US Army Corps of Engineers
Baltimore District

Codorus Creek Flood Risk Management Rehabilitation Project

The U.S. Army Corps of Engineers, Baltimore District, is planning major repairs to the Codorus Creek Flood Risk Management component of the Indian Rock Dam/Codorus Creek Project in the vicinity of York, Pennsylvania. Baltimore District operates and maintains the dam and Codorus Creek project. 

                                                               

The Codorus Creek project consists of eight independent levee systems: York Northeast, York Northwest, York East Loucks Mill, York West Willis Run, York East Downtown, York West Downtown, York Southeast and York Southwest. The project is 4.8 miles in length, and includes a widened and deepened creek channel, levees, floodwalls and bank protection elements.  

  

The incorporated area within the City of York covers a little more than 5 square miles, and lies on both banks of Codorus Creek, which flows through York and is 10 miles upstream of the confluence with the Susquehanna River. These projects work jointly to help reduce flood risks to people and property in York, Pennsylvania, as well as communities downstream.

It cost approximately $5 million to construct both the dam and levee systems in the 1940s. These projects were authorized by the Flood Control Act of 1936. It is estimated that the dam and levee systems have prevented more than $55 million in flood damages since their construction. The dam and levee systems are inspected annually and receive a more thorough investigation every five years.  

The fiscal 2018 President’s Budget included $15.9 million for operation and maintenance of the aging Codorus Creek Flood Risk Management Project. The following work is planned: Replacement of the floodwall near Penn Street; repairment of bulge/instability issues in the floodwall near the Market Street Bridge; additional cleaning and inspection of approximately 100 (out of 270 total) drainage conduits; repairment or replacement of drainage conduits based on completed inspection results; installation of riprap (large rocks placed along the shoreline to prevent erosion) at the upstream end of the southeast levee system where the York system begins until the South Richland Ave. Bridge; and development of a comprehensive long-term maintenance plan for the system. The riprap and bulge components of the project will be designed in house.  

The team is working expeditiously to award the necessary contracts in fiscal years 2018 and 2019 to resolve the known maintenance concerns with the Codorus Creek project. The project is estimated to take 1.5 to 2 years to complete. 

Milestones: 

  • Contract awarded for the design of the Penn St. floodwall on June 21, 2018, for ~$506,000. Construction contract award is anticipated in spring 2020. 
  • Contract awarded for the pipe cleaning and inspection on July 27, 2018, for ~$91,000.
  • Contract for installation of rip rap anticipated for award in spring 2019.
  • Contract for bulge repair construction anticipated for award by the end of fiscal 2019.

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The Corps has a comprehensive levee safety program in which it communicates flood risk to local communities and inspects the levees in its portfolio annually and more in depth every five years. The Corps looks critically and rigorously at the resiliency and vulnerability of its levees, nationwide, and determine ways to help drive down flood risk with all of its partners.

The last periodic inspections for the east and west banks of Codorus Creek were conducted in May 2015, leading to unacceptable ratings for the project.

Notable deficiencies documented for the project include excess vegetation concerns; insufficient sod cover to prevent erosion; levee encroachments; severe cracking and tilting of the Penn Street Floodwall (York Southeast system); extensive shoaling; bulge/instability issues in the floodwall near the Market Street Bridge from mortar erosion (York West Downtown system); more deteriorated joint material along the floodwall; conduit obstruction (interior drainage structures) from debris (sediment and vegetation) that is causing access issues for inspections to determine which ones need to be repaired or replaced.

Inspection results are based on observations at the time of the inspection. The condition of any system depends on numerous and constantly changing factors and is evolutionary in nature.

Federal projects compete nationwide for scarce resources. Baltimore District was fortunate to receive what it requested in the fiscal 2018 budget for the necessary operations and maintenance of this project.

The majority of the levee systems in Baltimore District's portfolio are federally constructed but are now owned by local entities, or “non-federal sponsors,” to handle the operations and maintenance, both physically and financially.

This project (comprised of east and west systems) spans several different jurisdictions, making it more difficult to come to an understanding on how the operations and maintenance (O&M) will be ‘divided and conquered.’ There are other levee systems with this same situation that have been turned over to local entities; for instance, local entities came together to create a flood protection authority for Luzerne County. This initiative has not been taken by York or its surrounding communities. Without a local entity volunteering to take on these responsibilities and without a formal authority stood up, the O&M duties have been the responsibility of the Corps.

