4.8 Hydrology and Water Quality

4.8 HYDROLOGY AND WATER QUALITY

This section discusses and analyzes the flooding, floodplain management, sea level rise, and water quality characteristics of the Planning Area. Sea level rise is more thoroughly discussed in Section 4.13, Energy and Climate Change. The information provided in this section is based on a number of sources, including the City of San Mateo’s Flood Management Strategies and the Storm Drain Master Plan.

4.8.1 EXISTING SETTING

SURFACE WATER

The City of San Mateo is located along the edge of the San Francisco Bay in San Mateo County and consists of approximately 15.7 square miles, which includes land area and portions of the San Francisco Bay and its associated tidelands and marshlands (3.2 square miles of bay water). The City of San Mateo has several forms of surface water sources including creeks, lagoons, tidal marsh, and bay waters. Discussion of these surface waters is included in Section 4.9, Biological Resources.

City of San Mateo Watersheds

San Mateo County encompasses four hydrologic basins and a total of 34 watersheds, all of which ultimately drain west to the Pacific Ocean or east to the San Francisco Bay. The City of San Mateo comprises four major drainage basins – the San Mateo Creek complex, the North San Mateo complex, the Marina Lagoon complex, and the 3rd and Detroit watershed, each composed of numerous stream channels, culverts, and storm drainage piping systems. The Marina Lagoon complex is further divided into four minor drainage basins; therefore, there are a total of seven major/minor drainages basins (both artificial and natural) within the City of San Mateo.

Figure 4.8-1 delineates the City’s seven watersheds, with the first three draining directly to San Francisco Bay, either by gravity or pumping, and the latter four draining to the Marina Lagoon, whose water is pumped into the Bay:

1. North Shoreview Pump Stations 2. San Mateo Creek 3. East 3rd Avenue and Detroit Drive Pump Station 4. 16th Avenue Drain 5. 19th Avenue Drain 6. Laurel Creek 7. Direct Drainage to Marina Lagoon

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FIGURE 4.8-1 CITY OF SAN MATEO WATERSHEDS

San Francisco Bay

The City of San Mateo is located along the western shoreline of San Francisco Bay. The entire San Francisco Bay comprises a group of interconnecting bays and rivers including the Sacramento River, San Joaquin River, and Napa River; the Suisun Bay, San Pablo Bay, and the main San Francisco Bay; and the Carquinez Strait. The main part of San Francisco Bay measures between 3 and 12 miles wide from east to west and 48 to 60 miles north to south. However, the Bay has been deliberately filled in since the mid-1800s by as much as a third, making the actual size of the Bay difficult to accurately measure. The areas of the Bay that were filled were primarily wetlands, which once consisted of many thousands of acres that formed the edges of San Francisco Bay.

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PRECIPITATION

The Planning Area climate is temperate and subhumid and is modified greatly by marine influence. Summer fog is common in this area. Annual temperatures range from an average maximum of 66.8 degrees Fahrenheit (°F) to an average minimum of 47.1°F (Western Regional Climate Center, 2009). Average total mean annual precipitation for the San Mateo area is 20.16 inches and the mean freeze-free period is about 250 to 300 days.

FLOODING AND FLOODPLAIN MANAGEMENT

The City of San Mateo is particularly vulnerable to flooding conditions, especially areas within the lowland areas of the City. Substantial land settlement in the City has resulted in the need for additional flood control features.

Historical Flooding Conditions

Historic flooding has occurred at several locations throughout the City of San Mateo with the most impacted areas on the eastern side of San Mateo. In the past, flooding has occurred at several locations within the Marina Lagoon drainage complex due to inadequate channel and storage capacities or blockages during storms. In the 1970s, Laurel Creek Dam was overtopped, flooding a substantial portion of the San Mateo Village neighborhood. In the 1980s, East Laurel Creek Dam was overtopped, damaging homes immediately downstream. San Mateo Village was also flooded in 1955, 1966, and 1982. San Mateo Creek flooded in 1955 and 1958, flooding a number of homes and businesses downstream, including a number of downtown businesses.

Flooding Conditions

Portions of the City are located within the Federal Emergency Management Agency (FEMA) 100-year floodplain (see Figure 4.8-2). The first Flood Insurance Study was conducted by FEMA for the City of San Mateo in 1975; the study determined that all floods of any consequence occurred in the lowland areas of the City. In 1996, the City’s second Flood Insurance Study was conducted in which areas north of State Route (SR) 92 were determined inadequately protected by the levee system. In 2004, the Map Modernization Program initiated another review of the Flood Insurance Maps, and in 2008 a preliminary map was produced that determined the areas of the City that are still in danger of flooding. This new map will become final in the spring of 2010.

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FIGURE 4.8-2 FEMA 100-YEAR FLOODPLAIN

Sources of Flooding

San Mateo faces two distinct but interrelated sources of flooding: San Francisco Bay and storm drain runoff. Figure 4.8-3 illustrates different flooding sources in the City.

San Francisco Bay

The City of San Mateo confronts substantial flood risks from the San Francisco Bay. The potential for flooding is due to the combined effects of high tides, very heavy storm flows, and sea level rise due to global warming. A series of outboard levees, located within San Mateo and Foster City, protect the City from San Francisco Bay tidal flooding. Without adequate levee protection, areas between the railroad tracks and the Bay are directly exposed to saltwater inundation. High tides, specifically, can exacerbate flooding in the low-lying areas between El Camino Real

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Storm Drain Runoff

Precipitation that falls on land from the Santa Cruz Mountain foothills to the bayland area generates stormwater runoff. This runoff flows downhill toward the Bay and is conveyed in a number of natural and man-made flood protection systems. The City’s seven drainage watersheds control the storm runoff and direct it toward the Marina Lagoon or directly into San Francisco Bay.

