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Home My WebLink AboutHARMONY CROSSING PUD - Filed SER-SUBSURFACE EXPLORATION REPORT - (2)02/26/96 12:17 FAX 9702244564 EEC Q 002 December 30, 1993 Richland Homes, Inc. 8791 Wolff Court, Suite 200 Westminster, Colorado 80030 Attn: Mr. Jerry Rolhfs Re: Subsurface Exploration Report Addendum Number one -Pavements Proposed Harmony Crossing P.U.D. Fort Collins, Colorado EEC Project No. 1932048 Mr. Rolhfs: Our subsurface exploration report for the referenced project was provided to your attention on December 1, 1993. In that report, we provided preliminary estimates for pavement sections based on an assumed R-value for subgrade soils and assumed traff is loading information. The assumed information was not available at the time of our December 1, report. The purpose of this addendum is to present the results of the laboratory R-value testing and provide final pavement section recommendations based on those test results and projected traffic loadings provided by the City of Fort Collin's Engineering Department. Hveem stabilomete.r R-values of 9 and 151were determined in laboratory testing of two samples of near surface subgrade materials obtained from the project site. Results of the R--value testing along with corresponding index testing of the soil samples are shown an Table I below. The Hveem stabilometer R-value of 9 would correspond to a resilient modular value of 5995 using the American Association of Highway and Transportation Officials AASHTO) standard correlation. That Resilient Modulus value was used for design of the pavement sections. 02/26/96 12:17 FAX 9702244564 EEC I1003 e FUF%b ER&*eFing wmuh=u, Ina Harmony Crossing Addenduz #1 December 30, 1993 Page 2 TABLE I: LABORATORY TEST RESULTS - COMPOSITE SAMPLES ATTERBERG LIMITS MATERIAL 200 R-VALUE LL PL PI Silty Lean Clay 39 22 17 61.3 9 Light Brown Silty Lean 30 18 12 46.8 15 Clay/Clayey Sand Reddish Brown Estimates for the twenty year average equivalent daily load axles EDLA) were provided by the City of Fort Collins Engineering Department. Those values are shown below in Table II. The 1986 AASHTO "Guide for Design of Pavement Structures" was used to help evaluate alternative pavement sections for this project. Design parameters used in that evaluation are also shown in Table II. TABLE II: ESTIMATED TRAFFIC AND DESIGN PARAMETERS Roadway classification EpLA Reliability P$I Design 20 yr.-ELA) Loss WSW North Collector 15 85 2.0 2.48 Entrance 109,500) South Collector 0 85 2.0 2.59 Entrance 146,000) To West End of street) Interior Local 15 70 2.5 1.88 streets 36;500) Alternative pavement recommendat'ons based on the outlined analysis are shown in Table III. Other s etions could be considered and we would be pleased to evaluate other alternatives at your request. 02/26/96 12:17 FAX 9702244564 EEC 11 004 Mirth JCnU mxring consmit.nta, Inc. Harmony Crossing Addendum i1 December 30, 1993 Page 3 TA13LE III: RECOMMENDED PAVEMENT SECTIONS Pavement North Entrance sSauth Entrance Local Streets Alternatives A) COMPOSITE HBP 4" tI4" 3" Aggregate Base 711 8" 5" B) COMPOSITE/STABILIZED HBP 3" 3" 311 Aggregate Base Of 4" 411 Stabilized 12" 12" 81' Subgrade Asphaltic concrete (HBP) for use in the pavements should be compatible with the City of Fort Collins standard specifications for SCl or SC2 blends. Aggregate base should be compatible with Colorado Department of Transportation (CDOT) requirements for Class 5 or Class 6 base. Those materials should be placed and compacted as outlined in our December, 1 subsurface exploration report for this project. Concerning stabilization of the pavement subgrades, we estimate 12 to 14 percent Class C Fly Ash would be required to develop the strengths necessary to utilize a fly ash stabilized subgrade as part of the pavement structure. The quantity of fly ash is based on dry weight of subgrade soils and the Class C Fly Ash. Additional laboratory testings will be required to confirm the quantities estimated. Based on previous work in this general area, it is our opinion that stabilization of the silty clay subgrade soils wo ld be effective in developing a stable subgrade for placement of the overlying 02/26/96 12:17 FAX 9702244564 EEC r` I1005 I%b E eM=ring WMUI .nia.Inc- Harmony Crossing Addendum ii December 30, 1993 Page 4 pavement structure. We recommend the stabilization, if used, extend beneath the site curb and gutter. We would be pleased to provide additional information concerning stabilization of the subgrades, if desired. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the enclosed report, or if we can be of further service to you in any other way, please do not hesitate to contact us. i very truly yours, Earth =gincering Consultants, Inc. Lester L. Litton, P.E. Principal Engineer cc: RBD Curtiss L_ Palin, P-E. i Principal Engineer