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1. What is a levee?

About

A levee is a man-made structure designed and constructed to contain, control or divert water to prevent flooding. CDID#1’s levees are primarily made of material dredged from the Cowlitz and Columbia Rivers. The Columbia River levee consists of coarse river sand to silt and clay. Part of the Cowlitz River levee was constructed of impervious clay and the remainder was constructed of a gravel cap over silt, sand, clay, gravel and occasional cobble. The levees are built at an elevation to match the Columbia River 1884 flood elevation plus 5-feet of freeboard. Most of our levees are built on easements, which means that anyone wanting to do work within the levee right-of-way must apply for a permit.

Area

The federal portion of our levee system was built by the USACE. It begins at the Cowlitz River north of Fishers Lane in Kelso, extends to and along the Columbia River to Willow Grove Road, continues along backwaters to the Coal Creek Slough and terminates at our Main Pump Station on Pacific Way in Longview.

A separate interior levee extends westerly along Pacific Way in Longview from 30th Avenue to our Main Pump Station. This non-federal levee intercepts runoff from hill side areas above Longview so the water can be collected and pumped out to the Columbia River.

2. Is the levee accredited?

About

Yes. In 2014, the U.S. Army Corps of Engineers (USACE) published a report concluding that CDID# 1’s levee system can be reasonably expected to protect against the 1% annual chance exceedance flood (also referred to as the 100-year flood). Their report was a pre-requisite for levee accreditation from the Federal Emergency Management Agency (FEMA) and eligibility for participation in the National Flood Insurance Program (NFIP). 

CDID# 1’s NFIP levee system evaluation will expire on July 31, 2024.

CDID# 1 also participates in two programs administered by the USACE to ensure we maintain our levee system in conformance with federal standards.

Inspections

• Rehabilitation and Inspection Program, Engineer Regulation (ER) 500-1-1:
  A routine annual inspection which takes about one day to complete. It involves driving the levee system to evaluate whether the flood control works will provide the intended degree of protection, and assess whether our maintenance program is adequate.
• Periodic Inspection, National Levee Safety Program Act of 2007:
  A thorough review of all CDID# 1 levees and stormwater facilities conducted every five years. The inspection is conducted entirely on foot, takes approximately four days to complete, and consists of a large multi-disciplinary team of engineers.