Section 3.6
Hydrology and Water Quality
3.6.1 Introduction
This section describes the existing hydrologic conditions at the project site and surrounding area,
and evaluates the potential impacts to storm drain facilities or patterns, water quality, and
surface water runoff. As determined in the Initial Study, the proposed project would not result in
a significant impact relative to groundwater supplies and recharge; thus, these topics are not
addressed further in this section. Impacts to water supplies, including groundwater resources,
are addressed in Section 3.11 Utilities of this EIR.
3.6.2 Existing Conditions
The project site is located within the Los Angeles River Watershed, which covers an
approximately 834-square-mile area from the Santa Monica Mountains, Simi Hills, and Santa
Susana Mountains in the west to the San Gabriel Mountains in the east. Two major stream
channels traverse the City: Arroyo Seco and Eaton Wash.
The Arroyo Seco lays 2.5 miles to the west of the project site. The Arroyo Seco originates in the
San Gabriel Mountains and flows in a south-southwesterly direction along the eastern side of the
San Rafael Hills, eventually discharging into the Pacific Ocean via the Los Angeles River. The
Arroyo Seco is an impaired 303(d)-listed waterbody, which requires a pollution control plan (or
Total Maximum Daily Load [TMDL]) for each associated pollutant/stressor on the list. The Arroyo
Seco has a TMDL requirement listed for Benthic-Macroinvertebrate Bioassessments, Coliform
Bacteria, and Trash.34 The TMDL serves as the means to attain and maintain water quality
standards for the impaired water body.
The Eaton Wash lays 1.9 miles to the east of the project site. Eaton Wash exits the San Gabriel
Mountains and flows in a southerly direction, ultimately draining into the Pacific Ocean via the
Rio Hondo River and Los Angeles River. The Eaton Wash is not 303(d)-listed as an impaired
waterbody.
Both stream channels have been modified by flood control dams near the base of the San Gabriel
Mountains, and both have been confined to manmade channels or storm drains in their lower
reaches across the valley. In most years, both channels carry very little water, with peak
discharges typically of less than 1,000 cubic feet per second (cfs) for Arroyo Seco and less than
500 cfs for Eaton Wash. The heaviest peak discharges in these watersheds have occurred most
often between November and March, during the wet weather season. Annual precipitation in the
City is an average of approximately 20 inches. However, in 2013, the average precipitation was
34
2010 California 303(d) List of Water Quality Limited Segments, Category 5. Accessed on March 3, 2014, online at:
http://www.waterboards.ca.gov/water_issues/programs/tmdl/2010state_ir_reports/category5_report.shtml
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Section 3.6 • Hydrology and Water Quality
1.78 inches.35 In the past five years, the maximum precipitation was 5.8 inches the week of
January 17, 2010.36
The existing drainage pattern of the project site is toward the south. Much like the vast majority
of the City, which is of a developed nature, the existing project site is an impervious area and does
not generate sediment. Stormwater runoff from the project site enters drains along Colorado
Boulevard and Hill Avenue and discharges into the Eaton Wash.37,38 The Eaton Wash drains into a
segment of the Rio Hondo River that is also not listed as 303(d)-impaired.39
3.6.3 Regulatory Framework
3.6.3.1 Federal
Clean Water Act
The federal Clean Water Act (CWA), enacted by Congress in 1972, is the principal statute
governing water quality in the U.S. and forms the basis for several state and local laws throughout
the nation. Its objective is to reduce or eliminate water pollution in the nation’s rivers, streams,
lakes, and coastal waters by regulating the discharge of pollutants from all point sources. At the
federal level, the CWA is administered by the U.S. Environmental Protection Agency (EPA), which
has the authority to implement water pollution control programs, including setting water quality
standards for contaminants in surface waters, establishing wastewater and effluent discharge
limits from various industry categories, and imposing requirements for controlling nonpointsource pollution. At the state and regional levels, the CWA is administered and enforced by the
State Water Resources Control Board (SWRCB) and the Regional Water Quality Control Boards
(RWQCBs).
