This message is being sent on behalf of Mr. David Fox, Director of Licensing and Compliance for STS Hydropower.
In an effort to improve communications with stakeholders, STS Hydropower (STS) is providing regular email updates on the status of the Morrow Dam spillway gate replacement project necessary to ensure dam and public safety, and the associated reservoir drawdown. This is the eighth bi-weekly email status update.
Gate Replacement Project Status
We continue to make progress and remain on schedule to complete the installation of new spillway gates in December 2020. Crews are working seven days per week, twelve hours per day to complete the work in an accelerated manner. Morrow Lake reservoir refill will begin immediately following installation of the new gates in accordance with consultation from resource agencies.
On November 2nd we completed dredging activities to remove sediment immediately upstream of the dam. Removing this sediment allows STS to maintain Kalamazoo river flows by discharging flows through the powerhouse generating unit bays while simultaneously enabling us to complete the installation of the bulkhead dewatering system necessary for removal and replacement of the spillway gates.
Following completion of sediment removal, STS implemented the first of 3 approved run-of-river flow modifications on November 3rd. The flow modification was necessary to facilitate the installation of the bulkhead dewatering system to isolate spillway gate #4 and to ensure worker/diver safety.
Both of these critical work sequences were authorized by Michigan EGLE Water Resources Branch Permit # WRP025847 v.1 which was issued on October 23, 2020. As part of the permitting process, the impacts of these activities were carefully reviewed with State Regulators and sediment control measures outlined in an approved, formal Mitigation Plan minimized any potential impacts. These measures included installation of sediment control curtains upstream and downstream of the dam, environmental monitoring protocols and strict stop work orders, and a specific flow discharge ramping protocol.
STS implemented the Mitigation Plan as planned. No material increase in turbidity levels was detected. During the flow modification process, minimum discharge rates averaged 340 CFS and did not fall below 270 CFS, both of which were well above the expected 100 CFS rate authorized by the permit.
STS expects that the duration of the second and third flow modification will be reduced and that minimum discharges will not fall below 365 CFS. Currently, the 2nd flow modification is expected to occur on November 19th. This schedule is subject to change, and STS will provide additional updates closer to the scheduled date.
Removal of the old spillway gate #4 is now complete. The newly fabricated replacement gate #4 has been delivered to the site and will be installed in the coming days.
Assessment and Mitigation Activities
STS continues to work with Resource Agencies to finalize the draft Field Investigation Plan (FIP). The FIP details the initial sampling and investigation activities that will be performed to assess the extent, physical characteristics, and composition of downstream sediments. These activities will include collecting sediment cores and grab samples from targeted locations both upstream and downstream of the dam. As part this scope, STS is also in the process of conducting a bathymetry survey (i.e., a survey of the river bottom) downstream of the dam. The results of this survey will be compared against pre-drawdown conditions to begin understanding the extent and volume of post-drawdown sediment. It is expected that implementation of the FIP will begin prior to Thanksgiving and be completed by the end of the year.
Please feel free to forward this status update to others that may be interested. If you know of stakeholders who would be interested in receiving updates, please ask that they contact Melissa Sonnleitner at firstname.lastname@example.org so that they can be added to our stakeholder list.
If you have any questions or concerns, please contact me directly via email at email@example.com.