Subject Approval of Keystone's KeySystem I Retaining Wall System by gcw21244


									                                     STATE OF NORTH CAROLINA
                           DEPAR1MENT OF TRANSPORTAllON
MICHAEL F. EASLEY                                                                     L YNOO TIPPElT
     GoVERNOR                                                                              SECRETARY

 October26, 2007

 Mr. Scott Vollmer
 Keystone Retaining Wall Systems, Inc.
 7312 Still Pond Court
 Raleigh, NC 27613

 Subject: Approval of Keystone's KeySystem I Retaining Wall System

 DearMr. Vollmer:

 The Geotechnical Engineering Unit (GEU) has fully approved Keystone's KeySystem I
 Retaining Wall System for use on North Carolina Department of Transportation (NCDOT)
 projects in accordancewith the "NCDOT Policy for Mechanically Stabilized Earth Retaining
 Walls". The policy includes restrictions for MSE wall systems with segmental retaining wall
 (SRW) units and may be obtained from:
  ht.m:/ /www .ncdot.orP.! doh/ureconstruct/hilrhwav/     geotech/msewalls/

  Keystonecalculatedmaximumreinforcement   loadsin accordance with theAASHTOStandard
  Specification HighwayBridgesusingthe Simplified Coherent                     in
                                                              Gravity approach the
  Evaluation oftheKeySystem RetainingWall by the HighwayInnovativeTechnologyEvaluation
  Center(HITEC). Keystonealsosubmittedcalculations  usingthe Meyerhof CoherentGravity
  approach determinemaximumreinforcement                            and
                                             loadsfor the surcharge backslope     design
  examplesin the HITEC report. Basedon thesecalculationsand in accordance with NCDOT's
  Standard MechanicallyStabilizedEarthRetainingWalls SpecialProvision,the coherentgravity
  methodis acceptable analysis.The provisionmaybe obtainedfrom:

  AASHTO Standard Specificationsfor Highway Bridges reduces the allowable tensile stress for
  grid reinforcing members connected to a rigid facing element to O.48F However, Keystone has
  submitted justification for not applying this reduction to the KeySystem I Retaining Wall System.
  Keystone's KeySystem I Retaining Wall System will be allowed a design exception to AASHTO
  to use an allowable tensile stress for reinforcements, in the wall backfill away from the wall face
  connections, ofo.55Fy'

          MAILING ADDRESS:                   TELEPHONE: 919-250-4088                LOCATION:
     NC DEPARTMENT TRANSPORTATION               Fax: 919-250-4237             CENTURY CENTER COMPLEX
      GEOTECHNICALENGINEERING UNIT                                                 ENTRANCE B-2
         1589 MAIL SERVICE CENTER         Website:          1020 BIRCH RIDGE DRIVE
          RALEIGH NC 27699-1589                                                  RALEIGH NC 27610
October26, 2007
Mr. ScottVollmer

Keystonefiberglass                                          component accordance
                  pins arerequiredanddefinedasa miscellaneous       in
with the standardMSE RetainingWalls provision.

If you have any questions, I can be reached at (919) 250-4088.


 111,Jk- .,(;{l.a..:"","A"{'~~-
NjorogeW. Wainaina

cc:     K. J. Kim, Ph.D.,P.E., EasternRegionalGeotechnicalManager(wI HITEC report,details
            and calculations)
        JohnPilipchuk, L.G., P.E., WesternRegionalGeotechnical  Manager(wI HITEC report,
            detailsand calculations)
        Don Moore, L.G., GeotechnicalContract Administrator (wI HITEC report, details and
        GregPerfetti,P.E., StateBridge DesignEngineer
        DaveHenderson, .E., StateHydraulicsEngineer
        Cecil Jones, .E., StateMaterialsEngineer
        RodgerRochelle,P.E., StateAlternative Delivery Engineer
        TommyCozart,P.E., SpecialDesignEngineeringSupervisor
        RandyGarris,P.E., StateContractOfficer
        Mike Robinson,P.E., StateBridge Construction Engineer
        Bridge Maintenance  Unit

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