National Pollutant Discharge Elimination System
Section 402(d) of the CWA establishes a framework for regulating nonpoint source (NPS)
stormwater discharges under the National Pollution Discharge Elimination System (NPDES)
permitting program (33 USC 1251). The NPDES program regulates stormwater discharges from
major industrial facilities, storm drain systems that serve a population of 50,000 or more, and
construction sites one acre or more in size. Los Angeles County and 85 incorporated cities
therein, including Pasadena, receive coverage under the Municipal Separate Storm Sewer Systems
(MS4) stormwater permitting program under NPDES Permit No. CAS004001. The permit, first
issued by the Los Angeles RWQCB in 2001, regulates municipal stormwater and urban runoff
discharges within the jurisdictions covered by the permit and requires that permittees develop
and implement programs for stormwater management. The City of Pasadena Public Works
Department is the local enforcing agency of the MS4 NPDES permit (Order R4-2009-0130).
35
Weather.com, accessed on February 21, 2014, online at:
http://www.weather.com/weather/wxclimatology/monthly/USCA0840
36
Wolfram|Alpha knowledgebase, accessed on February 21, 2014, online at:
http://www.wolframalpha.com/input/?i=Average+yearly+precipitation+pasadena+ca
37
Los Angeles County Hydraulic Water Conservation Division and Environmental Programs Division, 2006.
38
City of Pasadena Public Works and Transportation Department, Storm Drain Index Map.
39
2010 Integrated Report on Water Quality with Web-Based Interactive Map.
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Section 3.6 • Hydrology and Water Quality
3.6.3.2 State
Porter-Cologne Water Quality Act
The Porter-Cologne Water Quality Act is the primary water quality control law for California
(Water Code Sections 13000 et. seq.). The act sets out specific water quality provisions and
discharge requirements regulating the discharge of waste within any region that could affect the
quality of state waters. Under this act, the SWRCB has ultimate control over state water rights and
water quality policy, and has authority to issue NPDES permits, as delegated by the EPA.
Water Quality Control Plan for the Coastal Watersheds of Los Angeles and Ventura
Counties
The SWRCB is divided into nine RWQCBs. Each RWQCB is required to prepare and periodically
update a Water Quality Control Plan (Basin Plan) that identifies existing and potential beneficial
uses for specific water bodies. The Basin Plan is the master policy document that contains
descriptions of the legal, technical, and programmatic bases of water quality regulation in each
region.
The City is within the jurisdiction of the Los Angeles RWQCB Region 4 (LARWQCB), which
adopted the Water Quality Control Plan for the Coastal Watersheds of Los Angeles and Ventura
Counties in 1995. This Basin Plan gives direction on the beneficial uses of the state waters,
provides the water quality objectives, and specifies the actions necessary to maintain the
standards to control nonpoint and point sources of pollutants to the state’s waters. All
discretionary projects requiring permits from the RWQCB (i.e., waste and pollutant discharge
permits) must implement Basin Plan requirements (i.e., water quality standards), taking into
consideration the beneficial uses to be protected.
NPDES Construction General Permit
Pursuant to the CWA, in 2009, the SWRCB issued a statewide NPDES General Construction
Activity Permit (NPDES No. CAS000002, also referred to as the “Construction General Permit”), in
which discharges of stormwater from construction sites with a disturbed area of one or more
acres are required to either obtain individual NPDES permits or be covered by the Construction
General Permit. Administration of the Construction General Permit by the SWRCB is currently
implemented through Order 2009-0009-DWQ amended by 2010-0014-DWQ and 2012-0006DWQ. Coverage by the Construction General Permit is accomplished by obtaining, prior to start of
construction, approval from the SWRCB of a Notice of Intent (NOI) specific to the proposed
construction activity. The NOI includes specific information on the types of construction activities
that would occur at construction sites, particularly as related to ground disturbance. In addition,
the NOI must include a site-specific plan called the Storm Water Pollution Prevention Plan
(SWPPP) to minimize the discharge of pollutants during construction. The SWPPP must include a
description of the Best Management Practices (BMPs) that will be employed to avoid or reduce
stormwater pollutants. This includes implementation of BMPs aimed at sediment control, erosion
control, and construction materials control (i.e. paint, solvents, concrete, petroleum products) to
prevent stormwater pollutants from leaving construction sites, as well as a detailed description of
(and schedule for) all monitoring and reporting. Construction activities that are subject to the
project include, but are not limited to: clearing, grading, demolition, excavation, construction of
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Section 3.6 • Hydrology and Water Quality
new structures, and reconstruction of existing facilities involving removal and replacement that
results in soil disturbance.
