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| Basin – A
basin functions the same way as a dam, but usually does not
require an embankment to impound water. Basins are dug into the
ground and store water at or below grade. Basins have outlet
pipes that release flows at a predefined rate. Any flows that
enter the basin at a rate in excess of the outlet pipe’s
capacity are temporarily stored in the basin. |
Best Available Technology (BAT)
– BAT is the acronym for best available technology economically
achievable. BAT is the technology-based standard established by
congress in the CWA for industrial dischargers of storm water.
Technology-based standards establish the level of pollutant
reductions that dischargers must achieve, typically by treatment
or by a combination of treatment and best management practices,
or BMPs. For example, secondary treatment (or the removal of 85%
suspended solids and BOD) is the BAT for suspended solid and BOD
removal from a sewage treatment plant. BAT generally emphasizes
treatment methods first and pollution prevention and source
control BMPs secondarily.
The best economically achievable technology that will result in
reasonable further progress toward the national goal of
eliminating the discharge of all pollutants is determined in
accordance with regulations issued by the Environmental
Protection Agency Administrator. Factors relating to the
assessment of best available technology shall take into account
the age of equipment and facilities involved, the process
employed, the engineering aspects of the application of various
types of control techniques, process changes, the cost of
achieving such effluent reduction, non-water quality
environmental impact (including energy requirements), and such
other factors as the permitting authority deems appropriate.
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| Beneficial Uses
- are defined as the uses of water necessary for the survival or
well being of man, plants, and wildlife. These uses of water
serve to promote the tangible and intangible economic, social,
and environmental goals. “Beneficial Uses” of the waters of the
State that may be protected against include, but are not limited
to, domestic, municipal, agricultural and industrial supply;
power generation; recreation; aesthetic enjoyment; navigation;
and preservation and enhancement of fish, wildlife, and other
aquatic resources or preserves. Existing beneficial uses are
uses that were attained in the surface or ground water on or
after November 28, 1975; and potential beneficial uses are uses
that would probably develop in future years through the
implementation of various control measures. “Beneficial Uses”
are equivalent to “Designated Uses” under federal law.
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| Bid Estimate
– An estimate of the total cost of the construction project.
There are generally two types of bid estimates. The first is the
“engineer’s estimate”, which is the estimate prepared by the
District Engineer during the design process for budgeting
purposes. The other is the “Contractor’s Estimate”, which is
received during the bidding process. The contractor’s estimate
is the estimate of the contractor’s costs (including profit) to
complete the project. Generally, the District will publicly
announce the proposed project and a date by which all bidders
must return a sealed proposal including the contractor’s bid
estimate. On that date, the District will open all the sealed
proposals and announce the contractor with the lowest estimate.
If that contractor meets all minimum qualifications to perform
the work, they will be awarded the contract. |
| Bid Items –
A list of “Items of Work” that have been identified, the
complete list of which would define all work necessary to
complete the construction contract. These items are usually
listed towards the front of the contract document. The list,
referred to as a proposal, includes the Bid Item, the unit of
measurement (Lump Sum, Cubic Yards, Lineal Feet, Each, etc), and
the estimated quantity of material necessary to complete that
item of work. This identification of bid items and quantities is
usually prepared by the District’s Design Engineer. Detailed
descriptions of the bid item requirements are included in the
Special Provisions and Detailed Specifications portion of the
Specifications and Contract Document. |
| Blue Line Stream
- Any stream shown as a solid or broken blue line on 7.5 Minute
Series quadrangle maps prepared by the U.S. Department of the
Interior Geological Survey (USGS). A blue line stream may be any
creek, stream or other flowing water feature, perennial or
ephemeral, indicated on USGS quadrangle maps, with the exception
of man-made watercourses. The United States Army Corps of
Engineers uses USGS blue line stream markings as a preliminary
indicator of “Waters of the United States”. Streams identified
on USGS maps in such a manner are therefore generally subject to
federal environmental regulations. |
| BMP – Best
Management Practices (BMP) are the practice or combination of
practices that are determined to be the most effective,
practicable means of preventing or reducing the amount of
pollution generated by point and non-point sources to a level
compatible with water quality goals (including technological,
economic, and institutional considerations). BMPs are defined as
schedules of activities, prohibitions of practices, maintenance
procedures, and other management practices to prevent or reduce
the pollution of waters of the United States. Best Management
Practices include practices to control runoff during
construction (such as silt fences). Other examples of BMPs may
include public education and outreach, proper planning of
development projects, proper clean out of catch basin inlets,
and proper sludge or waste handling and disposal, among others.
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| Boundary Survey
- A survey for the express purpose of locating the corners and
boundary lines of a given parcel of land. This involves record
and field research, measurements, and computations to establish
boundary lines in conformance with the Professional Land
Surveyors Act. Easement lines may also be located and/or
established with this type of survey. |
Budget Hearing
– Each year the District holds public hearings for the specific
purpose of receiving flood control project requests. These
hearings are held in a centrally located public place in each of
the District’s seven taxing zones. Any individual or group from
the private or public sector may make a request for a flood
control project by appearing at the hearing or by submitting a
written request to the District prior to the hearing. Support
for existing budgeted projects may also be offered.
At the public hearing, all requests will be considered by the
District's Zone Commissioners and staff and, where appropriate,
an open discussion may occur. After the public hearings the
District staff prepares cost estimates of all new project
requests and ongoing projects and then prioritizes them on the
basis of public need, necessity and funds available. A draft
budget is then prepared by the District staff and is presented
to the Zone Commissioners at a second set of public meetings
(work sessions) which are tentatively scheduled for January.
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| Budget Workshop
– The work session that finalizes the tentative budget proposal
for that taxing zone. The District presents the draft budget to
the Commissioners, who review it in detail with District staff
and make adjustments as they deem appropriate before making a
recommendation for approval. The work session is a public
meeting however, the Commissioners do not take requests or
testimony at this session. |
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| California Endangered Species Act
(CESA) - The Act was originally
adopted in 1970. It requires the California Department of Fish
and Game to inventory all threatened fish and wildlife, develop
criteria for rare and endangered species and report to the
Governor and Legislature every two years on the status of those
species. In 1984 the Act was amended to more closely resemble
the federal Endangered Species Act. One of the Acts many
requirements include that all government agencies undertaking
activity that alters the bed, channel or bank of any stream,
creek or river obtain a Section 1601 Streambed Alteration Permit
from the California Department of Fish and Game. Species
protected under CESA are not necessarily protected under the
federal ESA and vice versa. |
California Environmental Quality Act
(CEQA) - First enacted in 1970 to
provide long-term environmental protection, the law is the
foundation of environmental law and policy in California. CEQA
encourages the protection of all aspects of the environment by
requiring state and local agencies to prepare multidisciplinary
environmental impact studies. Any project that requires the
discretionary approval of a state or local legislative body must
comply with CEQA requirements. CEQA has six major objectives: 1)
to disclose to decision makers and the public the significant
environmental effects of proposed activities, 2) to identify
ways to avoid and reduce environmental damage, 3) to prevent
environmental damage by requiring implementation of feasible
alternatives or mitigation measures, 4) to disclose to the
public reasons for agency approval of projects with significant
environmental effects, 5) to foster interagency coordination in
the review of projects and 6) to enhance public participation in
the planning process.
The act requires projects subject to the regulations to prepare
an Initial Study (IS) to determine whether the project could
have significant environmental impacts. If no impacts are found,
a Negative Declaration (NEG DEC) can be filed. If potentially
significant impacts are discovered, an Environmental Impact
Report (EIR) is required to analyze the level of impacts and
suggest mitigating measures. These documents must be made
available to the public for review and comment. At the end of
the comment period, the agency may revise the project and
environmental documents per any legitimate comments received and
may file a Notice of Determination (NOD) stating that the agency
is carrying out the project as proposed. |
| Cast In Place Pipe (CIPP)
– A storm drain construction method where the pipe is formed in
the pipe trench. The process is accomplished with a slip form
and requires soils that are stable at steep slopes. CIPP
construction methods are generally less expensive than RCP
construction methods. Unfortunately, the proper soil conditions
for CIPP construction are rare. Catch Basin - Curbside opening
that collects rainwater from streets and serves as an entry
point to the storm drain system. |
| Change Order
– A negotiated amendment to the Original Construction Contract
Document that covers a specific change in the design of and/or
payment for the project. Change orders are usually required when
an unforeseen problem arises in the field. The problem could be
a utility line discovered in the field that conflicts with the
projects alignment, a mistake on the plan sheets, an unknown
soil condition that prevents the expected progression of the
work, or a myriad of other things. Change orders usually require
the coordination and cooperation of the contractor, the
District’s Design Engineer and the District’s Inspection Staff.
