Leaser Lake is a 117-acre Commonwealth-owned impoundment located near Allentown in Lynn Township, Lehigh County,
Pennsylvania. A dam located on Jacksonville Branch of the Ontelaunee Creek, a tributary of Maiden
Creek, creates Leaser Lake. The impoundment is very popular with outdoor recreation enthusiasts
in southeast Pennsylvania.
The PFBC leases the public use areas around the lake to Lehigh County
and has done so since 1970. Lehigh County maintains park facilities and is responsible for maintenance
of the areas used by lake visitors. The PFBC is responsible for the dam.
DAM AND APPURTENANCES
Leaser Lake Dam consists of an earth embankment approximately 430 feet long by 53 feet high and a
top of dam is 24 feet wide. The flood discharge facilities for the dam consist of a combined primary
and emergency spillway located on the right abutment (looking downstream). The spillway structure
consists of a trapezoidal concrete-lined spillway discharge chute that terminates with a concrete
plunge pool at the toe level of the dam. Water flows over a 61-foot-long trapezoidal concrete weir.
The weir’s elevation is approximately
eight feet below the top of the dam’s crest.
The primary outlet works consist of a reinforced concrete box culvert
and a control tower located at the center of the embankment. The conduit is equipped with a trash
rack device on the upstream end and an endwall at the discharge end. Stop logs located in the control
tower control the flow through the conduit. The stop logs divide the control tower into inflow and
outflow chambers. The stop logs in the control tower extend from the bottom of the box culvert to
the pool elevation. The flow entering into the intake chamber of the control tower through the upstream
portion of the outlet conduit rises to the top stop log and spills over into the outflow chamber,
which in turn discharges into the downstream portion of the outlet conduit. Under normal pool conditions
the top stop log is set at the same elevation as the emergency spillway. The lake can be drawn down
below the normal pool elevation by removing the stop logs. The control tower is not equipped with any mechanical device
for removing the stop logs. This outlet system constitutes the emergency drawdown facility for the dam.
the dam, Sinking Creek generally flows east, meandering for approximately 4 miles, and joins Maiden
Creek in the village of Kempton. It is estimated that failure of the dam would pose a serious public
safety threat. Approximately 900 residents and 291 homes would be inundated if a dam failure were
The dam has a history of seepage problems dating back to the initial filling. Concern about the quantity of seepage
discharge and the possible undermining or erosion of foundation materials beneath the concrete chute spillway
on the right abutment led to the lake being drawn down in the summer of 1999 (July-Sept.).
is responsible for dam inspection and other requirements associated with maintaining the dam. In
2000, the Commission contracted for a dam assessment with Schnabel Engineering at a cost of approximately
$95,000. The assessment included videotaping the existing embankment drains. The videotapes show
sediment and drainage aggregate in the pipes. This is an indication of piping and erosion within the embankment.
Lake was drawn down 21 feet to enable the dam to withstand a 100-year storm
event (required by regulations) without activating the emergency spillway. Today the pool size is
approximately 40 acres and 24 feet deep versus the normal pool of 117 acres and 45 feet deep.
HYDRAULIC AND HYDROLOGICAL ANALYSIS
The dam/spillway was constructed
in 1970 at the regulatory standards of the time. Due to an increase in the standard Spillway Design
Flood (SDF) the dam/spillway are not up to current regulations. In developing the Emergency Action
Plan (EAP) for Leaser Lake Dam, a hydraulic analysis showed that the dam/spillway could only pass/store
59% of the SDF.
REPAIRS TO THE DAM/SPILLWAY
The engineering assessment indicates the repairs/upgrades
must address the embankment seepage issues as well as the inadequate spillway issue. The dam embankment
may require a grout curtain to repair the embankment leakage. Further investigation is needed to
determine the necessity of a grout curtain. The total estimated cost of the capital project is $3.7
to $5.3 million (depending on the necessity for a grout curtain). Once the Commission
secures the necessary funding it will taken approximately two (2) years for design/permitting and
an additional two (2) years for construction. The PFBC anticipates the repairs will be functional
for 50 years.
PFBC DAM FUNDING NEEDS
Leaser Lake is one of five (5) PFBC lakes drawn down in recent
years to address dam safety concerns. The Commission continues to work to secure funding
for repairs on each of the dams.
The Commission remains optimistic that a funding source outside
of the day-to-day operating revenues in the fish and boat funds will be found and will be available
for the substantial infrastructure improvement needs the Commission has. The total need for dam repairs
alone is estimated
at more than $83 million.