JEawb
Civil/Environmental
- Jul 10, 2009
- 2
Have a project with two wet ponds with the same permanent pool and top of bank elevations. There is a flat equalizing pipe connecting them. This project drains into a previously approved project, but there is at least a foot of drop between the proposed ponds and the existing project's ponds. However, the ponds on the other project are all pretty flat and modeled as separate ponds.
I submitted a design with the ponds modeled in a single node with dynamic routing. It is only a 17 AC site, and the ponds are oversized with an appropriately sized leveling pipe between them. The reviewers for DOT and the local stormwater agency made comments that I have to separate the ponds and model the inlet that is in the equalizing pipe run. In my opinion, what I originally modeled is the appropriate model as the downstream pond will push water upstream before it crests the outfall weirs, and the leveling pipe is adequately sized to accommodate that. They both insisted it needed to be separated without providing any technical reason for it. I indicated that I doubted it can be done without significant oscillations, but said I would take a look.
When the ponds are separated, dynamic routing produces significant warning 80 (downstream pond exceeds upstream) and some oscillation warnings. This does not surprise me because the downstream pond's DA is much larger than the upstream pond's DA. If I change it to sim routing and adjust the DT, the oscillation severity is significant, even at the smallest time step. I do not think is possible to model it appropriately without combining the ponds into a single node. Connecting to the other project only complicates it more as the oscillation warnings exist in the previously approved model.
Beyond the help menus, are there any additional guides or information from Hydrocad that would validate my original desire to keep the ponds as a single node? Or maybe a hydrocad recommended leveling pipe sizing method to further confirm my pipe size?
I submitted a design with the ponds modeled in a single node with dynamic routing. It is only a 17 AC site, and the ponds are oversized with an appropriately sized leveling pipe between them. The reviewers for DOT and the local stormwater agency made comments that I have to separate the ponds and model the inlet that is in the equalizing pipe run. In my opinion, what I originally modeled is the appropriate model as the downstream pond will push water upstream before it crests the outfall weirs, and the leveling pipe is adequately sized to accommodate that. They both insisted it needed to be separated without providing any technical reason for it. I indicated that I doubted it can be done without significant oscillations, but said I would take a look.
When the ponds are separated, dynamic routing produces significant warning 80 (downstream pond exceeds upstream) and some oscillation warnings. This does not surprise me because the downstream pond's DA is much larger than the upstream pond's DA. If I change it to sim routing and adjust the DT, the oscillation severity is significant, even at the smallest time step. I do not think is possible to model it appropriately without combining the ponds into a single node. Connecting to the other project only complicates it more as the oscillation warnings exist in the previously approved model.
Beyond the help menus, are there any additional guides or information from Hydrocad that would validate my original desire to keep the ponds as a single node? Or maybe a hydrocad recommended leveling pipe sizing method to further confirm my pipe size?