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| Channel – A
flood control conveyance system that is partially exposed to the
atmosphere. Water in channels flow due to the forces of gravity.
Channels include natural waterways, concrete flumes and other
similar conveyances. Channels can be lined with a number of
materials or combinations of materials. Selection of material
type is usually dependent on environmental constraints and
channel velocities. Analysis of channels can be done with a
number of software packages including WSPGW for prismatic
channels and/or HEC-2/HEC-RAS for more complex non-prismatic
channel systems. Channels are usually set in the ground such
that the design water surface elevation is at least one foot
below adjacent ground. |
| Clean Water Act (CWA)
- The Clean Water Act (CWA) contains a number of provisions to
restore and maintain the quality of the nation’s water
resources. One of these provisions is Section 303(d), which
establishes the TMDL program. It also includes provisions
regulating point source and nonpoint source pollution.
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| Concrete –
Concrete is a mixture of two components: aggregate and paste.
The paste, comprised of Portland cement and water, binds the
aggregates (sand, gravel and crushed stone) into a rocklike mass
as the paste hardens due to the chemical reaction between the
water and the cement. Concrete is usually made up of 60-75%
aggregates and 25-40% paste. The quality and strength of
concrete is greatly dependent on the paste, which must
completely coat each particle of aggregate and fill all the
space between the aggregates. Concrete is excellent at resisting
compressive forces. Its ability to resist tensile forces (forces
that stretch or pull), however, is generally only about 10% of
its ability to resist compressive forces. The District uses
concrete to construct channels, storm drains, catch basins and a
number of other structures required for flood control. Different
structures require different qualities of concrete. The District
generally specifies 3 classes of concrete, which are
differentiated by the amount of cement required and the minimum
required compressive strength. Class “A” Concrete is used for
retaining walls and other structural concrete facilities. Class
“B” concrete is used for nonstructural flood control features
like cutoff walls. Class “C” concrete is often called “slurry”
and is used to fill voids that can form behind existing concrete
linings or be placed in other areas where erosion resistant fill
is required. See the chart below for more detail: Typical
District Concrete Class Specification and Uses Concrete Class
Minimum Cement Requirement Minimum Compressive Strength Use A 6
sacks/CY 4,000 psi Structural Flood Control Components B 5
sacks/CY 3,000 psi Non Structural Flood Control Components C 2
sacks/CY n/a Fill voids, erosion resistant cover |
Concrete Compressive Strength
– A measurement used to analyze the quality and strength of
concrete. The measurement usually specifies the minimum
compressive strength that must be attained by a concrete sample
by the 28th day after its placement. It is defined as the
measured maximum resistance of a concrete specimen to axial
loading, expressed in pounds per square inch. Strength tests are
usually performed on test cylinders at the 7-day and 28-day
marks. ASTM C192 specifies the collection procedure for samples
used to determine compressive strength. The test requires that a
sample of the concrete mix be placed in a cylinder 12 inches by
6 inches in diameter. The wet concrete is placed in the cylinder
in 3 approximately equal layers, with each layer being rodded
(by a small diameter steel rod) 25 times. After the third layer
is rodded, the test cylinder is capped and taken to a lab for
safe storage. ASTM C617 specifies the necessary preparations to
test the cylinders and ASTM C39 specifies the actual test. The
test procedure specifies that the cylinder be placed in a
machine that applies a compressive force on the test cylinder.
The force is gradually increased until the cylinder fails.
Dividing the maximum applied force to the cylinder by the
cylinder’s cross sectional area provided the maximum compressive
strength of the test specimen.
This strength is then compared to the minimum concrete
compressive strength required by the District’s design
engineers. Concrete Construction Specifications – That section
of the District’s Specification and Contract Documents, within
the Detailed Specifications Section, that covers the
requirements, materials, methods, testing, measurement and
payment for concrete construction. The section also specifies
how concrete is to be placed and cured, the location and types
of joints and weep holes, and any specific requirements for the
various types of concrete structures to be placed in the field
(reinforced concrete box, channel wall, channel invert, cutoff
walls, catch basins, etc.). |
| Condemnation
– The process by which property is acquired for public purposes
under the power of eminent domain. Government agencies pursuing
condemnation must prove that a public necessity exists that
requires the taking of the property. |
| Conditional Letter of
Map Revision (CLOMR) - This letter
from FEMA provides comments on a proposed project and its
resulting affect on revising a FIRM if the project is
constructed. It indicates whether the project meets NFIP
criteria. Documentation justifying the proposed projects impact
on the floodplain within the District’s jurisdiction must be
reviewed and approved by the District’s Floodplain Management
Staff prior to being submitted to FEMA for a CLOMR. The
Floodplain Management Staff also prepare CLOMR studies for
proposed District Project’s within FEMA jurisdiction. The
studies consist of a number of elements including a pre-project
hydraulic model that is capable of matching the existing FEMA
hydraulic model (Duplicate Effective Model) and a post project
hydraulic model representing the changes the project will
generate. |
| Confluence
– The joining of two flood control facilities. |
| Critical Depth
– Identified as the depth of flow that requires the least energy
to perpetuate for a given flow rate. Critical depth is important
to design engineers because its occurrence can be predicted.
Knowing where critical depth can occur allows a design engineer
to establish or verify control points in their hydraulic model.
It is also important because critical depth can be difficult to
maintain. Slight perturbations in a channel or storm drain
section could cause significant changes in flow depth. For this
reason, engineers often design channels so that they will be
well into the subcritical or supercritical flow regimes.
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| Construction Survey
- Construction staking of improvements shown on improvement
plans for control of construction on developments for storm
drains, channels, roads, etc. |
| Contour
– An imaginary line on the ground, all points of which are at
the same elevation above a specified datum surface. A contour is
illustrated by the shoreline of an imaginary body of water whose
surface is at the elevation represented by the contour. A
contour forming a closed loop around lower ground is termed a
depression contour. The District orthophoto and design maps
generally use NGVD29 as the datum surface. |
| Contour Interval
– The vertical difference represented between each contour line.
For district orphophoto mapping, the contour interval is 4 feet.
This means there is a 4-foot elevation change between each line
plotted. |
| Control Survey
- Precise location of horizontal and vertical positions of
points for use in boundary determination, mapping from aerial
photographs, construction staking, and other related purposes.
Court Exhibit Survey - Analysis of various legal descriptions
and survey maps; field locating of record, existing monuments,
and physical features; and mapping showing this information for
the purpose of presenting a visual exhibit to be used in a
courtroom. |
| County Surveyor
– On April 9, 1850, the legislature adopted an Act prescribing
the duties, and fixing the compensation of County Surveyors. In
general, the county surveyor is authorized to practice land
surveying and is subject to all provisions of the Professional
Land Surveyors Act. The county surveyor is an ex officio deputy
recorder for the purpose of copying each map filed for record
and is required to make all county, road, district, and other
maps and all assessors block books for the county. The County
Surveyors office performs most survey functions for the County
of Riverside. The District has its own in house survey staff,
but is required to file Records with the County Surveyor’s
Office. |
| County Recorder
– The recorder's office is responsible for providing
constructive notice of private acts and creating and maintaining
custody of permanent records for all documents filed and
recorded in Riverside County. The office of recorder provides
public access to information regarding land and land ownership.
The county recorder files records of survey and maintains
indexes by the name of grant, tract, subdivision, or United
States Public Lands. Copies of the record of survey are
available to the public and the original can be produced upon
demand. |
| Cubic foot per second
(ft3/s, or cfs) - Rate of water
discharge representing a volume of 1 cubic foot passing a given
point during 1 second, equivalent to approximately 7.48 gallons
per second or 448.8 gallons per minute. In a stream channel, a
discharge of 1 cubic foot per second is equal to the discharge
at a rectangular cross section, 1 foot wide and 1 foot deep,
flowing at an average velocity of 1 foot per second.
