Hydrologic and Hydraulic Assessment for Shadow Lake Dam Alternatives. Weston & Sampson sent this to the Vermont Dam Safety Engineer Program. VTDEC DSP is reviewing the hydraulic models for various rehabilitation alternatives.
We don’t have a timeline for how long that will take.
HEC-RAS : Hydraulic Engineering Center River Analysis Software
HEC – HMS Crucial tool used for dam management and flood control.
Powerful tool used for dam safety risk.
Regional Priority Projects are high priority economic and community development projects that meet certain eligibility requirements (see priority project form). The Regional Project Prioritization (RPP) lists are used by federal, state, regional and local organizations to understand the funding needs of the region and allow regional economic and community development staff to help match federal and state funding announcements to projects. The Regional Project Prioritization (RPP) lists express the highest priority projects for each region and the top ten projects from each county will be included in a consolidated statewide list, which is submitted bi-annually to the Vermont Agency of Commerce and Community Development (ACCD), to be used by state and federal agencies when making funding decisions. Lists are developed and review annually. Attached is Glover’s Regional Project Prioritization (RPP) application. We will inform the town once it is accepted.
Support letters for Glover’s request to the Northeastern Vermont Development Association, for inclusion in the Regional Project Prioritization, will facilitate efforts to secure funding for repairs on the Shadow Lake Dam.
Letters of Support
W&S BUDGET AMENDMENT
The State of Vermont is in support of a time extension request for the Shadow Lake Dam A&E
FEMA EXTENSION LETTER
Water Testing
Summary of meeting (10.01.25) with Ben and Steve at VT DSP
SLD Update: Zoom Meeting with VT Dam Safety Engineers, Hydraulic Engineers, W&S, and Flood Plain Director Sacha Peeler
https://drive.google.com/file/d/1GhXw6DW15JfXZC1WZx2VjE72ZIDvmHmW/view
Shadow Lake Emergency Plan 2025 update
SLD Survey Map
Weston & Sampson drilled borings at Shadow Lake Dam on Thursday, June 5th.
Weston & Sampson Phone Conversation August 7, 2025 In Thomas’s voice.
7/24/2025 Weston & Sampson Update:
- Working on setting up a meeting with Ben Green to discuss the possibility of extending the dam on the left and right sides on to private properties that would be purchased by the town to allow raising of the dam crest and maintaining historic lake levels.
- Stability analysis nearly complete. It appears the downstream slope of the dam meets the minimum factor of safety requirements provided the dam maintains 1.5 feet of freeboard during the design storm.
- The seepage analysis indicates an inadequate factor of safety values, which should not be a surprise since seepage through the dam is observed. Seepage through the dam when water levels rise above historic lake levels is a deficiency that will need to be addressed. We will likely control seepage with the use of sand filters installed within the dam embankment.
- The poor condition of the auxiliary spillway and persistent seepage below this spillway is another deficiency that will need to be addressed. We are currently looking at the most cost-effective measures to correct this deficiency.
- We (Weston & Sampson and the town) should meet at some point in August to discuss the dam rehabilitation alternative the town would like to pursue. I assume that this will be largely dependent on the town purchasing private properties on both sides of the dam and the opinion of VT DSP to allow raising of the dam crest. We need the selected alternative to run our model and review results with VT DSP.
Update: July 22, 2025 Shadow Lake Boat Launch
Two Signs have been erected at the Boat Launch.
The sand that has gathered at the bottom of the cement launch pad has been considered and hopefully will be removed by Fish and Wildlife.
They measured the depth of the water, took photos, and located the end of the boat launch.
I will continue to keep you updated regarding new information.
Theresa
As you all know the boat launch is problematic with the lowering of the lake. I contacted Mike Wichrowski with Fish and Wildlife to discuss the boat ramp because they are the party responsible.
He appreciates that I informed them of the situation, although he had already heard about our situation through Ben Green, VT Dam Safety Engineer. Fish and Wildlife will be involved from this point forward to deal with the launch reconstruction. I let him know that it is likely the lake will stay at the 2′ lower level.
They are extremely busy this year and will begin the process of investigating the launch and survey data to gather information on the existing launch. It is possible that it is the only thing they will accomplish this year.
He will put the launch on his list of things to do and begin the process of renovating the launch. That includes surveys, elevation study, permits, dredging, etc. He is also going to include the problematic situation with the boat wash runoff. He was already aware of that problem and plans to include it in the engineering and design of the reconstruction of the launch.
Apparently, had I told him in January of the situation he may have been able to solve this problem this year. However, I told him I only found out about the “Permanent” drop of 2′ just this past month when we received the scenarios of the dam.
I am pleased with the nugget of hope in the remedy of the boat launch.
Theresa Perron
Spillway Modification Alternatives
Update: 4/22/25
Weston and Sampson engineers have evaluated several alternatives to correct deficiencies at the dam and plan to discuss advantages and disadvantages of each alternative with the town over the next few weeks.
Update: 4/1/2025
Weston & Sampson Engineers finished up incorporating the new survey data into hydraulic models (HEC-HMS) provided by DSP. This updated model allows us to evaluate spillway modification alternatives so the dam can pass the design storm. This evaluation should be completed towards the end of this week. Once these alternatives are developed, we will run them through additional hydraulic models (HEC-RAS) to assess downstream impacts, which is a critical aspect of this project. In the next week or so, we should be in a position to review alternatives with you.
More info here: https://shadowlakedam.org/
