Weir Dam damage in recent storm

10/26/2023 UPDATE:

Our engineers from GEI were onsite last Thursday and were able to perform a thorough assessment of the wooden structure or weir that holds back the water in our pond.

On close underwater inspection, they found rot in the structural members of the weir, the large 6" x 8" posts. By their calculations, there is likely up to 2" of degraded wood material on each face of each post, undermining the safety of our weir significantly.

These posts were replaced at some point in the last 100 years and are due for replacement again.

GEI will continue to advise us on the safe repair of this structure in the coming months. This repair will require the placement of a temporary coffer dam to hold back the pond water and allow a dry and safe place for workers to replace the structures.

Of interest, the more ancient parts of the dam, the horizontal wooden structures at the base of the weir, are free of rot, once again affirming the value of old wood and sound engineering.

We are in the process of working with GEI to determine if any permits need to be filed and with what relevant local government units and agencies. Parallel to that work, GEI will work with their team to re-engineer the wooden structure for possible replacement in the spring and to calculate the project's costs.

As we have more information, we will share it with the community.

10/19/2023 UPDATE

Engineers from GEI Engineering's Waterfront Practice, including Matt Kehoe, Adon Austin and a diver are on site at the Weir dam today for a survey of the current state of the dam and spillway. We expect updates as they conclude their investigation, but not prior to sending this week's ASJ. More details will follow as they are available.

10/12/203 UPDATE:

Our engineering team from GEI was unable to be with us this week to inspect the weir dam, but will be on site this coming Wednesday. An update will follow.

10/5/2023 Report:

This weekend’s extremely high volume of rain increased the pressure on our wooden weir dam at the north end of our pond significantly, causing a failure in one of the topmost boards on the east end of the weir.

The weir is the wooden structure that holds back the pond water. The weir is installed in the concrete bulkhead that forms the spillway. The spillway creates the space in the earthen dam that allows the weir to moderate water flowing into the lower spillway and from there into the harbor.

The weir is constructed out of a series of boards that slide in and out of a track so that, should we want to, we could reduce the volume of water in the pond lowering its level, or increase the volume of water, raising its level. This weekend’s dam failure allowed about 12 inches of water to flow from the pond into the spillway and harbor - which is significant.

On Monday, with the help and support of Steve DiSimone from the Fish Hatchery and a team from our Memorial Cemetery, we accomplished an emergency stop-gap repair using old boards on hand. This is the second failure and repair of this kind in the last 3 years. Since Monday we have been able to raise the level of the pond by 6-8 inches.

Additionally, we have invited a team of engineers to assess the dam's health and help us understand the relative urgency and extent of the repairs we will need to take. They will soon send a team, including a diver, to assess the health of the weir and make some recommendations about repair or replacement. They will also provide a suggested time frame for that work.

These engineers are from GEI Engineering, a Long Island firm, and are the same team contracted for work at the Cold Spring Harbor Beach Club. They were universally recommended to us by our partners and we feel confident that they are qualified to advise us in this.

This is not the first study of the weir dam or the spillway, but the third in recent history. Two previous studies have been commissioned by prior buildings and grounds committee heads, the most recent and extensive performed by engineers in 2015. We have provided our new team of marine engineers full access to that study and its recommendations.

The health and safety of the pond are of great concern to the church for both aesthetic and environmental reasons. We are aware that should the dam fail it is an open question about whether we would be allowed to replace it. Repair in advance of failure is the better course of action.

We will update the Vestry and the Congregation regularly as we have more information to share.

- Gideon L. K. Pollach
Rector