FIGURE 4.8-3 SOURCES OF FLOODING

Flooding Hazards

Flooding within City of San Mateo is generally gradual (slow-rise flooding as opposed to flash flooding) and not necessarily life-threatening from flooding directly. However, access by emergency vehicles could be restricted, which could cause a life-threatening situation. Accordingly, emergency preparedness, as discussed in Section 4.3, Human Health/Risk of Upset, becomes an important component in San Mateo’s flood preparedness program. The City of San Mateo Fire Department and Public Works Department and the Department of Emergency Services monitor low-lying areas and storm runoff. The San Mateo Fire Department is responsible

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Bay Water Flooding

The City of San Mateo confronts substantial flood risks from the San Francisco Bay, as described above. The potential for flooding is due to the combined effects of high tides, very heavy storm flows, and sea level rise due to global warming. A series of outboard levees, located within San Mateo and Foster City, protect the City from San Francisco Bay tidal flooding. Without adequate levee protection, areas between the railroad tracks and the Bay would be directly exposed to saltwater inundation.

Dike Failure

San Mateo’s levees are structurally stable, with the exception of approximately 1,000 feet of levee adjacent to Foster City which will be reconstructed in the near future. The probability of levee failure is very low. However, failure could result from a major earthquake or severe storm conditions. Should a failure occur at high tide, property could be inundated up to an elevation of 4.7 feet (San Mateo datum/7.06 ft. NGVD) or to a maximum water depth of about 6 feet in the lowest areas of the Shoreview neighborhood.

Tsunami

Tsunamis, or seismically generated sea waves, are rare in California due to the lack of submarine earthquake faults. An Alaska-generated tsunami would have to reach a height of at least 20 feet at the Golden Gate to overtop San Mateo’s levees with a minimum run-up of 5 feet at higher high tide. The highest tsunami affecting the area during the last 120 years had a height of 7.4 feet at the Golden Gate, causing a 2-foot run-up along the City of San Mateo shoreline. Since the City’s shoreline is adjacent to the San Francisco Bay, the threat of a tsunami is relatively low.

Tsunami Warning System

The West Coast/Alaska Tsunami Warning Center (WCATWC), operated by the Alaska Region of the National Weather Service and located in Palmer, Alaska, is one of two National Oceanic and Atmospheric Administration (NOAA) Tsunami Warning Centers in the United States. The WCATWC area of responsibility (AOR) consists of Canadian coastal regions, Puerto Rico, the Virgin Islands, and the ocean coasts of all the states except Hawaii. The other center is the Richard H. Hagemeyer Pacific Tsunami Warning Center (PTWC) located in Ewa Beach, Hawaii. The two centers collaborate to provide tsunami warning service, and mutual backup, to tsunami-threatened areas throughout the United States and many other countries throughout the world (NOAA, 2008).

The WCATWC detects, locates, sizes, and analyzes earthquakes throughout the Pacific, Atlantic, and Arctic basins. Earthquakes that activate the center’s alarm system initiate an earthquake and tsunami investigation which includes automatically locating and sizing the earthquake, earthquake analysis and review, sea level data analysis to verify the existence of a tsunami and to calibrate models, and disseminating information to the appropriate emergency management officials. Tsunami bulletins are then issued to state/province departments of emergency services, federal disaster preparedness agencies, National Weather Service offices, the U.S. Coast Guard’s military bases, local emergency managers, United States Geological

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Survey offices, and many other recipients. Warnings are issued when a potentially tsunami- producing earthquake over the threshold magnitude (7.0 in the Pacific AOR, 6.75 in the Atlantic AOR) occurs in the AOR. The WCATWC issues tsunami warnings, but the warnings and subsequent evacuations are implemented by state and local emergency management.

Earthquakes large enough to be felt near the coast, but below the tsunami warning/watch/advisory threshold size, prompt informational statements to the same recipients as warnings to help prevent needless evacuations (NOAA, 2008).

Dam Failure

There are a total of six dams that affect the City of San Mateo in regard to potential flooding. These dams are Crystal Springs, San Andreas, Laurel Creek and East Laurel Creek, and Tobin Creek in Hillsborough (See Figure 4.8-4). Lower Crystal Springs Dam is the largest of the dams that affects San Mateo. This dam maintains the majority of the water in the Crystal Springs reservoir, which retains a water supply for San Francisco and most cities within San Mateo County, including the City of San Mateo. San Andreas Dam is located on San Andreas Creek in Burlingame and is also used to impound water for San Francisco and much of San Mateo County. Laurel Creek Dam is located at the end of Laurelwood Drive and reduces the peak stormwater runoff. East Laurel Creek Dam is located at the end of East Laurel Creek Drive and is also used to control peak storm runoff. Two other small dams are located in Belmont (East Laurel Creek) and in Hillsborough (Tobin Creek).

In the case of a major seismic event, dam failure could occur at any one of the six dams. The California Division of Safety of Dams (DSOD) reviews and inspects the dams for potential failure due to a major seismic event. According to the most recent reports for each of the dams under the jurisdiction of the DSOD (Lower Crystal Springs, San Andreas, Laurel Creek), the DSOD indicates that the dams are structurally safe and will perform without failure. The Lower Crystal Springs Dam specifically has been evaluated for the potential of an earthquake with a maximum magnitude of 8.3 on the Richter scale and determined that the potential for dam failure would be low. The area of potential inundation due to dam failure is shown in the figure below.

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FIGURE 4.8-4 POTENTIAL FLOOD HAZARDS

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Stormwater Drainage

Stormwater drains through San Mateo to the Bay via four major drainage basins – the San Mateo Creek complex, the North San Mateo complex, the Marina Lagoon complex, and the 3rd and Detroit watershed, each composed of numerous stream channels, culverts, and storm drainage piping systems.

The San Mateo Creek drainage basin is 35 square miles in size, only 4 square miles of which are in San Mateo. Approximately 30 percent of the City drains into San Mateo Creek. Storm flows are regulated in the upper reaches of the creek by Lower Crystal Springs Dam and the two reservoirs. The San Francisco Water Department controls winter and springtime releases from the dam to approximately 1,000 cubic feet per second (cfs), which is the capacity of the creek channel at Polhemus Bridge. Uncontrolled releases may occur should reservoir levels exceed the storage capacity during a major storm and can increase to approximately 1,340 cfs.

There are six bridges between El Camino Real (SR 82) and the Bay along San Mateo Creek. The first constriction is the Mills Culvert beneath El Camino Real and extending to San Mateo Drive, which can accommodate 1,400 cfs. With normal winter operation at Crystal Springs Reservoir, no or minimal spill is anticipated at El Camino Real. Figure 4.8-3 in the General Plan shows that this area will have a spill of less than 1 foot during a 100-year storm, which is not classified as a special flood hazard area by FEMA.