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| D-Load
– A design criterion used by engineers to specify the strength
of precast reinforced concrete pipe (RCP) for storm drains. The
D-Load represents the maximum force that will bear down on the
RCP once it has been put in place and backfilled. The load
includes the dead load (weight of the fill over it) and the live
loads (weight of the largest vehicle expected to pass over the
RCP). The D-Load represents the combination of the dead and live
loads, with factors of safety, divided by the diameter of the
pipe. The manufacturer produces the pipe to meet the specified
loading criteria. District Materials Inspection Staff usually
require the pipe manufacturer to supply a few sections of pipe
for testing purposes to ensure that they meet the minimum
loading requirements. |
| Dam
– Dams are usually constructed by making a large embankment that
blocks an existing watercourse. This embankment is used to
control the release of flood waters downstream of the Dam. Dams
usually contain a small outlet pipe that limits the amount of
water that can exit the dam. Any flows in excess of the capacity
of the dam outlet are stored behind the dam. Most dams are
regulated by the Department of Water Resources, Division of
Safety of Dams. |
| Design Mapping
– Mapping requested by Design Engineers specifically for the
preparation of plans for a specific District project. Depending
on the project, the mapping can be provided at horizontal scales
of 1”=50’, 1”=40’ or 1”=20’. The contour interval of the mapping
is generally 1 foot. The mapping generally includes a number of
additional planimetric features not provided on typical
orthophoto mapping. |
| Detailed Specifications
- A detailed, exact statement of particulars, prescribing
materials and methods, quality and payment for specific items of
work for the project. The detailed specifications cover items
such as mobilization, water control, traffic control, clearing
work, earthwork, trench safety systems, concrete construction,
precast reinforced concrete pipe, cast in-place concrete pipe,
fences and gates, miscellaneous construction items, dust
abatement and NPDES requirements for District Projects. This is
where you would find information on strength, testing and
placement of materials. See the “concrete construction
specifications” for a more detailed example of the information
provided in the Detailed Specifications. |
| Digital Terrain Map
(DTM) – a three-dimensional computer
model of the terrain of a given area. These maps are created
using digital photogrammetric equipment. The raw maps are then
supplemented by any additional survey data that has been
collected. The photogrammetrist generates the final contour maps
from the DTM. DTMs are also provided to the District’s
engineering staff for design and planning purposes. District
Engineers can use CAD software to manipulate the DTMs for the
purposes of generating cross sections or profiles along a
project alignment. The DTMs can also be used to estimate
earthwork quantities. |
| Discharge
- Another term for stream flow; it is the measured volume of
water that moves past a point in the river in a given amount of
time. Discharge is usually expressed in cubic feet per second.
The average discharge of the Columbia River in September at The
Dalles, Oregon, is about 120,000 cfs, which would fill the
Seattle Kingdome in less than 10 minutes. Dry Density – Soils
are made of three components – air, water and solids (soil
particles). Dry Density is a ratio of the mass of the solids in
a compacted soil sample to the total volume of the sample
(including the volume taken by air, water and the solids). The
dry density of a soil sample is usually obtained by determining
the volume of a given sample of soil, baking it to evaporate all
the water, then measuring its mass. |
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| Eminent Domain
– The right by which a sovereign government, or a person or
agency acting under its authority, may acquire private property
for public or semi-public use upon payment of reasonable
compensation and without consent of the owner. |
| Easement
– A non-possessing interest held by the District in the land of
another whereby the District is accorded partial use of such
land for a specific purpose. An easement restricts but does not
abridge the rights of the fee owner to the use and enjoyment of
the land. Easements may be given for surface rights, subsurface
rights or overhead rights. For example, the District may use an
easement to obtain rights to construct a storm drain through
someone’s property. The easement would give the District the
right to perform maintenance of the facility and would restrict
the property owner from placing structures over the facility.
The easement would allow the owner to continue to plant grass or
otherwise use the property, while saving the District the costs
of having to outright purchase the property. |
| Endangered Species Act
(ESA) - An act passed by Congress in
1973 intended to protect species and subspecies of plants and
animals that are of “aesthetic, ecological, educational,
historical, recreational and scientific value.” It also protects
the listed species’ “critical habitat”, the geographic area
occupied by, or essential to, the protected species. The U.S.
Fish and Wildlife Service (USFWS) and the National Marine
Fisheries Service (NMFS) share authority to list endangered
species, determine critical habitat and develop recovery plans
for listed species. Currently, approximately 830 animals and 270
plants are listed as endangered or threatened nationwide at
Title 50, Part 17, sections 11 and 12 of the Code of Federal
Regulations. Further, under a settlement with environmental
groups, USFWS has agreed to propose listing another 400 species
over the next few years. A number of endangered or threatened
species are found in Riverside County. These include least
bell's vireos, southwestern willow flycatchers, California
gnatcatchers, Stephen’s' and San Bernardino kangaroo rats, quino
checker spot butterflies, arroyo toads and Delhi sands
flower-loving flies. |
| Ephemeral stream
- A stream or part of a stream that flows only in direct
response to precipitation; it receives little or no water from
springs, melting snow, or other sources; its channel is at all
times above the water table. |
| Evapotranspiration
- The process by which water is discharged to the atmosphere as
a result of evaporation from the soil and surface-water bodies,
and transpiration by plants. Transpiration is the process by
which water passes through living organisms, primarily plants,
into the atmosphere. |
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| Fast Tract Project
– A streamlined land-use approval and permit process, saving
qualified businesses precious time and money through expeditious
processing of commercial and industrial projects. To qualify the
project must create a minimum of 75 permanent full-time jobs,
invest a total of at least $10 million in land, buildings and/or
equipment or produce $25 million in taxable annual sales. The
process allows developers to meet with County and District
Subdivisions Staff prior to official submittal of the project to
the County. This process allows the developers to identify and
correct for potential constraints on their developments prior to
their first submittal. Once a project is qualified and is
submitted under the Fast Track process, it is guaranteed
expedited review from the various County Agencies. |
| Fee
– Real property owned outright by title, generally without any
limitations or restrictions (also known as Fee Simple), but
subject to the limitations of eminent domain, police power and
taxation. Federal Emergency Management Agency (FEMA) -
administers the NFIP and disaster planning and recovery
programs. FEMA works closely with states and communities and
provides financial and technical assistance and flood hazards
maps and data to better manage floodplains. |
| Field Density Test
– Determines the density of a compacted fill to see if it meets
predefined specifications. The District performs Field Density
Tests using a nuclear gauge. The device has a probe containing a
radioactive material that is inserted into a hole punched into
the compacted soil. The rate of radiation penetration through
the soil is detected and used to determine both the wet density
and water content of the soil. The dry density can then be
calculated and compared to the maximum dry density obtained by
previous soils testing (most likely from the modified proctor
test). |
| Flight Height
– is defined as the height of the camera above the mean ground
elevation. Photogrammetric mapping requires that a certain ratio
of flight height to contour interval be maintained in order to
assure minimum accuracy of the mapping. Flight Line – A line
drawn on a map or chart to represent the track of the aircraft
during the period taking aerial photographs. |
| Flood Insurance Rate Map
(FIRM) – A FIRM is the official map
of a community on which FEMA, the Federal Emergency Management
Agency, has delineated both the special flood hazard areas and
the flood risk premium zones applicable to the community. The
base maps are usually USGS 7.5- Minute Quadrangles and can be
found in the floodplain management section. Flood risk
information presented on FIRMs is based on historic,
meteorologic, hydrologic, and hydraulic data, as well as
open-space conditions, flood control works, and development. To
prepare FIRMs that illustrate the extent of flood hazard in a
flood prone community, FEMA conducts engineering studies
referred to as Flood Insurance Studies (FISs). Using information
gathered in these studies, FEMA engineers and cartographers
delineate Special Flood Hazard Areas (SFHAs) on FIRMs. SFHAs are
those areas subject to inundation by a flood that has a
1-percent or greater chance of being equaled or exceeded during
any given year. This type of flood is referred to as a base
flood. A base flood has a 26-percent chance of occurring during
a 30-year period ... the length of many mortgages. The base
flood is a regulatory standard used by Federal agencies, and
most states, to administer floodplain management programs, and
is also used by the National Flood Insurance Program as the
basis for insurance requirements nationwide. |
| Flood Insurance Studies
(FIS) - Flood hazard areas are
determined using statistical analyses of records of river-flow,
storm tides, and rainfall; information obtained through
consultation with the community; floodplain topographic surveys;
and hydrologic and hydraulic analyses. The FIS covers those
areas subject to flooding from rivers and streams, along coastal
areas and lake shores, or shallow flooding areas. Actual copies
of FISs can be ordered from FEMA’s Map Services Center. The
results of the Flood Insurance Study that define flood risk
areas for each community are available in a technical document
that provides information used for floodplain management. This
is known as the Flood Insurance Study Report. Regulatory
floodways and other floodplain management information may be
shown on a separate flood map known as a Flood Boundary and
Floodway Map (FBFM). If the FBFM for the FIS is available, it is
distributed with the Flood Insurance Study report. Floodplain:
The relatively flat area of low lands adjoining, and including,
the channel of a river, stream, watercourse, bay, or other body
of water which is subject to inundation by the flood waters of
the 100-year frequency floods. |
| Floodway
- The channel of a river or other watercourse and the adjacent
land areas that must be reserved in order to pass the 100-year
flood without cumulatively increasing the water surface
elevation more than one foot. The floodway also includes all
land necessary to convey a ten-year flood without structural
improvements. Private development may not encroach into floodway
limits without construction of a FEMA approved flood control
facility that is to be maintained by a public agency and without
first obtaining a CLOMR. |
| Freeboard
– Generally defined as the difference in elevation from the top
edge of a flood control facility (channel, dam, basin) to the
design WSE. Freeboard provides a factor of safety and protects
against unknown factors such as wave action. Freeboard varies
based on the type of project and velocities of flows, but is
generally between 1-3 feet. |
| Frequency Analysis
- a statistical technique used by hydrologists for estimating
the average rate at which floods, droughts, storms, stores,
rainfall events, etc., of a specified magnitude recur. The
District generally performs frequency analysis on rainfall data.
