
from tributaries
 Extra capacity of Evergreen Lake
Reservoir resulted in more reserve
capacity at start of drought
Responses to the Drought of 2005
 Contracted
with Wittman Hydro Planning
Associates for Drought Response Plan
and Draft Drought Ordinance
 Performed Intensive In-House and
Contracted Studies of Dealing with Taste
and Odor Causing Compounds
 Expand Existing Source Water Protection
Efforts
Responses to the Drought of 2005
(continued)
 Initiate
Phytoplankton Surveillance
Program and Investigate In-Lake
Treatment Methods
 Continue Supplemental Water Supply
Activities
 Update Master Plan, including Blending
Options
 Coordinate TMDL Plans with Drought
Strategies and Emergency Plans
Mahomet Aquifer
Source: Illinois State Water Survey,
Center for Groundwater Science
Acknowledgements
Dave Stockton, Mayor, City of Bloomington
Bloomington City Council, Tom Hamilton, City Manager
Brian Brakebill, Deputy City Manager
Craig Cummings, Director of Water
Jill Mayes, Bloomington Water Treatment Plant
Dr. John O’Connor, H2O’C Engineering
Dr. Jack Wittman, Wittman Hydro Planning Associates
The Staff of the Bloomington Water Treatment Plant and Water Department
Our Water Customers