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SUPPLEMENTAL AGREEMENT NUMBER 3 to <br />CONSULTANT AGREEMENT NUMBER 15-054 <br />This SUPPLEMENTAL AGREEMENT is entered into between the City of Tukwila, <br />Washington, herein after referred to as "the City" and KPFF Consulting Engineers <br />hereinafter referred to as "the Consultant", in consideration of to the mutual benefits, <br />terms, and conditions hereinafter specified. <br />The City desires to supplement the agreement entered into with the Consultant and <br />executed on, March 18th, 2015 and identified as Agreement No. 15-064. All provisions in <br />the basic agreement remain in effect except as expressly modified by this supplement. <br />The changes to the agreement are described as follows: <br />Cathodic Protection Background <br />The purpose of this supplement is to prepare cathodic protection system design and <br />specifications to the bid package for cathodic protection for the steel sleeve that carries the <br />sewer force main under the BNSF rail tracks and extend the time for the consultant to <br />complete the design package. <br />SCOPE: ON SITE TESTING <br />The testing will involve collecting in-situ soil resistivity at various depths at accessible <br />locations to determine the electrically conductive of the soil. <br />1. Conduct on-site soils testing at locations of the casing crossing. Measure soil <br />resistance at depths of 2.5, 5.0, 7.5, 10, and 15 -foot depths. This testing will involve <br />passing a known current through appropriately installed soil pins and calculating <br />resistance based upon voltage levels. This testing will not require excavation. <br />2. Collect two soil samples for laboratory analysis. The analysis will determine soil pH, <br />chloride, and sulfate levels in order to classify corrosive characteristics. <br />3. Provide a report detailing the results of the testing along with recommendations for <br />corrosion control strategies should the soil prove to be corrosive to steel materials. <br />BUDGET/SCHEDULE <br />The field testing with laboratory analysis results will be within ten days after soil collection. <br />The cost for completing these tasks will be $2,130.23. <br />SCOPE: COATINGS AND CATHODIC PROTECTION DESIGN <br />Based upon the results of the soil corrosivity analysis, provide a protective coating <br />specification for the external surfaces of the sewer casing. <br />Page 1 of 2 <br />15 <br />