By Joe Kutkuhn
Automated monitoring of the Au Sable River at each of three sites near Grayling--the project’s Phase 3--began on schedule in late March and has since continued virtually uninterrupted. Self-powered flow-sensing units above the city at Pollack Bridge on the river’s mainstream and at the Tank Bridge on its East Branch, as well as below the city on the mainstream at Rayburn Bridge, are recording river stage (or depth), temperature, oxygen and conductivity every 15 minutes. Such monitoring will proceed for at least another four months.
But while the streamflow gauging part of Phase 3 has proceeded with little difficulty, collateral sampling for runoff pollutants as well as natural background properties has not. Several unforeseen developments impeded full project implementation as originally envisioned. Most notably, inter-unit performance of the deployed auto-sampling equipment proved ultimately to be more limited than anticipated despite considerable troubleshooting over several months. The resulting delay in providing an acceptable auto-sampling protocol--the product of Phase 2--thus confounded prearranged sample-retrieval logistics, and several runoff-sampling opportunities were missed. Finally, protracted dry weather since last winter produced uncharacteristically few runoff events to begin with, let alone the lowest river stages in recent years. Working together to overcome frustrating equipment-related obstacles, all parties eventually agreed as follows to a compromise streamflow sampling strategy in the context of a revised Phase 2 package: When activated automatically by a given amount of rainfall or rise in river stage, or remotely by cellular telephone, each flow-sensing unit’s integrated sampler begins to collect subsequent runoff at 15-minute intervals for 24 or more hours. These composite ‘wet-weather’ samples are complemented by others taken manually at each site, as well as at the three largest of Grayling’s stormwater/snowmelt outfalls, immediately following the onset of predefined runoff events. Four series of ‘dry-weather’ background samples, one for each season, complete the array of streamflow material from which baseline snapshots of chemical and biological runoff constituents are to be developed. To date, only two series of baseline ‘dry-weather’ samples--summer and fall-- have been collected and analyzed. However, project volunteers remain fully prepared and on standby to capture ‘first-flush’ samples during upcoming runoff events. It now appears likely that the project’s baseline window, initially scheduled to close at the end of April 2001, will need to be kept open for up to six more months to embrace additional runoff data.
Though procedurally modified by necessity as described above, Phase 3 still promises long-sought facts about the volume and content of local urban runoff, facts deemed essential both as the groundwork for justifying treatment measures and later as a reference, or baseline, for gauging treatment effectiveness. Synthesis of the flow-monitoring and -sampling data will yield not only a baseline ‘runoff index’ but reveal how urban runoff influenced river flow and its contaminant load during the baseline period. As dictated by this information, the contractor’s final report (due by the end of next year) will convey recommendations for immediate or future follow-up action in the form of proposed stormwater/ snowmelt runoff ordinances and treatment prescriptions. It will also include a ‘build-out’ analysis projecting the potential adverse effects on the river of indiscriminate growth in surface imperviousness across the greater Grayling area.
The George A, Griffith Foundation, Huron Pines RC&D, their
river-stewardship partners, and all others concerned about the Au Sable’s future
deeply appreciate the financial support this fact-finding project continues
to receive from many groups and individuals. We are pleased to recognize as
the most recent donors among the former the McIntyre and Towsley Foundations,
Great Lakes Council of FFF, Red Cedar Fly Fishers, Trout Unlimited (Mason
and Mershon Chapters), Anglers of the Au Sable and Au Sable River
System Property Owners Association.
RWOL
© Copyright 2001, Joe Kutkuhn. All rights reserved. Page (but not copy) last modified November 29, 2001