The San Mateo Creek watershed located within city limits is fully urbanized and little additional runoff is anticipated from new development. The majority of the remaining watershed area is conservation lands meant to protect the water quality of Crystal Springs Reservoir and will remain undeveloped.

The North San Mateo complex comprises the northeastern portion of the City, including the North Shoreview neighborhood and portions of the North Central neighborhood. This complex drains directly to the Bay via major piping systems under Poplar and Peninsula avenues.

The Marina Lagoon complex comprises four minor watersheds, including 16th Avenue, 19th Avenue, Laurel Creek, and Direct Marina Lagoon Drainage. These watersheds are located in the southern two-thirds of San Mateo. The complex is a watershed of 10 square miles originating in the western hills of San Mateo and Belmont, and draining into Marina Lagoon. Peak storm flows from the western hills are controlled by three dams on Laurel Creek. The watershed is almost entirely urbanized with the exception of Sugarloaf Mountain, and little increase in runoff due to future development is anticipated. Control of erosion and impervious surfaces on Sugarloaf Mountain is important to reduce runoff into Laurel Creek.

The 3rd and Detroit watershed comprises a small area near the City’s Wastewater Treatment Plant and a portion of the Shoreview neighborhood. Stormwater from this area is controlled by a pump station that pumps the water directly into the Bay.

A Storm Drain Master Plan was completed in 2004 that analyzed the local stormwater collection system including these seven major/minor watersheds. Upgrade improvements were identified for some of these facilities to provide adequate flood protection.

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Flood Control and Storm Drainage Improvements

Flood Management Strategies

The Public Works Department consulted with Schaaf and Wheeler, Consulting Civil Engineers, in 2002 to analyze the City’s potential flood hazards and determine which areas of the City may be eligible for removal of the mapped special flood hazards. This study specifically identified capital improvements needed to provide a level of flood protection consistent with the policies of the Federal Emergency Management Agency (FEMA) as administered through the National Flood Insurance Program (NFIP). Additionally, this study reviewed a cost/benefit analysis for specific flood protection measures and possible alternative funding mechanisms for the necessary capital improvements.

Storm Drain Master Plan

In 2004, the Public Works Department again consulted with Schaaf and Wheeler, Consulting Civil Engineers, to update the City’s 1966 Storm Drain Master Plan and subsequent individual area plans. Schaaf and Wheeler examined the flood risks within the City related to the interior storm drain system and identified needed projects that would mitigate risks to an appropriate level. Additionally, the update identified capital improvements needed to provide a level of flood protection consistent with the policies of FEMA as administered through the National Flood Insurance Program and policies established by the City through this master planning process. Derived from this plan, several objectives were identified and/or already accomplished:

1. A geographical information system (GIS) based storm drain model for the entire City has been built, allowing City staff, other engineers, and developers to easily locate relevant data on a computer screen.

2. Storm drainage criteria for various system elements are presented. These criteria will govern future infrastructure design and are used to evaluate the performance of existing facilities and plan remedial improvements.

3. The capacities of existing storm drain facilities throughout San Mateo to meet these criteria have been evaluated. System deficiencies are categorized in terms of the risk to public safety.

4. Projects that can improve storm drain operations are identified.

5. A prioritized Capital Improvement Program (CIP) is outlined.

6. Maintenance guidelines and replacement schedules are presented.

7. Projected capital improvement costs and funding requirements are summarized.

SEA LEVEL RISE

The effects of climate change are more thoroughly discussed in Section 4.13, Energy and Climate Change. Climate change is a global problem, and greenhouse gases (GHGs) impact the global atmosphere; this means that activities that take place in one part of the world impact the entire atmosphere. It will take a global effort to reduce GHG emissions to the point where global climate change does not pose a serious threat to communities. Climate change has impacted and will continue to impact the environment in a variety of ways and will also cause

General Plan Update City of San Mateo Draft Environmental Impact Report July 2009 4.8-10 4.8 HYDROLOGY AND WATER QUALITY economic and social effects. Potential climate change impacts directly affecting San Mateo include sea level rise and increased flooding, water supply issues, wildfire risk, public health concerns, air quality threats, more intense storm events, and energy demand and supply. Sea level rise and increased flooding is one of the primary concerns from global warming for the City of San Mateo due to the City’s proximity to the San Francisco Bay and the low-lying areas that exist within the City.

According to a U.S. Environmental Protection Agency (USEPA) study, the environmental impacts resulting from sea level rise would consist primarily of shoreline retreat, saltwater intrusion into shoreline wetland habitats including marshes, estuaries, and aquifers, and increased flooding. One of the most significant environmental impacts from sea level rise would be the inundation of thousands of square miles of wetlands due to the importance of wetlands as critical habitats for many marine species. Additionally, sea level rise models indicate that a 30 cm (11.8 inch) rise in sea level would shift the 100-year storm surge-induced flood event to once every 10 years (BCDC, 2007). Flooding would occur as a result of extreme high tide events in conjunction with wave run-up and watershed flooding in combination with a high tide. With an increase in flood events, San Mateo could experience loss of valuable real estate and natural resources and impacts to critical public infrastructure. Additionally, sea level rise could worsen the overtopping to sea walls, jetties, breakwater barriers, roadways, and other coastal erosion structures.

In 2009 the City consulted with Schaaf & Wheeler, Consulting Civil Engineers, to specifically determine the potential impacts of sea level rise on the City of San Mateo. Their study reviewed numerous reports and studies that predicted different levels of sea level increase. Currently, the City of San Mateo is prepared for some rise in sea level; however if the extreme predictions of a 4.6-foot rise in sea level by 2100 occurs, the City’s current levees will not be sufficient. Considering that there is no definitive estimate and that sea level rise will likely occur slowly over time, the City will continue to address FEMA’s current certification standards. If FEMA increases its requirements, the City will consider raising the outboard levees to meet FEMA’s certification. However, for the City of San Mateo to be fully protected, the Burlingame and Foster City will also need to raise their levees.

