PROJECT BACKGROUND


The Sunbury project, authorized under the Flood Control Act of 1936, was designed and built by the US Army Corps of Engineers. The project provided for the construction of a system of levees and concrete floodwalls with total length of 26,624 feet. Structures for the disposal of interior drainage consist of six pumping stations, eight interceptor sewers, and other minor relief outlets. Incidental works consist of approximately 8,300 feet of 4 kv single-ciruit an approximately 1,050 of 4 kv double-circuit transmission lines to pump stations, 3 aluminum flood barriers, 2 stoplog closure structures, four sandbag closure structures, and several ramps to afford access over or through the project.

Protection provided
The flood protection works provides protection on the Susquehanna River 3 feet above the computed flowline for the confined flood of 556,000 cubic feet per second and substained protection of 620,000 cfs in 1972. The maximum confined discharge which the city will be protected against by utilizing the freeboard will be about 620,000 cfs. Along Shamokin Creek, a freeboard of 3 feet is provided against a discharge of 16,000 cfs occurring when the Susquehanna River is at 556,000 cfs. By utilizing the discharge capacity to the top of the freeboard, Shamokin Creek can discharge about 45 percent more than the design flow with 556,000 cfs in the Susquehanna and can discharge 75 percent more than the design flow during low stages in the Susquehanna River.

Construction history
Following the May 1946 flood, full protection for Sunbury was started that same year and was completed in 1948 for the Shamokin Creek Section; construction for the upper Susquehanna River section started in 1947 and was completed in 1949; the lower Susquehanna River section was started in 1948 and completed in 1951; the closure structures were completed in 1948; and bank stabilization consisting of stone protection gravel filter blanket, and filling voids from Island Park bridge to the railroad bridge was completed in 1950. Construction cost was 6.6 million dollars.

Floodwall
Floodwall was provided where clearance is too restricted for levee construction. Floodwall is constructed of reinforced concrete with a steel sheet pile cutoff. The wall consists of “T” and “I” types, the “T” type wall has an average height of 19.2 feet above the original ground and is about 4,040 feet long. The “I” type wall has an average height of about 11.8 feet above the original ground and is about 8,060 feet long. The riverbank along the line of the floodwall is provided with riprap protection consisting of an 8-inch gravel base and 1.5 feet of dumped rock on the slope, and 2 feet to 3.5 feet of dumped rock at the toe.

Levees
The levees are constructed of impervious fill and have a crown width of 8 feet and side slopes of 2.5 feet horizontal to 1 foot vertical. The levee along Shamokin Creek has an average height of about 16 feet and the sections of levee along the Susquehanna River and the levee tying into high ground at Mt. Pleasant Road have an average height of about 18 feet. The total length of levee is approximately 2.6 miles and is divided in 3 sections. The Shamokin Creek section - 9,940 feet, the Lower Susquehanna River Section - 2,000 feet and the Upper Susquehanna River Section - 1,800 feet. Pumping Stations Four combination storm water and sanitary sewage pumping stations and two storm water pumping stations were constructed, complete with approach channels, sewer inlets, trash racks, collecting basins, gravity by-pass culverts, discharge chambers, pumping equipment, control gates and other necessary facilities. The combination stations are located along the landward toe of the levee at the mouth of Spring Run, at the foot of Hopper Alley, Church Street, and Reagan Street. Flood pumps installed in all stations, except the Underpass pumping station, are vertical mixed-flow propeller type pumps. The Underpass storm water pumping station is located just west of the point where Front Street under passes the railroad bridge at the upstream end of the protective works. The Shikellamy Avenue stormwater pumping station (built by the City of Sunbury) is located at the upstream end of the levee in the upper Susquehanna River section at Mount Pleasant Road. All stations except Underpass are supplied with 3-phase 4160-volt service for flood pump operation, and with 3-phase, 120-240-volt service through banks of two-10 KVA and one-15 KVA Hframe mounted transformers for sewage pumps and stations use. Underpass station is supplied with 3-phase 240-volt service for flood pump operation and single phase 120-volt service for station use.

Closure Structures
Openings were left in levees and walls where it was not practicable, for economic or other reasons, to ramp railroads or highways over the flood protection structures. These openings must be closed during periods of high water. Aluminum barriers or stoplog closures are provided at larger openings while smaller openings, particularly those within or near freeboard range requiring less frequent closures, are closed by sandbagging. Recent modifications to the closure structures have changed both the type and location of structures since the original construction. Today there are now 3 aluminum panel closure structures, one located on the North end of the project across the CP rail line on Shikellamy Ave., one on the east side of the project across the North Shore rail line located behind Zimmerman’s Dodge car dealership and one located on South Tenth street. A single stoplog structure is located on East Market street and 2 sandbag closures are located at the North and South end of the project.

Flood Monitoring
Surrounding river and creek elevations are monitored 24 hours a day through the use of 3 computerized telemetry systems. Telemetry systems take elevation readings and calculate rate of rise or fall every 15 minutes and are accessed via computer. In addition, the units have the capability to call during the night should problems arise. The units have back-up batteries and can also be accessed via telephone. Should the units fail during an event, back-up staff gages allow uninterrupted monitoring of elevations.
The telemetry units are located on both the Susquehanna River and Shamokin Creek. The Susquehanna river unit is located just below the inflatable dam. This location was selected to prevent interference of readings during inflation of the dam. The remaining two units are located on Shamokin Creek. One near our water filtration plant just off Route 61 and the other at the Spring Run pump station just south of the south Tenth street bridge.

Forecast Monitoring
The Flood Operations Center is linked directly with GOES-8 (Geo-Stationary Operational Environmental Satellite) and GOES-10 via a land based receiver. All data issued by weather and river forecast agencies (graphical and text) is received "real time" at the Operations Center via the GOES satellite network. The Sunbury Municipal Authority is also data collection site for the National Weather Service. Data collected daily at our site is transmitted directly to the agency's primary ROSA (Remote Observation System Automation) computer in Charleston, West Virginia. This data is then compiled with data collected from other sites and disseminated to forecast centers across the nation.