chapter 7 maintenance considerations to ensure data quality
Contents
1. The amount of offset is generally determined by the reflectivity of the guard and screen In case of using plastic screens it is a good practice to use black screens or paint the screen with black antifouling paint For copper screens once the copper has taken on the patina color the amount of offset decreases Another option would be to soak the parts in salt water to patina them before your calibration Source NIW Bay NERR If copper tape is used and replaced every deployment then new offset must be determined every time the guard is re taped 152 Pressure Offset Pressure Offset Pressure Offset meter meter meter 680 1 088 730 0 408 780 0 272 681 1 074 731 0 394 781 0 285 682 1 060 732 0 381 782 0 299 683 1 047 733 0 367 783 0 313 684 1 033 734 0 353 784 0 326 685 1 020 735 0 340 785 0 340 686 1 006 736 0 326 786 0 353 687 0 992 737 0 313 787 0 367 688 0 979 738 0 299 788 0 381 689 0 965 739 0 285 789 0 394 690 0 952 740 0 272 790 0 408 691 0 938 741 0 258 791 0 421 692 0 924 742 0 245 792 0 435 693 0 911 743 0 231 793 0 449 694 0 897 744 0 218 794 0 462 695 0 884 745 0 204 795 0 476 696 0 870 746 0 190 796 0 489 697 0 856 747 0 177 797 0 503 698 0 843 748 0 163 798 0 517 699 0 829 749 0 150 799 0 530 700 0 816 750 0 136 800 0 544 701 0 802 751 0 122 801 0 557 702 0 789 752 0 109 802 0 571 703 0 775 753 0 095 803 0 585 704 0 761 754 0 082 804 0 598 705 0 748 7552. 0 694 0 684 0 673 0 663 0 653 0 642 0 632 0 622 0 611 0 601 0 591 0 580 0 570 0 559 0 549 0 539 0 528 0 518 0 508 0 497 0 487 0 477 0 466 0 456 0 445 0 435 0 425 0 414 0 404 0 394 0 383 0 373 0 363 Pressure in Hc 28 90 28 93 28 96 28 99 29 02 29 05 29 08 29 11 29 14 29 17 29 20 29 23 29 26 29 29 29 32 29 35 29 38 29 41 29 44 29 47 29 50 29 53 29 56 29 59 29 62 29 65 29 68 29 71 29 74 29 77 29 80 29 83 29 86 29 89 29 92 29 95 29 98 30 01 30 04 30 07 30 10 30 13 30 16 30 19 30 22 30 25 30 28 30 31 30 34 30 37 155 Offset meter 0 352 0 342 0 332 0 321 0 311 0 300 0 290 0 280 0 269 0 259 0 249 0 238 0 228 0 218 0 207 0 197 0 186 0 176 0 166 0 155 0 145 0 135 0 124 0 114 0 104 0 093 0 083 0 073 0 062 0 052 0 041 0 031 0 021 0 010 0 000 0 010 0 021 0 031 0 041 0 052 0 062 0 073 0 083 0 093 0 104 0 114 0 124 0 135 0 145 0 155 Pressure in Hc 30 40 30 43 30 46 30 49 30 52 30 55 30 58 30 61 30 64 30 67 30 70 30 73 30 76 30 79 30 82 30 85 30 88 30 91 30 94 30 97 31 00 31 03 31 06 31 09 31 12 31 15 31 18 31 21 31 24 Jia 31 30 31 33 31 36 31 39 31 42 31 45 31 48 31 51 31 54 31 57 31 60 31 63 31 66 31 69 31 72 31 78 31 78 31 81 31 84 31 87 Table 7 3 Depth Offset in Hg Source CDMO 2207 Offset meter 0 166 0 17
3. MAINTENANCE CONSIDERATIONS TO ENSURE DATA QUALITY 7 1 INTRODUCTION To ensure good quality data during a water quality monitoring project a maintenance program must be in place for the monitoring sondes platforms and equipment employed There are three basic types of maintenance procedures U S Department of Energy e Reactive or corrective maintenance is an unscheduled action performed on a system equipment or one of its components in the attempt to restore it to a specified performance condition Basically the system or product is fixed once it brakes down or fails to perform as desired e Preventive maintenance is a scheduled action performed on a system equipment or one of its components to detect or mitigate performance problems degradations functional or potential failures etc with the goal of maintaining the systems or product s performance and it s level of reliability e Predictive maintenance is the action performed on a system equipment or one of its components to determine their performance and act in accordance of the results For example instead of changing the oil in the car every X miles preventive the oil is analyzed to determine its performance and depending on the results the oil will be kept or changed Thus the oil can be changed before the X miles or kept for extra miles The need for maintenance is determined by the condition of the system equipment or component analyzed Even though it is most pro
4. Turb Turb PETTITT I Battery voltage i ON remove ext power 650 6038 E V remove ext power Calculated pi slope Interval min Start date mevddyyy Start time su time hh mm ss Duration days Data file name Battery life days Free memory days Set clock status YorN Free bytes status K Parameters recorded Date Time Temp C SpCon Sal DO DO mg L Depth pH Turb Batt Comments Pre Comments Post Figure 7 3 NERRS 6 series calibration log 156 HYDROLAB MULTIPROBE CALIBRATION MAINTENANCE LOG Calibration Post Calibration Initials Time Instrument Battery Voltage If this is a post calibration give date of original calibration _ Standard Standard Reading to specie conducnee CC omemmacn ECCE E I E E a OI OI DATA NEEDED FOR DISSOLVED OXYGEN CALIBRATION o o DATA NEEDED FOR DISSOLVED OXYGEN CALIBRATION ana panel Barometric Pressure Formulas BP mm CBP mm 2 alitude 2100 BP mm 760mm 2 5 altitude 7100 For older Hydrolabs Table DO value xALTCORR xBAROCORR o DOstandard Calibration Post Calibration Initials Time Instrument Battery Voltage If this is a post calibration give date of original calibration _ Standard Standard Reading to a a a E r Te e e E E Dion nun DATA NEEDED FOR DISSOLVED OXYGEN POST CALIBRATION 7 DATA NEEDED FOR DISSOLVED OXYGEN POST CALIBRATION Barometric Pressure BP Options Barometric Pressure Formulas Fr
