This chapter shall be known as the "City of San Dimas Low Impact
Development (LID) Ordinance" and may be so cited.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
It is the purpose of this chapter to establish minimum stormwater
management requirements and controls to accomplish, among others,
the following objectives:
A.
Lessen the water quality impacts of development by using smart growth
practices and integrate Low Impact Development (LID) design principles
to mimic predevelopment hydrology through infiltration, evapotranspiration,
and rainfall harvest and use.
B.
Minimize the adverse impacts from stormwater runoff on the biological
integrity of natural drainage systems and the beneficial uses of waterbodies.
C.
Minimize the percentage of impervious surfaces on land developments
by minimizing soil compaction during construction, designing projects
to minimize the impervious area footprint, and employing Low Impact
Development (LID) design principles.
D.
Maintain existing riparian buffers and enhance riparian buffers when
possible.
E.
Minimize pollutant loadings from impervious surfaces such as roof
tops, parking lots, and roadways through the use of properly designed,
technically appropriate Best Management Practices (BMPs), including
source control BMPs Standard Urban Stormwater Mitigation Plan [SUSMP]
design standards, and treatment control BMPs).
F.
Properly select, design, and maintain LID and hydromodification control
BMPs to address pollutants that are likely to be generated, reduce
changes to pre-development hydrology, assure long-term function, and
avoid the breeding of vectors.
G.
Prioritize the selection of BMPs to remove stormwater pollutants,
reduce stormwater runoff volume, and beneficially use stormwater to
support an integrated approach to protecting water quality and managing
water resources in the following order of preference:
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
The city of San Dimas (hereinafter referred to as "city") finds
the following:
A.
Waterbodies, roadways, structures, and other property within and
downstream of the city are at times subject to flooding.
B.
Land development alters the hydrologic response of watersheds, resulting
in increased stormwater runoff rates and volumes, increased flooding,
increased stream channel erosion, increased sediment transport and
deposition, and increased nonpoint source pollutant loading to the
receiving waterbodies and the beaches.
C.
Stormwater runoff produced by land development contributes to increased
quantities of water-borne pollutants.
1.
Increases of stormwater runoff, soil erosion, and non-point
source pollution have occurred as a result of land development and
have impacted the water resources of the San Gabriel River Watershed.
2.
Increased stormwater runoff rates and volumes and the sediments
and pollutants associated with stormwater runoff from future development
projects within the city will, absent proper regulation and control,
adversely affect the city's waterbodies and water resources,
and those of downstream municipalities.
3.
Stormwater runoff, soil erosion, and non-point source pollution
can be controlled and minimized by the regulation of stormwater runoff
from development.
4.
Adopting the standards, criteria, and procedures contained in
this chapter and implementing the same will address many of the deleterious
effects of stormwater runoff.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
For purposes of this chapter, any term used in this chapter
shall be defined as the term in the Los Angeles Regional Phase I Municipal
Storm Water Permit, Order No. R4-2021-0105 (Permit), and any amendments
revisions or reissuance thereof. Terms not specifically defined in
this chapter shall have the meaning customarily assigned to them.
The following words and phrases shall have the following meanings
when used in this chapter:
is a statistical design storm defined through a hydrologic
analysis of long-term rainfall records for a particular geographic
area. At the most basic level, the design storm represents the 85th
percentile, 24-hour rainfall depth (typically measured in inches of
rain) among all 24-hour rainfall depths evaluated in the historical
record. Analyses that define this storm event often express the 85th
percentile, 24-hour storm event as an "isohyetal" or "isopluvial"
map with contour lines connecting areas with the same 85th percentile
24-hour rainfall depth. In some situations (e.g., in storm hydrographs),
the temporal distribution of rainfall during the 85th percentile,
24-hour storm event may be assumed.
means the Federal Water Pollution Control Act, also known
as the Clean Water Act as amended 33 U.S.C. 1251, et seq.
means any person proposing or implementing the development
of land.
as defined in the water quality control plan for ocean waters
of California (California Ocean Plan), ASBS are all those areas designated
by the State Water Board as ocean areas requiring protection of species
or biological communities to the extent that maintenance of natural
water quality is assured. All areas of special biological significance
are also classified as a subset of state water quality protections
areas. ASBS are also referred to as state water quality protection
areas — Areas of special biological significance (SWQPA-ASBS).