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General Plan
- The general plan is the master document for planning for
growth in the city or region. In California, state law requires
all cities and counties to adopt "a comprehensive, long-term
general plan for [its] physical development." This general plan
is the official city or county policy regarding the location of
housing, business, industry, roads, parks, and other land uses,
protection of the public from noise and other environmental
hazards, and for the conservation of natural resources. The
legislative body of each city (the city council) and each county
(the board of supervisors) adopts zoning, subdivision and other
ordinances to regulate land uses and to carry out the policies
of its general plan.
The local general plan can be described as the city's or
county's "blueprint" for future development. It represents the
community's view of its future; a constitution made up of goals
and policies upon which the city council, board of supervisors,
and planning commission will base their land use decisions. The
general plan is not the same as zoning. Although both designate
how land may be developed, they do so in different ways. The
general plan and its diagrams have a long-term outlook,
identifying the types of development that will be allowed, the
spatial relationships among land uses, and the general pattern
for future development and infrastructure. Zoning regulates
present development through specific standards such as lot size,
building setback, parking and landscaping requirements and a
list of allowable uses. Development must not only meet the
specific requirements of the zoning ordinance but also the
broader policies set forth in the local general plan.
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| General Provisions
– The portion of the Specification and Contract Document that
defines the relationship between the District and the
Contractor. It defines those items that tend to be common to all
construction project contracts. These items include the scope of
work, the authority and responsibilities of the parties, the
responsibility for supplying materials, legal relations,
expected progress, insurance requirements and guidelines for
payment for work. |
| GPS Surveys
– Global Positioning System (GPS) Surveys are based on a one-way
(Satellite to receiver) ranging system. GPS surveys are fast and
accurate. They also require expensive equipment and are
dependent on satellite availability/visibility. There are two
types of GPS surveys – Standalone navigational mode surveys –
which provide an accuracy of +/-2 to 10 meters (similar to
retail hand held units); and differential or relative
positioning surveys which yields centimeter accuracies. In
differential surveys, two GPS units are required. One unit is
placed on a known control point, or benchmark, the other is
placed on points where coordinating information is required. The
District uses various types of differential units, including
RTK, data logging and kinematic GPS units, to determine the
coordinates of unknown points quickly and accurately. Points can
often be located with differential units in a matter of seconds.
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| Hydraulic Analysis
- The analysis undertaken to determine the capacity of a
particular drainage work. This analysis is used to determine the
attributes of the flowing water such as, water level or surface
profile, velocity, total energy and erosive force (tractive
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| Hydraulic Grade Line
– The hydraulic grade line is defined as the static head of
water. For storm drains under pressure flow, it can be
represented by the height relative to the invert of the storm
drain to which water would rise if a tube were inserted in the
storm drain soffit. |
| Hydrograph
- A hydrograph is a graph that shows changes in discharge of a
river or stream at a given point over time. The time scale may
be in minutes, hours, days, months, years or decades. Hydrologic
soil group - A classification of a soil type on the basis of its
permeability after prior wetting and swelling of the soil, and
without the protective effect of vegetation. |
| Hydrology
- Science dealing with the occurrence, distribution and
circulation of water on the earth, including precipitation,
stormwater runoff and groundwater. |
| Hyetograph
– A graph of precipitation over time. The District has three
standard hyetographs that are used for hydrologic analysis. The
hyetographs represent precipitation patterns for 3-hour, 6-hour
and 24-hour duration rainfall events. |
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| Illicit Discharge
– is any discharge to a municipal separate storm sewer that is
not composed entirely of storm water except discharges pursuant
to a NPDES permit (other than the NPDES permit for discharges
form the municipal separate storm sewer) and discharges
resulting from fire fighting activities. |
| Impervious Surface
- 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. |
| Invert
– Generally considered to be the lowest point on a channel or
storm drain. |
| Isohyetal Maps
– A map describing the expected precipitation over an area based
on a given return frequency. Each isohyet, or line, represents a
line of equal precipitation. By identifying your location on a
map and determining the magnitude of the adjacent isohyets, you
can determine the magnitude of rainfall expected to occur during
a specific return frequency. The District hydrology manual
provides isohyetal maps for 2 year and 100 year return
frequencies. |
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Jetting – In jetting,
water is pumped under pressure through a steel tube into a soil. The
force of the jetted water moves and compacts the bedding or backfill
material below it. A sand material with few fines can be jetted to
produce good compaction, especially under pipe haunches or other areas
that are difficult to mechanically compact. The sand material must be
clean and free draining and the surrounding soil must be well drained,
or other means of draining the backfill must be provided. As with any
type of backfilling, material should be placed slowly and in lifts.
Jetted lifts can be places as thick as 4 feet. It should only be
practiced when the proper soils are available and mechanical compaction
is not feasible. Jetting is controversial. It is often difficult to
guarantee consistent compaction with the jetting process.
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| Lateral Pipe
– A small, usually reinforced concrete pipe, which conveys water
from catch basins or other inlets, to the mainline storm drain
or channel. |
| Land Use Permits
- These are permits obtained for particular development
proposals on already subdivided land. The zoning of the site
determines the types of uses allowed and the appropriate type of
application for that use to be filed with the Planning
Department. Common use cases are: Conditional Use Permits,
Second Unit Permits, Public Use Permits, Plot Plans subject to
the California Environmental Quality Act (CEQA), and Plot Plans
that aren’t subject to CEQA. Each type of permit has different
requirements for its public hearing process, the use of the
permit and the revocation of the permit. |
| Legal Description
– The description portion of the limit of real property in any
deed, trust deed, or other title document. It must be approved
by an individual authorized to practice land surveying. The
creation and recording of legal descriptions are regulated by
the Professional Land Surveyor’s Act. |
| Letter of Map Revision
(LOMR) - Issued by FEMA with an
accompanying copy of an annotated FIRM, this acknowledges
changes in the base flood elevation, floodplain boundary, or
floodway based on post-construction or revised conditions. LOMRs
are issued upon completion of a project. Most projects obtain a
CLOMR prior to construction to ensure that the proposed facility
will meet FEMA criteria. Obtaining a CLOMR is a way to guarantee
that unforeseen issues do not prevent the issuance of a LOMR.
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| Levee – An
elevated berm that is used to protect adjacent low lying ground
from floodwaters. The levee is usually lined with a structural
material such as concrete or rip-rap to ensure that it does not
fail from erosion. This lining usually extends many feet below
ground to ensure that scour caused by high water velocities
cannot undermine the levee. |
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| Manhole
– An opening in the top of a storm drain that allows access to
the storm drain from the manhole inlet (usually located in the
street). Manholes are significant because they introduce
hydraulic inefficiencies into the storm drain system.
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| Manning's Equation
- A formula for calculating the velocity of flow in a channel as
a function of relative roughness, cross-sectional configuration,
and gradient. |
Master Drainage Plan (MDP)
– A master drainage plan addresses the current and future
drainage needs of a given community. The boundary of the plan
usually follows regional watershed limits. The proposed
facilities may include channels, storm drains, levees, basins,
dams, wetlands or any other conveyance capable of economically
relieving flooding problems within the plan area. The plan
includes an estimate of facility capacity, sizes and costs.
