In section 4VAC50-20-50.C, the probable maximum flood (PMF) is defined as the "flood expected that might be expected from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible in the region". The key phrases in this statement are "most severe" and "reasonably possible", and these phrases only occur in the regulations for the definition of the PMF flood. However, in the guidance documents published by DCR, DCR has expanded the use of these phrases to state that the PEOR is to ensure "the worst case hydrologic/hydraulic scenarios are being utilized". The expansion of the term "worst case" is highly subjective, and puts an undue burden on the PEOR to try to prove to the Regional Engineer that this standard has been achieved. Without a clear definition of "worst case", there are an infinite number of scenarios that could be generated and we do not believe that this is a productive or necessary exercise. The intent of the regulations was to set a standard for dam owners that puts public safety as the number one goal, but also considers the responsibility and financial burden of the dam owner.

We request that if the standard is "worst case hydrologic/hydraulic scenario", that this be clearly stated and defined in the regulations. In addition, we believe the "worst case scenario" should be stipulated as something that is "reasonably possible" in the state of Virginia.   We believe "worst case" should be defined as the combination of hydrologic/hydraulic modeling that impacts the most properties and has the highest hazard classification. The PEOR should describe why the modeling submitted is the "worst case" qualitatively.  We believe "reasonably possible" should be defined as the hydrologic/hydraulic that utilizes standard engineering practice for determining watershed hydrology and hydraulics. Again, the PEOR should describe why the modeling is "reasonably possible" qualitatively.