Issue 4a 150 mg/L M&I Chloride Objective Richard A. Denton Water Resources Manager

Issue 4a
150 mg/L M&I Chloride Objective
Richard A. Denton
Water Resources Manager
Contra Costa Water District
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 1
150 mg/L M&I Chloride Objective
• Established in D-1485 (August 1978)
• Maintain a chloride concentration of 150 mg/L chloride or better
at either the Contra Costa Canal at Pumping Plant #1 or San
Joaquin River at Antioch Water Works Intake for at least a given
number of days each calendar year, depending on water year
type:
™
Wet
240 days
(66% of year)
™
Above Normal
190 days
(52%)
™
Below Normal
175 days
(48%)
™
Dry
165 days
(45%)
™
Critical
155 days
(42%)
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 2
Compliance Locations for 150 Objective
Antioch Pumping Plant
CCWD Pumping Plant #1
• Met at either
Pumping Plant #1
or Antioch
Pumping Plant
• Must be met
for 14 days
consecutively to
count
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 3
More Days of 150 mg/L Generally
Occur Than Required in 1995 Plan
Feb-June X2 in effect
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 4
No Difference Between Calendar Year
and Water Year Accounting
More Days with
Water Year
Accounting
More Days with
Calendar Year
Accounting
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 5
Conclusions
•
150 mg/L M&I objective should not be eliminated
™
•
Would degrade drinking water quality
Objective generally met historically without affecting
operations
™ One recent exception is 1992 drought year
™ X2 estuarine habitat objective (February – June)
makes 150 objective easier to meet
• No compelling reason to change from calendar year to
water year
™ If this was modified, need to ensure there is no net
degradation of water quality for CCWD
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 6
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 7
Pumping Plant #1 Chlorides During
Drought (1990-1992)
300
Chlo rides [mg /l]
250
200
150
100
50
0
1990
Pumping Pla nt #1
250 M&I Obje ctive
150 M&I Obje ctive
1991
1992
1993
a150_time_series1990_1992.m
09-Jan-2005 mm
SWRCB Public Workshop for Periodic Review
January 10, 2005 Slide 8