4.8.2 REGULATORY FRAMEWORK

FEDERAL

Federal Emergency Management Agency

The Federal Emergency Management Agency (FEMA) administers a National Flood Insurance Program (NFIP), in which participating agencies must satisfy certain mandated floodplain management criteria. The National Flood Insurance Act of 1968 adopted a desired level of protection with an expectation that developments should be protected from floodwater damage of the Intermediate Regional Flood (IRF). The IRF is defined as a flood that has an average frequency of occurrence on the order of once every 100 years, although such a flood may occur in any given year. The act made federally subsidized flood insurance available to property owners if their communities participate in the NFIP. A community establishes its eligibility to participate by:

• Adopting and enforcing floodplain management measures to regulate new construction; and

• Ensuring that substantial improvements within Special Flood Hazard Areas (SFHA) are designed to eliminate or minimize future flood damage.

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An SFHA is an area within a floodplain having a 1 percent or greater chance of flood occurrence within any given year. SFHAs are delineated on flood hazard boundary maps issued by FEMA. The Flood Disaster Protection Act of 1973 and the National Flood Insurance Reform Act of 1994 make flood insurance mandatory for most properties in SFHAs. The 1975 FEMA Flood Insurance Study for the City of San Mateo delineated an SFHA covering a substantial portion of the City. This SFHA was updated in 1996 and then again as a part of FEMA’s 2004 Map Modernization Program. A new preliminary map was issued in April 2008. This new SFHA map will go into effect sometime in the spring of 2010.

Executive Order 11988

Executive Order 11988 (Floodplain Management) addresses floodplain issues related to public safety, conservation, and economics. It generally requires federal agencies constructing, permitting, or funding a project in a floodplain to do the following:

• Avoid incompatible floodplain development. • Be consistent with the standards and criteria of the NFIP. • Restore and preserve natural and beneficial floodplain values.

Clean Water Act

The Clean Water Act (CWA) regulates the water quality of all discharges into waters of the United States including wetlands and perennial and intermittent stream channels. Section 401, Title 33, Section 1341 of the CWA sets forth water quality certification requirements for “any applicant applying for a federal license or permit to conduct any activity including, but not limited to, the construction or operation of facilities, which may result in any discharge into the navigable waters.” Section 404, Title 33, Section 1344 of the CWA in part authorizes the U.S. Army Corps of Engineers to:

• Set requirements and standards pertaining to such discharges: subparagraph (e);

• Issue permits “for the discharge of dredged or fill material into the navigable waters at specified disposal sites”: subparagraph (a);

• Specify the disposal sites for such permits: subparagraph (b);

• Deny or restrict the use of specified disposal sites if “the discharge of such materials into such area will have an unacceptable adverse effect on municipal water supplies and fishery areas”: subparagraph (c);

• Specify type of and conditions for non-prohibited discharges: subparagraph (f);

• Provide for individual state or interstate compact administration of general permit programs: subparagraphs (g), (h), and (j);

• Withdraw approval of such state or interstate permit programs: subparagraph (i);

• Ensure public availability of permits and permit applications: subparagraph (o);

• Exempt certain federal or state projects from regulation under this Section: subparagraph (r); and

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• Determine conditions and penalties for violation of permit conditions or limitations: subparagraph (s).

Section 401 certification is required prior to final issuance of Section 404 permits from the U.S. Army Corps of Engineers.

The California State Water Resources Control Board and the San Francisco Bay Regional Water Quality Control Board (RWQCB) enforce State of California statutes that are equivalent to or are more stringent than the federal statutes. RWQCB is responsible for establishing water quality standards and objectives that protect the beneficial uses of various waters. RWQCB is responsible for protecting surface waters and groundwaters from both point and non-point sources of pollution. Water quality objectives for all of the water bodies within the region were established by the San Francisco Bay RWQCB and are listed in its Basin Plan.

Total Maximum Daily Loads

Under CWA Section 303(d) and California’s Porter-Cologne Water Quality Control Act of 1969 (discussed below), the State of California is required to establish beneficial uses of state waters and to adopt water quality standards to protect those beneficial uses. Section 303(d) establishes the Total Maximum Daily Load (TMDL) process to assist in guiding the application of state water quality standards, requiring the states to identify waters whose water quality is “impaired” (affected by the presence of pollutants or contaminants) and to establish a TMDL or the maximum quantity of a particular contaminant that a water body can assimilate without experiencing adverse effects on the beneficial use identified. TMDLs are generally stakeholder- driven processes that involve investigation of sources and their loading (pollution input), make load allocations, and identify an implementation plan and schedule. Where stakeholder processes are not effective, TMDLs can be established by the RWQCBs or USEPA.

STATE

Porter-Cologne Water Quality Act

The Porter-Cologne Water Quality Act governs the coordination and control of water quality in the state and includes provisions relating to non-point source pollution. The California Coastal Commission, pursuant to the Coastal Act, specifies duties regarding the federally approved California Coastal Management Program. This law required that the State Water Resources Control Board, along with the California Coastal Commission, regional boards, and other appropriate state agencies and advisory groups, prepare a detailed program to implement the state’s non-point source management plan on or before February 1, 2001. The law also required that the state board, in consultation with the Coastal Commission and other agencies, submit copies of prescribed state and regional board reports containing information related to non- point source pollution, on or before August 1 of each year.

California Fish and Game Code Sections 1601–1607 (Lake or Streambed Alteration Agreement Program)

Under Sections 1601–1607 of the California Fish and Game Code, the California Department of Fish and Game (CDFG) regulates projects that affect the flow, channel, or banks of rivers, streams, and lakes. Sections 1601 and 1603 require public agencies and private individuals, respectively, to notify and enter into a streambed or lakebed alteration agreement with CDFG before beginning construction of a project that will have either of the following results:

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• Divert, obstruct, or change the natural flow or the bed, channel, or bank of any river, stream, or lake.

• Use materials from a streambed.

Section 1601 contains addition prohibitions against the disposal or deposition of debris, waste, or other material containing crumbled, flaked, or ground pavement where it can pass into any river, stream, or lake.

Sections 1601–1607 may apply to any work undertaken within the 100-year floodplain of any body of water or its tributaries, including intermittent stream channels. In general, however, it is construed as applying to work within the active floodplain and/or associated riparian habitat of a wash, stream, or lake that provides benefit to fish and wildlife. Sections 1601–1607 typically do not apply to drainages that lack a defined bed and banks, such as swales, or to very small bodies of water and wetlands such as vernal pools.

