Overall, I believe that the proposed regulations are an improvement over the existing regulations.  Below are some specific areas where I believe additional revision may be warranted:

1.         The term “planned land-use” is used several places in the regulations.  Is this intended to be total build out condition in accordance with a valid comprehensive plan-  Could this term be defined?

2.         4 VAC 50 – 20-54, B – Extending inundation mapping to a point downstream where the WSEL of the SDF with a failure is within 1-foot of the WSEL of the SDF without a failure appears excessive.  Extending the mapping to a point where the two conditions converge to within 2 to 3 feet should be adequate for the extreme events that are being considered (PMF to 100-year).

3.         4 VAC 50 – 20-54, B – Is it the intent of the regulations to require mapping to include profiles and cross sections in addition to the plan of the inundation mapping-  If so, what is the purpose of providing profiles and cross sections on the inundation mapping?  The modeling input data will include profile and cross section information, but the inundation mapping should not be required to include cross sections and profiles.

4.         4 VAC 50 – 20 – 40, C – Requires a dam break analysis by an engineer to support the appropriate hazard category, yet 4 VAC 50 – 20 – 54, E states that low hazard potential impounding structures do not require an engineer to prepare the inundation mapping.  This appears to be a contradiction as the evaluation to support a dam category of “low hazard” must be supported by a dam break analysis that includes the downstream inundation areas.  A professional engineer should be required for all inundation mapping, irregardless of the dam category. 

5.         4 VAC 50 – 20-54, F.2. -        States that a note must be placed on all maps that includes the statement “Mapping of flooded areas and flood wave travel times are approximate.  Timing and extent of actual inundation may differ from information presented on this map.”  This is the only place in the regulations that mentions flood wave travel time on inundation mapping.  The regulations need more direction as to what is desired and required for flood wave travel time on the inundation mapping.

6.         The economic impact statement asserts that the cost for inundation mapping is anticipated to average $16,417 each.  This is too low to prepare the level of detail that appears to be required by the regulations. 

• The inundation mapping must extend until the increase in WSEL during the SDF with a failure is less than 1-foot greater than the WSEL of a SDF without a failure.  This requirement will require long reaches to be mapped.
• Detailed survey is required, but the regulations do not specify what constitutes a detailed survey.  Does the survey effort required for inundation mapping need to meet the FEMA requirements for Flood Insurance Study mapping-
• Each structure located within or near the inundation zone will need to be located and its FFE shot.
• The cost to prepare the inundation mapping must reflect the time and care that must be taken in their preparation due to their critical use in emergency situations.

7.         The regulations do not provide any guidance as to the study survey requirements.  Inundation mapping is similar to the FEMA FIS studies.  Should FEMA survey requirements for FIS mapping development be required?

8.          4 VAC 50 – 20 – 175, G.7 – Dam owners are not equipped for rapid notification of downstream residents in the event of an emergency.  This notification is usually performed by the locality’s EMS.  What will the Emergency Action Plan process be if the locality refuses to sign the plan accepting any responsibility for notification?

9.         A lot of problems with inadequate operation and maintenance of dams in the past has occurred due to lack of financial resources on the part of dam owners.  Has any consideration been made to require prospective new dam owners to show adequate financial ability and commitment (similar to that required by sanitary landfill owners) to properly operate and maintain a dam after construction; prior to issuing a permit to construct?