5. sonde can remain deployed will decrease as water temperature increases monitoring sondes that can be deployed for three weeks to one month in winter may need to be changed on a weekly basis in summer 149 The sonde maintenance program must address at least the following procedures Prepare the sonde for deployment 3 Calibration for deployment gt Post deployment performance verification 7 2 1 PREPARE THE SONDE FOR DEPLOYMENT The sonde must be adequately prepared to handle the environmental factors that could influence data quality These physical biological and chemical factors are characteristic of the monitoring site location Therefore no unique solution exists to address these factors and the best approach to control them will have to take into account not only the site characteristics but also the deployment cycle and the design of the monitoring station Among the environmental factors special attention must be given to biofouling given that is one of the main factors affecting the operation maintenance and data quality of the sondes some examples of common and extreme biofouling are displayed in Figure 7 1 Among the many methods employed to reduce or prevent biofouling the most common ones are e Painting the housing of the sensors with anti fouling coatings e Covering the housing of the sensors with anti fouling copper tape e Using the adequate anti fouling probes wiper wipers e Painting the entire wi
6. Division U S Department of Energy Operations and Maintenance Energy Efficiency and Renewable Energy Federal Energy Management Program http www1 eere energy gov femp operations maintenance om strategies html U S Environmental Protection Agency 2002 Guidance on Environmental Data Verification and Data Validation EPA QA G 8 U S Environmental Protection Agency 2002 Guidance for Quality Assurance Project Plans EPA QA G 5 YS Incorporated 2008 6 Series Multiparameter Water Quality Sondes User Manual YSI Incorporated 2009 Calibration Tips for YSI 6 Series Sondes amp Sensors 176
7. be realized by correcting for atmospheric pressure changes during the deployment period and reporting the data to a common vertical reference datum Benefits of more accurate and vertically referenced water level data can facilitate AQ QC efforts by removing erroneous negative values while providing water level information in a more user acceptable format thereby increasing the use of water level data by a broader audience 174 7 7 EQUIPMENT MAINTENANCE As stated in ISO 9001 2600 The organization shall determine the monitoring and measurement to be undertaken and the monitoring and measuring devices needed to provide evidence of conformity of product to determined requirements The organization shall establish processes to ensure that monitoring and measurement can be carried out and are carried out in a manner that is consistent with the monitoring and measurement requirements Where necessary to ensure valid results measuring equipment shall a mi be calibrated or verified at specified intervals or prior to use against measurement standards traceable to international or national measurement standards where no such standards exist the basis used for calibration or verification shall be recorded be adjusted or re adjusted as necessary be identified to enable calibration status to be determined be safeguarded from adjustments that would invalidate the measurement result be protected from damage and deterioration during
8. convenient material The circular piece is made for a 4 inch PVC pipe adjust diameter for other types of pipes Cut two openings at opposite sides of the disk Make the openings big enough so the disk goes through the bolts easily Secure the disk to a telescopic pole The disk can be attached to the telescopic pole permanently or by a coupling so it can be easily removed Telescopic poles come in a variety of length with 24 ft the longest length that can be easily purchased in any home J improvement retailer If longer poles are needed a good option is to create your own extension to be attached at the end of the pole Measure distance bolts bottom inside the guard pipe Lower the pole inside the guard pipe until the disk hits the bolts Set a ruler on top of the guard pipe and mark the point where the ruler touches the pole with a rubber band This point is called TOP BOLTS distance TB Rotate the pole so the openings match the bolts and the disk goes through the bolts Lower the pole until the round piece hits the bottom Mark this point with a second rubber band TBInside This point is called TOP BOTTOM INSIDE distance TB Inside Remove the pole from the guard pipe TB j Measure distance top bottom around the guard pipe Cut two small pieces of duck tape and draw a line on them vvith a permanent marker Mark one of these lines as 1 and
