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One further note - in reviewing the literature, it was noted that limestone is more susceptible to weathering than a silicified <br />sandstone. In a BUREC study it was found that limestone riprap had failed at a 10 percent higher rate than sandstone <br />used in similar circumstances for bank protection. <br />With the PAP 790 formula available for sizing the riprap and the inclusion in the formula of the specific gravity of the stone <br />being used, the magnitude of the safety factor will probably be reduced. Further thought will be taken on that matter. <br />Item four - as noted in the response to the comments on the first submittal for the JBird technical revision the potential <br />discharge through the 100 year spillways will occur after the flow has peaked. This raises a question on DRMS's criteria <br />for for containment design - <br />Is it the Division's intent that the ponds be designed to hold a 10 year event and then be capable of passing through a <br />second event of up to 100 year flow? <br />This has some impact on how soon the pond will need to be dewatered after being filled It would also impact the spillway <br />design if it only needs to be designed for the calculated flow occurring after the pond has filled to it's 10 year design <br />capacity. <br />Not a major item of concern, more a matter of curiosity. <br />Again if you could clarify the Division's position on these items prior to the resubmittal of the JBird or Prince Albert <br />drainage plans it could help avoid additional resubmittals. <br />Thank you for your consideration. <br />Sincerely - <br />James Pierce, Jr. <br />P.S. I am also sending screenshots of the abstract for the 'Sandstone Materials Used as Riprap' and the flow chart for the <br />limestone field test which I believe could be modified for use in evaluating sandstone. <br />4 <br />