means a facility that is categorized in any one of the following
standard industrial classification (SIC) and North American industry
classification system (NACIS) codes (5013, 5014, 5511, 5541, 7532-7534
and 7536-7539).
means practices or physical devices or systems designed to
prevent or reduce pollutant loading from stormwater or non-stormwater
discharges to receiving waters.
means an LID BMP that reduces stormwater pollutant discharges
by intercepting rainfall on vegetative canopy, and through incidental
infiltration and/or evapotranspiration, and filtration. Incidental
infiltration is an important factor in achieving the required pollutant
load reduction. Therefore, the term "biofiltration" as used in achieving
the required pollutant load reduction. Therefore, the term "biofiltration"
as used is defined to include only systems designed to facilitate
incidental or achieve the equivalent pollutant reduction as biofiltration
BMPs with an underdrain. Biofiltration BMPs include bioretention systems
with an underdrain and bioswales.
means an LIP BMP that reduces stormwater runoff by intercepting
rainfall on vegetative canopy, and through evapotranspiration and
infiltration. The bioretention system typically includes a minimum
two-foot top layer of a specified soil and compost mixture underlain
by a gravel-filled temporary storage pit dug into the in-situ soil.
As defined in the permit, a bioretention BMP may be designed with
an overflow drain, but may not include an underdrain. When a bioretention
BMP is designed or constructed with an underdrain, it is regulated
by the permit as biofiltration.
means the city of San Dimas.
means the Federal Water Pollution Control Act enacted in
1972, by Public Law 92-500, and amended by the Water Quality Act of
1987. The Clean Water Act prohibits the discharge of pollutants to
waters of the United States unless the discharge is in accordance
with an NPDES permit.
means any development on private land comprised of one or
more buildings forming a complex of stores which sells various merchandise,
with interconnecting walkways enabling visitors to easily walk from
store-to-store, along with parking area(s). A commercial mall includes,
but is not limited to, mini-malls, strip malls, other retail complexes,
and enclosed shopping malls or shopping centers.
means any construction or demolition activity, clearing,
grading, grubbing, or excavation or any other activity that result
in land disturbance. Construction does not include emergency construction
activities required to immediately protect the public health and safety
of routine maintenance activities required to maintain the integrity
of structures by performing minor repair and restoration work, maintain
the original line and grade, hydraulic capacity, or original purposes
of the facility.
means the registered professional engineer responsible for
the design of the stormwater management plan.
means construction, rehabilitation, redevelopment, or reconstruction
of any public or private residential project (whether single-family,
multi-unit, or planned unit development); industrial, commercial,
retail, and other non-residential projects, including public agency
projects; or mass grading for future construction. It does not include
routine maintenance to maintain original line and grade, hydraulic
capacity, or original purpose of facility, nor does it include emergency
construction activities required to immediately protect public health
and safety.
means situated within 200 feet of the contiguous zone required
for the continued maintenance, function, and structural stability
of the environmentally sensitive area.
is the portion of the surface area that is hydrologically
connected to a drainage system via a hardened conveyance or impervious
surface without any intervening pervious area to mitigate the runoff
volume.
means any incident, whether natural, technological, or human-caused,
that requires responsive action to protect life or property (as defined
by the Federal Emergency Management Agency). The responsive action
should implement measures, to the fullest extent possible, to reduce
the threat to water quality.
means modular, vault type "high flow biotreatment" devices
contained within an impervious vault with an underdrain or designed
with an impervious liner and an underdrain.
means the general NPDES permit adopted by the State Board
which authorizes the discharge of stormwater from construction activities
under certain conditions.
means an LID BMP using planter boxes and vegetation to intercept
rainfall on the roof surface. Rainfall is intercepted by vegetation
leaves and through evapotranspiration. Green roofs may be designed
as either a bioretention BMP or as a biofiltration BMP. To receive
credit as a bioretention BMP, the green roof system planting medium
shall be of sufficient depth to provide capacity within the pore space
volume to contain the design storm depth and may not be designed or
constructed with an underdrain.
