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<br />-2- <br />I agree with Ground Engineering Consultant, Inc.'s observation. Size and <br />gradation specifications are usually stated as a range of constituency. It <br />would be unrealistic to expect a riprap sample to precisely match a given set <br />of gradation specifications. Apparently someone in charge provided an amended <br />specification table to the consultant. However, the Division was not informed <br />of this analytic exercise and it is not documented within the approved permit. <br />On November 1, 1988, Conrad Parrish, P,E., Colorado Registry No. 17937., <br />practicing with AC Z, lnc., prepared a letter certifying that "these drainages <br />have been constructed according to the design drawings and specifications <br />prepared by Water Engineering Technology". <br />Your letter of December 27, 1988, requested additional information in an <br />attempt to clarify the apparent incongruency. Mr. Parrish certified that <br />everything was in compliance with the approved design. However, the <br />documentation submitted by the applicant reports that the riprap gradation, <br />sizing and shape did not always comply with the unusually stated <br />specifications for gradation and sizing. In my opinion, your request was <br />appropriate, but your request may not have been sufficiently specific. The <br />company, in turn, responded, but didn't specifically address your actual <br />concern. <br />I suggest that the problem can be resolved by clarifying your specific <br />concern. As I understand it, you desire more information in support of <br />Mr. Parrish's opinion expressed in his November 1, 1988 certification letter. <br />Specifically, you desire additional information with which to resolve the <br />apparent inconsistency between the reports' as-built riprap gradation, sizing <br />and shape characteristics and the specified riprap gradation, sizing and shape <br />requirements. The reported results, including areas 41 and 51, are not far <br />from the specified distributions. Normally, ranges of constituency are <br />specified within the gradation distributions. The operator, or their <br />consultant, needs to specifically address what the appropriate specification <br />ranges are and include reference to the approved design documentation to <br />support their opinion. With this demonstration in hand, I believe your <br />problem can be resolved. <br />cc: Mike Savage <br />ern/4504f <br />