9. distance TB Inside is much smaller than the two TB Outside distances TBOutside1 Possible physical fouling or sediment build up occurred under the guard pipe Try to remove the physical fouling or built up sediment Removal is successful Bolts Bottom Distance i 1 3 TB Inside TB Outside 1 TB Outside 2 3 TB Removal is not successful Bolts Bottom Distance 1 2 TB Outside 1 TB Outside 2 2 TB I ca DI 6 The distance TB Inside is much bigger than the two TB Outside distances There is a hole under the guard pipe possibly due to the interaction of nearstation current circulation with the monitoring platform Bolts Bottom Distance 1 2 TB Outside 1 TB Outside 2 2 TS The three distances exhibit a significant difference showing a decline or an incremental pattern TBOutside1 BOutsidez The bottom surface shows a slope around the monitoring station Bolts Bottom Distance TB Inside TS 171 7 6 CORRECTION FACTOR FOR WATER LEVEL DEPTH DATA REPORTING Austin et al 2004 state that multiparameter sondes equipped with non vented pressure sensors are Most commonly used for continuous water quality monitoring Standard calibration protocols for the non vented sensor use ambient atmospheric pressure at the time of calibration Changes in atmospheric pressure between calibrations appear as changes in water depth A 1 0 millibar change in atmosphere
10. handling maintenance and storage All the equipment used to calibrate and post calibrate the sensors and field verifications must be maintained calibrated or pass some quality assurance check to ensure their accuracy and that they perform to accepted standards Equipment histories records and logs must be maintained 175 7 8 REFERENCE ANSI ISO ASQ Q9001 2000 Quality management systems Requirements American Society for Quality Austin Joy Terri Keffert Jim Goings and William Reay 2004 Enhancing the Value of SWMP Depth Data Poster presented at the inauguration of the Catlett Burress Research and Education Teaching Lab CDMO 2007 YSI 6 Series Multi Parameter Water Quality Monitoring Standard Operating Procedure Version 4 1 National Estuarine Research Reserve System Wide Monitoring Program SWMP Helsel D R and R M Hirsch 2002 Statistical Methods in Water Resources U S GEOLOGI CAL SURVEY Resources Inventory Committee 1999 Automated water quality monitoring Field manual Ministry of environmental lands and parks The Pro of British Columbia Sullivan G P R Pugh A P Melendez and W D Hunt 2004 Operations amp Maintenance Best Practices A Guide to Achieving Operation Efficiency US Department of Energy Texas Commission on Environmental Quality 2003 Surface Water Quality Monitoring Procedures Volume 1 Physical and Chemical Monitoring Methods for Water Sediment and Tissue Monitoring Operations
11. in a horizontal position close to the replacement sonde 2 Clean and dry the field cable connector of the deployed sonde If necessary use a was bottle to rinse the dirt from the field cable connector and sonde connector Dry the field cable connector and the sonde connector with a towel paper towel or kimwipe 3 Remove the field cable connector from the deployed sonde and clean the inside of the connector Use the cotton tipped sticks or kimwipes to clean and dry the inside of the field cable connector and the outside of the sonde connector Check that the pins either in the field cable connector or in the sonde connector are dry If not use the compress gas duster to dry them Connect the field cable to the replacement sonde Remove the waterproof cap from the replacement sonde and connect the field cable connector A built in key will ensure proper pin alignment Rotate the cable gently until the key engages and then tighten the connector together by rotating clockwise Attach the strain relief connector to the sonde bail Put the waterproof cap to the sonde that is going to be serviced 162 Fue Drama Ba 7 Fr Identification Number Effective Date DATALOGGER INFORMATION Retrieval out WEATHER INFORMATION Weather Conditions measured with Kestrel Wind Speed Cloud Cover Current Wind Speed m s 0 1 knots 0 1 m s Clear 0 10 ET Scatter partly Cloudy 10 5096 0 Air T
12. pressure corresponds to an approximate 1 0 centimeter change in water depth Therefore use of a non vented pressure sensor can result in significant water depth errors for large scale weather and storm events This error is eliminated for level sensors because they are vented to the atmosphere throughout the data sonde deployment time interval If proper atmospheric pressure data is available non vented sensor depth measurements can be post corrected for deployments between calibrations This correction combined with a common reference point from a survey station results in more accurate water depth data Austin et al demonstrate the relative ease of adjusting non vented depth sensor data for atmospheric pressure changes to reflect more accurate measurements Ambient laboratory atmospheric pressure was measured using a Varila pressure sensor with data being stored at 15 minute intervals on a Campbell 10X datalogger Following retrieval of the instrument from the field data can be downloaded and saved as an Excel file Atmospheric pressure data collected at the appropriate time interval and the atmospheric pressure at the time of calibration can be added to the Excel file The raw depth data is adjusted by the following simplistic equation calibration atm P PESSUT ambient 100 im Depth Depth aim pressure adjusted 172 In many cases adjustment of the raw data can correct depth levels to positive values which c