is standardized watershed classification system in which
each hydrologic unit is identified by a unique hydrologic unit code
(HUC). The HUC may consist of an eight to twelve digit number. The
eight-digit HUC identifies an area based on four levels of classification:
region, sub-region, hydrologic basin, and hydrologic sub-basin. The
watershed boundary dataset includes the twelve-digit HUC delineation,
which further divides each hydrologic unit into watersheds and sub-watersheds
based on scientific information and not administrative boundaries.
means the alteration away from a natural state of stream
flows or the beds or banks of rivers, streams, or creeks, including
ephemeral washes, which results in hydrogeomorphic changes.
means any man-made or modified surface that prevents or significantly
reduces the entry of water into the underlying soil, resulting in
runoff from the surface in greater quantities and/or at an increased
rate, when compared to natural conditions prior to development. Examples
of places that commonly exhibit impervious surfaces include parking
lots, driveways, roadways, storage areas, and rooftops. The imperviousness
of these areas commonly results from paving, compacted gravel, compacted
earth, and oiled earth.
means land development that is set aside for industrial development.
Industrial parks are usually located close to transport facilities,
especially where more than one transport modalities coincide: highways,
railroads, airports, and navigable rivers. It includes office parks,
which have offices and light industry.
means an LID BMP that reduces stormwater runoff by capturing
and infiltrating the runoff into in-situ soils or amended on-site
soils. Examples of infiltration BMPs include infiltration basins,
dry wells, and pervious pavement.
means low impact development. LID consists of building and
landscape features designed to retain or filter stormwater runoff.
means a binding agreement that sets forth the terms, measures,
and conditions for the maintenance of post-construction BMP requirements,
with exception of simple LID BMP's implemented on single-family
residences.
means a drainage system that has not been improved (e.g.,
channelized or armored). The clearing or dredging of a natural drainage
system does not cause the system to be classified as modified as defined
in hydromodification.
means land disturbing activities; structural development,
including construction or installation of a building or structure,
creation of impervious surfaces; and land subdivision.
means land area or facility for the parking or storage of
motor vehicles used for businesses, commerce, industry, or personal
use, with a lot size of five thousand square feet or more of surface
area.
means written narratives, specifications, drawings, sketches,
written standards, operating procedures, or any combination of these
which contain information pursuant to this chapter.
means development projects subject to permittee conditioning
and approval for the design and implementation of post-construction
controls to mitigate stormwater pollution, prior to completion of
the project(s).
means an LID BMP system designed to capture runoff, typically
from a roof but can also include runoff capture from elsewhere within
the site, and to provide for temporary storage until the harvested
water can be used for irrigation or non-potable uses. The harvested
water may also be used for potable water uses if the system includes
disinfection treatment and is approved for such use by the local building
department.
means "water of the United States" into which waste and/or
pollutants are or may be discharged.
includes, but is not limited to, the following: the expansion
of a building footprint; addition or replacement of a structure; replacement
of impervious surface area that is not part of a routine maintenance
activity; and land disturbing activities related to structural or
impervious surfaces. It does not include routine maintenance to maintain
original line and grade, hydraulic capacity, or original purpose of
facility, nor does it include emergency construction activities required
to immediately protect public health and safety.
means businesses primarily engaged in the retail sale of
prepared food and drinks for on-premises or immediate consumption.
Caterers and industrial and institutional food service establishments
are also included in this industry (SIC Code 5812).
means any facility engaged in selling gasoline and lubricating
oils - SIC 5541 and NAICS 447110 and 447190.
means a holding system for stormwater, either natural or
man-made, which does not have an outlet to adjoining watercourses
or wetlands and in which water is removed through infiltration and/or
evaporation processes.
include, but are not limited to projects conducted to the
following:
Maintain the original line and grade, hydraulic capacity, or
original purpose of the facility.
Perform as needed the restoration work to preserve the original
design grade, integrity, and hydraulic capacity of flood control facilities.
Includes road shoulder work, re-grading dirt or gravel roadways
and shoulders and performing ditch cleanouts.
Upgrade existing lines* and facilities to comply with applicable
codes, standards, and regulations regardless if such projects result
in increased capacity.
Repair leaks.
Routine maintenance does not include construction of new** lines
or facilities resulting from compliance with applicable codes, standards,
and regulations.
|
Notes:
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* Update existing lines includes replacing existing lines with
new materials or pipes.
|
|
** New lines are those that are not associated with existing
facilities and are not part of a project to update or replace existing
lines.
