TR-55 states that the composite CN value for disconnected impervious greater than 30% should be computed from Figure 2-3.
In the attached screen capture there is a 20ac site with 10ac unconnected pavement and 10ac pervious. HydroCAD is taking the weighted average to compute a composite CN of 69...
I wanted to check in with the experts on the current state of static GPS equipment and technology. Is it possible to achieve standard deviation errors of position at 0.254mm horizontal and vertical accuracy for structural deformation monitoring with any of today's equipment? How about 1mm?
If...
I would like to take a poll of geotechs, and if there are any experienced earthwork contractors out there, of how they have arrived at computing successful Fill factors for earthwork hauling.
In other words, how much Fill material does it take to fill a 1 cubic yard hole?
Three scenarios:
1)...
I am using the Weighted Q method and I am getting confusing output that states the entire site is 100% pervious.
Please see the attached file.http://files.engineering.com/getfile.aspx?folder=5d5bed87-247a-45b5-bf0e-59db12b52c59&file=Capture.JPG
Our soils report recommends at least 10% for 10 feet perpendicular to the foundation walls. If compaction was done to at least 90% ASTM D 698, how much tolerance in grade differential from 10% is the standard of care when examining these grades 7 years after construction?
Potential movement of...
Does HydroCAD have capability to internally route impervious area over pervious area (i.e, two-step technique) for subcatchments with greater than 30% total imperviousness?
thread162-321762
I second the HEC 15 motion.
Put the rock on a granular bedding, not filter fabric, it's too slippery and make a mess.
If you give me your channel dimensions, channel slope and flowrate, I can check rock size for you with HEC 15.
thread162-321197
"As indicated by psmart, the Tc is very small (less than 5 minutes). Thoughb the municipality expressed that it would be up to the engineer to choose a rainfall duration for design. I guess I should choose a standard duration but I do not know what that standard would be."
The...
thread162-302813
Typically when you are this close to the major drainageway there is a no-detention waiver. Because they want your stuff way down the road before the big peak comes. If you have a full detention pond sitting there when the river peak comes, you're just a liability to everyone.
thread162-316422
Tailwater condition man for that type of flatness! What are you using for a TW condition for HY8? How does it (can it) compare to HEC-RAS?
thread162-315874
This is simple, and you will want to know this to avoid possible litigation down the road. That's what really matters, right? You can not adversely impact the historical discharge point, or adversely affect the capacity down stream of the historical discharge point. So you will...
thread162-244410
StormCAD does not use hydrographs. It is a peak flow analysis model using standard step methodology for HGL/EGL. It is possible to get less flow downstream due to the longer "system" Tc's.
I work in a region where the storm sewer pipe system is initially sized for the Minor Storm event (2yr or 5yr depending on municipality). In the Major Storm event (100yr here) streets are allowed to have a depth above the gutter flowline of 12" in order to convey the major event as an open...
