The levee system was designed and constructed by the U.S. Army Corps of Engineers (USACE) and then turned over to the City of Portsmouth for ownership, operation, and maintenance on 15 May 1950.
The levee system is composed of earthen levee, concrete floodwall, pumping stations, traffic closures, and channel improvement. The earthen levee is constructed of compacted fill, with a top width of 12 feet and side slopes of 1 vertical (V) to 2.5 horizontal (H) on the protected and flood sides of the levee. The top of levee elevation is 549.3 feet. The embankment was built over an existing floodwall segment. This relic floodwall acts as the toe of the levee for a portion of the embankment. The floodwall consists of flat and sloped base conventional concrete keyed T-walls which reach an elevation of 548.5 feet. The top of the levee and flood wall are approximately 3 feet above the elevation of the January 1937 flood. The Portsmouth segment has two types of traffic closures; stop logs and a trussed system. The stop log closures are composed of either aluminum or steel and timber systems. The trussed closures are steel and timber constructions. In the Portsmouth segment, there are seven pump stations included in the flood protection works for the purpose of pumping surface drainage and sewage from the area behind the levee or flood wall and into the river during flood periods when the outfall sewers that normally provide drainage must be closed.
Project Authorization and Eligibility. USACE has authority under PL 84-99, Flood Control and Coastal Emergencies (FCCE) (33 U.S.C. 701n) (69 Stat. 186) for emergency management activities. Under PL 84-99, the Chief of Engineers, acting for the Secretary of the Army, is authorized to undertake activities including disaster preparedness, Advance Measures, emergency operations (Flood Response and Post Flood Response), rehabilitation of flood control works threatened or destroyed by flood, protection or repair of federally authorized shore protective works threatened or damaged by coastal storm, and provisions of emergency water due to drought or contaminated source. Under the authority of PL 84-99, an eligible flood control works can be rehabilitated if damaged by a flood event. ER 500-1-1, Para 5-6, Active Status, states "Only those FCW in an Active status at the time of the flood or storm event may receive Rehabilitation Assistance under authority of PL 84-99" Per ER 500-1-1, Para 5-11 Cost Share Determination, the flood control works are eligible for rehabilitation in accordance with the cost allocation defined in sub-paragraphs a through h and associated references of the ER and paragraph 5-11. All systems considered eligible for PL 84-99 rehabilitation assistance have to be in the Rehabilitation and Inspection Program (RIP) prior to the flood event. Acceptable operation and maintenance by the public sponsor are verified by inspections conducted by the Corps on a regular basis.
The Corps has the responsibility to coordinate flood control repair issues with interested Federal, State, and local agencies following natural disaster events where flood control works are damaged.
Justification for Project. The Ohio River experienced a flood event which reached the crest during 19 to 21 February 2018. During the 2018 flood, extensive foundation erosion and sagging of a drain line adjacent to the LPP occurred near Pump Station No. 5. The foundation is pervious and the upstream seepage entrance is close to the levee toe. Uplift pressures at the site are high and it has been identified in previous modeling work that this area of the project has serious under seepage-related stability issues, as well as, related slope stability due to extremely high pore pressure conditions at higher loadings. Recent observations during and post-2018 flood have provided further evidence that the foundation has been weakened and that progression towards failure has occurred.
On 24 February 2018, LRH was alerted to large boil-like activity, about 20-40 feet in diameter, occurring in the ponding area, where large quantities of muck and silt were upwelling. Site monitoring on 24 February 2018 resulted in the inspection of the brick-lined pipe system. Significant amounts of foundation soils were present in the conduit and the area surrounding the outlet. The water coming from the conduit was visibly carrying sediments, and inspection following ponding area tail water recession suggested that at least 25 cubic yards of material had been lost during the event, some of which was deposited at the outlet. Additionally, seepage and piping was occurring
from beneath and around the conduit leading to a lesser amount of foundation erosion than that occurring into and through the conduit, however this is a problematic failure mode and could lead to failure alone or in conjunction with conduit erosion. A sample was taken on 15 March 2018, and contained finer sediments deposited on top of the coarser sample. This material is likely foundation material eroded into the pipe.
On 15 May 2018, Huntington District inspected the Portsmouth levee in response to an application for PL 84-99 assistance. The sponsor advised on 11 May that separation was occurring where pump station discharge pipes enter the gatewell adjacent to the Ohio River. Upon investigation, measured separation of up to 1-1/4 inches had occurred where the western-most discharge pipe enters the gatewell. These pipe separations at the levee crest could be related to the large amount of foundation material erosion that has occurred at the project, which is a serious concern and would be indicative of progressive backwards erosion beneath the levee. The ponding area had some evidence of sediment accumulation from the February 2018 event. Most predominate was a sand delta at the base of Manhole 1. Due to the multiple crests of the February and March 2018 events, it is likely that other accumulations of sediment have been flushed from the area. Throughout the event, a minimum of 25 cubic yards of foundation material was observed being moved, and with the additional accumulations that were not observed and flushed out of the system, the foundation is compromised.
Project Repair Description. The primary purpose of the project is to install a flood protection levee seepage barrier located in Portsmouth, Ohio along the bank of the Ohio River at Lawson’s Run Creek, also the location of Flood Pump Station #5 of Portsmouth’s existing flood protection.
The project will include the following:
- Construction of a cement / soil-cement seepage barrier approximately 90’ high and 2,000 feet long. Multiple construction methods (ie. TRD, DMM, Dewind, Hydromill, CSM…etc.) may be proposed or considered. Construction of the seepage barrier will be along the center line of the levee and may require temporary lowering of the top of the levee during construction.
- Construction of a jet grout barrier at a 7’ x 7’ box culvert crossing of the proposed seepage barrier. Jet grout will likely penetrate through the ceiling and floor of the 7’ x 7’ box culvert to create a continuous barrier. This section of seepage barrier is likely to be bid as an RFP acquisition strategy with alternative potential designs proposed.
- Replace 3 existing 36 inch flood pump station steel discharge pipes over levee that have settled and separated at the joints due to foundation loss.
- Remove and replace approximately 120 feet of 16 inch diameter sewer treatment plant pump station discharge pipe to include replacement of a combination air valve. This relocation is the responsibility of the sponsor, however, it must be relocated then restored in conjunction with this work.
- Replace existing storm sewers, near the land side of the toe of the levee, which have been displaced by excessive uplift and under-seepage.
- Construct concrete supports at gate well structure to support 3 new 36 inch flood pump station discharge pipes.
For information on the upcoming Industry Day on May 21, please click here to contact the Huntington District, Deputy for Small Business at LRH.firstname.lastname@example.org, or Telephone: 304-399-5632.