Initial Distribution System Evaluation IDSE

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Initial Distribution System Evaluation (IDSE)

• Julie W. Roney
• Technical Assistance and Outreach
• Drinking Water Branch
• Division of Water

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Purpose of IDSE

• Comprehensive evaluation of a water systems
  distribution system
• Determine areas of elevated THMs and HAAs
• Improve THM and HAA monitoring
• Most importantly, protect public health
• Covers a 1-year period with increased monitoring
• Approximately 2 times the number of compliance
  sites
• Sampled more frequently
• In addition to Stage 1 monitoring

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Applicability of IDSE

• Applies to community water systems that use a
  disinfectant or deliver water that contains a
  disinfectant
• Covers ground water, surface water and purchasing
  systems
• Each water system will do their own IDSE, even
  the purchasers

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IDSE Options

• Standard Monitoring Plan (SMP)
• System-Specific Study (SSS)
• 40/30 Waiver
• Very Small System Waiver (VSS)

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Stage 2 Timeline
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Very Small System Waiver (VSS)

• For systems serving less than 500 in population
  with small, uncomplicated distribution systems
• Must have taken THM and HAA samples
• If as if under Stage 1 DBP Rule
• 1 sample per year at maximum point in warmest
  month
• Operational data is acceptable
• Some purchasing VSSs may not have THM and HAA data

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Very Small System Waiver (VSS)

• Waiver is effective immediately
• Is only a waiver from the IDSE, not the Stage 2
  compliance monitoring
• If begin Stage 1 THM/HAA monitoring then must
  continue until Stage 2 takes effect
• Waiver assumes that the 1 site is representative
  of the highest levels of THMs and HAAs

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Very Small System Waiver (VSS)

• State/EPA can deny the VSS Waiver
• No data
• Site sampled not representative of high THM and
  HAAs
• High DBP levels
• If denied, then the system must do either a
  Standard Monitoring Plan or a System Specific
  Study

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40/30 Certification

• Eligible systems must have taken all required
  Stage 1 THM and HAA samples
• For 8 consecutive quarters
• No single, individual sample can exceed
• 0.040 mg/L for THMs
• 0.030 mg/L for HAAs
• No THM or HAA MR violations
• States can allow operational data to be used
• Equivalent to Stage 1 data
• Certified lab, adequate number of samples,
  appropriate sample locations

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40/30 Certification Time Frames
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40/30 Certification

• 40/30 Certification Letter submitted to EPA/State
• Most likely will require submittal of 40/30 data
  and a schematic
• May also include sites selected for Stage 2
• This is only a waiver from the IDSE, not the
  Stage 2 compliance sites
• Must continue to comply with Stage 1 requirements

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40/30 Certification

• EPA/State may deny the 40/30 certification
• Data not under 40 ug/L for THMs or 30 ug/L for
  HAAs
• Stage 1 sites not representative or inadequate to
  be used to select Stage 2 sites
• 2 year time frame is not representative of normal
  operating conditions

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40/30 Certification

• If the 40/30 certification is denied, must do a
  Standard Monitoring Plan or System Specific Study
• If the submitted data is close to the 40/30
  limits, EPA/state may ask that a SMP or SSS be
  done anyway

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40/30 Certification

• Recordkeeping requirements
• Maintain 40/30 waiver and data for 10 years
• Make 40/30 Certification and any EPA/State
  correspondence available to the public

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System-Specific Study

• Can be done 2 ways
• Existing monitoring results
• High number of samples taken before the IDSE
  compliance date (5 years prior)
• Example 10,000-49,999 must have had 24 sites
  that result in 144 THMs and 144 HAAs
• Wont see any of this type of SSS
• Modeling
• Extended period water quality model with
  specifics outlined in rule and Guidance Manual
• Does include 1 round of monitoring outlined in
  the Standard Monitoring Plan
• Will go beyond what most systems currently have
  as an hydraulic model
• Will see some of these

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System-Specific StudyModeling

• Specific modeling criteria set forth in the
  regulation and in the IDSE Guidance Manual
• Minimum requirements
• Simulate 24 hour variation in demand and show a
  consistently repeating 24 hour pattern of
  residence time
• Includes
• 75 of pipe volume
• 50 of pipe length
• All pressure zones
• All 12 diameter pipe and larger
• All 8 diameter pipe and larger that connect
  different zones of pressure or source water,
  storage tanks, pumps control valves
• All 6 diameter pipe or larger that connect
  remotes areas to the main system
• All storage facilities, pump stations and control
  valves

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System-Specific StudyModeling

• Must be a calibrated model for the current
  distribution system configuration for the highest
  THM and HAA formation potential time period
• Must contain timing and number of THM and HAA
  samples for at least 1 monitoring period at
  locations required under SMP during the peak high
  historical month

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Standard Monitoring Plan

• Most systems will use this option
• Process for timing, selection of sites and number
  of sites is set by EPA in the regulation
• EPA is developing a Web-based IDSE Tool
• Should be available in March/April 2006

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Stage 2 Timeline
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Standard Monitoring Plan

• Required components of a SMP
• Distribution schematic
• Entry points, sources, storage facilities
• Locations and dates of current Stage 1 monitoring
• Locations and dates of proposed Stage 2
  monitoring
• Population served
• Source water type
• Justification of Standard Monitoring sites
• Include a summary of data used to justify the
  sites such as chlorine residuals, TCR data,
  operational samples, etc