3.6.3.3 Regional
Los Angeles Standard Urban Stormwater Mitigation Plan
In 1999, the National Pollutant Discharge Elimination System (NPDES) mandated local
jurisdictions to institute their respective stormwater management programs in order to comply
with the broad policies of the Clean Water Act. Cities are required to implement certain measures
under a permit issued by the LARWQCB. The County is the principal permittee, and the City of
Pasadena is a co-permittee. Under sections of the Permit entitled Development Planning Program,
the City is required to implement certain measures to regulate the quality of storm water flowing
from private developments to the network of storm drain channels that eventually drain into the
ocean.
The Los Angeles Standard Urban Storm Water Mitigation Plan (SUSMP), approved by LARWQCB
in 2000, was developed as part of the municipal storm water program to address postconstruction storm water pollution from new development and redevelopment projects. The
SUSMP defines water quality design standards to ensure that stormwater runoff is managed for
water quality concerns, and to insure that pollutants carried by storm water are confined and not
delivered to waterways. Depending on the types of pollutants that can be anticipated to occur in
stormwater runoff from a site, project applicants are required to select appropriate source
control and treatment control BMPs from the list included in the SUSMP.
In September 2002, the Pasadena City Council adopted Resolution 8151 which amended the
City’s storm water and urban runoff control regulations to effectively adopt the County of Los
Angeles SUSMP requirements.
In 2012, the LARWQCB issued an NPDES Permit and Waste Discharge Requirements (Permit No.
CAS004001, Order No. R4-2012-0175) for Los Angeles County, applicable to the County as
principal Permittee and the cities as Co-Permittees of the NPDES Permit, that included additional
requirements related to SUSMPs. Those additional requirements, commonly referred to as the
Low Impact Development (LID) provisions, place greater emphasis on stormwater quality BMPs
such infiltration, bioretention, and/or rainfall harvest and use.
3.6.3.4 Local
Stormwater Management and Discharge Control Ordinance
The City is required to implement certain measures to regulate the quality of storm water flowing
from private developments to the network of storm drain channels that eventually drain into the
ocean. The Pasadena Municipal Code (PMC) adopted the NPDES Permit requirements referenced
above. Specifically, Section 8.70.090(D) of the PMC states, “Where best management practices
guidelines or requirements have been adopted or required by any federal, State of California,
regional, county, or city agency for any activity, operation, or facility which may cause or
contribute to stormwater pollution or contamination, illicit discharges, or discharges of nonstormwater to the stormwater system, every person undertaking such activity or operation, or
owning or operating such facility shall comply with such guidelines or requirements as may be
identified by the enforcement official of any such agency.” Pursuant to the Los Angeles County
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Section 3.6 • Hydrology and Water Quality
SUSMP requirements, as can be found at http://www.lastormwater.org/wpcontent/files_mf/appxgsusmp.pdf, all eligible development projects are required to comply with
the following measures in order to reduce impacts from stormwater runoff:
Control post-development peak stormwater runoff discharge rates;
Conserve natural areas;
Minimize stormwater pollutants of concern;
Protect slopes and channels;
Provide storm drain system stenciling and signage;
Properly design outdoor material storage areas;
Properly design trash storage areas;
Provide proof of on-going BMP maintenance; and,
Implement structural or treatment BMP’s that meet design standards.
