AgdaPkt 2010-01-25 clsd and regular

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6.2A Page 39 Edgewood Road, a San Mateo County-designated scenic route. Trees within these areas of the proposed alignment may require removal as construction proceeds across or in the viewsheds of these three scenic routes. The exact number of trees requiring removal is not yet known, but could be approximately 20 trees in Fremont and approximately 30 trees along Edgewood Road, based on ground survey data presented on construction drawings and review of aerial photographs. The impact on local scenic routes would be significant because viewer exposure would be high from each of these routes and viewer sensitivity may also be high due to the number of trees that would be removed compared to the number of trees present. The SFPUC would replace the roadway, but not the affected trees, after construction is completed, which would result in significant aesthetic impacts on these scenic routes. . Mitigation Measure AES-l: Landscaping Plans. While this measure would somewhat reduce the overall effects on scenic resources in the Project area, aesthetic impacts on scenic resources from the removal of trees at Paseo Padre Parkway and Mission Boulevard in the City of Fremont and Edgewood Road in unincorporated San Mateo County would remain significant and unavoidable because the replacement trees would be planted outside the RIGHT OF WAY and may not contribute to the same scenic public setting as currently exists along these locally designated scenic routes. Impact CR-l b: Tunnel boring and shaft construction and disturbance of Holocene sediments could result in significant impacts on archaeological resource sites that are potentially NRHP- and CRH,R-eligible. The tunnel design requires that the tunnel be constructed within the San Antonio Formation, beneath the Young Bay Mud, due in part to physical characteristics of the sediments. The tunnel depth would range between 70 to 103 feet below mean sea level. The marine geotechnical testing (Bass 2006) established that Holocene-aged sediments could reach a depth of 80 feet below mean sea level and therefore a possibility exists tunnel construction could encounter prehistoric cultural deposit.s. However, given the depositional nature of both the Young Bay Mud and the San Antonio Fonnation discussed above, the potential for encountering significant archaeological resources during tunnel or shaft construction is low. Nevertheless, tunnel and shaft construction could result in significant impacts on archaeological resources. There is no feasible mitigation for impacts to potential archaeological deposits in Holocene sediments caused by tunnel shaft excavation and construction. The shaft construction method would preclude any archaeological monitoring or testing. Saturated soils within the shaft walls would be removed by a crane with a clam-shell bucket. These muddy soils would be loaded into a truck and hauled off site. Because of safety concerns, it would not be feasible for an archaeological monitor to inspect these soils prior to excavation. Observation of the excavated material after they are loaded in the truck would not yield useful infonnation because any arti~acts would be damaged and contextual information would be lost. , ".. '" ':':'IfupacfLU'1:' 'The "ProjecfwoUld'affect existing 'hilidus:e' cbaracter:byestabHshiiiga ".. .. ' construction site for four and half to five years at the Ravenswood Valve Lot, which is adjacent to residential land uses. The SFPUC has identified at least six locations where pipeline construction would be staged within the SFPUC RIGHT OF WAY. These include areas near the Irvington Tunnel Portal (0.7 acre), at the Ravenswood (13.9 acres) and Newark (2.6 acres) Valve Lots, and at open areas near the Pulgas Tunnel Portal (0.6 acre) and along Edgewood Road (1.2 acres). The largest construction storage and staging area within the SFPUC RIGHT OF WAY would be at the Ravenswood Valve Lot. The Ravenswood and Newark sites would be used for construction staging during the three- to four-year construction period as well as for tunnel maintenance and 29