October 2009
The leak repair completed in May 2009 was a success and Ballinger Lake returned to normal operating levels shortly after completion of the project. The remaining repairs include (1) the replacement of the trash rack and (2) the extension of the downstream outlet culvert with additional soil buttressing of the toe. The engineering analysis was completed by Princeton Hydro and includes the regrading of the downstream slope to an approximate 3H:1V and extending the concrete culvert as necessary to meet this grade. This will improve the overall performance of the dam and increase safety.
Princeton Hydro has completed all design documentation and engineering plans for the proposed repairs. An application to the New Jersey Department of Environmental Protection, Division of Dam Safety, for these repairs was submitted in July 2009 and is currently under review by the Department. An application to the Pinelands Commission has also been submitted and a response is expected soon. Upon receipt of a Pinelands Certificate of Filing, Princeton Hydro will submit the Erosion and Sediment Control Application and Plans to the Burlington County Conservation District for review and approval. Princeton Hydro is also in the process of completing a Department General Permit 18 application to authorize dam repair activities in State Open Waters. Princeton Hydro will update the Colony on the status of these applications as soon as information becomes available.
The Department has also indicated that several trees will need to be removed and areas of thick brush along the crest of the dam will need to be cleared. The Department completed an on site inspection with representatives of Princeton Hydro and the Colony to review which trees needed to be removed. Approximately five (5) trees along the downstream exit channel will need to be removed for safety reasons. The Department also requires the clearing of dense vegetation and small caliper trees along the southern portion of the dam crest, as required by Dam Safety Regulations.
A map is available at the Colony office if you wish to see the area that trees will be removed from Ballinger Dam.
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May 8, 2009
Work being completed to seal the cracks in the culvert. Dam is closed - do not expect to reopen the dam until fall 2009 - lake should return to normal level as soon as filled by the rain and springs.
May 1, 2009
DEP approved remedy for leak on April 29, 2009. Contractor selected yesterday to repair leak. Plan to begin work (3 day process at most) May 11, 2009 if not sooner. Dam will be closed during work and this allows lake to be at capacity water level for summer.
Work on culvert will continue in the fall - so please understand as much as we don't want to lower the lake - it will be lowered again in the fall to complete the necessary repairs on this class one dam.
Next Colony meeting is Monday, May 11 - a report will be given.
April 8, 2009
Ballinger Lake Update
The project Engineer has completed the studies required to determine the reason for the leaking outlet conduit. The result of the study indicates that the seals at the joints of the conduit (box culvert) are leaking due to breached gaskets.
Due to the sensitive nature of the failure it is extremely important to understand the mode of failure, this ensures an adequate repair solution. Any number of factors could have contributed to the failure observed, therefore, several studies were completed to assess the serviceability of the dam in its current configuration. After a detailed review of the originally approved documents and plans it was determined that several studies would be conducted to adequately assess the current dam condition.
These included the completion of an updated stability analysis of the dam to determine if the leaks are due to slope failure and downstream movement of the embankment. The second was the assessment of internal water movement through the embankment to ascertain if the flow, buoyancy, or pressures caused the leak. Sampling of the embankment soils was completed (boring investigation) to confirm quality/type of materials and ascertain if there was a mode of failure specific to the materials in the embankment.
The conclusions of the studies revealed the dam is not prone to downstream movement failure, the culvert/conduit shows no signs of unintended movement or deflection, and the embankment materials do not appear to have directly contributed to the failure. Due to the lack of apparent movement of the embankment it was possible to consider repairs that would not include the complete excavation of the conduit; saving time, effort, and resources.
Grouting will be used to seal the leaks in the conduit, pending official State approval. Two types of grout were considered including cement based grout and chemical grout. The cement based grout has required curing times, may require the further lower of the lake, and has some minor environmental concerns to the low pH of the cement. This type of grout was quickly looked past to find a more suitable solution.
Chemical grouting for the arrest of leaks is common in dams, sewers , and water utilities. For the purpose of this situation, with an active leak, a urethane based synthetic grout has been specified. The urethane is hydrophobic and reacts with water to expand into joints and void spaces.
The grout is non-toxic and non-reactive; so it won't affect fisheries or any natural systems. Due to the nature of the grout there is no curing time. The urethane grouts are installed in a moist environment (actually requiring the moisture) and will not require the further lowering of the lake.
A complete chemical grout injection operation from mobilization to completion could take approximately one (1) week to complete on this size conduit. The equipment is small and no excavation will be required. The grout will be delivered to the site in five (5) gallon pales and the injection tools will be hand operated.