Preparation of an MDP requires not only an understanding of the
existing flood hazards, but also an understanding of the future
development trends within a community. Planning engineers must
obtain the latest County and/or city General Plans to establish
the ultimate development pattern for the plan area. Once this is
known, the Planning engineer can estimate future runoff patterns
and prepare a plan that economically addresses both existing and
future problems.
MDP’s are prepared for a variety of purposes. First, the plans
provide a guide for the orderly development of the County.
Second, they provide an estimate of costs to resolve flooding
issues within a community. These plans are used by the
District’s Management, Zone Commissioners and Board of
Supervisors to determine Capital Project expenditures for each
budget year. Finally, the plans can be used to establish Area
Drainage Plan fees for a given community, which prevent existing
taxpayers from having to shoulder the burden of land development
costs. |
| Maximum Extent
Practicable (MEP) – Maximum Extent
Practicable (MEP) is the technology-based standard established
by Congress in the CWA that municipal dischargers of storm water
(MS4s) must meet. Technology-based standards establish the level
of pollutant reductions that dischargers must achieve, typically
by treatment or by a combination of treatment and best
management practices (BMPs). MEP generally emphasizes pollution
prevention and source control BMPs primarily (as the first line
of defense) in combination with treatment methods serving as a
backup (additional line of defense). MEP considers economics and
is generally, but not necessarily, less stringent than BAT. A
definition for MEP is not provided either in the statute or in
the regulations. Instead the definition of MEP is dynamic and
will be defined by the following process over time:
municipalities propose their definition of MEP by way of their
Urban Runoff Management Plan. Their total collective and
individual activities conducted pursuant to the Urban Runoff
Management Plan becomes their proposal for MEP as it applies
both to their overall effort, as well as to specific activities
(e.g., MEP for street sweeping, or MEP for municipal separate
storm sewer system maintenance). In the absence of a proposal
acceptable to the RWQCB, the RWQCB defines MEP. |
| Migratory Bird Rule
- The Army Corps of Engineers has broadened the commerce
definition of Waters of the United States to include ephemeral
streams and wetlands by incorporating the “Migratory Bird Rule”.
This rule states that any water or wetland that may support
migratory birds by default supports interstate commerce due to
hunting, bird watching and camping activities that occur along
migratory bird routes. This interpretation provides the nexus
that allows the USACE to regulate these water bodies.
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| Mitigation Fee
- A fee, also called a development fee, levied on the developer
of a project by a city, county or other public agency as
compensation for otherwise-unmitigated impacts the project will
produce. California Government Code Section 66000, et. seq.,
specifies that development fees shall not exceed the estimated
reasonable costs of providing the service for which the fee is
charges. To lawfully impose a mitigation fee, the public agency
must verify its method of calculation and document proper
restrictions on use of the fund. |
| Modified Proctor Test
– A compaction test that attempts to determine the maximum
possible density of a soil by performing a series of test on a
compacted sample of the soil. For each test, the amount of water
present in the sample at the time of compaction is varied. A
plot of the results, comparing water content (horizontal axis)
to relative dry density (vertical axis) is then made. The plot
usually resembles a bell curve. The plot provides the maximum
possible dry density achievable by the soil and the optimum
water content necessary to achieve that density. Results of the
Modified Proctor test are used by contractors to determine the
proper range of water content of the fill necessary to meet the
District’s specified compaction requirements. Modified Proctor
Tests are usually performed by a soils engineer many months
before construction begins. Field Density tests are used to
compare Densities achieved in the field to the theoretically
maximum density determined by the Modified Proctor Test.
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Municipal Separate Storm Sewer System
(MS4) - A MS4 is a conveyance or
system of conveyances (including roads with drainage systems,
municipal streets, catch basins, curbs, gutters, ditches,
natural drainage features or channels, modified natural
channels, man-made channels, or storm drains): (i) Owned or
operated by a State, city town, borough, county, parish,
district, association, or other public body (created by or
pursuant to State law) having jurisdiction over disposal of
sewage, industrial wastes, storm water, or other wastes,
including special districts under State law such as a sewer
district, flood control district or drainage district, or
similar entity, or an Indian tribe or an authorized Indian
tribal organization, or designated and approved management
agency under section 208 of the CWA that discharges to waters of
the United States; (ii) Designated or used for collecting of
conveying storm water; (iii) Which is not a combined sewer; (iv)
Which is not part of the Publicly Owned Treatment Works (POTW).
Historic and current development makes use of natural drainage
patterns and features as conveyances for urban runoff. Urban
streams used in this manner are part of the municipalities MS4
regardless of whether they are natural, man-made, or partially
modified features. In these cases, the urban stream is both an
MS4 and a receiving water. |
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National Flood Insurance
Program (NFIP) – In 1968, Congress
created the NFIP in response to the rising cost of taxpayer
funded disaster relief for flood victims and the increasing
amount of damage due to floods. The program is designed to
reduce the loss of life, damage to property and rising disaster
relief costs in these high-risk areas.
The NFIP makes federally backed flood insurance available to
communities that agree to adopt and enforce floodplain
management ordinances intended to reduce future flood damage.
This voluntary program is administered by FEMA and aims to end
the expensive cycle of flooding and rebuilding. National Flood
Insurance is available in more than 19,000 communities across
the United States and its territories. The program required that
new or replacement buildings in the flood hazard areas are
constructed to mitigate future flood damages. FEMA insists on
assurances that local upstream flood repair measures and
development within floodplains will not exacerbate flooding in
adjacent areas. It guides future development away from flood
prone areas and transfers the costs of flood losses from
American taxpayers to floodplain property owners. The NFIP,
through partnerships with communities, the insurance agencies
and the lending industry, helps to reduce flooding damages by
nearly $800 million a year. Further, buildings constructed in
compliance with NFIP standards suffer approximately 80% less
damage annual than those not built in compliance. Every $3 paid
in flood insurance claims saves $1 in disaster assistance
payments.
THE NFIP program is made of three components: Flood Insurance,
Mapping and Floodplain Management. The NFIP is managed by FEMA’s
Federal Insurance and Mitigation Administration and the
Mitigation Directorate. The Federal Insurance and Mitigation
Administration manages the insurance component of the NFIP. The
Mitigation Directorate overseas the floodplain management and
mapping components of the program. |
| National Geodetic
Vertical Datum of 1929 (NGVD29) and North American Vertical
Datum of 1988 (NAVD88) – Two
vertical control datum's for the North American Continent. The
Datum's are referenced to mean sea level. NGVD29 was based on sea
level measurements and leveling networks along the coast, NAVD88
was based on gravity measurements and uses the Great Lakes to
determine sea level. They are completely different datum's, based
on slightly different ellipsoid models of the earth. The
difference between models produces slightly different elevations
at any given point on the surface of the earth. It is very
important to understand which vertical datum your survey
information is based on. The elevation difference between the
datum's is generally less than 2.5 feet in Riverside County. Many
engineers have had to make costly changes to their design during
construction because they hadn’t noticed that a plan set they
had based a design on was on a different vertical datum than the
rest of the project. |
| National Environmental
Policy Act (NEPA) – The federal law,
adopted in 1969, that provided the model for CEQA. The law
requires that agencies make a diligent effort to involve the
public in the project planning process. The law requires the
preparation of an Environmental Assessment (EA) to determine if
the proposed project will have any adverse environmental
impacts. Upon completion of the EA, a Finding of No Significant
Impacts (FONSI) may be filed if no impacts are found. An
Environmental Impact Statement (EIS), which analyzes the
project’s impacts and potential mitigation measures, must be
prepared if significant impacts to the environment are found.
Both documents must be made available for public review. Upon
completion of the noticing/review period, any necessary changes
to the project and/or documents are made by the lead agency and
a Record of Decision (ROD) can be filed authorizing the project
as described in the revised documents. NEPA regulations must be
followed when a project is constructed on federal lands, is
constructed with federal funds, or is found to be regulated by
other federal environmental regulatory laws. The federal
agencies undertaking or funding the project are responsible for
ensuring that the project complies with NEPA. National Pollution
Discharge Elimination System (NPDES) – The national program for
issuing, modifying, revoking and reissuing, terminating,
monitoring, and enforcing permits, and imposing and enforcing
pretreatment requirements, under sections 307, 402, 318, and 405
of the Clean Water Act. NPDES permits pertain to the discharge
of waste to surface waters. All State and Federal NPDES permits
are also Waste Discharge Requirements (WDRs). |
Non Point Source (NPS)
– refers to diffuse, widespread sources of pollution. These
sources may be large or small, but are generally numerous
throughout a watershed. Non Point Sources include but are not
limited to urban, agricultural, or industrial areas, roads,
highways, construction sites, communities served by septic
systems, recreational boating activities, timber harvesting,
mining, livestock grazing, as well as physical changes to stream
channels, and habitat degradation. NPS pollution can occur year
round any time rainfall, snowmelt, irrigation, or any other
source of water runs over land or through the ground, picks up
pollutants from these numerous, diffuse sources and deposits
them into rivers, lakes, and coastal waters or introduces them
into ground water.
