PRECIPITATION CALIBRATION TESTS August 12, 2009

Transcription

1 BISHOP PAIUTE TRIBE ENVIRONMENTAL MANAGEMENT OFFICE PRECIPITATION CALIBRATION TESTS Augut 12, 2009 Thi report decribe the reult of everal precipitation calibration tet carried out in July 2009, following audit finding from November 2008 that indicated that one of the Tribe precipitation gauge wa reading low. The audit carried out by Dave Yoho from T&B Sytem howed that the Tribe precipitation gauge TR-525I, manufactured by Texa Electronic and purchaed from Climatronic wa reading 18.6 below the audit input, a hown below. The econd table how a correction for two 5-minute interval of data that were accidentally omitted from the data tranmiion to the auditor. Either way, the precipitation gauge appear to be out of calibration. T&B, November 11, :50 PST TO 11:00 PST Inche Inche Diff. Point Input DAS DAS Criteria: ±10 of input Comment: The audit reult do not meet the audit criteria. A calibration of the precipitation gauge i recommended. Correction lat two 5-minute interval of data accidentally omitted from data tranmiion to auditor. Inche Inche Diff. Point Input DAS DAS The original T&B audit wa carried out uing a Gatorade bottle with an adjutable nozzle that had been modified to be ued a a funnel and would yield a relatively low drip rate. Water wa obtained from a purchaed 500ml bottle of drinking water. The original audit took a little over an hour. In repone to the finding we determined that intrument calibration wa appropriate. Initially we attempted to reproduce the reult uing the manufacturer-pecified field calibration kit FC- 525 that i pecifically deigned for the TR-525 gauge. We utilized the bra #65 nozzle that i pecified to take 25 minute and yield 98 count plu or minu 2 count. The reult are hown below. Page 1

2 Firt Verification, July 7, 2009 Date 7/7/2009 Site Bihop Tribe EMO Start Time 8:50 PST Operator() Toni Richard, Walter Hanon Finih Time 9:20 PST Manufacturer Climatronic / Texa Electronic Manufacturer Texa Electronic Model GO Model FC-525 w/ #65 nozzle (bra) Diameter 6.06 e per manufacturer' pecification Difference Method ml e Tex -2.5 Electronic 470 We were pleaed with the reult but puzzled that they were o different from the audit reult. When we dicued thee reult with Dave Yoho at T&B ytem he advied u to try to replicate hi method uing a Gatorade bottle and a 500ml bottle of drinking water. A a conequence, we verified the volume of water in the beaker upplied a part of the kit uing a gla laboratory beaker. A value of 473 ml had been upplied by Texa Electronic to GBUAPCD and we meaured 470 ml, although it i unlikely that we could have detected uch a mall difference in our large beaker and uch a mall difference would not ignificantly alter our reult. Even after everal try, the volume wa reproducible. See photograph below. Page 2

3 Menicu on 1000ml beaker after being filled with water from FC-525 kit Precipitation Gauge Tet We then et up a tet replicating the T&B Gatorade bottle / water bottle method. We dicovered that Gatorade i no longer upplying that type of bottle in our area and ubtituted a imilar Propel bottle, with the bottom removed o that it could erve a a funnel. For the water, we ued 500ml Sparklett drinking water. To make the tet fair, we made ure that both the FC-525 funnel equipped with the bra #65 nozzle and the propel dripped at approximately the ame rate. In addition, we meaure the volume of a full Sparklett bottle one where the water wa near the rim jut below the cap on the bottle. We found thi type of bottle typically contained 520ml of water. See the photograph below. Page 3

4 Minucu from content of a 500ml Sparklett bottle In the proce, we noted that there appear to be ome variability in the volume of water in Sparklett bottle. All of the bottle in the next photograph are from the ame cae purchaed from Smart and Final. Page 4

5 Volume of water in Sparklett bottle Next we compared the two method on both the Texa Electronic TR-525I and a Davi Grow Weather precipitation gauge that i ituated on the ame platform, with the reult hown below. For the water volume, we ued the volume that we had ly meaured. Page 5

