Wet Weather Partnership National Association of Clean Water Agencies GREEN SOLUTIONS, WATER QUALITY

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Wet Weather Partnership National Association of
Clean Water AgenciesGREEN SOLUTIONS, WATER
QUALITY COMPLIANCE STRATEGIES AND KEY CSO
LONG-TERM CONTROL PLAN DEVELOPMENTSChicago -
April 2006

• Calculating Wet Weather Capture
• Presumption or DemonstrationIt Is About Getting
  to Yes
• Clyde Wilber

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Issues - With No Hard Rules

• Demonstration Approach When?
• Presumptive Approach When?
• Which of the Three Criteria??
• How to Calculate
• Obtaining LTCP approvals

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Demonstration Approach

• Show Through Monitoring and Modeling that the
  LTCP will meet the WQS

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Demonstration

• Demonstrate WQS met
• With control less than Presumption
• Or greater control than Presumption
• .. or WQS not met
• Due to nature background or pollution other than
  CSO
• Stormwater
• Upstream Load
• Urban Conditions
• Human Caused Conditions that can not be removed??

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Presumption or Demonstration

• Both Approaches must show WQS are met with Post
  Construction Monitoring

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PresumptiveApproach

• Meet one of the three criteria
• 4 to 6 overflows per year
• 85 of the CS volume
• Pollutant Mass capture equal to 85 volume
  control with Primary treatment ANDgtgtgt
• Permit Writer can REASONALBLY assume WQS will be
  met

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Why Presumption?

• Because data and modeling of wet weather events
  often do not give a clear picture of the level of
  CSO controls necessary to protect WQS.

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Presumption

• 4-6/year - Primary Treatment
• 85 Flow - Primary Treatment
• Equivalent Mass of the Pollutant of concern to
  85 Flow - Primary Treatment

Huh?
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4-6 overflows Easy? -Average? - Each CSO?

• How do I calculate the Combined Flow for 85
  Capture?

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Calculating the CSO Flow

• Combined Flow includes
• Captured Stormwater Runoff
• Sanitary Flow and I/I
• From the combined area
• From any upstream separate areas

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What portion of the hydrograph Is Combined Flow?
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Combined Flow from Hydrograph?
Combined Flow Begins When Hydrograph Departs Dry
Weather Pattern
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Combined Volume?
Combined Flow Ends When Hydrograph Returns to Dry
Weather Pattern
Combined Flow Begins When Hydrograph Departs Dry
Weather Pattern
Combined Volume
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Combined Flow - Hyetograph
Combined Flow Ends 4-24 hours after Rain Ends
Combined Flow Begins When Rain Begins
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Rainstorm Break Definition
Break in Rain or Combined Flow Less than 4 hours
one Storm
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Calculating Capture

• Step 1 Construct the wet weather combined
  sewage volume fora typical year. This includes
  looking at all precipitation events whererunoff
  occurs and including all the flow in the sewers
  during the runoffevent AND the tail of the
  hydrograph from the rain until dry
  weatherconditions return to the sewer flow. (no
  one seems to question adding inthe tail, even
  though the tail is after the event) Note this
  includesthe base sanitary and I/I flow in the
  sewer during the runoff event.
• Step 2 calculate the typical year overflow
  volume
• Step 3 calculate capture Capture 1-(CSO
  Volume/Totalcombined sewage Volume during
  runoff)

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There are no rules for Option iii Here is one
way

• Pollutant of Concern BOD
• Say 90 of the BOD is in 85 of the Flow
• Say primary treatment Removes 30 of the BOD
• 30 of 90 is 27
• So if you can remove 27 of the combined BOD you
  meet Option iii

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Can the POTW alone meet the Presumption
Approach?

• Start with a Treatment Plant that removes 85 of
  the incoming BOD
• If you collection System Delivers 32 of the
  Combined System flow(BOD) to the POTW -
• Then The plant will effectively remove 27 of the
  Combined BOD and meets the Presumption Approach -
• A system that can deliver 1.5 to 2.0 times dry
  weather flow to the POTW typically meets this
  criteria

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LTCP - Think!

• What makes Sense in your community?
• Are the CSOs in peoples backyards?
• Is there a CSO next to a park or school
• What do people want from the water?
• Are there CSOs near a POTW?

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Getting a to yes

• Face the WQS
• It helps to show you meet one of the presumption
  criteria
• The level of control that satisfies
• Two views

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Getting to yesTwo views of public spending

• Public Works
• Good Rate of Return, Cost/Benefit
• Public sees a Benefit They Want
• Environmental Activist/ Enforcement
• Meet Water Quality Standards as written, or if
  not feasible
• Eliminate pollution to the point your source will
  not cause or contribute to violations if all
  other sources were controlled
• Spend to Limit of Economic Capability

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What Part of dont you understand?
Show me the Money!