Part 1: Oversight

  1. The Municipality shall employ the services of a professional engineer to oversee the completion of all flow monitoring and planning tasks.

Part 2: Monitoring Plan Requirements

The Flow Monitoring Plan shall be consistent with current EPA guidance and provide data suitable for developing an LTCP/Wet Weather Control Plan. The Flow Monitoring Plan shall contain at a minimum the following items:

  • A GIS map showing the location of all flow monitoring sites
  • A delineation of the sewered area for each flow monitor
  • The Flow monitoring Technique to be employed
  • Manufacturer of Flow Monitors to be used at each site
  • Monitoring Crew experience conducting Flow Monitoring
  • Approaches to monitoring at or near overflows
  • A Data Quality Assurance and Control Plan
  • Methods to be used in approximating overflow volume, frequency and duration.
  1. Flow monitoring shall be performed as per the approved monitoring plan and according to manufacturer’s specifications for the monitoring equipment utilized.

Part 3: Rain Data

  1. An approved Monitoring Plan shall designate a rain gage as a source of rainfall data. The municipality shall use either the nearest available existing rain gage or propose to install a new rain gage at an appropriate location. Use of a multiple gage network may be necessary and appropriate. Use of radar-rainfall data or from alternate data sources shall be qualified on a case-by-case basis and subject to the approval of the Authority.

Part 4: Monitoring Locations

  1. Monitoring sites shall be designated following field inspection to determine optimal monitoring locations.
  2. Field investigations shall be conducted at selected monitoring locations to verify that hydraulic, site access, safety, and maintenance conditions are suitable for successful flow monitoring. Flow regime conditions such as surface turbulence and backwater interference from downstream pipes and structures shall be recorded. Observed site conditions shall be documented using standardized forms.

Part 5: Monitoring at Overflow Structures

  1. Following field evaluation, the feasibility of monitoring to quantify flows from an overflow shall be documented. A site-specific monitoring plan shall then be prepared in advance of monitoring overflow points. At a minimum, the overflow monitoring plan shall contain a description of the overflow, a dimensioned sketch, the proposed monitoring approach and/or technology to be used.
  2. The overflow monitor points shall be interrogated every three days following the start of monitoring until the equipment is performing properly. Thereafter, weekly interrogation shall be performed or as is appropriate to the approach employed in accordance with the monitoring plan. The sites must also be checked after every precipitation event over one inch in depth at its designated rain gage to check for possible washout or damage to the monitoring equipment. The reliability of monitoring data shall be assessed on a weekly basis for the month following commencement of monitoring. The monitoring results shall be evaluated quarterly thereafter and the findings of each evaluation shall be documented.
  3. Monitoring data shall permit flow estimates to be made in units of MOD.

Part 6: Monitor Installation

  1. A field sketch of each of the selected monitoring locations will be prepared. The sketch will include a dimensioned profile section and plan view of the monitoring manhole, the adjacent upstream and downstream manholes and connecting pipes, and the equipment installation configuration. Describe any adverse hydraulic conditions. Monitoring locations will be identified on a municipal sewer GIS map.
  2. Site set-up information such as measured sensor offsets, site name, manhole number, pipe size, meter number, should be provided on hard copy along with pre-installation calibration information verifying the initial calibration and calibrators name, dates of calibration and installation, and an explanation of any variance from manufacturer-recommended procedures.
  3. Bench and field calibration of flow metering devices shall be performed as applicable for the monitor type and in accordance with the manufacturer’s instructions, and defined in the Data Quality Assurance and Control Plan submitted by the Engineer. Calibration measurements and adjustments shall be documented and dates and time recorded on field sheets. If velocity profiling is performed, appropriate methods shall be employed for the pipe or channel of interest: the 0.9 times U-max or 0.2, 0.4, 0.8 methods will be employed for low flow conditions in smaller pipes; the 2-D method will be used for higher flows in larger pipes.
  4. The municipality shall report within 30 days if any monitoring devices are being moved or if there are any substantive changes to meter installations or adherence to the Data Quality Assurance and Control plan. The approved monitoring plan shall be amended and submitted to the Authority within 45 days of changes.

Part 7: Data Recording

  1. The memory modules shall be programmed for obtaining and storing readings at 15-minute intervals at the quarter hour (i.e. 2:00, 2:15, 2:30 not 2:03, 2:18, 2:33). To match flow data with rainfall data, care shall be taken to ensure all clocks in all the meters are synchronized. Make assurances that no data is lost by checking the manufacturer’s manual to determine the maximum period of record before new data wraps over previous memory module data.
  2. Flows shall be calculated and recorded in million gallons per day (MOD) not CFS. Data shall be formatted to three (3) decimal places (X.XXX). Levels shall be recorded in inches, and velocity will be calculated in FPS.

Part 8: Meter Maintenance and Interrogations

  1. Each monitor will be interrogated every three days following the initial meter installation until the equipment is performing properly. The monitors shall be interrogated a week later and bi-weekly thereafter for the duration of the monitoring period. The sites must also be checked after every precipitation event over one inch in depth at its designated rain gage to check for possible washout or damage to the monitoring equipment.
  2. Field data information, such as depth and velocity readings or flow-points, shall be measured every time a data interrogation is conducted and recorded on the site information sheets to verify the equipment is properly calibrated and providing reliable results. Interrogations shall be scheduled at differing times of day and weather conditions to obtain field data points over a wide range of flow depths.
  3. It may be necessary to take additional velocity measurements to get a representative range of field data points to ensure proper calibration.
  4. Maintenance of monitoring devices shall be performed during every interrogation. Battery charge, desiccants and vent tubes shall be checked. Sensors shall be inspected and paper, rags, oil, and/or debris shall be cleaned off the sensors in accordance with manufacturer’s instructions. It may also be necessary to remove sediment and gravel when it interferes with proper operation of the monitoring devices. Ensure the sensor surfaces remain clean, in good condition and properly formed.
  5. A field log of all measurements and interrogations shall be maintained as documentation and shall be available upon request by the Authority.

Part 9: Data Submission

  1. Consistent file naming conventions will be adopted. Files will be named in accordance with the following format: SITE#MON.TXT,


  • SITE = 4 character municipality ill (BALD, WMIF , WHIT , PITT , and BREN)
  • #  =  The monitor number within a municipality (e.g. BALD3, WMIFl, PITT2, etc.)
  • MON = month (APR for submission 1, MAY for submission 2, JUN for submission 3).
  1. Submit comma-delineated ASCII files of the flow monitoring data in the format below. Add header lines with monitor location and column headings consistent with the following example:

BALDIMAR.TXT -Main Interceptor along Glass Run Road


2, 26, 96, 11, 45, 3.56, 14.24, 2.49

2, 26, 96, 12, 00, 3.42, 13.92, 2.42

2, 26, 96, 12, 15, 3.38, 13.89, 2.40

2, 26, 96, 12, 30, 3.43, 13.94, 2.42

Excel files are also acceptable for data submission.

  1. Prepare and submit superimposed flow/level/rainfall versus time plots covering one-month intervals, beginning with the first day of the month. Monthly flow, level and rainfall (vertical axis) versus time (horizontal axis) plots will be prepared for each monthly data submission.
  2. Prepare and maintain other quality control documentation such as “scatter plots” (flow versus level or velocity versus level) covering the entire four-week reporting period. Consistent user-selected vertical axis scales shall be used as opposed to varying computer selected axis scales.
  3. Prepare and submit the field measurement information in a consistent format.