Dam Construction Update from March 9th Borough Council Meeting
At the regular Borough Council meeting of March 9th a special presentation was made by representatives of the engineering firms involved in the design of the dams for Upper and Lower Aetna. Final design documents were presented. The new dams will occupy a similar footprint to the original dams and constructed of Roller Compacted Concrete (RCC.) Upper Aetna will include a single spillway and a 22’ roadway capable of 2 way traffic and a total width of 26’. Lower Aetna will incorporate 2 spillways and a 12’ roadway for emergency vehicles only. A portage area will be included between Upper and Lower Aetna. No docks will be constructed from the Lower Aetna dam. The Colony plans to relocate the docks to Beach 1.
Spillways in both dams will be designed to pass the “100 year flood.” In the event of a more serious event, such as the July 12 flood, the dams are designed to overtop without any failure. The State requires that the dams can't change the existing flood characteristics upstream or downstream of the dams. The size of the
spillways affect how much water is passed through during any rain event. By not changing the spillway capacity, the same level of flood storage is provided to those communities as had been historically provided prior to the dam failure.
Aluminum stop logs in each dam will allow for the partial or complete lowering of the lake for maintenance purposes. The Borough will operate and maintain the dams and coordinate lake lowering activities for maintenance purposes with the Colony. Under no circumstance would stop logs be removed for rain events as the dams are designed to pass these events through the spillway or, in the event of a catastrophic storm, by overtopping.
The RRC dams themselves will require little maintenance other than keeping the grass on the dams maintained to control soil erosion and preventing the growth of shrubs on the dams.
Present best estimates for the cost of dam construction (in advance of actual bids being received) are $4.0 million per dam. This is consistent with the original 2004 cost estimates provided by the engineers but higher than the 2005 estimates. This is partially due to increased cost of steel sheeting (a significant component of the dam construction) which has gone up by a third as a result of the demand from Katrina related reconstruction activities. In addition, poor soils in the areas of the dam required a much deeper foundation then was originally hoped.
DEP Dam Safety has made final comments on the design documents and requested a redesign of the railing system which is being provided by our Engineers. Borough Council passed a resolution instructing the Borough Manager and Engineers to advertise and go to bid on the dam reconstruction. This bidding process will move in parallel with final design approval by the DEP. An approval hearing with the Pinelands Commission is scheduled for March 17th.
The engineers and members of the Flood Recovery Task Force have identified six regional contractors capable of bidding the RCC dam reconstruction project and the best case scenario would be a contract award in late April or early May. Construction is estimated to be 8 months from start to finish although the Engineers will be working with the contractor in pre bid and pre construction meetings to coordinate with the Colony’s dredging efforts and accelerate the construction timeline wherever possible. Once completed and approved, it is estimated the lakes will require 4to 6 weeks to fill under normal rainfall conditions, quicker in the event of a significant rain fall.
In earlier discussions we had hoped that the lakes could be filled in advance of the completion and final approval of the RCC dam, however, the DEP would not permit such advance filling.
As part of the construction, an RCC Pug Mill will be constructed at the Beach 1 parking area. Much of the work involved in this type of construction has to do with the excavation, sheeting and foundation preparation. Once that work is complete, the actual laying of the roller compacted concrete is a continuous 24 hour, 7 day per week operation and is expected to take a week or so to complete.
The Borough continues to work hand in hand with the Colony as well as other affected parties such as the School District to coordinate the construction and dredging effort in as efficient and safe manner as possible.
Paul Weiss reported on behalf of the Colony regarding the lake dredging project. Initial bids have been received and the Colony is engaged in active negotiations on the dredging contract. At present, a contract award is anticipated in late March or early April and the dredging project should begin by late April pending final Pinelands and Soil Conservation approval. Dredging is estimated to take approximately 5 months, weather permitting. The Borough will be coordinating with the Colony to attempt to overlap and coordinate the two projects as much as possible. The Colony has already sent special assessments to the lakefront owners on Upper and Lower Aetna and the Mirror Lakes for this work.
The dredging permit is for “maintenance dredging” to restore the lakes to their original lake bottoms. It is presently estimated that approximately 80,000 cubic yards of material will be removed from the lakebeds. The contractor will be paid based on pre-survey and periodic survey measurements, not by the truckload. Dam demolition is a part of the dam construction project and will be handled by the Borough. The Borough will coordinate with the Colony’s dredging contractor to attempt to subcontract some spoils removal where possible.
Approximately 3.4 acres of the Upper Aetna Lakebed is actually in Medford and owned by Camp Ockanickon and not the Colony. As such this part of the lakebed is in the Camp’s protected Green Acres area and will most likely not be dredged. However, the Colony hopes to work with the Camp to provide some level of weed reduction and other possible minor improvements. The Colony plans to do complete dredging up to the Borough property line.