South Coast Air Quality Management District (SCAQMD) Rule 403
SCAQMD Rule 403 provides measures to ensure that construction activities associated with the
project do not generate fugitive dust, which also provide overlapping benefits for reducing
erosion. Such measures include the application of water or stabilizing agents to prevent
generation of dust plumes; pre-watering materials prior to use; use of tarps to enclose haul
trucks; stabilizing sloping surfaces using soil binders until vegetation or ground cover effectively
stabilize slopes; hydroseed prior to rain; and, washing mud and soils from equipment at the
conclusion of trenching activities (see SCAQMD Rule 403 Table 1 for additional details).
Land Use Element of General Plan
The 2004 Land Use Element of the City’s General Plan aims to reduce polluted stormwater runoff
through the following policies:
Policy 18.4 Water Quality: Coordinate with local, regional, State, and federal agencies
(including LARWQCB and the Los Angeles County Flood Control District) to continue to define
appropriate standards to improve water quality.
Policy 18.5 Water Pollution Prevention: Continue to require, monitor, and enforce NPDES
permits, SUSMPs, BMPs, TMDLs for impaired water bodies, SQMPs, and SWPPPs, as applicable
and appropriate.
3.6.4 Methodology
The impacts analysis related to surface water drainage is qualitative and evaluates the rate and
volume of stormwater flows coming off the site in consideration of the existing developed nature
of the site and vicinity. The impacts analysis related to surface water quality considered the types
of pollutants likely to be associated with construction and operation of the proposed project. In
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Section 3.6 • Hydrology and Water Quality
addition, relevant regulatory permits/requirements, including BMPs and applicable policies,
were evaluated to determine how compliance may ensure that the proposed project would not
significantly degrade existing surface water quality. The environmental setting and analysis is
based primarily on information provided by the following:
Site reconnaissance;
General Plan of the City of Pasadena;
East Colorado Specific Plan;
Stormwater Management and Discharge Control Ordinance;
City of Pasadena Storm Water and Urban Runoff Control Regulations;
City of Pasadena Storm Drain Index Map;
City of Pasadena Catch Basin Data Summary Sheet;
Geologic map of the Pasadena quadrangle, Los Angeles County, California;
Soil Survey of Pasadena Area, California, USDA, Soils Bureau;
Phase I and Phase II Environmental Site Assessments;
County of Los Angeles Department of Public Works Hydrology Manual; and
Statewide 2010 Integrated Report (Clean Water Act Section 303(d) List/305(b) Report).
3.6.5 Thresholds of Significance
As discussed in greater detail in Appendix A, the several impacts associated with Hydrology and
Water Quality were determined to be less than significant. The following thresholds were carried
forward for further analysis in this EIR:
Violate any water quality standards or waste discharge requirements.
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 a substantial
erosion or siltation on- or off-site.
Substantially alter the existing drainage pattern of the site or area, including through the
alteration of the course of a stream or river, or substantially increase the rate or amount of
surface runoff in a manner which would result in flooding on- or off-site.
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.
Otherwise substantially degrade water quality.
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Section 3.6 • Hydrology and Water Quality
3.6.6 Project Impacts
HYDRO-1. Would the project violate any water quality standards or waste discharge
requirements?
Construction activities associated with the proposed project would include clearing, grading, and
excavation which would expose soils. Grading activities, in particular, lead to exposed areas of
loose soil and sediment stockpiles, which are susceptible to uncontrolled sheet flow. In addition,
construction activities would use fuels, solvents, and paints.