Regional Water Quality Control Board, San Francisco Bay Region

The San Francisco Bay Regional Water Quality Control Board (RWQCB) regulates surface water and groundwater quality in San Francisco Bay. The area under the RWQCB’s jurisdiction comprises all of the San Francisco Bay segments extending to the mouth of the Sacramento-San Joaquin Delta (Winter Island near Pittsburg). In its efforts to protect surface waters and groundwaters of the San Francisco region, the RWQCB addresses regionwide water quality concerns through the creation and triennial update of a Water Quality Control Plan (Basin Plan) and adopts, monitors compliance with, and enforces waste discharge requirements and National Pollutant Discharge Elimination System (NPDES) permits.

San Francisco Bay Regional Water Quality Control Plan (Basin Plan)

The Basin Plan is a master policy document that contains descriptions of the legal, technical, and programmatic bases of water quality regulation in the San Francisco Bay region. This plan describes the beneficial uses to be protected in these waterways, water quality objectives to protect those uses, and implementation measures to make sure those objectives are achieved. On July 17, 2007, the State Water Resources Control Board approved the Basin Plan amendment that established new water quality objectives for mercury in the tissues of Bay fish and a TMDL for mercury in San Francisco Bay. Also, on June 22, 2007, San Francisco Bay Regional Water Quality Control Water Board staff released a proposed Basin Plan amendment for the incorporation of a TMDL for polychlorinated biphenyls (PCBs) in all segments of San Francisco Bay. This TDML project for PCBs in the San Francisco Bay is still in development and has not been approved.

National Pollutant Discharge Elimination System

The San Francisco Bay Area Region operates under a National Pollutant Discharge Elimination System (NPDES) permit renewed in July 2004, which will expire in July 2009 (a renewal, as a revised tentative order, is currently being reviewed). The permit regulates discharge or reuse of extracted and treated groundwater resulting from the cleanup of groundwater polluted by volatile organic compounds (VOC). Upon the approval of the revised tentative order, the City will revise its requirements to comply.

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Bay Conservation and Development Commission

The Bay Conservation and Development Commission (BCDC) is the federally designated state coastal management agency for the San Francisco Bay segment of the California coastal zone. This designation empowers the Coastal Commission to use the authority of the federal Coastal Zone Management Act to ensure that federal projects and activities are consistent with the policies of the San Francisco Bay Plan and state law.

The Bay Conservation and Development Commission is dedicated to the protection and enhancement of San Francisco Bay and to the encouragement of the Bay’s responsible use. The Commission has been remarkably successful in achieving its mission. Before 1965, an average of about 2,300 acres were being filled each year. Now only a few acres are filled annually – all for critical water-oriented needs. Even this small loss of water area is being mitigated by opening diked areas. As a result, the Bay is now larger than it was when BCDC was established.

LOCAL

San Mateo Countywide Water Pollution Prevention Program

Water pollution degrades surface waters making them unsafe for drinking, fishing, swimming, and other activities. The San Mateo Countywide Water Pollution Prevention Program (SMCWPPP) was established in 1990 to reduce the pollution carried by stormwater into local creeks, San Francisco Bay, and the Pacific Ocean.

The program is a partnership of the City/County Association of Governments (C/CAG), each incorporated city and town in the county, and the County of San Mateo, which share a common National Pollutant Discharge Elimination System permit. The federal Clean Water Act and the California Porter-Cologne Water Quality Control Act require that large urban areas discharging stormwater into San Francisco Bay or the Pacific Ocean have an NPDES permit to prevent harmful pollutants from being dumped or washed by stormwater runoff, into the stormwater system, then discharged into local water bodies. Cities in San Mateo, Santa Clara, Alameda, Marin, Solano, San Francisco, and Contra Costa counties have each obtained these permits. Certain types of businesses must also apply for individual coverage by filing a Notice of Intent (NOI) with the State Water Resources Control Board.

The Stormwater Management Plan outlines the priorities, key elements, strategies, and evaluation methods for the San Mateo Countywide Water Pollution Prevention Program. The comprehensive program includes pollution reduction activities for construction sites, industrial sites, illegal discharges and illicit connections, new development, and municipal operations. The program also includes a public education effort, target pollutant reduction strategy, and monitoring program.

San Mateo Municipal Code, Title 7

Ordinances addressing stormwater management and controlling non-stormwater discharge in the City of San Mateo are contained in Title 7, Chapter 39, Stormwater Management and Discharge Control, of the City’s Municipal Code. Included in this section is the City’s requirement for a Stormwater Pollution Prevention Program (STOPPP) construction permit. This permit regulates the discharge into the City’s stormwater system and is in coordination with the San Mateo County Water Pollution Prevention program above.

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San Mateo Municipal Code, Title 23

Ordinances addressing flooding damage prevention in the City of San Mateo are contained in Title 23, Chapter 33, Floodplain Management, of the City’s Municipal Code, which establishes San Mateo’s eligibility to participate in the National Flood Insurance Program. The City requires all new buildings in Special Flood Hazard Areas (SFHA) to be built with finished floors above base flood elevations established by FEMA. Individual development projects are required to complete a detailed hydrologic study prior to City issuance of development permits. These studies aim to identify downstream areas that experience localized flooding, detailing potential impacts that proposed projects could create on these areas, and identify both on- and off-site mitigation measures that would be required to prevent these impacts.

4.8.3 IMPACTS AND MITIGATION MEASURES

STANDARDS OF SIGNIFICANCE

A hydrologic impact of the proposed City of San Mateo General Plan Update would be considered significant if it would result in any of the following actions based on the following criteria:

1. Violate any water quality standards or waste discharge requirements.

2. Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (e.g., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted).

3. Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site.

4. Create or contribute runoff water which would exceed the capacity of existing or planned storm water drainage systems or provide substantial additional sources of polluted runoff.

5. Otherwise substantially degrade water quality.

6. Place housing within a 100-year flood hazard area as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map without complying with the requirements of Title 16.

7. Place within a 100-year flood hazard area structures that would impede or redirect flood flows.

8. Expose people or structures to a significant risk of loss, injury, or death involving flooding, including flooding as a result of a failure of a levee or dam.

