FIELD VERIFICATION OF REFERENCE FLOW AND WATER LEVEL METERS UNDER THE EPA'S ETV PROGRAM

摘要

A field verification of reference flow and water level meters was done as part of thernEnvironmental Technology Verification (ETV) program of the U.S. Environmental ProtectionrnAgency (USEPA), under the “Wet-Weather Flow Technologies” pilot program managed by NSFrnInternational during the summer of 2001. One of the technologies verified under this pilotrnprogram is the “Flow Monitoring Equipment”, which requires the verification of referencernmeters under the terms of the Generic Protocol entitled "Verification of Flowmeters forrnStormwater and CSO Applications in Mid-size Pipes". A full description of the ETV programrnand a copy of the Generic Protocol can be consulted on the following web site:rnhttp://www.epa.gov/etv.rnThis paper presents the testing site and the results of the field verification of the reference metersrnused to verify the vendors’ flowmeters as part of the ETV program. The testing site is a sectionrnof the Quebec Urban Community’s (QUC) interceptor network. The accuracy of three metersrnwas verified: one four-path transit-time flowmeter and two level meters, a bubbler and anrnultrasonic level meter. A total of nine active tests were performed: three tests B (dry-weatherrnflow with and without backflow), C (wet-weather flow without backflow) and D (wet-weatherrnflow with backflow and surcharge conditions). The verification of the accuracy was based on arncomparison with a reference method. The concentrations of blank, concentrated and dilutedrnsamples obtained from the lithium dilution analyses were used to estimate flow rates. Manualrnlevel measurements were used to verify water levels.rnThe Field Testing Organization recognized that the four-path transit-time flowmeter and both thernbubbler and ultrasonic level meters did not meet the accuracy requirements specified in thernGeneric Protocol in order to be validated as the reference meters. Nevertheless, in light of thernresults obtained using the revised flow accuracy margins and considering the unexpectedly lowrnaccuracy of the tracer dilution analysis results, as well as the good fit with the flow ratesrnestimated with the “flow under the gate” equation, the four-path transit-time flowmeter wasrnvalidated as the reference flowmeter to verify the vendors’ flowmeters. Furthermore, in light ofrnthe fact that the performance results are affected by the presence of waves during the two highestrnflow rates of Test C and knowing that the bubbler level meter is less impacted by waves than arernthe manual measurements and ultrasonic readings, the bubbler level meter was validated as thernprimary reference level meter and the ultrasonic as the secondary (or redundant) level meter tornverify the vendors’ flowmeters.