6 Method Comparion, July 15, 2009 Date 7/15/2009 Site Bihop Tribe EMO Start Time 7:35 PST Operator() Toni Richard, Walter Hanon Finih Time Manufacture r 8:35 PST Climatronic / Texa Electronic Manufacturer Texa Electronic Model GO Model FC-525 w/ #65 nozzle (bra) Diameter 6.06 e per manufacturer' pecification Difference Method ml e -2.5 Tex Electronic ml water e -3.7 bottle / propel 520 Date 7/15/2009 Site Bihop Tribe EMO Start Time 7:35 PST Operator() Toni Richard, Walter Hanon Finih Time Manufacture r 8:35 PST Davi Manufacturer Texa Electronic Model Grow Weather Model FC-525 w/ #65 nozzle (bra) Diameter 6.5 e per manufacturer' pecification Difference Method ml e 1.8 Tex Electronic ml water e -0.7 bottle / propel 520 To our relief, both method yielded imilar reult for each intrument. In each cae, the calibration took approximately 25 minute. Further dicuion with Bob Baxter at T&B ytem lead to the concern that the #65 Texa Electronic drip rate wa too rapid and a lower rate would yield more accurate reult. We then teted the Texa Electronic uing the FC-525 with the #70 nozzle yielding a calibration duration of 45 minute. We alo teted the Propel bottle adjuted for a drip rate lead to a calibration duration of 45 minute and one that led to a calibration duration of at leat 1 hour, to match the original audit time. Page 6

7 Third Verification, 45 minute, July 23, 2009 Date 7/23/2009 Site Bihop Tribe EMO Start Time 9:00 PST Operator() Toni Richard Finih Time 9:45 PST or Manufacture r Climatronic Manufacturer Texa Electronic Model GO Model FC-525 w/ #70 nozzle (aluminum) Diameter 6.06 e per manufacturer' pecification Difference Method ml Tex e -0.4 Electronic 470 Fourth Verification, Augut 4, 2009 Date 8/4/2009 Site Bihop Tribe EMO Start Time Operator() Toni Richard, Walter Hanon Finih Time or Manufacturer Climatronic Manufacturer n/a Model GO Model n/a per manufacturer' Diameter 6.06 e pecification minute minute Differenc e Method ml e -3.7 e ml water bottle / propel ml water bottle / propel 520 Even after multiple tet uing multiple method, we are unable to replicated the audit reult and our verification effort ugget that the Climatronic precipitation gauge i within pecification. To better undertand the EPA guidance on matter of calibration and verification, we conulted with Chri Lanane from GBUAPCD who provided the following information. The reference i EPA Volume IV: Meteorological Meaurement, of the Quality Aurance Handbook for Air Pollution Meaurement Sytem, EPA-454/B , March 2008, Section 4.3, Calibration, which tate, "For rate-enitive ytem uch a the tipping bucket, the rate of imulated Page 7

8 precipitation hould be kept contant to achieve 1 tip every 15 econd." That i 2.4 e per hour for calibration, however, in Section 4.5, ing, the document tate that, "For tipping bucket gauge, a rate of le than one per hour hould be ued and an amount which will reult in a minimum of 10 tip." By inference, the indication i that the precip gauge hould work anywhere between thoe two input, from 1 to 2.4 e per hour. (Emphai added.) We calculated that if we ue the #65 FC-525 nozzle, the rate would be 2.4 e per hour and the #70 FC-525 nozzle would yield a rate of 1.33 e per hour. Both eem to be within EPA Guidance for calibration. However, both rate exceed the guidance for audit. Finally, we conulted the manufacturer, Texa Electronic who indicated that the intrument wa enitive to change in the flow rate and that variability wa to be expected from any verification method that did not have a contant flow rate, uch a the two we conidered. We earched for other method of verification, including a model made by HydroLynx that ha a contant flow. However, thi gauge i better uited for horter high flow tet than the low rate pecified by the EPA auditing guidance and by our auditor. CONCLUSIONS After dicuion with both Bob Baxter at T&B Sytem and Chri Lanane at GBUAPCD, and our own experience, we conclude that everal thing, either ingly or in combination could have led to the dicrepancie between our finding and the audit reult. There had been no rain in October and only a fraction of an in November prior to the audit, o the gauge wa dry and potentially duty. Chri Lanane recommended wetting the tipping bucket prior to tarting an audit. We have noted variability in the volume of water in the Sparklett brand of drinking water and it i poible that the volume in the bottle ued by our auditor wa alo low. Of coure, both type of problem may have occurred. Page 8