13. 0 068 805 0 612 706 0 734 756 0 054 806 0 625 707 0 721 757 0 041 807 0 639 708 0 707 758 0 027 808 0 653 709 0 693 759 0 014 809 0 666 710 0 680 760 0 000 810 0 680 T11 0 666 761 0 014 811 0 693 712 0 653 762 0 027 812 0 707 713 0 639 763 0 041 813 0 721 714 0 625 764 0 054 814 0 734 715 0 612 765 0 068 815 0 748 716 0 598 766 0 082 816 0 761 717 0 585 767 0 095 817 0 775 718 0 571 768 0 109 818 0 789 719 0 557 769 0 122 819 0 802 720 0 544 7 0 0 136 820 0 816 721 0 530 771 0 150 821 0 829 722 0 517 772 0 163 822 0 843 723 0 503 773 0 177 823 0 856 724 0 489 774 0 190 824 0 870 725 0 476 775 0 204 825 0 884 726 0 462 776 0 218 826 0 897 727 0 449 777 0 231 827 0 911 728 0 435 778 0 245 828 0 924 729 0 421 779 0 258 829 0 938 Table 7 1 Depth Offset mm Hg Source CDMO 2207 153 Pressure mb 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 955 956 957 958 959 961 962 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 Offset meter Pressure 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 Pressure mb 0 340 1030 0 329 1031 0 319 1032 0 309 1033 0 299 1034 0 289 1035 0 2
14. 6 0 186 0 197 0 207 0 218 0 228 0 238 0 249 0 259 0 269 0 280 0 290 0 300 0 311 0 321 0 332 0 342 0 352 0 363 0 373 0 383 0 394 0 404 0 414 0 425 0 435 0 445 0 456 0 466 0 477 0 487 0 497 0 508 0 518 0 528 0 539 0 549 0 559 0 570 0 580 0 591 0 601 0 611 0 622 0 632 0 642 0 653 0 663 0 673 PL E TEE NERRS SWMP Water Quality Calibration Log 5 Reserve Site Name File Name Date of Calibration mm dd yyyy Technicianis TURB ODO TURB ODO Wipers replaced Wipers park 180 from optics Batteries replaced DO membrane replaced Format flash disk Membrane integrity test Dat T dnd Proba Identification Nang Datasonde DO ODO pH Conductivity Turbidity Comments u EHE RE tum on pH mV and DO Chrg in Report menu Pre Deployment Post Deployment Standards Before Cal Calibrated Error DO 100 sat pa s RP DO chrg range 25 75 BP cal Rapid Pulse mm Hg mm Hg RP DO gain 0 8 1 7 Optical DO 100 sat Optical DO gain BP cal Optical mm Hg mm Hg DO warm up test hi lo Baro Pres Depth Calib 760 0 mmHg 7604 for vented sonde Depth ofe m m mm Hg 760 0 for vented Cell const 4 6 5 45 m O oa pH 7 0 50 mV pH 10 180 50 mV mS cm pH 4 180 50 mV Calculated pH slope SpCond mem mem mS cm pH 7 pH 10 pH 4 DO chrg range 25 75 DO warm up test hi lo pH 7 0 50 mV pH 10 180 50 mV pH 4 180 50 mV
15. 78 1036 0 268 1037 0 258 1038 0 248 1039 0 238 1040 0 227 1041 0 217 1042 0 207 1043 0 197 1044 0 187 1045 0 176 1046 0 166 1047 0 156 1048 0 146 1049 0 136 1050 0 125 1051 0 115 1052 0 105 1053 0 095 1054 0 085 1055 0 074 1056 0 064 1057 0 054 1058 0 044 1059 0 034 1060 0 023 1061 0 013 1062 0 003 1063 0 007 1064 0 017 1065 0 028 1066 0 038 1067 0 048 1068 0 058 1069 0 068 1070 0 079 1071 0 089 1072 0 099 1073 0 109 1074 0 119 1075 0 130 1076 0 140 1077 0 150 1078 0 160 1079 Table 7 2 Depth Offset mb Source CDMO 2207 154 Offset meter 0 170 0 180 0 191 0 201 0 211 0 221 0 231 0 242 0 252 0 262 0 272 0 282 0 293 0 303 0 313 0 323 0 333 0 344 0 354 0 364 0 374 0 384 0 395 0 405 0 415 0 425 0 435 0 446 0 456 0 466 0 476 0 486 0 497 0 507 0 517 0 527 0 537 0 548 0 558 0 568 0 578 0 588 0 599 0 609 0 619 0 629 0 639 0 650 0 660 0 670 Pressure Offset in Hc 27 40 27 43 27 46 27 49 27 52 217 56 27 58 27 61 27 64 27 67 27 70 27 18 27 76 27 79 27 82 27 85 27 88 27 91 27 94 27 97 28 00 28 03 28 06 28 09 28 12 28 15 28 18 28 21 28 24 28 27 28 30 28 33 28 36 28 39 28 42 28 45 28 48 28 51 28 54 28 57 28 60 28 63 28 66 28 69 28 72 28 75 28 78 28 81 28 84 28 87 meter 0 870 0 860 0 849 0 839 0 829 0 818 0 808 0 798 0 787 0 777 0 767 0 756 0 746 0 736 0 725 0 715 0 704
16. Even though the brush is tough on the anti fouling paint many pipes stay in year after year and in these cases the anti fouling paint is not an issue and a chimney brush works well to clear the pipe of hard and soft biological fouling In certain types of guard pipe installations e g on river or stream bank it is a good practice after brushing the pipe to rinse it by pouring a bucket of surface water down the pipe NOTE Any evidence of physical and biological fouling that could have affected the monitoring data must be recorded for further analysis 7 4 TELEMETRY EQUIPMENT MAINTENANCE Proper maintenance of the Telemetry equipment is essential to obtain accurate data Equipment must be in good operating conditions routine and schedule maintenance and inspection must be peformed must include at least the following activities to ensure that your telemetry equipment is mounted far enough above sea level to be clear of wave action and storm surges due to hurricanes Take out equipment EPA 2002 Battery Campbell Scientific Cyclic service life of rechargeable batteries The industry definition of the cyclic service life of a battery is the period until it dorps to 6096 of its rated capacity For a 7 Ahr battery this is when after repeated recharging the battery can only deliver 4 2 Ahrs When choosing a battery you should also consider the number of recharge cycles you can expect from the battery until it reaches the end of tis cy