Non-Structural Floodplain Management Controls – Management
controls that prevent structures from impacting floodplains.
Zoning ordinances that limit developments within mapped
floodplains are the most common non-structural control. Other
controls include designating low-lying areas and wetlands as
overflow areas that for storing excessive floodwaters and/or
relocating residents located within mapped floodplains. These
techniques are often viable in developing areas or rural areas,
but can be very controversial in highly urbanized areas.
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| North American Datum (NAD)
- .The horizontal control datum for the North American
Continent. It was first established in 1927 (NAD27) by geodetic
surveying methods, using Meades Ranch in Kansas as its base
position. A new datum was established in 1983, based on a more
accurate geodetic model of the earth’s surface (NAD83). NAD83
coordinate points cannot be directly interchanged with NAD27
coordinate points. Both datum's refer to the x coordinate as an
“Easting” and the y coordinate as a “Northing”. Coordinates
increase as you head east and north. |
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| Ordinance 458
– The purpose of the ordinance is to protect public health and
safety, public welfare and minimize public and private costs
caused by flooding by regulating development within flood hazard
areas. This ordinance was adopted to meet the criteria of the
National Flood Insurance Program and proposes regulations that
meet the requirements of the program. The ordinance regulates
FEMA mapped floodplains as well as specified non-FEMA mapped
floodplains (Ordinance 458 Floodplains). |
| Orthophoto Mapping
– The District’s general purpose mapping. Usually plotted at a
scale of 1”=200’ or 1”=400’. The maps have a contour interval of
4 feet. The maps cover a one square mile area and are indexed to
the U.S. Rectangular Survey System (Township/Range/Section
system). The maps generally identify contours, stream courses
and known survey control points. |
| Orthophotograph
– A photographic copy, prepared from a perspective photograph,
in which the displacements of images due to tilt and relief have
been removed. |
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| Perennial stream
- A stream that normally has water in its channel at all times.
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| Photogrammetry
– The science of obtaining reliable measurements by photography.
The District uses stereoscopic photographic methods to generate
maps. The stereoscopic method uses binocular vision to form a
single three-dimensional image from two photographic images of
the same terrain taken from slightly different vantage points.
With proper optical or digital equipment, all measurements
needed in map construction can be made from this visual model.
The digital stereoscopic technology is similar to the 3d
technology that IMAX theatres use to make and present 3D movies.
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| Photogrammetric Surveys
– Photogrammetric surveys are conducted using aerial photography
and ground survey control. Surveyors establish initial ground
control that can be identified from the aerial photographs taken
at high altitude by specialized aircraft. The control is used to
correct for edge distortions in the photographs. Photogrammetric
surveys are used to accurately and quickly map large tracts of
land. Photogrammetric methods allow for faster compilation of
data, but can provide inaccurate results in areas with dense
cover and extremely flat terrain. These areas may need to be
supplemented with additional total station or GPS survey data.
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| Planimetrics
– mapping features for which only horizontal data is presented.
These features generally include property lines, street
centerlines, structure footprints, utility lines, location of
vegetation and other natural or cultural features that may be
pertinent to the purpose of the map. |
| Point Source
– is any discernible, confined, and discrete conveyance,
including, but not limited to, any pipe, ditch, channel, tunnel,
conduit, well, discrete fissure, container, rolling stock,
concentrated animal feeding operations, landfill leachate
collection systems, vessel, or other floating craft from which
pollutants are or may be discharged. |
| Pollutant
– is broadly defined as any agent that may cause or contribute
to the degradation of water quality such that a condition of
pollution or contamination is created or aggravated. Under Clean
Water Act (CWA) Section 502(6) a pollutant is defined as dredged
spoil, solid waste, incinerator residue, sewage, garbage, sewage
sludge, munitions, chemical wastes, biological materials,
radioactive materials, heat, wrecked or discarded equipment,
rock, sand, cellar dirt, and industrial, municipal, and
agricultural waste discharged into water. |
| Pollution
- as defined in the Porter-Cologne Water Quality Control Act,
pollution is “the alteration of the quality of the waters of the
State by waste, to a degree that unreasonably affects the either
of the following: (1) The waters for beneficial uses; or (2)
Facilities that serve these beneficial uses.” Pollution may
include contamination. |
| Porter-Cologne Water
Quality Control Act – also referred
to as the ‘Porter-Cologne Act’. It is the principle law
governing water quality regulation in California. It is the
policy of the state, as set forth in Porter-Cologne, that the
quality of all the waters of the state shall be protected, that
all activities and factors affecting the quality of water shall
be regulated to attain the highest water quality within reason,
and that the state must be prepared to exercise its full power
and jurisdiction to protect the quality of water in the state
from degradation. Porter-Cologne directs the State Water
Resources Control Board to formulate and adopt state policies
for controlling water quality and designates the State Board as
the state water pollution control agency for all purposes stated
in the Clean Water Act. Porter-Cologne establishes the policies
that are to be implemented and authorities that are to be used
in achieving the goals of the Clean Water Act. |
| Post-Construction BMPs
– are a subset of BMPs including structural and non-structural
controls which detain, retain, filter, or educate to prevent the
release of pollutants to surface waters during the final
functional life of development. |
| Professional Land
Surveyor’s Act – In 1891, the State
of California became the first state to license Professional
Land Surveyors. The Board for Professional Engineers and Land
Surveyors administers the current version of the Professional
Land Surveyors Act (PLSA) defining the scope of practice and
license requirements for professional land surveyors. The PLSA
is revised periodically by the legislature to ensure the
protection of the public health, safety and welfare and to
reflect changes in technological advancements and licensure
requirements based on economic, social, and political
conditions. The Act regulates the profession of surveying and
defines how various types of surveys are to be undertaken and
recorded. |
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| Rational Method
– A means of computing flow rates (Q) by use of the formula Q =
CIA, where C is a coefficient describing the physical drainage
area, I is the rainfall intensity and A is the area. The method
is easy to apply and works well on small watersheds. It is
generally not suited for the analysis of watersheds over 300
acres in size. |
| Record of Survey
– A legal record of a survey undertaken to establish or
reestablish land boundaries or property boundaries. Every survey
relating to land boundaries or property lines by a professional
land surveyor using existing township plats or notes,
subdivision maps, official maps, or records of survey that
discloses a discrepancy with an existing record of survey or
establishes a new point or line for a parcel in a property
description that is not shown on another record of survey, must
file a record of survey with the County Surveyor within 90 days
after completion of the survey. Reinforced Concrete – A
composite material made of concrete and steel. Steel is placed
inside the concrete structure in areas where the structure will
be exposed to tensile forces. It is generally more economical to
use reinforced concrete to offset the tensile forces than it is
to design an entirely concrete or steel section capable of
resisting the compressive/tensile forces. The reinforced
concrete structure must be carefully designed to ensure that the
materials act as a single composite material. Reinforced
Concrete Pipe (RCP) – A storm drain construction method using
pre-cast sections of pipe that are delivered to a site. The
sections, usually 8 feet long, are linked together in the pipe
trench to form a continuous storm drain system. |
| Relative Compaction
– This is the ratio of field dry density test results to the
theoretical maximum dry density test results obtained by a
Modified Proctor Test. District design engineers specify a
minimum relative compaction to be achieved by a contractor
during placement of the fill. The specified Relative Compaction
can vary based on the type of fill being placed. Relative
compaction specification can vary with the type of fill.
