Medford Lakes is a borough in Burlington County, New Jersey that consists of 22 lakes, and more than 10% of the homes there are log cabins. Located just 25 miles east of Philadelphia, within the New Jersey Pinelands Commission Management Area, the Borough is overseen by the Medford Lakes Colony (MLC), a homeowners association that manages social events and recreation activities for the community and also manages its “Lake Restoration Fund.” All homeowners in the community contribute to the Fund, which is used to manage and monitor lake water quality and maintain water control structures like dams and culverts.
Medford Lakes and its surrounding neighborhoods contain approximately 60 dams. The MLC retained Princeton Hydro to provide various engineering services for multiple dam structures throughout the Borough, including periodic visual inspections, dam breach and inundation analysis, and maintenance and repair work.
Ballinger Lake, located at the intersection of Lenape Trail and Stokes Road, contains a dam that is registered as a Class I – High Hazard Dam with NJDEP Division of Dam Safety. Immediately downstream from the dam is Main Street Medford Lakes, a congested portion of the Medford Lakes Borough.
The dam, originally constructed in the 1920s, is an earthen embankment dam with a clay core. Between 2000 – 2001, a reconstruction project took place that included the creation of both a primary and auxiliary spillway and a concrete culvert. The primary spillway consists of a concrete drop box and culvert that passes through the embankment. The auxiliary spillway, armored with articulated concrete block, is a low point on the embankment along Stokes Road.
In 2008, the Ballinger Lake Dam was inspected by Princeton Hydro and the NJDEP, Division of Dam Safety. The results of these inspections revealed considerable seepage at one of the concrete joints within the concrete culvert, a non-compliant trash rack assembly, a distressed gate valve assembly, and unstable downstream conditions.
Under Princeton Hydro’s direction, the lake was lowered to reduce the hydraulic load on the dam and to facilitate the required remediation and repairs. Princeton Hydro provided full turn-key engineering services that encompassed the development of the engineering documents and plans and preparation of all the permitting requirements (NJDEP Dam Safety, Pinelands Commission Certificate of Filing (CoF), NJDEP Dam Safety Emergency Permit, Burlington County Soil Conservation Erosion and Sediment Control, and NPDES permits). Our team also prepared the contractor bid specifications and provided construction oversight and management throughout the course of the repairs.
Throughout this process, Princeton Hydro completed multiple studies to characterize the hydraulic, hydrologic, structural, stability, geotechnical, and groundwater conditions at the dam under pre and post-repair conditions. The team eliminated the leakage and brought the dam back into compliance. In 2019, MLC contracted Princeton Hydro to perform additional maintenance and improvements to the Ballinger Lake Dam spillway, outfall, and sluice gate.
The scope of work for the 2019 engineering and construction project included the following:
- Replacement of the failed sluice gate structure
- Installation of a baffled culvert extension on the downstream side of the existing culvert
- Regrading of the downstream embankment to a shallower, uniform 3H:1V slope
- Regrading of the levee crest to a uniform elevation
- Riprap armament of the downstream channel
- Various repairs to joints and spalls within the existing concrete dropbox and culvert structures.
Construction began on September 19, 2019 with the lowering of Ballinger Lake to facilitate the work within the existing dropbox structure. The lake lowering process was performed by a 6-inch centrifugal pump, which discharged water into the downstream channel. The photo above, taken on September 23, 2019, shows a view of the lowered lake level and pumping intake hose. After the lake was lowered below the dropbox crest, all of the concrete was power washed and work began to waterproof and repair all of the joints within the culvert.
In October, the team began removing portions of the existing stream bed riprap in preparation for pouring a flowable fill-based mud mat to level the foundation of the culvert extension. The area was dewatered with a submersible pump, with the discharge filtered through a sediment bag and directed back into the downstream channel at a point upstream of the installed turbidity barrier. The above photo, taken on October 17, 2019, shows the riprap being removed from the streambed prior to pouring the flowable fill concrete mud mat.
The installation of the sluice gate valve support structure began in November 2019. Princeton Hydro oversaw the process to ensure the installation was being completed according to the design drawings and NJDEP Dam Safety regulations. The above photo taken by Princeton Hydro shows the grate being prepared for the installation of the sluice gate valve operating mechanism.
In December 2019, the team completed a topsoil application, seeding, and soil erosion matting installation to all disturbed areas of the site. All areas disturbed by construction activities (approximately 6,400 square feet) were graded to pre-construction conditions. The topsoil was applied to these areas and hand-raked to re-establish the original grades. The area was then seeded with perennial ryegrass, fertilized, and covered with a soil erosion mat. The above photo, taken on December 5, 2019, shows the soil mat being installed.
Following the final site inspection performed by Princeton Hydro in April 2020, we completed the Ballinger Lake Dam Spillway & Sluice Gate Improvements Closeout Report and presented it to MLC. The report confirmed that the site was considered stabilized in accordance with the approved project plans, the Standards for Soil Erosion and Sediment Control in New Jersey, and all NJDEP Bureau of Dam Safety requirements.
Princeton Hydro has designed, permitted, and overseen the reconstruction, repair, and removal of dozens of small and large dams in the Northeast. Click below to read about an emergency repair we completed on the Lake Wauwauskashe Dam. A concerning blockage developed in Lake Wauwauskashe Dam’s spillway and water was backing up at the upstream outlet structure causing a number of issues and potential hazards. Medford Lakes Colony, Princeton Hydro, and other project partners employed innovative solutions that lead to a successful emergency repair.
To learn more about our dam and barrier engineering services, visit bit.ly/DamBarrier.