17. Wrap the sonde in the towel leaving some excess towel at the bottom of the sensor guard so it can be folded to ensure the guard is completely covered Place the towel wrapped sonde in a bucket a cooler or other container for transportation to the monitoring site t is good practice to transport the sondes in a container of sufficient size to allow the sondes to lie horizontally across the bottom The sonde is transported in a 5 gallon bucket filled with tap water Drill one or two holes on the lid about 3 4 inches in diameter Place some type of cushion on the bottom of the bucket to minimize shocks and vibrations f necessary place some kind of weight on the bottom to prevent the bucket to tip over during transit due to the sonde s weight Fill the bucket with tap water so that the probes stay submerged Some kind of structure can be built to accommodate several buckets in a stable position during transit in this case there is no need to place a weight inside the bucket 164 7 3 STATION MAINTENANCE The following activities must be included in the station maintenance program e Verification of station conditions during deployment retrieval of monitoring sensors e Schedule on site verification and cleaning of guard pipes e Schedule retrieval of guard pipes for cleaning and painting once a year minimum e Schedule cleaning and rebuilding of monitoring platforms e Maintenance procedure
18. an result in more accurate and less confusing information Figure 7 8 Table 7 4 pe D e Figure 7 9 Raw vs corrected YSI depth data from the York River over time accuracy 0 018 m l Calibration Raw Depth Adjusted Depth Ambient Pressure Table 7 4 Example of raw depth data using atmospheric pressure at time of calibration vs adjusted data using ambient atmospheric pressure from weather station 06 00 1013 9 1020 30 Additionally extreme storm events such as hurricanes are marked by large depression in atmospheric pressure during the storm s passage For example in the case of Hurricane Isabel a 30 millibar drop was observed resulting in a 0 30 m error in water depth level 173 Given atmospheric pressure data at the time of instrument calibration and during instrument deployment water depths are easily corrected Figure 7 9 D 3 e Atmospheric Pressure EEE KE u e aj v j SeNRADNNRABDWNER Figure 7 10 Raw vs corrected YSI depth data using atmospheric pressure at time of Hurricane Isabel To further enhance the value of water level data traditional optic or advanced GPS surveying systems can be used to reference water quality monitoring platforms in instruments to a standard vertical datum Common local datums include mean sea level MSL mean lower low water MLLW and mean higher high water MMHW Increase accuracy and value of water depth data can
19. bable that in a water quality monitoring endeavor all three of these types of maintenance procedures are going to be applied the maintenance program must be focused on preventive and predictive maintenance To implement a successful maintenance program the following three areas must be covered a Training the personnel that perform maintenance activities e g calibration and post calibration of monitoring sensors equipment and station inspections cleaning and replacement of instruments or parts must have the adequate training to ensure that they possess the necessary competence to do an effective and efficient job b Procedures and record management procedures and record management must be in place to ensure that among other things The maintenance activities are well documented All instruments calibrated will conform to required specifications The operation and control of the processes are effective Methodologies to assess the root cause of problem are known Maintenance schedules are established Maintenance records are well kept and easily accessed and traceable Evidence of conformity of calibration is provided 148 c Procurement and spare parts management to ensure the reliability of the monitoring endeavor each monitoring equipment or system must have an adequate spare parts procedure to guarantee the availability of resources There are three main hardware systems that need to be ad
20. clic life Several factors affect the cyclic service life including ambient temp during charging and storage number of discharge cycles depth of discharge cycles and charging voltage Clearly these are complex relationships The following may help you assess your batteries service life 1 temperature warmer temperatures decrease life because heat hastens chemicals reaction that cause corrosion of the internal electroedes The temperature effects are graphed and described on the following page 166 Depth of discharge Determine minimum and maximum battery voltages in your daily data Analyze the data using tool to count the number of times the voltage dropped below certain values Check for more info http www mpoweruk com life htm 167 7 5 MEASURE THE DISTANCE FROM THE SONDE s HOLDI NG BOLTS TO THE BOTTOM SEDI MENTS Water depth is one of the parameters measured by a monitoring sonde A differential strain gauge transducer is generally employed to measure the pressure of the water column plus the atmospheric pressure above the water To have an accurate water depth measurement a program must be utilized to eliminate the errors produced by atmospheric pressure variations Water depth is the distance from the water surface to bottom sediments The sonde measures water depth as the distance from the transducer to water surface therefore to have an accurate water depth the distance from the transducer to the bottom sediments