In conjunction with the Codorus Creek levee project, Indian Rock Dam continues to reduce flood risk to York and downstream communities. There are no plans to make any major modifications to the dam beyond regular maintenance work. Baltimore District is committed to ensuring the continued performance of the dam through annual and as-needed inspections. Annual Congressional operations and maintenance funding is applied toward taking care of any maintenance concerns with the dam.

The team is working expeditiously to design parts of the project and award as many contracts as possible in fiscal years 2018 and 2019 to resolve the known maintenance concerns with the project. The project is anticipated to take 1.5 to 2 years to complete.

There are various challenges associated with this project that may impact the schedule. The floodwall replacement portion of the project will require real estate actions and coordination with York College regarding the demolition of part of the paper mill building that they now own. This annex was constructed decades ago prior to it being owned by York College and abuts the floodwall, and needs to be removed for the replacement project. There are also site access concerns for the repair of the bulge/instability issues along Market Street Bridge. Work will likely have to occur from within the channel.

 

 

The fiscal 2018 President’s Budget included $15.9 million for operation and maintenance of the Codorus Creek Flood Risk Management Project. 

The following work is planned: Replacement of the floodwall near Penn Street; repairment of bulge/instability issues in the floodwall near the Market Street Bridge; additional cleaning and inspection of approximately 100 (out of 270 total) drainage conduits; repairment or replacement of drainage conduits based on completed inspection results; installation of riprap (large rocks placed along the shoreline to prevent erosion) at the upstream end of the southeast levee system where the York system begins until the South Richland Ave. Bridge; and development of a comprehensive long-term maintenance plan for the system. 

 

The levee is not accredited because it does not meet FEMA’s National Flood Insurance Program standards for freeboard. Therefore, the project is not shown on flood insurance rate maps. Freeboard is a term used by FEMA to describe a factor of safety usually expressed in feet above the 1-percent-annual-chance flood level (100-year flood event). This levee system project does not have the required three feet of extra “protection” or “cushion” above the 100-year flood event.

In order to raise the levee, the Corps would need a Congressionally-authorized study as well as Congressional funding for a project. The benefit to cost ratio would also need to be determined to evaluate if there is federal interest in the project. This ratio compares the benefits (monetary value and resources in the leveed area) of constructing the project with the costs of construction.

FEMA also has freeboard deficient procedures for accreditation, but it would not be feasible across the entire project.

Baltimore District is working with the state and York and Lancaster counties emergency management offices to revise an Emergency Action Plan for the Codorus Creek Flood Risk Management Project that includes the Indian Rock Dam. Local emergency managers are in charge of implementing the actual evacuation notifications and procedures, based on risk levels determined by the Corps.

Th Corps always urges those living near dams and behind levee systems to know their risks and take steps to reduce these risks to include purchasing flood insurance, moving valuables to higher grounds, waterproofing homes or businesses and having or knowing flood emergency preparedness plans.

Corps levee systems are designed to reduce flood risk against a certain flow rate, likely equivalent to the flood of record when the levee was designed.

This project was commissioned in 1947 and was originally designed and constructed by the Corps to contain a water flow of 24,000 cubic feet per second (with 3 feet of freeboard for levees and 2 feet for floodwalls). The flood of record at the time when the Indian Rock Dam and Codorus Creek levee projects were being designed occurred in August 1933. If the dam had been in existence at the time, it would have held back (stored) some of the flood flow; therefore, the flood of record flow calculation was reduced by the approximate amount of flow that would have been stored by the dam. The flow rate was then increased by 33 percent to add an additional layer of safety (freeboard) because the flood of record at that time was bound to be exceeded. This is how the 24,000 cfs was calculated.

Currently, the levee system roughly equates to risk reduction from a 155-year flood event, though this number continuously changes based on new flood data. Though it reduces risk from a 100-year flood event, it does not meet FEMA's freeboard requirements for accreditation.

Storm risk changes over time and so does the development and population behind levee systems. This is why it is critical that levee risk is being monitored and managed on a regular basis.

In conjunction with Indian Rock Dam, this flood risk management system has prevented well over $55 million in flood damages.

The public cannot fully rely on levees to protect communities from flooding. Levees reduce flood risk; they do not prevent it. The public needs to be prepared for a stronger storm that would overwhelm the levee system and cause flooding.