Dam Updates
October 8th, 2023
Garnet Lake Value Engineering Memo DRAFT.pdfJuly 24th, 2023
GLCA communication July 17 2023 FINAL.pdfFrequently Asked Questions About New Garnet Lake Dam 2023-07-23.pdfCost Estimate April 4th, 2023
Page 14
Garnet Lake Dam Replacement Report.pdfGarnet Lake Dam 2-16-23.pdfComplete files can be downloaded from the public folder
Plan Update Feb. 16, 2022
Garnet Lake Dam 2-16-23.pdf75% completed plans January 10th, 2023
2023.01.10.Garnet Lake Dam 75% to Client.pdfTo All Members,
The Dam Committee and Board have approved going for Option 4 of Kathryn's (CT Male's) four options with modifications (4A see plans below). This option seemed to be the best to provide us with a water level somewhat near our previous historical level (summertime boards). Note, this is the option which has 5 culverts. The bottoms (inverts) of four of them are 6" higher than the fifth culvert invert. We requested a modification to Option 4 to increase the water level of our lake to closer to what it had historically been based on the boards used in the past. Her original Option 4 would basically leave the water level at its current level - at the bottom of the present dam inverts, but with a transient level 6" higher until the water level comes down to the lowest culvert. Kathryn agreed to review the impact of raising the height of the bottom of all Option 4 culverts by 6 inches. This would have the effect of potentially raising the water level to about 12" above current low levels after a big rain for a relatively short time. The level would then decrease to the lower culvert level which is 6" above current levels. It should be noted that measurements of the “waterline” around the lake on exposed cliffs, rocks and the face of the dam seem to demonstrate that our previous water level was from 8 to 12” higher than present. It is expected that these low water levels in addition to putting stumps everywhere, have also contributed to the demise of previous floating bogs in certain areas of the lake. The possibility of putting a small "V" in the lower culvert to keep a minimal flow going might be in the next design phase.
Kathryn submitted Option 4A to us on October 13 which addressed our comments. The Dam Committee and Board have reviewed the Option 4A and have provided a few comments which appear to be more applicable after the next phase of project development. We have had a few more questions on bridge width, construction, wing walls, which she says would be part of reviewing the 75% design phase. For information, we have completed the 35% design phase and are now in the 75% design phase which according to her original proposal letter “includes complete design of the new dam, wing walls, downstream slope armoring, energy dissipation, flashboards or gates (if chosen), re-grading, etc. 75% level plans are sufficient to develop a cost estimate for the project but are not considered construction-level plans.”
Roy Keats, Chair Dam Committee
C-104 - Option 4A.pdf2022.07.28.Concepts_Garnet Lake Dam.pdfPossible dam designs for discussion an the dam committee meeting 7/29/22
Wetland boundary marking May 3rd.
Our dam design project has begun! Surveyors were at work around the dam on April 15th, 2022.
GLCA Update & Donor Recognition March 20th, 2022
This is a video recording of the Garnet Lake Conservation Association meeting of March 20, 2022. The meeting started with a President's update on the dam project. It is followed by special recognition of our donors to our "Save the Lake" fundraising campaign. You will also hear from our diamond donor Barbara Wolfe. It concludes with a presentation of the much anticipated and upcoming book about Garnet Lake by the author, Candace O'Connor.
March 19, 2022
To: Board, Officers, Dam Committee
Subject: Minutes of videoconference with Kathryn Serra of CT Male on 3/15/2022
Attendees: Anne & Joe Bernat, Cindy & Paul Beer, Diane Burgess, Bob & Carl Manning, Roy & Sue Keats, Jeff Pohl, Phil Murphy, Alan Walters, Steve Weymouth, Judy & Steve Thomson (partial)
Kathryn first went through a general discussion of her work plan for our grant. She noted that she will be doing 5 possible conceptual designs. These designs are expected to be generated in June. They will use more detailed survey maps than the earlier analysis. Kathryn’s goals for this project are to meet regulations, be cost effective, and minimize impact on property owners. She understands the property owners concerns. She also noted that there will need to be signed access agreements from the landowners similar to what was done for the previous (1988-1989) installation of our Auxiliary Spillway.
The first phase of on-site work will be the land survey performed by Ryan Biggs/Clark Davis “as soon as the snow melts” possibly in early April. All property owners who might be affected by the work on the dam, should send copies of their deeds to Kathryn (or other necessary paperwork) to help expedite both the deed search and the survey work. The next phase will be core borings from mid April to mid May by Atlantic Testing to determine the location of bedrock under the dam area.
The designs from the Engineering Assessment were brought up by Roy. Kathryn indicated that the 80’ by 7’ high culvert/bridge design from that study is expected to be reduced in extent with the new more detailed surveys and analyses. Kathryn also discussed the use of failing flash boards to increase our lake height by about 6” over the bottom of the culverts. This would bring the level in the summertime up to more normal levels when boards were used to raise the level. She also mentioned the possibility of Gates to control flow and the addition of a low level drain if we really do a major change to the dam.
After that she talked about the possibility of adding “freeboard” to our finished design to possibly take into account future climate change related issues. This has been done in some NYC Catskill (Reservoir) dams. This would require a “higher” dam height to contain larger floods, and would increase our costs. This might be required of larger dams in the future. Note our rainfall analysis requirement is 16” in a 6 hour period.
Kathryn also noted that the DEC is now allowing controlled overtopping of High Hazard Dams with 500 year floods with armoring. This change should enable our bridge length to be shorter than the earlier recommendation.
We discussed a few options sent in by GLCA:
Split the Dam and Bridge: It would simplify the dam. However, the Town would have to be on board. They would have to figure out where to put it; obtain landowner permission, DEC and APA approval of the new location (wetlands involved). this would be very costly for the town, so they wouldn’t be eager to agree to this option. It would extend the time of construction.
Move the Dam Downstream: Kathryn says this “opens up a can of worms.” This would bring up a lot of new issues. It would possibly involve new landowners. It would also require permits from the DEC (Fish and Wildlife), APA, and then getting new easements on new properties. It would also require extensive rework of the terrain. Could take 10 years to get approval.
Lower Dam Height and lake level: The Intension would be to basically not be a high hazard dam anymore. Disadvantage - smaller lake, more silt in lake, possible algae blooms, possible fisheries issues.
Possibilities for Town Contributions: Kathryn suggested the Town might pay for the temporary bridge needed to build the new dam/bridge. This would most likely be located immediately to the north of the dam. This bridge would be priced into our project.
Temporary Bridge: Need easements - land use attorney - public works - Johnsburg - would it be a “road by use” or a “right of way.”. NOTE - the Town has the ability to get state funding and the ability to Bond and tax. How do we get Town to get more $$ if needed?
Construction Season: July - October. A coffer dam would be used to hold back water during construction.
Final Note - the meeting was very productive in that we learned more about our journey, and that Kathryn seems to understand our concerns.
Thanks for attending.
Roy Keats (Dam Committee Chair)