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2012-08-01_HYDROLOGY - M2011028
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2012-08-01_HYDROLOGY - M2011028
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Last modified
8/24/2016 5:04:26 PM
Creation date
8/1/2012 4:05:33 PM
Metadata
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Template:
DRMS Permit Index
Permit No
M2011028
IBM Index Class Name
HYDROLOGY
Doc Date
8/1/2012
Doc Name
RIP RAP CHANNEL DESIGN COMMENTS
From
DRMS
To
RUSSELL ENGINEERING
Email Name
TC1
Media Type
D
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No
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/L1- 201(-- 02 S <br />Cazier, Tim <br />From: Cazier, Tim Cr%kl"O <br />Sent: Wednesday, August 01, 2012 10:51 AM <br />To: 'Steve Winters TasrE�{ <br />Cc: Pickford, Kate <br />Subject: RE: Animas Glacier Gravel Pit - riprap channel design comments <br />Attachments: M- 11- 28_BasinRiprap v4.pdf; M- 11- 28_RiprapCheck.pdf <br />Steve, <br />I've gone through your calcs and checked what I could (I could not check Cv, as I don't know the channel bend radius). <br />You appear to be on the right track, but there are some assumptions that need to be adjusted or revised: <br />1) 1 strongly recommend not using rounded riprap. Angular riprap is much more stable due to better interlocking. <br />2) Your flow depth & velocity appear to be based on a Manning's n of 0.02. This is too low for riprap. Riprap <br />channel designs need to be evaluated for both stability (i.e., velocity) and capacity. A range of Manning's n <br />between 0.035 and 0.040 is typically sufficient and good engineering practice. Flow depth is an important <br />parameter from a shear stress perspective. <br />3) Your selection of the variable Vss implies you intend to armor only the side slopes. The bottom of the channels <br />need to be armored as well. <br />4) Your K1 value uses an angle of repose of 40 degrees. I suspect that is not valid for rounded riprap, but I don't <br />have any definitive information there. Again, I strongly recommend angular riprap. <br />I've attached my comments for the first page and a summary calculation sheet with my results. Those may vary from <br />what you end up with depending on channel bend radius, angle of repose for the riprap and the velocity distribution <br />coefficient. <br />I am still reviewing the drainage report. <br />Please let me know if you have any questions. I'll be out of the office Thursday afternoon and Friday this week. <br />Tim Cazier, P.E. <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />ph: 303- 866 -3567 x8169 <br />fax: 303 -832 -8106 <br />tim.cazier@state.co.us <br />From: Steve Winters [mailto:stevew@russellpe.com] <br />Sent: Tuesday, July 31, 2012 11:16 AM <br />To: Cazier, Tim <br />Subject: RE: Animas Glacier Gravel Pit <br />Hey Tim, <br />Can you take a look at the rip rap calculations prior to me including them within the Drainage Study? I haven't used this <br />method before, and want to make sure that I'm not missing anything in the calculations or assumptions. Based on the <br />different flow rates and longitudinal slopes, I ran a few scenarios for the channels so we didn't end up significantly <br />oversizing large sections of the riprap. Also, since the undisturbed channel requirements are so small, we'll likely just go <br />with a D50 of 6" to keep it simple. <br />
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