Examples include sub grade (90%), over excavation fill (90%), or
dam embankment (95%). |
| Return Frequency
- A measure of how often (on average) an event (precipitation,
flood, etc.) will occur that is greater than some chosen value
(100 year, 10 year, 5 year, etc); the inverse of the exceedance
probability. |
| Right of Way
– Any strip or area of land, including surface, overhead, or
underground, granted by deed or easement, for construction or
maintenance according to designated use, such as for drainage
channels, storm drains, flowage easements or impoundment of
surface water. |
| Routing
– A type of hydrologic analysis used to determine the reduction
in the peak flow caused by friction losses and storage in a
stream channel or reservoir. It is determined by mathematically
modeling the passage of the hydrograph through the stream
channel or reservoir over time. |
| Runoff –
Surface water flow that is generated from a rainfall event. The
amount of runoff generated is generally a function of the amount
of rainfall, the permeability of the soils, ground cover and the
amount of land development. Many other factors can also
influence the amount of runoff including the size of the
watershed, the sequence of storms within the watershed (are
soils already saturated from previous rainfall?),
evapotranspiration, and terrain type. |
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| Section 7 Consultation
- Section 7 of the federal Endangered Species Act requires
federal agencies to insure that actions they authorize, fund, or
carry out are not likely to jeopardize the continued existence
of threatened or endangered species or result in the destruction
or adverse modification of critical habitat for these species.
The U. S. Fish and Wildlife Service (FWS) and National Marine
Fisheries Service (NMFS) share responsibilities for
administering the Act and performing the Section 7 Consultation.
The opinion issued at the conclusion of consultation with
FWS/NMFS will include a statement either authorizing the take of
any habitat or species that may occur incidental to an otherwise
legal activity or denying the activity because, as proposed, it
would put the continued existence of the species in jeopardy
(known as a jeopardy finding). The District usually enters
Section 7 Consultations as part of the CWA Section 404
permitting process with the United States Army Corps of
Engineers. |
| Section 18
– That portion of the District’s enabling act (passed in 1945)
requiring a public hearing before any project or plan may be
undertaken by the District. The Act requires that the Board of
Supervisors authorize a Notice of Intention for the District
project or plan, which must to be publicly advertised. After 30
days, the Board of Supervisors can hold a public hearing on the
project. If the Board receives a written protest from the
majority of registered voters within the District’s Zone
containing the project, the Board may not proceed with the
project. |
| Section 401 Permit
– Section 401 of the Clean Water Act requires that a state
(California) must certify that federal licenses or permits which
may result in a pollutant discharge into navigable waters (i.e.
a Section 404 Permit) meet state water quality standards
(including NPDES standards). The state may certify, condition or
deny the proposed activity. If the state conditions the
activity, those conditions must be incorporated into the Section
404 permit. In California, the Regional Water Quality Control
Boards are responsible for issuing the Section 401 Water Quality
Certifications. |
| Section 404 Permit
– Under Section 404 of the Clean Water Act, a permit is required
from the United States Army Corps of Engineers (USACE) for the
discharge of dredged or fill material into Waters of the United
States (including wetlands). Guidelines for implementation of
the permit are referred to as the Section 404 (b)(1) Guidelines
and were developed by the Environmental Protection Agency (EPA)
in conjunction with USACE. Under the USACE guidelines, any
activity that disturbs wetlands areas, including flood control
maintenance activities and construction of flood control
facilities in Waters of the United States, can be construed as
requiring a Section 404 permit. The Guidelines allow the
discharge of dredged or fill material into the aquatic system
only if there is no practicable alternative that would have less
adverse impacts. Adverse impacts can be offset through
mitigation. Mitigation commonly takes the form of the purchase
of nearby lands that can be made to function as wetlands,
thereby offsetting the areas disturbed by the discharge of
dredged or fill materials. Section 404 also requires that
federal guidelines for water quality (Section 401 Water Quality
Certificate) and Endangered Species Act requirements (Section 7
Consultation) be met prior to the issuance of the permit.
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| Section 1601 Streambed
Alteration Permit - Under this
section of the Fish and Game Code, public agencies are required
to notify the California Department of Fish and Game (CDFG)
prior to any project that would divert, obstruct or change the
natural flow, bed, channel, or bank of any river, stream, or
lake. Preliminary notification and project review generally
occurs during the environmental process. When an existing fish
or wildlife resource may be substantially adversely affected,
CDFG is required to propose reasonable project changes to
protect the resource. These modifications are formalized in a
Streambed Alteration Agreement that becomes part of the plans,
specifications and bid documents for the project. |
| Separate Application
– An application for development within a FEMA mapped floodplain
or an Ordinance 458 floodplain. This application is required for
developments that are not otherwise conditioned to meet
floodplain ordinances through the usual land division process or
that are not covered by other ordinances. Special Applications
are generally required for projects that can be approved through
grading or building permit only. These projects include things
like construction or remodeling of a single custom home on an
existing lot. |
| Soffit
– The highest point of the interior of the storm drain pipe.
Soils Compaction – The densification of soils by the application
of energy, usually mechanical energy (mechanical compaction).
Soils are compacted to increase stability, enhance resistance to
erosion, decrease permeability and decrease compressibility.
This is usually accomplished by placing the soil in shallow
lifts (layers) up to eight inches thick, then using heavy
mechanical equipment to compress the lifts. The equipment
usually applies energy to the soil by static loading, impact,
vibration or kneading action. The type of compaction depends on
the type of soil and the purpose of the soil compaction.
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| Soils Investigation
– An investigation of the geotechnical characteristics of the
project site. The District usually enters contracts for
geotechnical work with private geotechnical firms. Geotechnical
studies vary with the objective of the project, but are
generally accomplished by taking samples from soils borings or
trenches. Soils investigations usually provide guidelines for
temporary excavations, for suitability of soils for pipe bedding
and trench backfill and for various soils design parameters such
as allowable bearing pressure and lateral earth pressure. Soils
investigations are also used to assess the suitability of soils
for special construction techniques such as Cast-In-Place-Pipe
(CIPP) placement. |
| Special Provisions
– This portion of the Specification and Contract Document covers
those items of the contract between the District and the
Contractor that are unique to this project. They include items
such as the expected time of completion, site maintenance, work
hours, any encroachment permits or interagency agreements that
the contractor must abide by and any special state or federal
requirements that the contractor must abide by. Other items
could include minimum notification times required to obtain the
services of a District Surveying team, required disposal sites
for excess materials or contaminated materials and location of
project signs. It could also specify the authority of the
District to select from multiple construction options for a
particular portion of the project by some predefined point in
time during the construction process. |
| Special Flood Hazard
Areas (SFHA) - A darkly shaded area
on a FIRM or Flood Hazard Boundary Map, FHBM, identifying an
area with a one percent chance of being flooded in any given
year; hence the property is in the 100- year floodplain.
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| Specifications and
Contract Document – This document is
prepared by the Project Engineer in the Design Engineering
Section. The Document is a complete description of the project
to be constructed, including contractual obligations of the
District and Contractor as well as the estimated time, costs,
and methods and materials of construction to be used. It
contains the general provisions, the special provisions, the
detailed specifications and the drawings (plans) that detail the
project to be constructed. This document is used by contractors
interested in bidding on the project to determine their probable
cost of construction, it is used by the inspectors to police and
control the project construction and it is used by the surveyors
to place the survey control necessary to align and construct the
project. Stage - The river stage is the height of the water in
the river, measured relative to an arbitrary fixed point.
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| Standard Plans
– Details of standard structures, devices or instructions
referred to on the Plans or in the Specifications, usually by
title or number. Standard Plans are plans for structures that
are commonly constructed in a way that can be described
generically. Examples of structures that have “standard plans”
are catch basins, channel sections and street sections. There
are many different sources of standard plans. The District has a
set of Standard Plans for Drainage Structures. Caltrans has a
set of Standard Plans for Freeway Construction (which also
includes some standards for drainage structures), the Public
Works Standards Association also produces a set of Standard
Plans for general construction project items. Depending on the
structure and location, the District can and does reference
several of these Standard Plans in the Specification and
Contract Documents. It is not uncommon, though, that District
projects will require modifications or abandonment of a standard
plan due to site constraints. In these cases, the District’s
Design Engineers will create and specify a specific design for
that particular structure. |
| Standard Specifications
for Public Works Construction –
Commonly referred to as the “Greenbook”, or “Standard
Specifications” this document was originally published in 1967.
The last 10 editions were produced by a joint committee of the
Southern California Chapter of the American Public Works
Association and the Southern California Districts of the
Associated General Contractors of California. Since 1996, the
manual has been produced by the Public Works Standards, Inc., a
corporation headed by members of a number of public works
associations. The book provides standard language for the
general provisions of contract documents; standard criteria and
testing methods for construction materials and standards for
construction methods. The District generally references these
standards in our Specifications and Contract Documents.
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| Standard Specifications
of the State of California, Department of Transportation
– Commonly referred to as “State Standard Specifications”, this
manual is prepared by Caltrans. It provides alternative, but
similar, standards for construction methods and materials. The
District usually references the State Standard Specifications
when we are constructing projects that are within Caltrans
Rights of Way or when we use Caltrans Standard Plans for the
design of specific facilities (i.e. reinforced concrete box).