Once the Colony is issued its permits and begins work, all residents will be prohibited from entering the lakebeds for any reason, and will not be allowed to conduct any work on bulkheads or docks until the project is completed. In particular, lakefront owners may not move or remove any sediment in or from the lakebed during the restoration process, as this would violate the expected requirements of the Colony’s permits and could lead to a suspension of the project and/or penalties and fines.
Follow the link below to view the dam design documents:
Dam Design Documents
Spillways in both dams will be designed to pass the “100 year flood.” In the event of a more serious event, such as the July 12 flood, the dams are designed to overtop without any failure. The State requires that the dams can't change the existing flood characteristics upstream or downstream of the dams. The size of the
spillways affect how much water is passed through during any rain event. By not changing the spillway capacity, the same level of flood storage is provided to those communities as had been historically provided prior to the dam failure.
Aluminum stop logs in each dam will allow for the partial or complete lowering of the lake for maintenance purposes. The Borough will operate and maintain the dams and coordinate lake lowering activities for maintenance purposes with the Colony. Under no circumstance would stop logs be removed for rain events as the dams are designed to pass these events through the spillway or, in the event of a catastrophic storm, by overtopping.
The RRC dams themselves will require little maintenance other than keeping the grass on the dams maintained to control soil erosion and preventing the growth of shrubs on the dams.
Present best estimates for the cost of dam construction (in advance of actual bids being received) are $4.0 million per dam. This is consistent with the original 2004 cost estimates provided by the engineers but higher than the 2005 estimates. This is partially due to increased cost of steel sheeting (a significant component of the dam construction) which has gone up by a third as a result of the demand from Katrina related reconstruction activities. In addition, poor soils in the areas of the dam required a much deeper foundation then was originally hoped.
DEP Dam Safety has made final comments on the design documents and requested a redesign of the railing system which is being provided by our Engineers. Borough Council passed a resolution instructing the Borough Manager and Engineers to advertise and go to bid on the dam reconstruction. This bidding process will move in parallel with final design approval by the DEP. An approval hearing with the Pinelands Commission is scheduled for March 17th.
The engineers and members of the Flood Recovery Task Force have identified six regional contractors capable of bidding the RCC dam reconstruction project and the best case scenario would be a contract award in late April or early May. Construction is estimated to be 8 months from start to finish although the Engineers will be working with the contractor in pre bid and pre construction meetings to coordinate with the Colony’s dredging efforts and accelerate the construction timeline wherever possible. Once completed and approved, it is estimated the lakes will require 4to 6 weeks to fill under normal rainfall conditions, quicker in the event of a significant rain fall.
In earlier discussions we had hoped that the lakes could be filled in advance of the completion and final approval of the RCC dam, however, the DEP would not permit such advance filling.
As part of the construction, an RCC Pug Mill will be constructed at the Beach 1 parking area. Much of the work involved in this type of construction has to do with the excavation, sheeting and foundation preparation. Once that work is complete, the actual laying of the roller compacted concrete is a continuous 24 hour, 7 day per week operation and is expected to take a week or so to complete.
The Borough continues to work hand in hand with the Colony as well as other affected parties such as the School District to coordinate the construction and dredging effort in as efficient and safe manner as possible.
Paul Weiss reported on behalf of the Colony regarding the lake dredging project. Initial bids have been received and the Colony is engaged in active negotiations on the dredging contract. At present, a contract award is anticipated in late March or early April and the dredging project should begin by late April pending final Pinelands and Soil Conservation approval. Dredging is estimated to take approximately 5 months, weather permitting. The Borough will be coordinating with the Colony to attempt to overlap and coordinate the two projects as much as possible. The Colony has already sent special assessments to the lakefront owners on Upper and Lower Aetna and the Mirror Lakes for this work.
The dredging permit is for “maintenance dredging” to restore the lakes to their original lake bottoms. It is presently estimated that approximately 80,000 cubic yards of material will be removed from the lakebeds. The contractor will be paid based on pre-survey and periodic survey measurements, not by the truckload. Dam demolition is a part of the dam construction project and will be handled by the Borough. The Borough will coordinate with the Colony’s dredging contractor to attempt to subcontract some spoils removal where possible.
Approximately 3.4 acres of the Upper Aetna Lakebed is actually in Medford and owned by Camp Ockanickon and not the Colony. As such this part of the lakebed is in the Camp’s protected Green Acres area and will most likely not be dredged. However, the Colony hopes to work with the Camp to provide some level of weed reduction and other possible minor improvements. The Colony plans to do complete dredging up to the Borough property line.
Once the Colony is issued its permits and begins work, all residents will be prohibited from entering the lakebeds for any reason, and will not be allowed to conduct any work on bulkheads or docks until the project is completed. In particular, lakefront owners may not move or remove any sediment in or from the lakebed during the restoration process, as this would violate the expected requirements of the Colony’s permits and could lead to a suspension of the project and/or penalties and fines.
Follow the link below to view the dam design documents:
Dam Design Documents
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