We are proposing to use concrete box culverts for inline detention beneath the streets. Does anyone know of a product or method of closing off/sealing the upstream ends of the boxes? I found a company in Canada that manufactures plugs, but they only deal in metric sizes. I've been unable to get...
Thanks for all the comments folks. We ran the model using SCS hydrograph data and submitted it. We were then told that we needed to use a Clark's Unit Hydrograph to generate the input data. At least now I have some direction. Now I get to figure out how to do that.
Thanks guys. I see my next step is to sit down with Public Works and see if the actually do have criteria regarding the rainfall distribution. Since they have not been using SWMM in the past it might be something they haven't considered.
I've been given an assignment to model 2- and 100-year storms for a 70-acre site using EPASWMM. Previously, the local jurisdiction wasn't particular about what software was used on a project, but for some reason they are requiring SWMMM for this one. We have the appropriate IDF curves and...
Simple question: Are wye fittings ever used on water mains? I'm used to seeing tees where a water line connects with another one, but I have a set of drawings in front of me on which the engineer is showing a lot of, what I consider unnecessary, wyes. The water mains are primarily 8" and 12".
Generally, at least down here, the City or local governing agency owns and maintains water, sanitary, and storm sewers in the public right-of-way or dedicated easements. Design is governed by their criteria.
On private property those utilities are owned and maintained by the property owner...
Construction joints and contraction joints are definitely not the same thing. Construction joints are placed at starting and stopping points where the concrete pour is interrupted for some reason (e.g., end of shift, equipment breakdown, etc). They are are formed using a bulkhead made of steel...
Richard: The design called for three parallel barrels of 30" HDPE pipe in a common trench, spaced 55" center to center. The contractor instead dug three separate trenches that appear to be spaced almost ten feet C-C. He claims that he provided six inches between the pipe and the trench wall, but...
We designed an underground detention system using 30" HDPE pipe. According to our details and ASTM 2321 the trench is supposed to have a minimum clearance between the pipe and the trench wall of 10", backfilled with compacted Class I or II material. The contractor instead set the pipe in a...
Some municipalities allow you to use the parking lot for detention. Down here you can include up to nine inches above your inlet grate as part of your detention storage.
In Houston/Harris County TX we (engineers) typically prepare SWPPP plans and include them in the plan sets issued for permit and construction. The contractor is responsible for obtaining the permits. Either the contractor or owner submits the NOI and NOT.
I believe, for permitting purposes, all...
When I was in college somebody decided that the engineering curriculums were too technical. In Civil Engineering they added three additional semesters of English, two or three "cultural herritage" electives, and gave you a choice among many subjects that used to be mandatory. I am seeing the...
A parking lot we designed was recently completed. Visual inspection revealed areas with what appears to be fine, loose asphalt on the surface. Core density reports done on the pavement showed compaction below what was specified in 14 of 16 samples. Twelve of the samples show a core depth more...
In many cases there is no information on the hydraulics of the system you are tying into, other than the sizes and slopes of the pipes. Rather than require one to model the receiving storm sewer all the way from its outfall, which might be several miles away, the procedure I mentioned is my...
The City's new guidelines state that on roadway projects the starting tailwater elevation for extreme event analysis should be the 10-year water surface elevation at the outfall. If the project location is a considerable distance from the outfall channel, the 10-year WSE can be assumed to be 48%...
The City has a set of IDF curves covering rainfall frequencies from two years through 100 years. However, the LEED SS6.1 template asks for 1- and 2-year runoff amounts.
Is there a way to generate b, d, and e coefficients for a 1-year frequency if 2-, 3-, 5, 10, 25, and 100-year coefficients are...
Thanks cvg. This is the equation I have been using for a long time, but was recently told by people smarter than me that I should be using something different.
Thanks also amb2002. I compared the two equations, and the results were almost identical.
