This report is submitted in order to obtain Waterway Approval for the replacement of the structure described.
State Route 2001, commonly referred to as Wykoff Run Road, crosses Laurel Run at
Segment 0120, (approximately 5.3 miles north east of S.R. 1011 and 4.5 miles south west of S.R.
120) in Gibson Township, Cameron County. This site was formerly known as Legislative Route
12001, Station 294+56. Since both the existing and the proposed structure will carry Laurel Run under State Route 2001, this project can be deemed water dependant.
State Route 2001 is classified as a Rural Major Collector with an Average Daily Traffic
(ADT) count of 320 (8% trucks), and a Maintenance Functional Classification (MFC) of “D”. As a rural major collector, Pennsylvania’s Department of Transportation Strike-Off-Letter (SOL)
431-99—11 requires this structure be designed for a 25 year return period with a flood risk assessment based on a 100 year return period.
Skewed at 50 degrees, the existing structure is a timber deck steel I-beam stringer bridge having an effective span of 20’ and a rise of 6’-8” and supports a clear roadway width of 23’-6” from face to face of guiderail.
Although no agency specifically lists Laurel Run, it is a tributary to Wykoff Run, which is identified as follows:
- Pennsylvania Department of Transportation’s Design Manual, Part 2, Chapter
10, lists Wykoff Run as a “Stockable Warmwater and Trout Stream.”
- The Pennsylvania Fish and Boat Commision has identified Wykoff Run with
“Verified Trout Reproduction.”
- Pennsylvania Department of Environmental Protection’s Water Quality
Standards lists Wykoff Run as being “High Quality-Cold Water Fishery”
waters.
The proposed bridge replacement project has minimal earth disturbance impacts. There are no wetlands present in the project area. The project will have temporary impacts to the waterway, in the form of potential erosion and sedimentation. Proper erosion and sedimentation procedures will ensure that any impacts are minimized. No permanent impacts to the productivity of the waterway are anticipated. Due to these minimal temporary impacts, a mitigation plan is not applicable.
The drainage area accommodated by this structure was plotted on the Driftwood, Pa
7.5 minute quadrangle. It was found to be 2.95 square miles. See topographic map, Section L, page 2.
The design discharge calculations follow the method set forth in the National Flood
Frequency Program-USGS WRI 00-4189 and yields the following results:

Design Flood
Q
25
Q
50
Q
100
See Section L, page 7.
Discharge
577 c.f.s.
740 c.f.s.
932 c.f.s.
The hydraulic dimensions of the existing structure were combined with the discharges derived from NFF and plotted on the H.D.S. 5, Chart 8, Headwater Depth for Box Culverts with
Inlet Control. This chart provided the following values:
Design Flood
Q
Q
Q
25
50
100
HW/D
.72
.86
1.02
D
4.68’
5.59’
6.63’
See Section L, page 8.
The proposed structure for this site is a single cell, post-tensioned, pre-cast concrete box culvert with a span of 20’-0” and a rise of 7’-0”.
Applying the hydraulic dimensions of the proposed structure (20’-0” span x 7’-0” rise) and the NFF Design Flood values to H.D.S. 5, Chart 8, yields the following values:
Design Flood
Q
25
Q
Q
50
HW/D
100
.65
.75
.88
D
4.55’
5.25’
6.16’
See Section L, page 13 & Culvert Design Form, page 18.
This box culvert will be designed for a 8’-0” rise and will be depressed 1’-0” into the streambed. The design will include standard fish baffles to provide a low flow channel, and flared wingwalls.
Pennsylvania’s Department of Transportation’s Strike-Off-Letter 431-99-11, specifies this structure, classified as a rural major collector, be designed for a 25 year design flood frequency. A flood risk assessment shall be done based on a 100 year design flood frequency.
From the hydraulic analysis, the proposed structure (underclearance of 7.00 feet) will pass a 25 year event with a depth of water of 4.55 feet and a 100 year event with a depth of water of 6.16 feet. Roadway flooding and structure inundation should not occur under these two flood events.

Should flooding occur, damage will be minimized because of several reasons:
There are no homes in the vicinity.
There is no industry in the vicinity.
There are no parks or recreational facilities in the vicinity.
A cost comparison was done using the Department of Transportation’s BRADD-2 software. This comparison, and an estimate by a precast concrete fabricator is as follows:
Prestressed Adjacent Box Beam Bridge…………….$145,427.05
Prestressed Spread Box Beam Bridge………………$132,648.85
Steel Rolled Beam Bridge…………………………..$133,255.05
Single Cell Precast Concrete Box Culvert………….$110,585.90
Not only is the box culvert the more cost effective of the choices, the box culvert is one of the more maintenance-free structures that the Department installs. These qualities make the precast, post-tensioned, concrete box culvert the structure of choice.
The project site lies within an area noted as “SPECIAL FLOOD HAZARD AREAS
INUNDATED BY 100-YEAR FLOOD”, but is designated “ZONE A NO BASE FLOOD
ELEVATIONS DETERMINED”. No other data exists for this site.
The purpose of this project is to:
1) Eliminate a bridge that is need of major rehabilitation
2) Install a new box culvert
3) Improve the drainage
4) Provide a wider, safer roadway for the traveling public

It is the Department’s recommendation that the approval be given for the following structure:
S.R. 2001
Station 294+56
Single Cell, Precast, Reinforced Concrete Box Culvert
Span = 1 @ 20’-0”
Rise = 7’-0” (8’-0” depressed 1’-0”)
Skew = 50 degrees
Also, approval is requested for the installation of R-6 rock rip-rap protection around culvert apron and wingwalls at both inlet and outlet.