9. Inundation by seiche, tsunami, or mudflow.

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METHODOLOGY

The hydrology analysis is based on a review of published information, reports, and plans regarding regional hydrology, climate, and geology. Information was obtained from private and governmental agencies and Internet websites. These reports included the flood reports prepared by the City including the City’s Storm Drain Master Plan and the Flood Management Strategies. Agencies consulted include the Bay Conservation and Development Commission and the City of San Mateo Public Works Department.

PROJECT IMPACTS AND MITIGATION MEASURES

Construction and Operational Water Quality Impacts

Impact 4.8.1 Infill development or redevelopment under the proposed General Plan Update would include construction-related activities that could expose soil to erosion during storm events, causing degradation of water quality. Also the proposed General Plan Update could increase impervious surfaces and, as a result, alter drainage patterns and increase drainage rates and runoff over existing conditions. Runoff from urban uses may also contribute to the degradation of water quality in the area. This is considered to be a less than significant impact.

Construction Water Quality Impacts

Construction associated with development under the proposed General Plan Update would consist of grading, demolition, and vegetation removal activities that would increase soil erosion rates on the areas proposed for infill or redevelopment. Grading operations may impact the surface runoff by increasing the amount of silt and debris carried by runoff. Areas with uncontrolled concentrated flow would experience loss of material within the graded areas, potentially impacting waters outside the project area.

Additionally, refueling and parking of construction equipment and other vehicles on-site during construction may result in oil, grease, or related pollutant leaks and spills that may discharge into the City’s storm drains. Improper handling, storage, or disposal of fuels and materials or improper cleaning of machinery close to area waterways could cause water quality degradation.

Measures included in subsequent grading plans for infill or redevelopment projects would be required to comply with the City’s Grading Ordinance and drainage requirements, as well as employ best management practices (BMPs) for the prevention of erosion and the control of loose soil and sediment, to ensure that proposed construction does not result in the movement of unwanted material into waters within or outside the project site. During construction of projects in the City, the dischargers, through individual NPDES permits, must eliminate non- stormwater discharges to stormwater systems, develop and implement a Storm Water Pollution Prevention Plan (SWPPP), and perform monitoring of discharges to stormwater systems.

Operational Water Quality Impacts

Subsequent development under the proposed City of San Mateo General Plan would result in infill and other development within the city limits. Direct surface water quality impacts could occur from the following general land use activities in the City:

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• Residential: Maintenance of yards associated with the use of fertilizers, herbicides, and pesticides, and motor vehicle operation and maintenance.

• Commercial: Maintenance of landscape areas associated with the use of fertilizers, herbicides, and pesticides, and motor vehicle operation and maintenance.

• Recreation: Maintenance of parks associated with the use of fertilizers, herbicides, and pesticides, and motor vehicle operation and maintenance.

Runoff typically contains oils, grease, fuel, antifreeze, and byproducts of combustion (such as lead, cadmium, nickel, and other metals), as well as nutrients, sediments, and other pollutants. Additionally, sizable quantities of animal waste from pets (e.g., dogs and cats) could lead to fecal contamination of water sources. Precipitation during the early portion of the wet season (December to April) displaces these pollutants into the stormwater runoff, resulting in high pollutant concentrations in the initial wet weather runoff. This initial runoff, containing peak pollutant levels, is referred to as the “first flush” of storm events. It is estimated that during the rainy season, the first flush of heavy metals and hydrocarbons would occur during the first 5 inches of seasonal rainfall.

The amount and type of runoff generated by the various projects would be greater than that under existing conditions due to increases in impervious surfaces. There would be a corresponding increase in urban runoff pollutants and first flush roadway contaminants such as heavy metals, oil, and grease, as well as an increase in nutrients (e.g., fertilizers) and other chemicals from landscaped areas. These constituents would result in water quality impacts to on- and off-site drainage flows to area waterways.

Additionally, changes from current drainage conditions may potentially result in indirect impacts to water quality in San Mateo Creek or San Francisco Bay. This would be due to a corresponding increase in urban runoff pollutants and roadway contaminants such as heavy metals, oil, and grease, and an increase in nutrients (such as fertilizers) and other chemicals from landscaped areas.

Potential impacts to water quality from construction and operation activities are currently addressed through the existing requirements of the City’s Grading Ordinance and drainage requirements and individual NPDES permits. The policy provisions identified below would utilize BMPs, adopt a set of BMPs consistent with stormwater recommendations from the State Water Resources Control Board, support alternatives to impervious surfaces in new development, and avoid the use of pesticides and nonorganic fertilizers.

General Plan Policies and Implementation Programs

The following policy provisions are proposed in the General Plan Update to address construction and operational water quality.

S 1.3: Erosion Control. Require erosion control measures for all development sites where grading activities are occurring, including those having landslide deposits, past erosion problems, the potential for storm water quality impacts, or slopes of 15% or greater which are to be altered. Control measures shall retain natural topographic and physical features of the site if feasible.

C/OS 2.6: Water Quality. Continue to strive for the highest possible level of water quality reasonable for an urban environment in City creeks, channels, Marina Lagoon, and

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the Bay through the provision of administrative, maintenance, and treatment measures. At a minimum, water quality levels must meet Environmental Protection Agency (EPA) standards, allow for limited water recreation and sustain aquatic/wildlife habitat appropriate to the water flow. The more stringent requirements applicable to contact water recreation would apply to Marina Lagoon and beach areas.

C/OS 3.2: Low-Impact Development. Regulate the location, density, and design of development throughout the City in order to preserve topographic forms and to minimize adverse impacts on vegetation, water, and wildlife resources.

Standard Conditions of Approval

The City of San Mateo has developed specific conditions of project approval that reduce impacts to water quality due to development in the City.

Stormwater Pollution Prevention Permit – The applicant must obtain a Stormwater Pollution Prevention (STOPPP) construction permit, paying the required fees and posting the required cash deposit, for all work associated with the stormwater pollution prevention program (SMMC 7.39). The fee amount will be based upon the City Council resolution in effect at the time the building permit application is made. The permit shall be issued prior to issuance of the first building permit.

For project sites which involved land disturbance of one or more acres (Type IV projects): The project applicant shall file a Notice of Intent (NOI) with the State Water Resources Control Board to obtain coverage under the State General Construction Activity NPDES permit. Proof of permit must be provided to the Public Works Department prior to issuance of the STOPPP construction permit.

