Certification of Levee Systems for the National Flood Insurance Program
The newly-issued draft Engineer Technical Letter (ETL) 1110-2-570 provides a consolidated document of USACE procedures for levee/floodwall systems certification determinations in support of the NFIP as administered by FEMA. The ETL will be used to respond to requests for local sponsor levee systems certifications.
The ETL is consistent with 44 CFR 65.10 while updating methods and references to current USACE practices and criteria. The intent is that the guidance in the ETL and 44 CFR 65.10 will eventually converge into common criteria.
FEMA fully participated on the ETL Project Delivery Team and will be part of the Independent Technical Review.
USACE and FEMA agree that the local sponsor seeking recognition of the levee system for NFIP purposes is responsible for providing certification documentation. USACE will continue to certify levees it operates and maintains. For all other levees within the USACE program, funding must be provided by the local sponsor.
The ETL will undergo peer review prior to final publication.
Policy Highlights:
Systems Approach - NO PARTIAL CERTIFICATIONS - A levee system includes all components that are interconnected and necessary to insure flood and storm damage reduction for the associated floodplain – levee/floodwall sections, closure structures, pumping stations, culverts, interior drainage works, and system operation and maintenance. No certification of individual components of the system is allowed.
Professional Engineer Signatory –Certifications will be signed by the district Levee Safety Officer (LSO) or an equivalent registered PE competent in the areas of design, construction, operation, inspection, and evaluation of levee systems.
Risk-informed methodologies for analyzing the full suite of engineering and operational elements of a levee system or dam are under development for USACE dam and levee safety assessments. Methodologies are expected to be adapted to levee certification determinations and made part of this ETL as they mature.
Maximum period of validity for USACE certification will be 10 years and consistent with the cycle of inspection and assessment provisions. Certification may be reviewed any time before the maximum period of validity.
USACE will examine and report all elements of residual risk and public safety by providing a statement regarding project exceedance; as methods mature, this could eventually include loss-of-life.
USACE in 1997 issued guidance to incorporate risk and uncertainty (R&U) to determine levee height for certification in lieu of FEMA’s fixed three feet of freeboard. The draft ETL uses the R&U’s 90-95% certainty level of the base flood elevation (BFE) while maintaining the concept of a two foot minimum freeboard above the mean value (50%) of the BFE. USACE will use the higher of these two values to determine levee height.
Emergency operations and flood warning plan required for systems under evaluation.
Looks toward resiliency for wave overtopping as way forward for coastal and large lake environments.