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  1. DMcGrath

    Chicago Stormwater Challenge

    Crowdsourcing = "we want you to work for free". This "development method" is already gaining traction in advertising and IT development, please don't let this happen to engineering.
  2. DMcGrath

    Water tight pipe joints for significant hazard dam

    You might also check with the concrete pipe supplier for a recommendation. We had a similar joint alignment issue in a small dam and the supplier recommended ConSeal CS-212 Joint Wrap (www.conseal.com) to provide the watertightness, then cover with grout to secure and protect the joint.
  3. DMcGrath

    No-Rise Certification Question

    Not that is much consolation, Builder, but the owner of that dam has been through this no-rise ordinance with the county recently for a simple structure downstream. I was not the (lucky?) consultant, but I have heard the stories about the process! Yuck! Unfortunately I don't know what the...
  4. DMcGrath

    Head over a double sided weir formula?

    Perhaps you have a labyrinth weir? Google will kick out a significant amount of info on these.
  5. DMcGrath

    Half-Moon Baffle in culvert calculation

    I have a 48" culvert with a steel plate installed in the lower half that blocks flow until the water level is at least two feet deep before it would overflow this plate and enter the culvert. How would I go about calculating a rating table for this culvert? I don't see an option for anything...
  6. DMcGrath

    Upstream Boundary Conditions for Dam Break Analysis in HEC-RAS

    You might try adding some flow data prior to your breach event, say 50 to 200 cfs for a couple of minutes to give the model something to chew on while it starts. HEC-RAS does not like large, abrupt changes in flow, nor does it like to run dry (e.g. no inflow hydrograph. Considering the...
  7. DMcGrath

    CN Adjustment for Infiltration

    Virginia is starting to implement a "Runoff Reduction Method" that accounts for temporary storage on site to reduce the overall amount leaving the site. Effectively you calculate the volume of storage as an initial abstraction (S), then back into a revised CN. psmart notes this method above...
  8. DMcGrath

    Culvert Rehabilitation

    ISCO has a snap-fit PE-sliplining system that is pretty easy to install. http://www.isco-pipe.com/reference_center/pipe_installation.asp
  9. DMcGrath

    Pavement design using roller-compacted concrete

    fattad, Any chance when the project goes to construction you could give us a heads up? I believe you and I are in the same vicinity, and if the project is nearby I would like to see the RCC placement process if possible. Dan
  10. DMcGrath

    HEC RAS Dam Break Analysis

    Been there, done that...After a while you get used to seeing the red status line appear during the run. Four things I have done that seem to help at times: 1. For your hydrograph, select the check box for "time step adjustment options" and put in a reasonable flow change in the box, say 10 or...
  11. DMcGrath

    Effect of sulfur on concrete

    The Virginia DOT has a research program dedicated to high-sulfur soils - concrete degredation is part of the problem. This presentation has a couple of good examples of concrete attacked by high-sulfur soils...
  12. DMcGrath

    Coffer Dam Design / Sheet Pile Design Resources

    There are other options besides sheet piling. One may be a portable coffer dam (http://www.portadam.com). I haven't seen it in practice myself, but the concept looks good. A good resource book is "Handbook of Temporary Structures in Construction" by Robert T. Ratay.
  13. DMcGrath

    Passing of Vic Milligan

    Here's the story from Golder: http://www.golder.com/default.asp?PID=1257&VID=349&LID=26
  14. DMcGrath

    Vactor Waste Facility Design

    I would think that your mix of wastes would most closely resemble Municipal Solid Waste, since it could contain most anything. One caution would be to verify that it is not so contaminated (petroleum, lead, etc.) that it would classify as a hazardous waste. Your state environmental solid waste...
  15. DMcGrath

    Roof Infiltration Hydrology

    I would think that for a roof, volume of rain in = volume of stormwater out. Mine works that way most of the time! As psmart mentions, you could oversize it for the whole volume, but in reality that volume arrives over time, thus the need for hydrograph analysis. What might be more...
  16. DMcGrath

    SCS Storms

    The new Virginia Impounding Structure Regulations require analysis of the 6, 12 and 24-hour storm events, although there is no guidance on how. Wide open for a little "Voodoo Hydrology". (Stormwater Magazine) http://stormh2o.com/july-august-2006/urban-hydrology-methods.aspx
  17. DMcGrath

    Portable V notch weir

    No, you weren't dreaming...The approach section to a weir is very important for accurate water flow measuring. What you saw was a flume. Do a search for "H Flume" and you'll see all sorts of manufacturers. Make sure you select the appropriate flume (H, HS or HL) for your anticipated flow...
  18. DMcGrath

    Portable V notch weir

    The United States Bureau of Reclamation has a Water Measurement Manual that has all sorts of weir designs, installation, etc. http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/wmm.html
  19. DMcGrath

    How to insulate a shallow water line

    Insulation won't prevent freezing, only make the process take longer. Freezing would cause two issues: loss of supply and potential pipe rupture. Since this line cannot be allowed to freeze, I would think two agencies would need to weigh in on the line depth issue: the local fire code...
  20. DMcGrath

    Free contour maps

    I found this site to be very handy - the most USGS maps I have ever seen in one place on-line. Full TIFF images of Quad sheets. http://libremap.org/data/

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