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means any runoff including stormwater and non-stormwater
from a drainage area that reaches a receiving water body.
means an area that is determined to possess an example of
biotic resources that cumulatively represent biological diversity
for the purpose of protecting biotic diversity as part of the Los
Angeles County general plan.
means, one acre or greater property located in an area with
known erosive soil conditions, where the development contemplates
grading on any natural slope that is twenty-five percent or greater
and where grading, contemplates cut or fill slopes.
means land or water area where any "facility or activity"
is physically located or conducted, including adjacent land used in
connection with the facility or activity.
means any schedules of activities, prohibitions of practices,
maintenance procedures, managerial practices, or operational practices
that aim to prevent stormwater pollution by reducing the potential
for contamination at the source of pollution.
means any facilities or any part of those facilities, including
streets, gutters, conduits, natural or artificial drains, channels,
and watercourses that are used for the purpose of collecting, storing,
transporting, or disposing of stormwater and are located within the
city of San Dimas.
means water that originates from atmospheric moisture (rain
or snow) and that falls onto land, water, or other surfaces. Without
any change in its meaning, this term may be spelled or written as
one word or two separate words.
means the runoff from:
means that part of precipitation (rainfall or snowmelt) which
travels across a surface to the storm drain system or receiving waters.
means the Los Angeles Countywide Standard Urban Stormwater
Mitigation Plan. The SUSMP was required as part of the previous municipal
NPDES permit (Order No. 01-182, NPDES No. CAS004001) and required
plans that designate best management practices (BMPs) that must be
used in specified categories of development projects.
means any engineered system designed to remove pollutants
by simple gravity settling of particulate pollutants, filtration,
biological uptake, media absorption or any other physical, biological,
or chemical process.
(Ord. 1306, 7/23/2024)
These procedures and standards set forth in this chapter apply
to priority development projects that fall under the city's planning
and building authority for which specific requirements, including
the implementation of structural BMPs meeting the performance requirements
of the Los Angeles Regional Phase I Municipal Storm Water Permit Order
No, 2021-0105 (Order) and all amendment, revisions, or reissuance
thereof. The standards set forth in Order minimum standards to be
complied with by developers and in no way limit the authority of the
city of San Dimas to adopt or publish and/or enforce higher standards
as a condition of approval of developments.
A.
Priority development projects include the following:
1.
New development projects within any of the following categories
or meeting the following criteria:
a.
All development projects equal to one acre or greater of disturbed
area and adding more than ten thousand square feet of impervious surface
area (collectively over the entire project site).
b.
Industrial parks ten thousand square feet or more of surface
area.
c.
Commercial malls ten thousand square feet or more of surface
area.
2.
Redevelopment projects that create and/or replace five thousand
square feet or more of impervious surface (collectively over the entire
project site) on any of the following:
3.
New development and redevelopment projects that create and/or
replace five thousand square feet or more impervious surface (collectively)
over the entire project site) and support one or more of the following
uses:
4.
New development and redevelopment projects that create and/or
replace two thousand five hundred square feet or more of impervious
area that are likely to impact a sensitive biological species or habitat;
and are located or directly adjacent to an area of special biological
significance or sensitive ecological area (SEA) such as San Dimas
Canyon/San Antonio Wash.
5.
Street and road construction of ten thousand square feet or
more of impervious surface area shall follow the city of San Dimas
Green Streets Policy to the maximum extent practicable. Street and
road construction applies to streets, roads, highways, and freeway
projects, and streets within larger projects.
6.
Redevelopment projects meeting the redevelopment thresholds
that result in the alteration to more than fifty percent of impervious
surfaces of a previously existing development, shall address the entire
project.
7.
Redevelopment projects meeting the redevelopment thresholds
that result in the alteration to less than fifty percent of impervious
surfaces of a previously existing development, only the alteration
must be mitigated, not the entire project site.
8.
Single-Family Hillside Homes. During the construction of a single-family
hillside home, the following measures shall be considered to the maximum
extent practicable:
a.
Conserve natural areas.
b.
Protect slopes and channels.
c.
Provide storm drain system stenciling and signage.
d.
Divert roof runoff to vegetated areas before discharge unless
the diversion would result in slope instability.
e.