Compliance with federal and state regulations and the SUSMP requirements relative to water
quality, as discussed in detail in Section 3.6.3, would address project-related impacts to
stormwater quality. Compliance with the requirements of the Construction General Permit,
including submittal of all the Permit Registration Documents required to receive an approved NOI
from the SWRCB, and implementation of the SWPPP throughout the construction phase of the
proposed project would address anticipated pollutants of concern as a result of construction
activities. Table 3.6-1, General Construction BMPs, lists general BMPs typically included in
construction SWPPPs. In addition, as described in Section 3.6.3, the SCAQMD Rule 403 requires
measures including, but not limited to, using soil binders until vegetation or ground cover
effectively stabilize slopes, and hydroseeding prior to rain. Furthermore, as required by USEPA,
Spill Prevention, Control and Countermeasure Plans are required in order to avoid, prepare for,
and clean up any spills.
Table 3.6-1 General Construction BMPs
Category
Purpose
Construction Site
Planning and
Management
Ensure the integrity
and effectiveness of
BMPs
Structural Source
control BMPs
Reduce the potential
for pollutants to enter
runoff; prevent a net
increase in sediment
load in stormwater
discharges
Treatment Control
BMPs
Treat contaminated
stormwater before
the water is
discharged offsite
Nonstructural
Source Control BMPs
Reduce the potential
for pollutants
resulting from
activities onsite to
enter runoff
Examples
Routine inspections and maintenance
Inspections performed before and after rain events
Erosion, sediment, and runoff controls
Temporary diversion dikes
Collect and dispose of all debris and waste materials in trash
or recycle bins
Vehicle/equipment maintenance and washing areas
Proper containment of stockpiles of soil
Biofiltration through constructed project landscape elements
such as bioswales, infiltration trenches, and/or infiltration basins
Filters
Education of owners and employees; activity restrictions, such as
requiring that trash can lids be closed at all times
Contractor training and certification
Periodic inspections of water quality features
such as catch basins and filters
Source: U.S. EPA, 2014. National Menu of BMPs, available online at:
http://cfpub.epa.gov/npdes/home.cfm?program_id=6
The operation activities associated with the proposed project would also comply with all state
and federal requirements pertaining to the preservation of water quality and would not be
expected to increase pollutant concentrations in runoff. For instance, under the SUSMP, the
proposed project would be required to retain or treat the first 0.75-inch of rainfall in a 24-hour
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Section 3.6 • Hydrology and Water Quality
period.40 This is a measure to allow water to separate any pollutants prior to its release into
storm drain channels, catch basins and eventually to larger natural bodies of water.
Therefore, through compliance with federal, state and local requirements and implementation of
BMPs, the construction and operation phases of the proposed project would comply with all
applicable water quality standards and waste discharge requirements. Accordingly, this impact
would less than significant.
Mitigation Measures
No mitigation measures would be required.
Residual Impacts
The proposed project would not violate any water quality standards or waste discharge
requirements; impacts would be less than significant.
HYDRO-2. Would the project 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 a substantial erosion or siltation on- or off-site?
As mentioned above, construction activities would include clearing, grading, and excavation
which may result in temporarily exposed areas of loose soil and sediment stockpiles, which are
susceptible to sheet erosion. However, implementation of construction BMPs would decrease
erosion and sediment load into receiving waters and result in a less than significant impact for
construction activities. In addition, as described in Section 3.6.3, the SCAQMD Rule 403 requires
measures including, but not limited to, using soil binders until vegetation or ground cover
effectively stabilize slopes, and hydroseeding prior to rain. Other common BMPs41 to address
erosion and sedimentation from the proposed project would include but not limited to the
following:
Erosion Control
Surface roughening, trackwalking, scarifying, sheepsfoot rolling, imprinting.
Soil bioengineering techniques (e.g., live staking, fascines, brush wattles).
Groundcover to stabilize site soils.
Composting.
Seeding.
Sodding.
Dust control.
40 The first 0.75-inch of rainfall in a 24-hour period or the 85th percentile 24-hour runoff event if a volumetric treatment
control BMP, or the flow of runoff produced from a rain event equal to at least 0.2 inches per hour intensity or the flow of
runoff produced from a rain event equal to at least two times the 85th percentile hourly rainfall if a flow-based treatment
control BMP.