We have submitted the specification and narrative of methodology to Dam Safety for review and approval and have advertised the specification package for competitive pricing. We are targeting specialty contractors that complete this type of work on a regular basis.
Our goal is to receive approval by the end of April and concurrently have a contractor ready to complete the repair immediately upon approval. The outlet should be closed and ready to refill by the mid-May lake lower permit date deadline.
Keithe J. Merl, PE, CPESC
Associate
Princeton Hydro, LLC
1200 Liberty Place
Sicklerville, New Jersey 08081
February 27, 2009
Princeton Hydro, the engineer, has completed a detailed inspection and
analysis of Ballinger Lake Dam and the leak within the conduit. Based
upon the information reviewed, Princeton Hydro is completing an
engineering design for the best solution to bring Ballinger Lake Dam
into compliance with DEP DSS regulations. The leak can be permanently
fixed with a polyurethane grout that will be injected from the interior
of the conduit, without any major excavation. To accurately assess the
conditions of the earthen embankment and clay core, it is necessary for
Princeton Hydro to complete two (2) geotechnical borings on the dam.
This information is integral to the adequate assessment and design of
the urethane injection operations.
Princeton Hydro has also recommended to extend the length of the
conduit, by adding approximately 17 feet of conduit to the outlet of
Ballinger Dam. This will result in a gentler more stable slope, improve
the overall performance of the dam, reduce the downstream scour of the
outlet, and reduce maintenance issues with the outlet.
The trash rack at the inlet will be replaced to conform with current DEP
DSS regulations. This will include the fabrication of a new trash rack
from a durable metal formed into a 6" grid. This can be manufactured
off-site and delivered to the site for installation. It is expected that
as a result additional fencing will be required to restrict access to
the trash rack, due to safety concerns. In conjunction with the trash
rack replacement the operator rod will be replaced with corrosive
resistant material to increase the operational longevity of the gate.
It is expected that the proposed improvements can be completed without
further impact to the level of the lake. Princeton Hydro is in the
process of completing the borings on the dam in the near future
concurrent with the vetting of contractors to complete the repairs.
Jennifer E. Oltman, EIT
Project Engineer
Princeton Hydro, LLC
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December 18, 2008
Engineer from Princeton Hydro wrote in an email "The lake will not be completely lowered. We are lowering the lake in two distinct phases. The first phase will lower the lake 3' to see if the leak in the outlet structure stops, and to allow a more thorough inspection of the outlet pipe. If the leak does not stop we have approval then to lower the lake another 2' (total of 5') which may necessitate a fish salvage at that time, we simply do not know. We are expecting that the 2nd phase, if it happens will not occur until after January 1, 2009."
December 12, 2008
Due to the poor condition of the dam at Ballinger Lake (corner of Lenape and Stokes Road) repairs are necessary. These mandatory repairs required by Department of Environmental Protection, Dam Safety Section (DEP DSS) were discovered during an engineering inspection on October 15, 2008. Since that time the Medford Lakes Colony Lake Restoration Chairperson, Nina Stanton, has been working with our engineer at Princeton Hydro, and DEP DSS to bring the Ballinger Lake Dam into compliance with DEP DSS regulations.
The October 15, 2008 Advisory Condition of Ballinger Dam found that repairs are necessary but there is no imminent danger. After preliminary tests were completed the DEP DSS has required Ballinger Lake to be lowered enough to take the hydrological pressure off of the dam. Therefore a lake lowering permit was granted and Ballinger Lake will be lowered enough to accomplish the goal of taking the hydrological pressure off of the dam and assessing the necessary repairs. Our goal is to expedite the mandatory repairs/compliance issues in a timely fashion.
Significant water lowering will begin on December 15, 2008. For all updated information please log into our website – www.medfordlakescolony.org, click on the Ballinger Lake tab.
Ballinger Lake update December 9, 2008
Ballinger Dam is leaking at a rate of 6 gallons per minute. The Department of Environmental Protection for the State of New Jersey, Dam Safety Section is requiring Ballinger Lake to be lowered far enough to stop the leak. Once the leak has stopped our engineer will be better able to access the situation and write a plan for repair. Once we have this plan bids will be taken from contractors to repair the dam.
As of today Medford Lakes Colony does not have the Lake Lowering permit required. As soon as we have the permit the lake will be lowered about four feet.
The Fire Department of Medford Lakes will be notified that Ballinger Lake will not be available for fire fighting. Tanker trucks will be used in the event of a fire.
Medford Lakes Colony Lake Restoration Chairmen - Nina Stanton will keep us all up to date.
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