21. ctivity DO Gain DO Charge Range 4 6 to 5 45 Range 0 8 to 1 7 Range 25 to 75 FOULING CONDITIONS Possible Fouling Description Slime Mud Sediment slimy sticky rusty thick Worm tubes Seaweed Grasses Algae Amphipods amphipod tubes Barnicles Mussels Branching Bryozoan Encrusting Bryozoan Coral Lattice Tunicates etc TURBIDITY CHLOROPHYLL ODO Animals of Physical Fouling Found in Guard Wipers Condition Parked YN YN YN Fouled YN Y N YN E THERMISTOR OPTICAL PROBE FACES CONDUCTIVITY CHAMBERS pH BULB DEPTH CHANNEL Figure 7 5 YSI 6 series post calibration log 159 During field verification it is a good practice to take an independent measurement for each sensor parameter Generally field verification is performed during the monitoring sonde exchange phase A possible sonde switch out process could be 1 Set the replacement sonde in the water to allow the probes to equilibrate to ambient conditions The replacement sonde is deployed in a temporary position at the same depth as the deployed sonde to Allow the sonde a few minutes to equilibrate to the water temperature before taking the readings Obtain simultaneous readings with the deployed sonde It is good practice to place a snap hook in the station to hang the replacement sonde The rope to hang the replacement sonde will have the necessary length to ensure the sonde is placed at the monitoring depth 2 Perform the field ver
22. dressed in a water quality monitoring maintenance program SH Monitoring sondes A Monitoring stations AAAA Verification equipment When addressing the maintenance program of these systems it is important to consider that Not all equipment or components have equal importance and equal impact on data quality The probability of failure or mal function is different between equipment parts and structures Service or maintenance cycles differ between equipment Y There is limited financial and personnel resources Y NOTE To assure data quality a quality assurance control amp maintenance program for the monitoring data must be in place To obtain guidelines on how to approach this issue the reader should consult EPA QA G 5 EPA QA G 8 and Helsel and Hirsch 2002 7 2 SONDE MAI NTENANCE Data quality is directly related to the monitoring sonde performance Therefore it is crucial to have a sonde maintenance program In general the maintenance program would be based on maintenance cycles correlated to the time frame the sondes can stay deployed without affecting data quality The cycle will depend on the probes characteristics environmental conditions i e high fouling environments battery life and any other factors that affect the sonde s performance In most monitoring situations the maintenance cycles follow a seasonal pattern For example in high fouling environments the length of time the
23. dures as laboratory calibrations Field performance assessment activity conducted in the field As soon as the sensor is retrieved it is placed in a standard solution and readings are recorded Field verification indirect measurements of sonde performance Using field measuring equipment water quality measurements are taken and compared to sonde readings Probe performance records are used for continual improvement data analysis and nonconformity management As an example a post calibration log is presented in Figure 7 5 158 DEPLOYMENT INFORMATION DATE TIME WEATHER TIDE WIND SPEED HUMIDITY DEPLOYMENT RETRIEVAL DO mg l Water Temp Air Temp Secchi Depth Salinity pH DEPLOYMENT RETRIEVAL POST DEPLOYMENT DATA RETRIEVAL DATE OF DOWNLOAD NAME OF dat FILE TIME YSI STOP LOGGING NAME OF txt FILE POST DEPLOYMENT CALIBRATION DATE OF POST CALIBRATION Battery Volts pH mV mV range 50 50 Optimum 0 Time Corrected Y N pH mV mV range 230 lt gt 140 p Optimum 180 Faster Slower Difference in seconds pH mV mV range 130 lt gt 230 yii Optimum 180 Notes pH pas u Fivonescence o 123 Temp C sonde is reading in Rd WT Corrected reading from Rd WT Table a SH Notes oem Barometric Pressure mm Hg milibars Depth Offset at date s pressure Notes Depth Reading 00 Theoretical DO based on date s pressure DO Reading DO Membrane Puncture Y N Notes Condu
24. edures e Systems are in place to assure sensor s performance verification e Records are kept to provide evidence that the requirements have being met Two examples of calibration logs are presented in Figure 7 3 and 7 4 e Critical parts components and chemicals are in stock to ensure proper maintenance activities NOTE Many multiparameter sondes are equipped with depth sensors that measure water depth using a differential strain gauge transducer with one side of the transducer exposed to water and the other to a vacuum The transducer measures the pressure of the water column plus the atmospheric pressure YSI 2008 During calibration the depth is calibrated in air and a depth offset must be used if the pressure is different than 760 mm Hg To determine the correct depth offset record the barometric pressure at the time of calibration from a meteorological station at the calibration site or a reliable local station Tables 7 1 to 7 3 show offset correction as a function of atmospheric pressure These tables can be use to determine the offset to use during calibration CDMO 2207 When using a plastic or copper screen or copper tape at the bottom of the sensor guard there is a possibility that interference with turbidity readings could result from the screen To E cancel any affects it might have it is necessary to calibrate the turbidity probe 1 point in the zero standard with the deployment sensor guard installed