U.S. EPA, 2007. Developing Your Stormwater Pollution Prevention Plan: A Guide for Construction Sites. Available online at:
http://www.epa.gov/npdes/pubs/sw_swppp_guide.pdf.
41
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Section 3.6 • Hydrology and Water Quality
Mulching.
Riprap.
Soil retention.
Sediment Control
Gravel bag barrier.
Compost filter berm or sock.
Rock dams or brush filter or barrier.
Baffles or skimmers in sediment basins to increase effectiveness.
Lowering soil levels near streets and sidewalks to prevent runoff.
Level spreaders.
Energy dissipaters.
Silt fences or sediment traps.
Sediment filters and sediment chambers.
Storm drain inlet protectors.
Once in operation, the proposed project would occur on a similar amount of impervious surface
area compared to existing conditions. The proposed project would not change the receiving water
bodies nor require improvements to the tributary drainage area because the impermeable area of
the site would not substantially change. In fact, with the capture and treatment of the first 0.75
inch of rain on the project site that may include infiltration pursuant to LID requirements,
implementation of the proposed project could reduce the amount of stormwater flow from the
site, thereby improving water quality in the immediate area of the site. In addition, the hotel uses
associated with the operational activities of the proposed project would not generate any
sediment.
Therefore, the construction and operation of the proposed project would not result in erosion or
siltation on- or off-site and impacts would be less than significant.
Mitigation Measures
No mitigation measures would be required.
Residual Impacts
The proposed project would not substantially alter the existing drainage pattern of the site or
area, including through the alteration of the course of a stream or river; impacts would be less
than significant.
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Section 3.6 • Hydrology and Water Quality
HYDRO-3. Would the project substantially alter the existing drainage pattern of the site or
area, including through the alteration of the course of a stream or river, or substantially
increase the rate or amount of surface runoff in a manner which would result in flooding
on- or off-site?
As described above, the construction activities (i.e., grading and excavation) associated with the
proposed project may temporarily alter the direction of stormwater runoff from the project site.
However, with the implementation of BMPs as required by the NPDES Construction General
Permit, stormwater runoff would be properly managed onsite. Construction BMPs would help to
control surface water flows into drainage systems such that nuisance-flooding does not occur onor off-site. As required by the Construction General Permit, no BMPs would be allowed that would
cause flooding at or around the project site.
Once in operation, the drainage facilities included as part of the design of the proposed project
would accommodate the amount and velocity of stormwater runoff. These drainage facilities
would be designed in accordance with the standards under the County of Los Angeles
Department of Public Works Hydrology Manual and would be subject to review and approval by
the City’s Department of Public Works. Stormwater flow from the proposed project would be
comparable to, if not less than, existing conditions and is not expected to exceed the capacity of
the stormwater drainage system. As is the case currently, stormwater generated onsite would be
discharged into storm drains in the immediate vicinity of the project site which is subsequently
discharged into Eaton Wash and ultimately into the Pacific Ocean. In addition, the proposed
project would be subject to the City’s impact fees (Municipal Code Section 4.19.060), which would
be utilized to improve the City’s storm drain system. The City would continue to maintain the
culverts and storm drain system to prevent the accumulation of debris or other obstructions that
could hamper the effectiveness of the system during wet weather.
Therefore, compliance with existing standards and review processes would ensure a less than
significant impact related to flooding during the construction and operation of the proposed
project.
Mitigation Measures
No mitigation measures would be required.
Residual Impacts
The proposed project would not substantially alter the existing drainage pattern of the site or
area, including through the alteration of the course of a stream or river, or substantially increase
the rate or amount of surface runoff in a manner which would result in flooding on- or off-site;
impacts would be less than significant.
HYDRO-4. Would the project 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?