Direct surface flow to vegetated areas before discharge unless
the diversion would result in slope instability.
B.
Redevelopment Projects. Redevelopment projects subject to conditioning
and approval requirements outlined in this chapter for the design
and implementation of post-construction controls to mitigate stormwater
pollution prior to completion of the project(s) include the following:
1.
Redevelopment projects that result in an alteration to more
than fifty percent of impervious surfaces of an existing development
which had not been not subject to post-construction stormwater quality
control requirements at the time of the previous development shall
be required to mitigate the entire project site.
2.
Redevelopment projects that result in an alteration to more
than fifty percent of impervious surfaces of an existing development
which had not been not subject to post-construction stormwater quality
control requirements at the time of the previous development shall
be required to mitigate the entire project site.
3.
Redevelopment does not include routine maintenance activities
that are conducted to maintain original line and grade, hydraulic
capacity, original purpose of facility or emergency redevelopment
activity required to protect public health and safety. Impervious
surface replacement, such as the reconstruction of parking lots and
roadways, which does not disturb additional area and maintains the
original grade and alignment, is not considered a routine maintenance
activity. Redevelopment does not include the repaving of existing
roads to maintain original line and grade.
4.
Existing single-family dwelling and accessory structures are
exempt from the redevelopment requirements unless such projects create,
add, or replace ten thousand square feet of impervious area.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
All development projects that fit the project criteria listed in Section 14.13.050 of this chapter shall control pollutants, pollutant loads, and runoff volume by retaining the stormwater quality design (SWQDv) on site through the following:
A.
On-site infiltration, bioretention and/or rainfall harvest and use;
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
To demonstrate technical infeasibility, the project applicant
shall demonstrate to the city engineer that the project cannot reliably
retain one hundred percent of the SWQDv on site, even with the maximum
application of green roofs and rainwater harvest and use, and that
compliance with the application post-construction requirements would
be technically infeasible. This shall be demonstrated by submitting
a site-specific hydrologic and/or design analysis conducted and endorsed
by a registered professional engineer, geologist, architect, and/or
landscape architect and shall be subject to review and approval by
the city engineer.
When evaluating the potential on-site retention, each applicant
shall consider the maximum potential for evapotranspiration from green
roofs and rainfall harvest and use. If partial or complete on-site
retention is technically infeasible, the project applicant shall consider
the following alternative compliance measures.
A.
On-Site Biofiltration. Biofiltration systems shall meet the design
specifications provided in the Los Angeles County LID Manual (2014
and its revisions), or reissuance thereof equivalent LID manual. If
using biofiltration due to demonstrated technical infeasibility, project
must biofiltrate 1.5 times the portion of the SWQDv that is not reliably
retained on-site, as calculated by Equation 1 below:
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Equation 1:
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Bv = 1.5 x [SWQDv - Rv]
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Where:
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Bv = biofiltration volume.
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SWQDv = the stormwater runoff from a 0.75 inch,
twenty-four-hour storm or the eighty-fifth percentile storm, whichever
is greater.
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Rv = volume reliably retained on site.
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Biofiltration systems discharging to a receiving water that
is included on the Clean Water Act Section 303(d) list of water quality
impairments due to nitrogen compounds, shall be designed and maintained
to achieve enhanced nitrogen removal capacity.
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B.
Off-Site Infiltration. An applicant may use infiltration or bioretention
BMPs to intercept a volume of stormwater runoff equal to the SWQDv,
less the volume of stormwater runoff reliably retained on site, at
an approved off-site project located within the same subwatershed
(HUC-12) as the priority development project, and shall provide pollutant
reduction (i.e., treatment) of stormwater runoff from the project
site. The required off-site mitigation volume shall be calculated
by Equation 2 below:
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Equation 2:
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Mv = 1.0 x [SWQDv - Rv]
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Where:
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Mv = mitigation volume.
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SWQDv = runoff from the 0.75-inch, twenty-four-hour
storm event or the eighty-fifth percentile storm, whichever is greater.
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Rv = the volume of stormwater runoff reliably retained
on site.
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C.
On-Site Flow-Based
BMPs. If on-site biofiltration and off-site alternative compliance
measures are not technically feasible, the applicant may request authorization
by the city engineer to allow the use of on-site flow-based BMPs.
