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Hydrology / Water Quality (Continued)
<br />c -f) Construction activities associated with the proposed project would generally alter existing drainage patterns in a manner
<br />that could result in erosion or siltation as surfaces are exposed to wind and rain during the construction -pb ase of the
<br />project. After project implementation, on-site drainage patterns will be altered, as underutilized (Site 1) and vacant
<br />(Site 2) property as impervious surfaces are increased with project implementation. However, the proposed project is
<br />not anticipated to result in a substantial alteration of existing drainage patterns that could cause substantial erosion or
<br />siltation. The City' s on-going participation in the Alameda Countywide Clean Water Program and requirement that a
<br />SWPPP be implemented would minimize erosion and siltation on -and off-site.
<br />Mitigation Measure 47: The applicant will comply with applicable waste discharge requirements and municipal
<br />code requirements including preparation of a SWPPP for construction activities and compliance with the Alameda
<br />Countywide Clean Water Program (ACCWP). These permit programs are designed to prevent violation of water
<br />quality standards through mitigation and control of pollutant transport in stormwater runoff and infiltrating
<br />waters. The City of San Leandro Municipal Code ensures that permit conditions are met.
<br />Mitigation Measure #8: The applicant will submit, along with their building permit application, a Stormwater
<br />)Facility Operation and Maintenance Plan that includes a detailed maintenance schedule and maintenance
<br />requirements to ensure compliance with Best Management Practices, as well as the other requirements set forth in
<br />the Stormwater Control Plan prepared by Lea & Braze Engineering (September 25, 2008).
<br />g -i) The project site is not located within a FEMA defined 100 -year flood hazard area. Therefore, there would be no
<br />impacts of or to the 100 -year floodplain.
<br />The project site is located within the dam failure inundation zone for both the Lake Chabot and New Upper San Leandro
<br />Reservoir dams. The proposed project includes development of 200 multi -family residential units and a 329 to 345 -space
<br />BART parking garage within this dam failure inundation zone. This would expose more people to risks associated with
<br />darn failure inundation, which is a potentially significant impact.
<br />The EBMUD East Bay terminal reservoirs, such as Lake Chabot and the New Upper San Leandro Reservoir, function as
<br />secondary water sources that store runoff from local watersheds for system use. Lake Chabot, an earthen dam, is about
<br />130 years old and holds more than 3 billion gallons of water_ The Upper San Leandro Reservoir was built in 1977 and
<br />holds more than 13 billion gallons. Requirements for earthquake and flood safety for the East Bay dams are imposed by
<br />the State of California Division of Safety of Dams (DSOD), which routinely inspects dams statewide. DSOD requires
<br />that embankments under its jurisdiction are safe to withstand the maximum credible earthquake without an uncontrolled
<br />release of reservoir water_ In 2003, DSOD requested that EBMUD perform a stability evaluation of the Chabot dam.
<br />Studies are still in progress (EBMUD 2005). However, studies conducted by EBMUD have identified the time it would
<br />take for water to reach certain regions (Beaver, 2005).
<br />Mitigation Measure #9: To reduce imperviousness, the applicant shall minimize use of concrete walks and
<br />hardscape areas. Planters and landscape areas shall be maximized and bioswales, paver blocks, decomposed
<br />granite and other alternate a pavement materials will be utilized to promote groundwater recharge.
<br />Mitigation Measure ##10: The applicant shall enter into a Maintenance Agreement stating the parties responsible
<br />for and upkeep of the bioswales required with project implementation.
<br />Mitigation Measure #11: Applicant shall be required to demonstrate adequacy of the existing storm drain system
<br />to handle existing run-off from the drainage basin and project, upgrade the storm drain system to handle existing
<br />run-off from the drainage basin and project, or meter run-off from the site so that it leaves the site at current rate.