As described above, the amount of stormwater runoff generated at the project site and discharged
into the local stormwater drainage system would be similar to, if not less than, that of existing
conditions. As described in Section 3.5, Hazards and Hazardous Materials, of this EIR, past uses at
the project site has resulted in potential onsite soil contamination. Should contamination be
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Section 3.6 • Hydrology and Water Quality
encountered and identified, it would be handled in compliance with applicable federal, state, and
local regulations, as required by mitigation measure MM-HAZ-1. Thus, sources of polluted runoff
from previous uses of the project site would be minimized. In addition, although construction
activities associated with the proposed project could generate hazardous waste products (e.g.,
paints, solvents, adhesives, and other petroleum/gasoline products) that have the potential to
create sources of polluted runoff, compliance with the requirements of the Construction General
Permit, as described above, would ensure impacts are less than significant.
During the operation phase, compliance with existing regulations (i.e., the City’s adopted SUSMP,
which is part of the NPDES MS4 permit for Los Angeles County) would ensure that the proposed
project would not result in water quality exceedances nor would pollutants in project runoff
compromise the Eaton Wash channel or ultimately the Pacific Ocean.
Therefore, the construction and operation of the proposed project would not provide substantial
additional sources of stormwater or urban runoff and a less than significant impact would
occur.
Mitigation Measures
No mitigation measures would be required.
Residual Impacts
The proposed project would not create or contribute runoff water which would exceed the
capacity of existing or planned stormwater drainage systems or provide substantial additional
sources of polluted runoff; impacts would be less than significant.
HYDRO-5. Would the project otherwise substantially degrade water quality?
As indicated in the discussions above, compliance with federal and state requirements (i.e.,
Construction General Permit, NPDES MS4 permit, and SUSMP, as well as compliance with
regulatory requirements if contaminated soils are encountered during construction as required
under mitigation measure MM-HAZ-1 in Section 3.5, Hazards and Hazardous Materials) would
address the potential for the project to degrade water quality from construction and operation of
the project; the proposed project is not expected to violate any water quality standards or waste
discharge requirements during construction or operation. In addition, the incorporation of water
quality BMPs would control spillage, dumping or disposal of materials into the municipal
stormwater system and reduce pollutants in stormwater and urban runoff to the maximum
extent practicable. Therefore, impacts would be less than significant.
Mitigation Measures
No mitigation measures would be required.
Residual Impacts
The proposed project would result in a less than significant impact.
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Section 3.6 • Hydrology and Water Quality
3.6.7 Cumulative Impacts
The majority of the area surrounding the proposed project site is developed with predominantly
impervious or paved surfaces. While historically the majority of the City has been developed with
impervious surfaces, the majority of new development, replaces existing structures and existing
impervious surfaces. Each of these cumulative projects listed in Section 3.1, Environmental
Impacts Analysis Introduction, Table 3.1-1, Cumulative Projects is subject to the SUSMP Manual
issued by the Los Angeles County Department of Public Works (LACDPW) and requirements
under City’s Stormwater Management and Discharge Control Ordinance for compliance with the
MS4 Permit. The SUSMP and the Stormwater Management and Discharge Control Ordinance each
contain requirements for limiting post-project runoff rates to no more than pre-project rates. In
addition, past, present and reasonably foreseeable future projects would be required to
implement BMPs pursuant to the General Construction Permit relative to the generation of
pollutants that could enter stormwater and/or groundwater, and would be subject to federal,
state, and local regulations relative to the handling of contaminated soils if encountered during
construction, which, relative to the proposed project is required under mitigation measure MMHAZ-1 (i.e., potentially significant impact related to contaminated soil, which in turn could result
in surface water contamination, would be mitigated to less than significant with mitigation
and; therefore, would not result in a cumulatively considerable contribution to a significant
cumulative water quality impact). Thus, the proposed project would not contribute to a
cumulatively significant impact when considered in combination with city-wide past, present or
reasonably foreseeable future projects for water quality or surface waters and drainage.
Mitigation Measures
No mitigation measures would be required.
Residual Impacts
The proposed project, in combination with past, present and reasonably foreseeable future
projects, would result in less than significant cumulative impacts.
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