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  1. pjhealy

    Snow Storage in parking lots (new england)

    My site plan has been critiqued by a peer review engineer who stated that my snow storage areas are inadequate. I commonly provide 2-3% of the paved area or increase the minimum parking requirements to provide an area of the lot that can be used to pile snow. Some winters like the last see...
  2. pjhealy

    reporting invert of a culvert with reverse slope

    I would like you to confirm that this is an error in reporting and not in the calculations (HydroCAD 8.50). I entered a culvert outlet with a reverse slope from a pond to reflect the possibility that runoff could potentially back up a catch basin to manhole pipe, if the head were high enough...
  3. pjhealy

    RCN for crushed glass?

    We have a client who wants to use crushed glass as fill. Does anyone have a recommendation for the RCN to use for this surface during construction? or perhaps the porosity of crushed glass? Why it is not being recyled is beyond me, but he has a consistent supply available, and it is a clean...
  4. pjhealy

    subsurface detention

    Peter, the flows would be very shallow (<0.1 ft) in most storms, so it would seem more trouble than it's worth to create custom outflow curves. With the 140'+ widths of the weirs that are shown in the model I posted, some very spiky flows occur. I just cut and pasted these particular ponds out...
  5. pjhealy

    subsurface detention

    gbam, you understand exactly what I am trying to model: subsurface berms to encourage infiltration of most storms, but modelling the lateral flow through the stone above the berms for larger runoff. At this point, I have a series of three subsurface berms, each modelled as a pond, with...
  6. pjhealy

    subsurface detention

    Thanks, gbam, I see how I could model a custom outlet using Darcy's to model flow laterally under the weirs, but I am looking to model it over the weirs. PJ
  7. pjhealy

    subsurface detention

    I would like to model subsurface detention basin (crushed stone layer) under a parking lot that is sloped. There are a number of inlets through pervious pavement into the layer, so I thinnk they should be multiple Ponds. I added low (6" high) dams below each inlet, so that the infiltration will...
  8. pjhealy

    Calculate Separate Pervious/Impervious setting

    BTW, I am using Hydrocad 8.50.
  9. pjhealy

    Calculate Separate Pervious/Impervious setting

    I am modelling a subcatchment where there is a parking lot and roadway adjacent to the collection point (catch basin), but a large wooded area, Hydrologic Group A soils, contributing flow to the same point. Using the default calculation setting, this option on the advanced tab being un-checked...
  10. pjhealy

    Hydrocad Settings?

    Wayno64 - this is a typical result for the situation you described. You can take area away and show a higher rate of flow because the CN is higher, and you can shorten the Tc and get a higher rate of flow. If both occur on the same subcatchment, it is a huge difference. I am working on a site...
  11. pjhealy

    Modeling Athletic Field / Synthetic Surface - Subdrain

    How to model an athletic (football/soccer) field with sub-drains, pre- and post-development conditions? The existing field is 8" loam/sand mix over 8" gravel base over 4" perforated PVC pipe sub-drains spaced 25' apart (slope=0.025) within gravel, running to 6" solid PVC collector pipes...
  12. pjhealy

    Best way to model an underdrain?

    Sure, you can do it easily. Observe the pond to see how long (time) the pool (known volume) takes to empty. If it's very slow, measure what you can: depth of drop x known surface area at the elevation/1 hour. Either way, you have volume/time=Q. Create a custom outlet or secondary outlet with...
  13. pjhealy

    What rainfall method to use with NRCC rainfall?

    NRCC = Northeast Regional Climate Center. It is apparently located at Cornell University. http://met-www.cit.cornell.edu/ I was reading from the proposed regulation when I posted my question: "Stormwater facilities shall be designed to handle the extreme precipitation as shown in...
  14. pjhealy

    What rainfall method to use with NRCC rainfall?

    A local town is proposing regulations that will require stornwater management facilities to be designed to handle the "extreme precipitation" shown in the "Atlas of Extreme Precipitation in the Northeastern United States" published by the Northeast Regional Climate Center (at Cornell). Since I...
  15. pjhealy

    Truck Dock - Dolly Pad Placement

    Can any of you folks tell me what the proper size and spacing of the truck dolly pad should be from the truck dock. I am working on a warehouse site plan in the northeast where trailers will be parked for periods of time, and the client wants concrete pads rather than asphalt. Thanks, PJ
  16. pjhealy

    The PMP - Tips on Modeling?

    Your approach needs to be modified slightly. Reviewing NOAA data for southern VT The PMP for a 24-hour duration is approx. 23 in, and the PMP for a 48-hour duration is approx. 26 in. In my 20-year experience, I have never heard of a reviewer asking for the detention basin being sized for this...

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