The applicant shall document why none of the other alternative compliance
measures are feasible. Approval will only be granted to areas where
other alternative compliance measures are not feasible due to significant
technical issues. If approved the flow-based treatment control BMPs
must be sized and designed to do the following:
A.
Filter or treat either:
1.
The maximum flow rate of runoff produced from a rainfall intensity
if 0.2 inch of rainfall per hour, for each hour of a storm event;
or
2.
The maximum flow rate of runoff produced by the 85th percentile
hourly rainfall intensity (for each hour of a storm event), as determined
from the local historical rainfall record, multiplied by a factor
of two.
B.
Be certified for enhanced treatment under the Washington State
Department of Ecology's TAPE Program; or an appropriate future
BMP certification developed by the state of California.
D.
Off-Site Project-Retrofit Existing Development. Use infiltration,
bioretention, rainfall harvest and use and/or biofiltration BMPs to
retrofit an existing development, with similar land uses as the new
development or land uses associated with comparable or higher stormwater
runoff event mean concentrations (EMCs) than the new development.
The retrofit plan shall be designed and constructed as described in
the Los Angeles County Municipal Regional Storm Water Permit Order
No. R4-2021-0105, and any amendments, revisions, or reissuance thereof.
E.
Groundwater Replenishment. Regional projects to replenish regional
groundwater supplies at an off-site location, provided the groundwater
supply has a designed beneficial use, in accordance with compliance
performance standards detailed in the Los Angeles Regional Storm Water
Permit Order No. R4 2021-0105, and any amendments, revisions, or reissuance
thereof.
Projects approved for off-site mitigation or ground water replenishment
shall also provide treatment of stormwater runoff from the project
site. Project applicant shall design and implement post-construction
stormwater BMPs and control measures to reduce pollutant loading as
necessary to ensure that the controls implemented on the site are
designed so that stormwater discharges do not cause or contribute
to exceedances of receiving water standards.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
Planning priority projects located within natural drainage systems
shall implement hydrological control measures to prevent accelerated
downstream erosion and protect stream habitat.
A.
Natural drainage systems that are subject to the hydromodification
assessments and control include all drainages that have not been modified
using engineering controls or drainages that are tributary to a natural
drainage system. Examples of engineering modifications to drainage
include channelization, armoring with concrete, and application of
rip-rap.
B.
At the city's discretion the following new development and redevelopment
projects may be exempted from implementation of hydromodification
controls where it has been documented that adverse hydromodification
effects to natural drainage systems are unlikely:
1.
Projects consisting of replacement, maintenance, or repair of
an existing flood control facility, storm drain, or transportation
network.
2.
Redevelopment projects in the urban core that do not increase
the effective impervious area or decrease the infiltration capacity
of previous areas compared to pre-project conditions.
3.
Projects that have any increased discharge directly via a storm
drain to a sump, lake, into a waterway that has a one-hundred-year
peak flow (Q100) of twenty-five thousand cubic feet per second or
more, or other receiving water that is not susceptible to hydromodification
impacts.
4.
Projects that discharge directly or via a storm drain into concrete
or otherwise engineered channels which in turn, discharge into a receiving
water that is not susceptible to hydromodification impacts.
5.
LID BMPs implemented on single-family homes are sufficient to
comply with the hydromodification criteria.
D.
Projects disturbing an area greater than one acre, but less than
fifty acres will be presumed to meet pre-development hydrology if
one of the following demonstrations are made:
The project is designed to retain on site the runoff of the
ninety-fifth percentile twenty-four-hour storm; or
1.
The runoff flow rate, volume, velocity, and duration of the
post-development condition does not exceed the pre-development condition
for the two-year, twenty-four-hour storm event; or
2.
The Erosion Potential (Ep) in the receiving water is approximately
1. Ep shall be determined in accordance with the NPDES permit.
E.
Projects disturbing fifty acres or more will be presumed to meet
pre-development hydrology based on the successful demonstration of
one of the following conditions:
1.
The project site infiltrates on-site runoff from a two-year,
twenty-four-hour storm event; or
2.
The runoff flow rate, volume, velocity, and duration for the
post-development condition does not exceed the pre-development condition
for the two-year, twenty-four-hour storm event. These conditions must
be substantiated by hydrologic modeling.
