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<br />6.2A <br />Page 26 <br /> <br />. Mitigation Measure CR-lg: Distribute archaeological-resource '~ALERT" sheet to <br />contractors; suspend soil-disturbing activities, as necessary; submit a F ARR. <br /> <br />Impact CR -2: Impacts on adobe wall and contributors to the BDPL Nos. 1 and 2 Historic <br />District, respectively, that are NRHP-and CRHR-eligible. <br /> <br />Construction-related activities, such as vibration and trenching, can cause structural damage such <br />as loosening of paint or mortar, cracking of mortar or plaster, weakening of structural elements, <br />or crumbling masonry. Most equipment that would be used to construct the Project would not <br />produce vibration levels exceeding the damage thresholds. However, extremely fragile structures <br />close to the proposed Project alignment could result in significant structural impacts. For <br />example, the adobe wall at Flood County Park is within 30 feet of the centerline of the proposed <br />pipeline. In addition, heavy equipment (e.g., backhoes, bulldozers, etc) would be used within 10 <br />to 12 feet of the Redwood City Valve House and the Driscoll Road Flow-Metering Vault. This <br />equipment has the potential to exceed the maximum PPV criterion, potentially resulting in minor <br />structural damage, such as cracking of paint (architectural) or hairline masonry (structural) <br />cracks. In addition~ the use of sheet piling within 30 feet of the Driscoll Road Flow-Metering <br />Vault would likely exceed maximum PPV criterion, potentially resulting in minor stmctural <br />damage, such as cracking of paint (architectural) or hairline masonry (structural) cracks. <br /> <br />. Mitigation Measure CR-2a: Prepare a Historical Resources Plan <br />. Mitigation Measure CR-2b: Prepare and inlplement a strategy to minimize vibration <br />impacts <br />. Mitigation Measure CR-2c: Consult with a California licensed geotechnical engineer to <br />develop procedures to minimize vibration and other construction inlpacts on the adobe <br />wall at Flood County Park (HR-6); pre-construction survey <br />. Mitigation Measure CR-2d: Coordinate with the Historic Structures Monitor; use of low- <br />vibration equipment (or speeds); use appropriate trench shoring; monitor trenching and <br />shoring <br />. Mitigation Measure CR-2e: Monitor construction vibration; conduct a pre-construction <br />condition structural assessment; coordinate with the onsite San Mateo County <br />representative~ adjust site work as necessary; arrange for additional shoring or vibration- <br />arresting methods <br />. Mitigation Measure CR-2f Repair buildings or structures, as necessary <br />. Mitigation Measure CR-2g: Prepare materials describing and depicting proposed repairs <br />to any historical resources damaged by the Project; pursue and implement redesign of the <br />proposed repairs, as necessary <br /> <br />Impact CR-3: Impacts on historical resources that are NRHP- and CRHR-eligible. <br /> <br />During valve-lot construction, the SFPUC proposes to dri112-inch holes into the Redwood City <br />Valve House and Driscoll Road Flow-Metering Vault for utility conduits. Because these <br /> <br />....:u..u:.:.:.~~11~~dniliri~<>.g~:~d;~~ijffl~il~~~~~1~Jacis4.tt~~ih~iaP~in~~Jl~t~~~kfu~:~tri1%fu:~fr.~~... <br /> <br />damage. <br /> <br />. Mitigation Measure CR-3: Measures to reduce tangential cracking in masonry during <br />drilling; repair damage to control buildings <br /> <br />Impact CR-4: Impacts resulting in the deterioration of this NRHP- and CRHR-eligible <br />resource from decommissioning in place of the bay-crossing components of BDPL Nos. 1 <br />and 2. <br /> <br />16 <br />