Bathgate Watershed - Office of Physical Plant - Penn State University

Introduction and Objectives
Water Resource Publication
Bathgate Watershed
OPP-WRP-DM-BG:(4)-2010
The Bathgate Watershed is located at University Park, Centre County, Pennsylvania. The watershed boundary is defined
by the Bathgate Dam, which is a regulated dam (D14-122) by the Pennsylvania Department of Environmental Protection
(PaDEP) and has a drainage area of approximately 237 acres. The dam has a permanent pool with normal pool area of
approximately 1 acre in size. The maximum storage capacity is approximately 74 ac-ft. The dam discharges to Slab
Cabin Run at Millbrook Marsh via a 66” reinforced concrete storm drain outfall pipe. The dam’s primary function is to
control stormwater runoff including peak runoff rates (the 1 through 100-year events) and improve water quality. The
dam was also designed to safely pass ½ of the probable maximum flood (PMF). Bathgate Dam is classified as a High
Hazard (category 1), size class C structure by PaDEP.
The watershed is a mix of developed campus areas (Beaver Stadium, the Jordan Center, Holuba Hall, the Multisport
Indoor Complex, and parking areas), and open fields (refer to Figure 1). A large portion of the open fields are used six or
seven times a year for football parking events. The Bathgate Dam is designed for a maximum impervious area of 95.9
acres. The Imperviousness in the watershed in 2010 is 82.7 acres. There are over 7.5 miles of storm drains in the
Bathgate Watershed varying in size from 4 to 54 inches in diameter. These storm drains terminate near Porter Road and
stormwater is conveyed to the dam via a 1,600-foot long fabric-form concrete swale with an average slope of 4.8%.
N
Basin Outlet
Bathgate Dam
Surface Drainage
Basin 236.6 acres
Figure 1. The Bathgate Watershed
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Penn State University
Water Resource Publication
Soils and Geology
The majority of the Bathgate Watershed is identified as a Hagerstown Series by the Soil Survey of Centre County. The
most significant limitation identified in the soil survey of Hagerstown soils is possible sinkhole formation and ground
water pollution hazard if the soil is used for waste disposal. In addition to the Hagerstown soils, there are small amounts
of Nolin, Opequon-Rock, Opequon-Hagerstown complex, and Urban-Hagerstown complex also located within the
drainage basin. Although these soils are traditionally considered to be hydrologic soil group (HSG) C soils by the NRCS,
an intensive analysis conducted for the Spring Creek Drainage Basin (ACT 167 Plan) has shown that the soils more
reasonably respond as HSG B soils. The majority of the watershed is underlain by bedrock of the Nittany limestone (On)
formation, which is described by dark-gray, finely to coarsely crystalline dolomite.
Hydrologic Budget
Since late 2006, the University has instituted a continuous discharge-monitoring program at the Bathgate Dam. Because
the Bathgate watershed is mostly developed with directly connected impervious areas, the watershed outflows are highly
influenced by the imperviousness. Peak discharges from the watershed are well controlled, but runoff volume is not
reduced due to the absence of recharge areas given the watershed’s topography and underlying geology.
The dam has a normal pool elevation of 993.25; however, there are three small holes (bleed outs) with inverts at elevation
992.50 that slowly draw down the pool elevation. Because of these small holes, the dam usually discharges low flows
year round with the exception of dry periods in the late summer or fall. This slow release can be seen in Figure 2. There
is approximately 1 ac-ft of storage capacity between the normal pool elevation and the three small holes.
995.0
994.5
994.0
Elevation (ft)
993.5
993.0
992.5
992.0
9/1 9/16 10/1 10/16 10/31
Date
Figure 2. Dam Water Surface Elevation Over Time
The control structure at elevation 993.25 is a 4.25-foot wide broad crested weir, for which discharges can be reasonably
computed. The small bleed out holes are prone to minor clogging and while the peak runoff rates are not significantly
affected by this clogging, the computed runoff volumes can be.
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Penn State University
Water Resource Publication
During 2010, 37.7 inches of precipitation fell in the watershed resulting in the pond discharging approximately 185 ac-ft
of runoff, which is equivalent to a discharge to precipitation ratio of 0.20, which is the lowest percentage since data
collection started. Almost all larger precipitation events produced runoff. The graph of discharges from the dam for the
year can be seen in Figure 3.
