Flow Monitoring Advancements Help Utilities Keep More Money in Their Pockets

Prepared for the Florida Water Resources Conference (FWRC) 2014 by Greg Anderson, PE, Director of Infrastructure R&R Services, McKim & Creed, Inc.

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In this presentation, we will describe how a Florida county used an existing contract and very limited resources to address wet weather concerns.

This county’s service area includes approximately 1,150 miles of collection/conveyance pipe ranging in size from 4 inches to 48 inches, 141 pump stations, and one booster lift station. The system collects and conveys wastewater generated in the southern portion of the county to a water reclamation facility (WRF) with an average dry weather flow rate of approximately 21 mgd.

A rainfall event recorded on June 24, 2012 exceeded the average flow by a multiplier of five. The primary discharge points to the WRF were at maximum capacity during the event and pumped debris caused more than $150,000 in damages at the WRF’s headworks. The system did not fully recover from the initial introduction of storm water until nearly a week after the event.

With an impact of this magnitude, where does one start? As staff began assessing the overall impact of the event, it became apparent that the county needed to undertake flow metering immediately to provide both clarity and focus on how to address the situation. However, with limited funding available and a fairly short wet weather season, it would be difficult to complete the necessary work in a manner that would provide useful results.

This county used an existing contract and limited resources to quickly mobilize flow monitoring crews and identify areas within the collection system that caused the greatest wet weather concern. Working with the engineer of record, the county used an innovative open channel flow monitoring approach to pinpoint the problem areas. This approach minimized the required boots on the ground and allowed for a comprehensive evaluation to be conducted in a shortened time frame.

The engineer was able to further assist the county by preparing a smoke testing protocol manual and training staff on the correct way to perform smoke testing. This investment enables the county to supply these services on its own, when and where they are needed, without hiring an outside consultant.

As a result of this flow monitoring and smoke testing process, the county has been able to address the largest storm water inflow contributors immediately and prioritize future abatement activities based on both potential wet weather flow reduction and in-house staff availability.

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