25. emp C gt 10 20 Partly to Broken 50 90 p gt 20 30 10 15 Overcast gt 90 Foggy 5 gt 40 21 26 Cloud no percentages Hazy Precipitation Type Wind Direction fr East 90 deg S fr South 180 deg fr East NE 67 5 deg fr SE 135 deg Light Rain fr East SE 112 5 deg SSE fr South SE 157 5 deg fr North 0 deg SSW fr South SW 202 5 deg Squally fr NE 45 deg fr SW 225 deg 10 11 12 13 14 15 W fr West 270 deg Mixed Rain amp Snow WNW fr West NW 292 5 deg fr NW 315 deg WSW fr West SW 247 5 deg WATER INFORMATION Water and Secchi Depths VERIFICATION SAMPLES 0 0 1m Chla Filter Volume en 0 1 lt 0 3m 0 3 lt 0 6m 0 6 1 0m 10 lt 13m 5 asm WATER COLUMN DEPTH PROFILE Depth m Temperature Salinity DO Sat DO mg l 0 02 Secchi Depth m If Secchi can be seen at the bottom C1 Comments Figure 7 6 Field verification log Note Two conditions that must be met when transporting multiparameter sondes to and from the monitoring sites are e The sondes must be transported in a saturated environment e The sondes must be transported in a container that minimizes shocks and vibrations Two commonly employed methods are The sonde is transported wrapped up within a wet towel CDMO 2007 Soak a towel large enough to wrap around the entire sonde in tap water and wring out most of the water check that it is wet humid not damp
26. ible switch out process could be 1 Set the replacement sonde in the water to allow the probes to equilibrate to ambient conditions Allow the sonde a few minutes to equilibrate to the water temperature 2 Obtain at two simultaneous readings between the deployed sonde and the replacement sonde Collect stream or river water in a bucket or cooler Place the bucket in a secure area and place the replacement sonde inside the bucket Carefully remove the deployed sonde from the guard pipe and place it inside the bucket Perform a visual inspection of the retrieved sonde and record anything that it is considered important for post calibration or data quality purposes e g fouling conditions animals in the sonde guard broken probes physical fouling in case the fouling is detached or changed while the sonde is in the bucket Let the sondes stand in the bucket until two simultaneous readings are obtained Even though certain water parameters e g temperature will change inside the bucket while waiting for the readings the goal here is that the two sondes have two common water quality measurements that can be used for data quality control and assurance purposes 161 For monitoring stations with telemetry capabilities the following procedure is recommended to interchange the field cable connector between the deployed and the replacement sonde 1 Remove the deployed sonde from the guard pipe and put it
27. ification activities Field verification activities are performed following established measuring procedures A field verification log must be filled e g Figure 7 6 3 The monitoring sondes are exchanged It is good practice to obtain at least two simultaneous readings between the deployed sonde and the replacement sonde before the switch out This ensures that there will be two common water quality measurements that can be used for data quality control and assurance purposes Perform a visual inspection of the retrieved sonde and record anything that it is considered important for post calibration or data quality purposes e g fouling conditions animals in the sonde guard broken probes physical fouling In highly fouling conditions or broken probes it is good practice to take pictures of the deployed sonde for future addition to the MetaData or assist the scientist in understanding the data 160 For on stream amp river bank platforms a different method to obtain simultaneous readings between the replacement sonde and deployed sonde must be used if the station has only one guard pipe Possible reasons for using only one guard pipe are The guard pipe is placed where there is a small pooling of water or the sampling area is not big enough to accommodate two sondes Due to high flow conditions cost or maintenance issues it was decided to put only one guard pipe If only one guard pipe is used a poss
28. must be added In a fixed structure monitoring platforms the distance from the transducer to bottom sediments can be divided into two segments the distance between the transducer and the bolts where the monitoring sonde sits inside the guard pipe and the distance between the bolts and the bottoms sediments The distance from the transducer to the bolts is fixed and known The distance between the bolts and the bottom may vary given the bottom can change over time There are some environments In addition verification measurements must be taken that are more conducive to around the guard pipe to check if physical fouling or usus sesi ss Cer different bottoms movements occurred under the guard iSsesisie e esse fnere es peerene pipe that would cause an inaccurate water depth Jasin e measurement between the transducer to the bottom must be measured To determine the distance between the bolts and the frequently bottom a special tool is utilized made with an aluminum telescoping extension pole and a disk with two opposite openings Three measurements are taken one inside the pipe and two outside the pipe These three measurements are utilized to calculate the distance between the bolts and the bottom The procedure to determine the distance between the bolts and the bottom is shown in the following page 168 Build the measuring pole Cut a 3 3 4 inch diameter disk Materials fiber glass plastic wood or any other