Significant Runoff Events of 2010
Figure 3. Discharge from the Bathgate Dam for 2010
The 2010 year produced seven runoff events greater than 10 cfs and there were eight precipitation events greater than 1.0”
in total depth. The eight most significant runoff/rainfall events of the year are shown in the table below.
Basin Basin Q/P Q/P 5 Day
Outlet Outlet Ratio Ratio Max 5min Max 1hr Antecedent
Day Event P (in) Qp (cfs) Q (ac-ft) 237 ac 82 ac P (in) P (in) P (in)
1/25/10 1.90 19.3 11.0 0.29 0.85 0.08 0.52 0.09
3/14/10 1.83 8.5 10.7 0.30 0.86 0.04 0.19 0.30
5/12/10 1.15 11.2 7.5 0.33 0.95 0.09 0.46 0.43
6/10/10 1.14 9.4 7.1 0.32 0.91 0.06 0.32 0.19
7/10/10 2.12 22.0 11.4 0.27 0.79 0.19 1.21 0.00
8/22/10 1.49 14.6 7.7 0.26 0.76 0.10 0.58 0.00
10/1/10 3.66 28.1 19.5 0.27 0.78 0.12 0.79 1.04
11/30/10 3.07 20.2 20.3 0.33 0.97 na na 1.05
The event of October 1 st generated the highest peak runoff rate of the year, which was approximately 28.1cfs. The Walker
Building Weather Station recorded 3.66” of rainfall over an 18 hour period. The runoff hydrograph for the October 1 st
event can be seen in Figure 4. During early September, the dam’s water surface elevation was below the bleed out
elevations as can be seen in Figure 5.
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Penn State University
Water Resource Publication
Figure 4. Runoff Event of October 1, 2010
Water Quality and Thermal Issues
The Bathgate dam is a water quality and peak runoff rate control facility. No water quality sampling of surface water was
been conducted in 2010.
Because the dam acts as a retention pond with a permanent pool, thermal impacts occur due to the solar heating of the
water. Temperatures are recorded 1 foot below the normal pool elevation. Diurnal temperature fluctuations occur and
temperatures also go through an expected annual cycle with runoff event fluctuations.
Miscellaneous Information
Drainage Basins: Slab Cabin Run/Spring Creek/Bald Eagle Creek/West Branch Susquehanna River
PA Title 25, Chapter 93 Water Quality Classification: Cold Water Fishery (CWF)
USGS Quadrangle: State College
Hydrologic Unit Code: 02050204
Watershed Outlet Latitude/Longitude: 40° 48’ 46” / 77° 50’ 37”
Basin Municipalities: State College Borough, College Township
NPDES Permit for Basin: PAS10F106(3)
Municipal Separate Storm Sewer System (MS4) Permit: PAI-134807
Basin Stormwater Management Plan: Spring Creek Act 167, Adopted August 6, 2002
Bathgate Dam Permit: D14-122
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Penn State University
Water Resource Publication
References and Additional Information on the Basin
Berkey, L.A., L.E. Storm, C.R. Whitson, and A.T. Bain. 2003. Engineering, Permitting and Environmental Issues Related
to the Renovation of a Stormwater Management System at the Pennsylvania State University, University Park
Campus. Proceedings of the Pennsylvania Stormwater Management Symposium, Implementing Stormwater
Management, Integration of Planning, Regulation, Design, and Operations. Villanova University, PA.
Gannett Fleming. 1999. Bathgate Detention Pond Expansion and Storm Sewer Outfall System. Engineering Study. PSU
Project No. 01-70653. Unpublished Technical Report for Penn State University. March 1999.
L. Robert Kimball. 1991. Storm water Management Report for the Pennsylvania State University Construction of
Commuter Parking Lots (original Bathgate Dam Design Report). Unpublished Technical Report for Penn State
University. Revised February 1991.
Figure 5. Dam on September 9 th , 2010 when Water Surface Elevation was Lowest of the Year
Publisher: Penn State University, Office of Physical Plant, Energy and Engineering Division, Engineering Services
Editor: Larry Fennessey, OPP Stormwater Engineer, Ph: (814) 863-8743, email: laf8@psu.edu
OPP-WRP-DM-BG:(4)-2010