City of Lawrence

Department of Utilities

Memorandum

TO:	Dave Corliss, City Manager Cynthia Boecker, Assistant City Manager Diane Stoddard, Assistant City Manager
FROM:	Mike Lawless, Assistant Director of Utilities
CC:	Dave Wagner, Director of Utilities Philip Ciesielski, Assistant Director of Utilities Beth Frailey Krishtalka, Management Analyst
DATE:	September 3, 2008
RE:	Additional Information on Long-term Flow Monitoring

The following is additional information related to the contract renewal for long-term flow monitoring with Marsh McBirney – Hach.

The long-term flow monitoring program is an on-going program that is proposed to continue as long as it provides beneficial information. The program has been collecting data since October of 2006 and has established good baseline data. The Utilities Department is just beginning to see the benefits.

This baseline data will be used to develop and calibrate a dynamic model of the sanitary sewer system for the new Wastewater Master Plan. In the previous Master Plan, limited flow monitoring data was extrapolated to the entire wastewater system. In preparation for the CIP projects at Alvamar, 24^th & Crossgate, Harvard & Wakarusa and at Pump Station 16, additional flow monitoring was performed to confirm and correctly size the projects identified in the Master Plan. With the exception of Pump Station 16, each of these projects was able to be reduced in scope and/or size thus lowering the total cost of the projects.

In addition, when system improvements are made such as the 2008 CIPP and Manhole Rehabilitation Projects, flow monitoring will quantify the reduction in flows achieved by the projects when measured against the base data. Analysis of the changes in flow will lead to better decisions on the location of future projects to best utilize the funding that is available.

Staff has used the flow data and alarm features to identify and correct problems in the system. Recently, an old pipe repair failed and was obstructing flow in the main. Data from the flow monitoring indicated a problem when flow conditions reached a certain level in the pipe. An alarm from the flow meter during a rain event lead to the discovery of a surcharging condition upstream of the problem. The line was televised and revealed the failure. The main was repaired and the flow data now shows a normal condition.  Attached is a map of the location of the meter and a scatter graph of what the flow data looked like. The obstruction was found in the 12” main between the meter and the 15” pipe circled in green. The attached picture is what was removed from the line, a portion of an old plastic bucket and concrete used to repair the main.

Long-term uses of the flow data in conjunction with the wastewater system model will provide actual system capacities that will be used to evaluate the impact of proposed developments on the system.