Stormwater Best Management Practices in an Ultra-Urban Setting: Selection and Monitoring
4.5 Monitoring Program Implementation Phase
The implementation of a water quality evaluation program requires that decisions made in the monitoring design phase be translated into an operational field monitoring program. Decisions must be made regarding:
- Equipment installation and testing.
- Finalization of field operating procedures.
- Sample handling and processing.
- Preliminary review of testing and/or initial monitoring results.
- Sampling design plan and implementation review.
Public awareness and involvement are also important aspects of the monitoring program. Prior to commencement of the BMP program, community surveys and meetings concerning community expectations of aesthetic and recreational aspects of the design should be considered. A well-informed public would see the need for pollution control and would likely support the BMP program and monitoring effort. The public will also want to be informed in a timely manner. Carefully prepared public releases or articles are very effective in communicating ideas or results to the public. Additional information should be available to those who show a particular interest, and key project personnel should make time to be available for questions.
Proper installation of automated monitoring equipment and operation is critical to the success of the sampling program. All sensors and sensor lines need to be securely fastened, located in a representative location, and positioned so as to minimize the trapping of debris, which may affect their operation. Suppliers of automated monitoring equipment often supply installation equipment and detailed information to help guide this process.
The initial installation of the water intake line needs special attention. Before selecting a final position for the intake line above the channel or streambed, some tests of representativeness should be conducted. This can be done, as mentioned earlier, by collecting depth-integrated samples, using standard sediment sampling procedures (e.g., USGS, 1982), at the same time automatic samples are collected. It can also be done by mounting the intake line on a vertical rod with a hand-adjustable fitting that allows for quick adjustments to the intake position. This arrangement permits a series of water samples, at different depths, to be collected quickly, by manually adjusting the depth of the intake line and at each depth manually triggering the automated water sampling equipment. The analytical results of these samples can be used to guide the final placement of the intake line.
Automated sampling equipment also needs to be calibrated and programmed based on the triggering and sample type requirements of the sample design plan. Testing of the proper triggering of equipment can be performed, for example, by artificially triggering the sampling equipment with a sensor located in bucket of water for triggering procedures that rely on stage height or by pouring some water in a rainfall sensor for rainfall-triggered sampling equipment.
Installation of a staff gauge to visually monitor stage at each sampling site is also strongly recommended for two reasons: (1) to permit the use of chalk to mark the staff plate prior to sampling as means of checking that the stage sensor has operated properly over the entire range of flow depths for a particular event, and (2) to monitor for sensor drift, which may occur over time due to sensor fouling or age.
Development of a rating curve for the site should begin following the completion of equipment testing. While a theoretical rating curve may have been developed in the sampling design plan, a rating curve based on field measurements is required for in situ rating curves and also as a check on the accuracy of an installed primary measuring device. A minimum of 15 pairs of stage and discharge measurements should be used in the development of the rating equation developed from the curve (USDA, 1993). This curve should be checked periodically since sediment scouring or deposition in the streambed can cause changes in the rating curve (USGS, 1977).
Revisions to SOPs are often the outcome of decisions on equipment selection, site conditions, and staff availability. SOPs must be consistent with site and equipment characteristics, and with the results of field testing of the equipment and of sampling protocols established earlier, and also with the sampling collection, preservation, and sample procedure requirements for the constituents to be sampled.
These SOPs also provide documentation of the data collection methods and sampling procedure used during the course of a monitoring program. Each type of field operation will likely need to develop its own SOP.
These procedures cover all aspects of field work from the type and frequency of equipment maintenance, to calibration, cleaning, and adjustment procedures. Records of equipment maintenance, malfunction, calibration, adjustment, and repairs need to be kept for each monitoring station. These SOPs can be based on existing published standards for flow measurement or water quality sampling (e.g., ASTM) and modified for existing field conditions. Equipment manufacturers and vendors also supply equipment-specific use, calibration and maintenance procedures that can be incorporated into an SOP. Procedures for the handling and holding of water samples before their final submission to the laboratory also need to be well documented. Prior to their completion and incorporation into a monitoring program, all SOPs need to be tested in the field. Data collected in the field should be recorded in a bound notebook. A description of the field conditions such as weather, temperature, or any activity that might affect sampling results needs to be recorded.
In addition to proper sample handling, preservation, and storage, the effectiveness of any monitoring program depends on the successful implementation of the QAPP. The results of this plan provide a quantitative measure of the accuracy of the collected data.
Prior to submission for data analysis, all field data needs to be reviewed, summarized, and put into a format suitable for data analysis. Data of suspect quality must be flagged as such along with the supporting rationale. In some cases, data may have to be summarized or processed prior to submission for analysis. Stage data, for example, must be converted to discharge data using a rating curve before data analysis. The development and accuracy of the rating curve data needs to be submitted with the corresponding discharge information. To prevent the unnecessary reformatting of data submitted for analysis, the final format for data to be used for analysis must be established as early as is feasible.
Once sampling is under way and as soon as is feasible, a review of the results and operating procedures of the field implementation phase should be completed. Following the first review, a regularly scheduled review process should be implemented. The purpose of the review is to ensure that all automated equipment is operating and functioning as intended. A review of the water quality monitoring results is particularly important. Assumptions made in the design phase concerning analytical detection limit requirements are now being tested. If some parameters are not being detected, changes in either the analytical technique or the sampling methodology may be required.
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