29. om local source after correction CBP BP mm CBP_ mm 2 5 altitude 100 Estimated from altitude only BP mm 760 mm 2 5 altitude A 100 For older Hydrolabs Table DO value x ALTCORR xBAROCORR DO standard ___ Check previous maintenance and use do the following before calibration Polish conductivity electrodes Must be polished within the last Date Name comments two months or once every 15 field trips Change pH reference probe solution Must be renewed within last Date Name comments two months or once every 15 field trips Inspect DO membrane for nicks or bubbles Must be changed ne Date Name comments within last six months or once every 15 field trips Change battery in 400 series sonde Change once a year Change Name comments Date internal batteries for newer generation products according to guidelines in product manual Figure 7 4 Multiprobe calibration log Source Texas Commission on Environmental Quality 2003 157 7 2 3 POST DEPLOYMENT PERFORMANCE VERI FI CATI ON Sonde post deployment performance verification should include post calibration or field performance assessment and field verification activities Post calibration activity done in a controlled laboratory environment after retrieval of the monitoring sensor The sensor readings are compared to standard solutions to determine its performance On site post calibration can be performed following the same proce
30. per body including the undersides with anti fouling paint e Using sensors with copper alloy housings e Using copper alloy sonde guard or painting the sensor guard with anti fouling coatings do not paint the threads Figure 7 1 Copper tape on guard and probes NOTE Black anti fouling paint is strongly recommended The black color will eliminate any chance of stray reflection from the infrared light source when the probe is making measurements YSI 2009 Painting the body of the instrument is not recommended Instead of using paint the body can be wrapped with plastic wrap and secure with duck tape or with plastic electrical tape In addition to the use of anti fouling paint or copper product during long term deployments in extreme fouling environments the deployment cycle must be adjusted to the appropriate length to ensure data integrity 150 a a _ fl yr T T 1 i 8 ir d z b r 1 a muse lan um M u Behr s rua fue Qo qp ier S T a ne Eam elle 3 os N N iw i eh ski a MAE k NERR CICORE Figure 7 2 Biofouling examples Source CBNERRVA NIW 151 7 2 2 CALIBRATION FOR DEPLOYMENT It is crucial that all sensors are calibrated following strictly the manufacturer s calibration procedures Therefore management must assure that e Laboratory personnel have the necessary competence for the effective and efficient application of the calibration proc
31. s and spare parts management IT IS A GOOD PRACTICE TO CLEAN THE INSIDE AND OUTSIDE OF THE GUARD PIPE AFTER THE DEPLOYED SONDE IS RETRIEVED AND BEFORE THE NEWLY CALIBRATED SONDE IS DEPLOYED The guard pipe must be cleaned on a frequent basis to minimize the influence of biological fouling and to eliminate any physical fouling that could be interfering with the measurements Figure 7 7 Cleaning inside th d pi The best way to clean the inside of the guard pipe is by using Paus some kind of brush or mop The brush can be purchased in any retail store or easily assembled For example a cleaning brush can be constructed using a 16 foot extension pole Figure 7 7 and 7 8 To add extra cleaning power two scrub brushes can be bolted to the extension pole Care must be taken when brushing the guard pipe to minimize brushing off the anti fouling paint If cleaning is performed on a regular basis minimum fouling will occur on the guard pipe therefore a medium soft brush will be enough to maintain the guard pipe in good condition To clean the outside of the pu guard pipe also a particular Figure 7 8 Guard pipe cleaning brushes brush can be purchased in any retail store or easily assembled For example Figure 7 8 displays a brush to clean the outside of the guard pipe constructed by bolting two scrub brushes to a 8 inch long half 6 inch PVC pipe 165 In some situation a chimney sweep brush is a good option
32. the other as 2 Set the ruler on top of the guard pipe to be used as a reference mark 169 Select one random point at a distance of approx 20 cm from the guard pipe and lower the pole until the disk hits the bottom Move the pole around that point to verify that the depth remains constant and the pole is not sitting on top of a physical object e g stone If this is the case choose another random point If the depth is different than the top bottom inside distance mark this point with the duck tape 1 This point is called TOP BOTTOM OUTSIDE 1 distance TB Outside 1 Repeat this process select a second point If the depth is different than the top bottom inside distance or TB Outside 1 mark this point with the duck tape 2 This point is called TOP BOTTOM OUTSIDE 2 distance TB Outside 2 Calculate Bolts Bottom Distance Two things that must be taken into account Changes of the bottom topography under the guard pipe due to currents Physical fouling under the guard pipe Following four different scenarios are presented TBOutside1 TBOutside2 The three distances are similar EI Se de TB Inside ZTB Outside 1 2 TB Outside 2 The bottom under and around the guard pipe is uniformly distributed in a horizontal plane There are no physical objects below the guard pipe Bolts Bottom Distance 1 3 TB Inside TB Outside 1 TB Outside 2 3 TB 170 The
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