Storm Drain Inlets and Waterways – Per the County’s C.3 Stormwater Pollution Prevention Program requirements, the applicant shall mark with the words “No Dumping! Flows to Bay,” or equivalent, using methods approved by the City standards on all storm inlets surrounding and within the project parcel.

Implementation of General Plan policy provisions and the Standard Conditions of Approval, as well as compliance with the City’s Grading Ordinance and drainage requirements, would reduce impacts to construction and operational water quality to a less than significant level. This impact is avoided through the use of effective BMPs that include site preparation, runoff control, sediment retention, and other similar features. The effectiveness of BMPs has been recognized in the California Stormwater Quality Association, California Stormwater Best Management Practice Handbooks.

Flood Hazards

Impact 4.8.2 Implementation of the proposed General Plan Update would result in the exposure of additional people and/or structures to potential risks from flooding hazards and sea level rise. This is considered a less than significant impact.

Flooding

Portions of the City, per the FEMA National Flood Insurance Program, are located within the 100- year floodplain (see Figure 4.8-2) due to the City’s proximity to San Francisco Bay. The proposed

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General Plan Update generally would continue to allow new development and redevelopment within the City areas designated by FEMA as Special Flood Hazard Areas, consistent with the Code of Federal Regulations for the National Flood Insurance Program. The City of San Mateo Municipal Code requires new structures and “substantial improvements” built within a FEMA- designated Special Flood Hazard Area to meet requirements set forth under the Floodplain Management Ordinance (Title 23 Building and Construction, Chapter 33 Floodplain Management, 23.33).

The City utilizes the City Storm Drain Master Plan and Flood Management Strategies which provide recommendations for storm drainage improvements and tidal inundation improvements.

Sea Level Rise

The implementation of the proposed General Plan Update could expose additional people and/or structures to the hazards associated with sea level rise, including inundation, increased flooding, and loss of natural wetland habitat. Additionally, reports indicate that if San Francisco Bay rises by 30 cm (11.8 inch), the 100-year storm surge-induced flood event would be shifted to occur once every 10 years (BCDC, 2007). The areas within the City that are located with the FEMA 100-year floodplain are depicted in Figure 4.8-2.

Additionally, with increased flood event and tidal inundation, San Mateo could experience loss of valuable real estate, critical public infrastructure, and natural resources.

The proposed improvements in the Storm Drain Master Plan and Flood Management Strategies will improve tidal inundation problems and flooding hazards associated with future sea level rise. The City’s current levees are adequate to meet some increase in sea level rise; however, further monitoring and additional studies as outlined above will be necessary to determine the City’s future risks and areas of deficient protection from sea level rise. Sea level rise is expected to broadly occur well beyond the time horizon of this General Plan Update.

Drainage

The proposed infill and redevelopment within the City would have stormwater conveyed into the existing and planned stormwater infrastructure of the City. The City of San Mateo storm drainage infrastructure is divided into a series of seven watersheds for the management of stormwater runoff in the City (see Figure 4.8-1). The watersheds drain via local pump stations and/or the storm drainage network to Marina Lagoon, San Mateo Creek, or directly to the adjacent wetlands of San Francisco Bay. The storm drainage system in the City of San Mateo can often cause ponding of rainwater in various places on streets and driveways where the areas are lower than the nearest storm drains due to a lack of gradient. Additionally, increased ponding is expected to increase as settlement continues in low-lying areas. However, the stormwater infrastructure has adequate capacity to support any future development within the City.

The planned improvements outlined in the Storm Drain Master Plan and Flood Management Strategies for stormwater drainage and the policy provisions identified below would reduce impacts from flooding and drainage conditions within the City to a less than significant level.

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General Plan Policies and Implementation Programs

The following policy provisions are proposed in the General Plan Update to address flooding and drainage.

S 2.1: Creek Alteration. Prohibit any reduction of creek channel capacity, impoundment or diversion of creek channel flows which would adversely affect adjacent properties or the degree of flooding. Prevent erosion of creek banks.

S 2.2: Development Adjacent to Creeks. Protect new development adjacent to creeks by requiring adequate building setbacks from creek banks and provision of access easements for creek maintenance purposes.

S 2.3: Development Within Flood Plains. Protect new development within a flood plain by locating new habitable floor areas to be above the 100-year flood-water level or by incorporating other flood-proofing measures consistent with Federal Emergency Management Agency (FEMA) regulations and the City of San Mateo’s Flood Plain Management regulations.

S 2.4: Crystal Springs Reservoir. Encourage the City of San Francisco to develop an operations model or capital improvement projects for the entire San Francisco Water Supply System and Lower Crystal Springs Reservoir. These projects would facilitate acceptance of heavy and prolonged stormwater runoff without the necessity of releasing hazardous volumes of stormwater into San Mateo Creek.

S 2.5: Stormwater Drainage System. Implement the improvements identified in the City of San Mateo's seven watershed areas to improve and maintain drainage capacity adequate to convey water during a typical storm event. Include consideration of creek maintenance and an education and/or enforcement program to minimize illegal dumping of debris and chemicals.

S 2.6: Lowlands Protection. Protect lowlands from the potential rise in the sea level, high tides and tsunamis. Raise levees to meet FEMA current standards and continue to monitor sea level rise estimates. Protect new habitable buildings in areas subject to flooding in the event of levee failure.

Implementation of the above policy provisions and their associated implementation programs would help to reduce flood, tidal inundation, sea level rise, and drainage impacts in the City of San Mateo. Refer to Section 4.9, Biological Resources, for a discussion of the impact of the potential flood improvement on natural resources along the Bay including wetlands, marshlands, and baylands.

Policy provisions for flooding and tidal inundation would require new development and “substantial improvements” proposals in areas subject to flooding to provide a minimum flood protection equal to a 100-year storm event, pursue sources of state and federal funding, and establish and maintain an effective emergency response program that anticipates the potential for disasters. Policy provisions and Standard Conditions of Approval for drainage would require construction or upgrade of storm drainage facilities for new development.

Thus, implementation of the above proposed General Plan Update policy provisions, continued implementation of Municipal Code standards for flood protection, and continued

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Mitigation Measures

None required.