<br />If the Upper San Leandro Reservoir were breached, much of its contents would surge into Lake Chabot, overflowing it
<br />and flooding highly populated areas downstream in a matter of minutes. At 40 mph, it would take just 13.1 minutes to get
<br />from Chabot to Estudillo Avenue near Bancroft Avenue. About five minutes later, the water there would peak at a height
<br />of 22 feet. Further west, at the intersection of Davis and Alvarado streets, the water would peak at 15 feet. The City of San
<br />Cornerstone at San Leandro Crossings Initial Study 9 March 2009
<br />POTENTIALLY
<br />ISSUES
<br />POTENTIALLY
<br />SIGNIFICANT
<br />LESS THAN
<br />No
<br />SIGNIFICANT
<br />UNLESS
<br />SIGNIFICANT
<br />IMPACT
<br />SOURCES
<br />ISSUES
<br />MITIGATION
<br />IMPACT
<br />INCORPORATED
<br />Hydrology / Water Quality (Continued)
<br />c -f) Construction activities associated with the proposed project would generally alter existing drainage patterns in a manner
<br />that could result in erosion or siltation as surfaces are exposed to wind and rain during the construction -pb ase of the
<br />project. After project implementation, on-site drainage patterns will be altered, as underutilized (Site 1) and vacant
<br />(Site 2) property as impervious surfaces are increased with project implementation. However, the proposed project is
<br />not anticipated to result in a substantial alteration of existing drainage patterns that could cause substantial erosion or
<br />siltation. The City' s on-going participation in the Alameda Countywide Clean Water Program and requirement that a
<br />SWPPP be implemented would minimize erosion and siltation on -and off-site.
<br />Mitigation Measure 47: The applicant will comply with applicable waste discharge requirements and municipal
<br />code requirements including preparation of a SWPPP for construction activities and compliance with the Alameda
<br />Countywide Clean Water Program (ACCWP). These permit programs are designed to prevent violation of water
<br />quality standards through mitigation and control of pollutant transport in stormwater runoff and infiltrating
<br />waters. The City of San Leandro Municipal Code ensures that permit conditions are met.
<br />Mitigation Measure #8: The applicant will submit, along with their building permit application, a Stormwater
<br />)Facility Operation and Maintenance Plan that includes a detailed maintenance schedule and maintenance
<br />requirements to ensure compliance with Best Management Practices, as well as the other requirements set forth in
<br />the Stormwater Control Plan prepared by Lea & Braze Engineering (September 25, 2008).
<br />g -i) The project site is not located within a FEMA defined 100 -year flood hazard area. Therefore, there would be no
<br />impacts of or to the 100 -year floodplain.
<br />The project site is located within the dam failure inundation zone for both the Lake Chabot and New Upper San Leandro
<br />Reservoir dams. The proposed project includes development of 200 multi -family residential units and a 329 to 345 -space
<br />BART parking garage within this dam failure inundation zone. This would expose more people to risks associated with
<br />darn failure inundation, which is a potentially significant impact.
<br />The EBMUD East Bay terminal reservoirs, such as Lake Chabot and the New Upper San Leandro Reservoir, function as
<br />secondary water sources that store runoff from local watersheds for system use. Lake Chabot, an earthen dam, is about
<br />130 years old and holds more than 3 billion gallons of water_ The Upper San Leandro Reservoir was built in 1977 and
<br />holds more than 13 billion gallons. Requirements for earthquake and flood safety for the East Bay dams are imposed by
<br />the State of California Division of Safety of Dams (DSOD), which routinely inspects dams statewide. DSOD requires
<br />that embankments under its jurisdiction are safe to withstand the maximum credible earthquake without an uncontrolled
<br />release of reservoir water_ In 2003, DSOD requested that EBMUD perform a stability evaluation of the Chabot dam.
<br />Studies are still in progress (EBMUD 2005). However, studies conducted by EBMUD have identified the time it would
<br />take for water to reach certain regions (Beaver, 2005).
<br />Mitigation Measure #9: To reduce imperviousness, the applicant shall minimize use of concrete walks and
<br />hardscape areas. Planters and landscape areas shall be maximized and bioswales, paver blocks, decomposed
<br />granite and other alternate a pavement materials will be utilized to promote groundwater recharge.
<br />Mitigation Measure ##10: The applicant shall enter into a Maintenance Agreement stating the parties responsible
<br />for and upkeep of the bioswales required with project implementation.
<br />Mitigation Measure #11: Applicant shall be required to demonstrate adequacy of the existing storm drain system
<br />to handle existing run-off from the drainage basin and project, upgrade the storm drain system to handle existing
<br />run-off from the drainage basin and project, or meter run-off from the site so that it leaves the site at current rate.
<br />If the Upper San Leandro Reservoir were breached, much of its contents would surge into Lake Chabot, overflowing it
<br />and flooding highly populated areas downstream in a matter of minutes. At 40 mph, it would take just 13.1 minutes to get
<br />from Chabot to Estudillo Avenue near Bancroft Avenue. About five minutes later, the water there would peak at a height
<br />of 22 feet. Further west, at the intersection of Davis and Alvarado streets, the water would peak at 15 feet. The City of San
<br />Cornerstone at San Leandro Crossings Initial Study 9 March 2009
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