All stormwater plans shall be subject to review and approval
by the city engineer.
A.
If the proposed plan is not sufficient as originally submitted, the
city engineer, or designee, will notify the applicant in writing,
setting forth the reasons for withholding and will state the changes
necessary to obtain approval.
B.
If staff determines that all the required information has not been
received, the applicant may request that the matter be tabled to allow
for the submittal of the required information.
C.
If all the required information has been received, staff shall approve,
approve with conditions, or recommend denial of the stormwater plan,
including waiver submissions. Recommendations for action on the stormwater
plan can be part of the recommendation for action on the site plan
or subdivision plat.
D.
If the plan is approved, the city will require the following:
1.
The applicant shall provide copies of all necessary state, federal,
or local permits relating to stormwater management to the city.
2.
A satisfactory maintenance covenant agreement that assures long-term
maintenance of all drainage improvements shall be submitted as part
of the final plan. The maintenance covenant shall include a listing
of the BMPs and their location; an operation and maintenance plan;
monitoring plan (where required); and verification of ongoing maintenance
provisions for LID BMPs. The property owner shall be required to document
proper maintenance and operations and maintain such records for a
period of two years. Maintenance agreements and records shall be provided
upon request to the city inspector at any time for compliance verification.
Failure to do so will result in enforcement actions per the city code.
The approved covenant shall be recorded with the Los Angeles County
recorder prior to issuance of occupancy.
3.
A satisfactory maintenance covenant shall at a minimum include
the developer's signed statement accepting responsibility for
maintenance until the responsibility is legally transferred, and either:
a.
A signed statement from the public entity assuming responsibility
for BMP maintenance; or
b.
Written conditions in the sales or lease agreement, which require
the property owner or tenant to assume responsibility for BMP maintenance
and conduct a maintenance inspection at least once a year; or
c.
Written text in project covenants, conditions, and restrictions
(CCRs) for residential properties assigning BMP maintenance responsibilities
to the homeowners' association; or
d.
The applicant shall post cash or a letter of credit in an amount
not less than one hundred percent of the cost of the stormwater facilities.
This deposit shall be held for two years after the date of completion
of construction and final inspection of the stormwater facilities,
until accepted by the city. The percentage cost for cash or letter
of credit may be reduced to ten percent for projects longer than two
years.
4.
This deposit shall be returned to the applicant (in the case
of cash) or allowed to expire (in the case of a letter of credit),
as provided above, provided all stormwater facilities are clean, unobstructed,
and in good working order, as determined by the city engineer.
5.
Reproducible mylars and electronic files (in AutoCAD format)
of the as-built storm drains and stormwater BMPs shall be submitted
by the applicant or his/her engineer to the city along with the final
plan, or upon completion of system construction. The mylars are to
be of quality material and three mils in thickness. Complete development
agreements (including deed restrictions) must be submitted for the
city's review and approval prior to recording.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
Fees and escrow account payments shall be sufficient to cover
administrative and technical review costs anticipated to be incurred
by the city of San Dimas including the costs of on-site inspections,
as set forth by resolution of the city council.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
A.
Purpose of maintenance agreement. The purpose of the maintenance
agreement is to provide the means and assurance that maintenance of
stormwater BMPs shall be undertaken. As a condition for issuing a
certificate of occupancy for a new development or redevelopment project,
the applicant, facility operator(s), and/or owner(s), as appropriate,
shall construct and/or employ all stormwater control BMPs identified
in the approved LID Plan; and submit a signed certification statement
that the project site and all BMPs will be employed and maintained
in compliance with the city's LID ordinance and other applicable
regulatory requirements until the responsibility for such maintenance
is legally transferred to another party.
B.
Maintenance Agreement Required. A maintenance agreement shall be
submitted to the city for review by the city engineer and/or designee
and, if necessary, city attorney. The designers may select any combination
of stormwater BMPs which meet the performance standards provided this
selection and identified in the order and any amendment, revision,
or reissuance thereof. A formal maintenance and inspection plan shall
be included in the maintenance agreement.
C.
Maintenance agreement provisions.
1.