4.8.3 CUMULATIVE SETTING, IMPACTS, AND MITIGATION MEASURES

CUMULATIVE SETTING

The cumulative setting consists of potential cumulative impacts to increased stormwater runoff to the San Mateo watersheds and San Francisco Bay. Additionally, the cumulative setting includes anticipated development in the hillside communities of the unincorporated areas of San Mateo County.

CUMULATIVE IMPACTS AND MITIGATION MEASURES

Cumulative Flood Hazards

Impact 4.8.3 Implementation of the proposed General Plan Update could increase impervious surfaces and alter drainage conditions and rates in the Planning Area, which could contribute to cumulative flood conditions in the City of San Mateo. This impact is considered less than cumulatively considerable.

The City of San Mateo is an urbanized community with less than 1 percent of developable vacant land. Additional development in the City of San Mateo is not expected to increase the impervious surfaces or alter drainage conditions to a significant degree. Additional development in the San Mateo Highlands single-family neighborhood (unincorporated San Mateo County) will not impact San Mateo’s downstream watersheds to a significant level because there is also very little developable land. Future development as a result of the General Plan Update would result in infill/redevelopment in the City of San Mateo.

Some of this infill/redevelopment may be within areas of the City that are located within the 100- year floodplain. Additionally, the infill/redevelopment associated with the proposed General Plan Update could expose future residences and structures to flood hazards. As noted above, new development and redevelopment will be required to meet the City of San Mateo Municipal Code standards for new structures and substantial improvements built within a FEMA-designated Special Flood Hazard (Title 23 Building and Construction, Chapter 33 Floodplain Management, 23.33) in order to mitigate flood hazards.

The implementation of the General Plan policy provisions and their associated implementation programs from Impact 4.8.2 would help to reduce any flood, tidal inundation, sea level rise, and drainage impacts in the City. The General Plan policy provisions and Standard Conditions of Approval for flooding and tidal inundation would require new development and remodeling proposals in areas subject to flooding to provide a minimum flood protection level equal to a 100-year storm event, pursue sources of state and federal funding, and establish and maintain an effective emergency response program that anticipates the potential for disasters. Thus, implementation of the General Plan Update policy provisions and continued implementation of Municipal Code standards for flood protection, and the Standard Conditions of Approval would reduce this impact to less than cumulatively considerable.

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Mitigation Measures

None required.

Cumulative Water Quality Impacts

Impact 4.8.4 Land uses and growth under the proposed General Plan Update, in combination with current land uses in the surrounding cities of Belmont, Burlingame, and Foster City and the Town of Hillsborough and land use activities and development of the cities and other agencies in the county, could introduce additional non-point source pollutants to surface waters. This impact would be less than cumulatively considerable.

As described under Impact 4.8.1, subsequent infill and redevelopment proposed in the General Plan Update could contribute to water quality degradation from construction, operation, and alteration of drainage patterns. Cumulative development in the adjacent cities could result in cumulative water quality impacts, due to their adjacent location to San Francisco Bay, Marina Lagoon, and San Mateo Creek.

All future development in the City of San Mateo would be required to comply with the City’s Grading Ordinance and drainage requirements, as well as employ best management practices (BMPs) for the prevention of erosion and the control of loose soil and sediment. BMPs would also be used for the treatment of post-construction stormwater. During construction of projects in the City, the dischargers, through individual NPDES permits, must eliminate non-stormwater discharges to stormwater systems, develop and implement a Storm Water Pollution Prevention Plan (SWPPP), and perform monitoring of discharges to stormwater systems.

Potential impacts to water quality from construction and operation activities are addressed by the existing requirements of the City’s Grading Ordinance and drainage requirements and individual NPDES permits. The policy provisions identified below would utilize BMPs, adopt a set of BMPs consistent with stormwater recommendations from the State Water Resources Control Board, and work with San Mateo County to ensure implementation of all applicable National Pollutant Discharge Elimination System requirements.

General Plan Policies and Implementation Programs

The following policy provisions are proposed in the General Plan Update to address water quality:

C/OS 2.6: Water Quality. Continue to strive for the highest possible level of water quality reasonable for an urban environment in City creeks, channels, Marina Lagoon, and the Bay through the provision of administrative, maintenance, and treatment measures. At a minimum, water quality levels must meet Environmental Protection Agency (EPA) standards, allow for limited water recreation and sustain aquatic/wildlife habitat appropriate to the water flow. The more stringent requirements applicable to contact water recreation would apply to Marina Lagoon and beach areas.

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Standard Conditions of Approval

The City of San Mateo has developed specific conditions of project approval that reduce impacts to water quality due to development in the City.

Implementation of General Plan policy provisions and Standard Conditions of Approval, as well as compliance with the City’s Grading Ordinance and drainage requirements, would reduce the City’s contribution to cumulative water quality impacts to a less than cumulatively considerable level. This impact is reduced through the use of effective BMPs that include site preparation, runoff control, sediment retention, and other similar features. The effectiveness of BMPs has been recognized in the California Stormwater Quality Association, California Stormwater Best Management Practice Handbooks.

Mitigation Measures

None required.

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REFERENCES

California Climate Change Center. 2006. Scenarios of Climate Change in California: An Overview.

California Energy Commission. 2006. Our Changing Climate: Assessing the Risks to California. Publication CEC-500-2006-077.

City of San Mateo. 2002. Flood Management Strategies.

City of San Mateo. 2004. City Storm Drain Master Plan.

City of San Mateo Planning Division. 2009. City of San Mateo General Plan. San Mateo, CA.

County of San Mateo. 2003. Storm Management Plan.

County of San Mateo. 2007. C.3 Stormwater Technical Guidance.

County of San Mateo. 2009. San Mateo Countywide Water Pollution Prevention Program website. http://www.flowstobay.org/ (accessed June 2009).

National Oceanic and Atmospheric Administration (NOAA). 2008.

San Francisco Bay Conservation and Development Commission (BCDC). 2007. Climate Change Action Plan.

U.S. Environmental Protection Agency (USEPA). 1984. Greenhouse Effect and Sea Level Rise: A Challenge for this Generation

U.S. Environmental Protection Agency (USEPA). 2006. The U.S. Inventory of Greenhouse Gas Emissions and Sinks: 1990-2004, April 2006.

Western Regional Climate Center. 2009.

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