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Standard Monitoring Plan

• Issue with security for distribution schematics
• Not considered Confidential Business Information
  by Feds so subject to FOIA
• Can get around this in 1 of 2 ways
• Schematic of pipes that indicate entry points,
  tanks and monitoring locations with no landmarks
  noted on map
• City road map without pipes that only indicate
  boundaries, entry points, tanks and monitoring
  sites

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Consecutive System
WTP
WTP
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Standard Monitoring Plan

• Requirements
• What, Where, How Often monitoring is conducted
• Must be dual sample sets (THM and HAA sampled
  together)
• Monitoring locations
• High THM
• High HAA
• Average
• Entry point
• Number of sites
• Based on population and source water (not number
  of plants)
• Frequency of monitoring
• Every 60 days, 90 days or annually at each site

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Standard Monitoring Plan

• Requirements (continued)
• Must sample once in the peak high historical
  month based on
• High THMs
• High HAAs or
• Month of warmest water
• If sampling more than once per year, must base
  sampling schedule around this time frame

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TTHM and HAA5 Standard Monitoring(1)

• For Surface Water and systems that purchase
  Surface water

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Standard Monitoring Plan

• Factors affecting THM and HAA formation in
  Distribution systems
• TOC (precursor) concentration
• Type and dose of disinfectant
• Water chemistry and temperature
• Residence time
• HAA biodegradation

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Standard Monitoring Plan

• Tools to use to help select sites for SMP
• Distribution system maps and operating data
• Water flow (pump runs, billing records, tracer
  study)
• Tank impacts
• Booster chlorination impacts
• Water use
• Entry points and sources
• Key components (tanks, boosters)
• Water quality data
• Source water quality
• DBPs
• Disinfectant residuals
• Bacts and HPCs

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Standard Monitoring Plan

• Selecting Near Entry Point sites
• Not the plant tap (after treatment and close to
  the 1st distribution system customer)
• If more entry points than needed for SMP
• Use entry points with highest flow
• If fewer entry points than needed for SMP
• Replace required entry point samples with
  alternating high THM then high HAA samples

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Standard Monitoring Plan

• Selecting Average Residence sites
• Use flow and population weighted analyses
• Distribution maps and operational data
• Hydraulic model or tracer study
• Pump run times, metered flow
• Distribution water quality data
• Average disinfectant residuals

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Standard Monitoring Plan

• Selecting High THM sites
• High residence times
• Downstream of tanks
• Close to dead ends
• Hydraulic dead ends and mixing zones
• Downstream of booster chlorination
• Areas where it is difficult maintaining chlorine
  residuals
• Low water use
• High historic THMs
• Avoid
• Actual dead ends
• Upstream of booster chlorination

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Standard Monitoring Plan

• Selecting High HAA sites
• High residence times but consider possible
  biodegradation
• Downstream of booster chlorination
• Sites with low but detectable chlorine residuals
• High historic HAAs
• Others such as tanks, before dead ends, hydraulic
  dead ends and mixing zones, low water use
• Avoid
• Areas with known biofilms (such as high HPCs)
• Areas where it is difficult to maintain a
  chlorine residual

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Standard Monitoring Plan

• Submit the proposed monitoring plan to EPA/state
• Have 1 to approve/disapprove
• Conduct the 1 year of monitoring
• Submit an IDSE report
• 3 months after completing IDSE
• Identify new Stage 2 THM and HAA sites
• Include a compliance monitoring plan
• Wont have to do this later
• Begin Stage 2 monitoring per water system
  schedule

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Standard Monitoring Plan

• Recordkeeping
• Keep copy of SMP and EPA/State approval or
  modifications for 10 years
• Must be available for review by EPA, state or
  public
• CCR for a given calendar year during which IDSE
  monitoring occurred must include those results
• Range of values

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Review of the Standard Monitoring Plans Form
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Walk Through Example SM Form

• System Information
• Population served 8,000
• Sources
• One surface water source produces 1 MGD
• Two wells produce 0.5 MGD each
• One consecutive connection draws 0.1 MGD
• Wholesale system serves 1 million people
• Compliance dates based on Schedule 1
• Wholesale systems schedule

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I. General Information
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I. General Information
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II. IDSE Requirements
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III. Selecting IDSE Standard Monitoring Sites
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IV. Justification Of IDSE Monitoring Sites
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IV. Justification Of IDSE Monitoring Sites


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IV. Justification Of IDSE Monitoring Sites


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IV. Justification Of IDSE Monitoring Sites


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IV. Justification Of IDSE Monitoring Sites


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V. Peak Historical Month
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V. Standard Monitoring Dates
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VI. Stage 1 DBPR Monitoring Dates
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VII. Distribution System Schematic
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VII. Distribution System Schematic
Booster
TP
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1
2
A
B
3
Connection
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VIII. Attachments
Next
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QUESTIONS??? COMMENTS???

• Julie W. Roney, Supervisor
• Technical Assistance and Outreach
• Drinking Water Branch
• 502/564-3410
• Julie.Roney_at_ky.gov
• www.epa.gov/safewater