The maintenance agreement shall include a plan for routine,
emergency, and long-term maintenance of all stormwater BMPs, with
a detailed annual estimated budget for the initial two years, and
a clear statement that only future maintenance activities in accordance
with the maintenance agreement plan shall be permitted without the
necessity of securing new permits. Written notice of the intent to
proceed with maintenance shall be provided by the party responsible
for maintenance to the city of San Dimas at least fourteen days in
advance of commencing work.
2.
The maintenance agreement shall be binding on all subsequent
owners of land served by the stormwater BMPs. A copy of the operation
and maintenance plan shall be kept on site for periodic review by
the city's inspectors.
3.
If it has been found by the city, following notice and an opportunity to be heard by the property owner, that there has been a material failure or refusal to undertake maintenance as required under this chapter and/or as required in the approved maintenance agreement as required hereunder, the city shall abate such violations, as a public nuisance, pursuant to the procedures set forth in Chapter 8.16 of the San Dimas Municipal Code.
4.
A fully executed "maintenance covenant for permanent BMPs requirements"
shall be recorded with the Los Angeles County registrar/recorder and
submitted to the public works department prior to the certificate
of occupancy. Covenant documents shall be required to include an exhibit
that details the installed treatment control devices as well as any
site design or source control best management practices (BMPs) for
post construction. The information to be provided on this exhibit
shall include, but not be limited to the following:
a.
8 1/2" x 11" exhibits with record property owner information.
b.
Types of BMPs (i.e., site design, source control and/or treatment
control) to ensure modifications to the site are not conducted without
the property owner being aware of the ramifications to BMP implementation.
c.
Clear depiction of location of BMPs, especially those located
below ground.
d.
A matrix depicting the types of BMPs, frequency of inspection,
type of maintenance required, and if proprietary BMPs, the company
information to perform the necessary maintenance.
e.
Agreement to retain documentation of proper maintenance for
a period of two years.
f.
Understanding that documentation of proper maintenance must
be presented to the city upon request.
5.
The owners of the land served by the stormwater BMPs shall certify
annually that all BMPs identified in the approved LID Plan have been
inspected and maintained in accordance with the approved BMP maintenance
plan. This certification shall be submitted to the city engineer by
September 30th annually.
6.
The city of San Dimas shall inspect new development/redevelopment
projects once every two years after the date of project completion,
to assess operational conditions for LID and hydromodification control
BMP repair, replacement, and/or re-vegetation.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
Any person violating any provision of this chapter shall be responsible for a municipal civil infraction and subject to the city's enforcement policy as set forth in the provisions of Title 1 and/or Chapter 8.16 of the San Dimas Municipal Code.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
Where there is work in progress that causes or constitutes,
in whole or in part, a violation of any provision of this chapter,
the city is authorized to issue a stop work order to prevent further
or continuing violations or adverse effects. All persons to whom the
stop work order is directed, or who are involved in any way with the
work or matter described in the stop work order shall fully and promptly
comply therewith. The city may also undertake or cause to be undertaken,
any necessary or advisable protective measures to prevent violations
of this chapter or to avoid or reduce the effects of noncompliance
herewith. The cost of any such protective measures shall be the responsibility
of the owner of the property upon which the work is being done and
the responsibility of any person carrying out or participating in
the work.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
In addition to any other remedies, should any property owner
fail to comply with the provisions of this chapter, the city may,
after the giving of reasonable notice and opportunity for compliance,
have the necessary work done, and the owner shall be obligated to
promptly reimburse the city for all costs of such work.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
When emergency measures are necessary to moderate a nuisance,
to protect public safety, health and welfare, and/or to prevent loss
of life, injury or damage to property, the city is authorized to carry
out or arrange for all such emergency measures. Property owners shall
be responsible for the cost of such measures made necessary as a result
of a violation of this chapter, and shall promptly reimburse the city
for all of such costs.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
A discharger shall be liable for all costs incurred by the city
as the result of causing a discharge that produces a deposit or obstruction,
or causes damage to, or impairs a storm drain, or violates any of
the provisions of this chapter. Costs include, but are not limited
to, those penalties levied by the Environmental Protection Agency
or Los Angeles Regional Water Quality Control Board for violation
of an NPDES permit, attorney fees, and other costs and expenses.
(Ord. 1231 § 1, 2014; Ord. 1306, 7/23/2024)
