Issues Facing the TCWID

The flood control structures in the Tehuacana Creek Watershed were constructed with a design life of 100 years.  The co-sponsor agreement with NRCS requires that the dams be inspected regularly and specifies that certain maintenance activities be conducted.  Though the structures have been well maintained, there are rehabilitation tasks that are being considered due to the age of the structures and changing land use patterns. 

Increased urban development in the District has changed the quantity and velocity of surface water flow.   Natural surface area in the watershed, comprised of soil and varying vegetative patterns, has been modified.  There is now significantly more impermeable surface cover in the watershed resulting in greater surface water flow than was assumed in original design standards that were used in the late 1950s. Increased runoff results in greater sedimentation which decreases the holding capacity of the flood retention pool.  Materials used to construct the drawdown pipes, the conduit between the flood retention basin and the stream channel, are aging and some need to be replaced. Some structures have also been subject to erosional damage and need rehabilitation to insure the continued integrity of the dams.

Dam design and construction standards for the structures are a function of land use below the flood retention pool.  Changing land use patterns have in some cases resulted in the construction of houses and other structures with the flood area below the dams and emergency spillways. This has resulted in a reclassification of the hazard assessment for the structure and requires that the dam be modified to reflect that hazard assessment.  This can cost hundreds of thousands of dollars.

Each structure location at which human life or habitable structures could be endangered in the event of a breach requires the completion of an emergency management plan (EMP).  This document outlines the ways by which first responders and individuals living in the inundation zone (flood area below the dam) will be contacted in the event of an emergency. 

Responding to rehabilitation issues, changing safety standards, increased maintenance activities, and preparation of emergency response plans requires funding in access of the amount generated by taxes.  .  The District is the process of a needs assessment and prioritizing activities to insure integrity of the dams and proper functioning of the retention pools

 
  Overview
       Background
       Current Issues
       History
       Enabling Legislation
       Legislative Authority
       Work Plan
       By-Laws
       Tax Structure