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| State Plane Coordinate
Systems – A plane-rectangular
coordinate system established by the United States Coast and
Geodetic Survey, one established for each state, used for
converting position on the earth’s curved surface to planar x
and y coordinates. The system allows surveyors to use plane
surveying methods over great distances. The system in each state
is divided into zones. Riverside County is in Zone VI of the
California Coordinate System. The x and y coordinate points are
generally referenced to a geodetic horizontal datum known as the
North American Datum (NAD). |
| Storm Drain
– An underground pipe used to convey runoff from urban areas to
an adequate outlet. An adequate outlet can be a connection to a
larger flood control facility or an outlet into an existing
watercourse, such as the Santa Ana River, that has adequate
conveyance capacity for the flow tributary to it. Storm drains
are usually designed using specialized hydraulic software such
as WSPGW. Analysis of storm drain capacity requires knowledge or
estimation of downstream and/or upstream water surface
elevations, material type, pipe slopes and diameter, inlet
locations and flow rates. |
| Storm Water
– is as defined urban runoff and snowmelt runoff consisting only
of those discharges which originate from precipitation events.
Storm water is that portion of precipitation that flows across a
surface to the storm drain system or receiving waters. Examples
of this phenomenon include: the water that flows off a
building’s roof when it rains (runoff from an impervious
surface); the water that flows into streams when snow on the
ground begins to melt (runoff from a semi-pervious surface); and
the water that flows from a vegetated surface when rainfall is
in excess of the rate at which it can infiltrate into the
underlying soil (runoff from a pervious surface). When all
factors are equal, runoff increases as the perviousness of a
surface decreases. During precipitation events in urban areas,
rain water picks up and transports pollutants through storm
water conveyance systems, and ultimately to waters of the United
States. |
| Storm Water Pollution
Prevention Plan (SWPPP) - A plan
required by and for which contents are specified in the State of
California General Permit for Storm Water Discharges Associated
with Industrial Activities, and the General Permit for Storm
Water Discharges Associated with Construction Activities. The
purpose of the plan is to help identify the sources of pollution
that affect the quality of storm water discharges from a site
and to describe and ensure the implementation of practices to
reduce pollutants in storm water discharges. |
| Structural Floodplain
Management Controls – The use of
dams, levees, channels, storm drains or other flood control
devices to confine and direct flows away from people and
property. This has been the historically preferred method of
protecting residents in urbanized floodplains. |
| Subcritical Flow
- A flow condition where the velocity is less than the critical
velocity and the depth is greater than the critical depth.
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| Supercritical Flow
- A flow condition where the velocity is greater than the
critical velocity and the depth is less than the critical depth.
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| Synthetic Unit
Hydrograph Method – A method that
estimates the amount and pattern of runoff due to a "unit" of
rainfall flowing into the watershed over a certain period of
time. The pattern is than factored according to the amount of
rainfall that actually fell for the time period. These
individual patterns are then added for each time step to get the
cumulative hydrograph from each basin. |
| Specific Plan
- A tool authorized by Government Code §65450 et seq. for the
systematic implementation of the general plan for a defined
smaller portion of a community's planning area. A specific plan
must specify in detail the development standards and
requirements relating to density, lot size and shape, sitting of
buildings, setbacks, circulation, drainage, landscaping,
architecture, water, sewer, public facilities, grading, open
space, financing and any other element needed for proper
development of the property. |
| Subdivision Map Act
- gives the local agency the authority to regulate and control
the design and improvement of the subdivisions within its
jurisdiction. Each city/county must adopt an ordinance
regulating and controlling subdivisions, in Riverside County
it’s Ordinance 460. The Map Act sets forth certain mandates that
must be followed for subdivision processing. It defines what tentative maps, final maps and parcel maps
are. It establishes
development rights. It establishes procedures for the filing of
maps, review of maps, exaction of dedications, imposition of
fees, posting of improvement securities, and monuments. A local
agency may impose conditions on the subdivision process when the
map act is silent. |
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| Temporary Construction
Easement – A temporary easement
giving the District rights to use others property for a
specified period of time. These easements are usually obtained
to allow a District contractor to gain access to a work site, to
provide additional work room during the construction process or
to do minor grading on lands adjacent to District properties
during construction. |
| Tentative Maps, Parcel
Maps and Final Maps - Land is
divided into any number of units of improved or unimproved land
or any portion thereof, for the purpose of sale, lease, or
financing, whether immediate or future. When under review
subdivisions of land into five or more parcels (lots) are
usually referred to as tentative tract maps and subdivisions
into four or less lots are usually referred to as parcel maps.
In Riverside County, these maps are approved, conditionally
approved or disapproved by the either the Planning Commission or
the Planning Director and that action is reported directly to
the Board of Supervisors. The conditioned approvals detailed the
developer's entitlements to develop and the requirements that the
developer must meet to receive those entitlements. Recorded
tentative tract maps are referred to as Final Maps and recorded
parcel maps are referred to as Final Parcel Maps. |
| Time of Concentration
— The time period necessary for surface runoff to reach the
outlet of a watershed from the most hydraulically remote point
in the tributary drainage area. |
| Total Maximum Daily Load
(TMDL) - is the maximum amount of a
pollutant that can be discharged into a water body from all
sources (point and non-point) and still maintain water quality
standards. Under Clean Water Act section 303(d), TMDLs must be
developed for all water bodies that do not meet water quality
standards after application of technology-based controls.
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| Total Station Surveys
– Total Station surveys integrate theodolites, electronic
distance measurement (EDM) and data recorders. They collect
vertical and horizontal data in a single operation. Data
recorders can record information in the field to take back to
the office for processing. Data recorders can also be used to
download previously determined data at the office for use in the
field to stake out or field locate construction control points
and boundaries. |
| Tulloch Rule
– An interpretation of Section 404 of the Clean Water Act by the
Army Corps of Engineers. The rule states that any activity in
Waters of the United States that could produce “incidental
fallback” can be construed as placing fill in Waters of the
United States, an activity that is regulated under the Section
404 permitting process. The incidental fallback concept has been
extended to dirt that may temporarily cling to the tracks of
heavy equipment then “fall back” into the watercourse. This
controversial interpretation has been used by the USACE to
regulate maintenance activities and other actions that would not
otherwise be regulated under the Section 404 process. The rule
is currently being reviewed by the courts. |
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| Urban Runoff
- is defined as all flows in a storm water conveyance system and
consists of the following components: (1) storm water (wet
weather flows) and (2) non-storm water illicit discharges (dry
weather flows). |
| U.S. Rectangular Survey
System – This system was devised
with the objective of locating, marking and fixing subdivisions
“for all time”. The system divides land into tracts
approximately 24 miles on a side based on meridians and
parallels of latitude. The tracts are further subdivided into 16
townships, which are 6 miles on a side. The townships are then
subdivided into 36 sections, approximately 1-mile square.
Townships are labeled using a range and township number. The
township number is related to its position north or south of the
base parallel of latitude. The range number is relative to the
base meridian. The Sections of each township and range are
numbered beginning northeastern most corner and ending in the
southeastern most section. For example, a property located in T4S
R3W S36 of the San Bernardino Base Meridian could be located in
the Township 4 rows South of the standard parallel, the Range 3
columns West of the base meridian (San Bernardino) in Section 36
(lower southeastern most section of township). The District’s
orthophoto maps are referenced to the U.S. Rectangular Survey
System. Property Descriptions also reference this system. Thomas
Brother Guides often include U.S. Rectangular Survey System
coordinates information on their map pages. This is a quick way
to reference properties of interest to available District
mapping. |
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| Water Quality Objectives
– are the numerical or narrative limits on constituents or
characteristics of water designated to protect designated
beneficial uses of the water. [California Water Code Section
13050 (h)]. California’s water quality objectives are
established by the State and Regional Water Boards in the Water
Quality Control Plans. |
| Water Surface Elevation
(WSE) – The depth of flowing water,
measured to a common datum (e.g. stream channel invert, sea
level, etc.), at a prescribed location. Water Surface Elevation
is also defined as the height of a channel (or storm drain)
above mean sea level (or other datum) plus the height of the
hydraulic grade line above the channel. |
| Waters of the United
States – Waters of the United States
can be broadly defined as navigable surface waters and all
tributary surface waters to navigable surface waters. Waters of
the United States are also considered to be all waters, which
are currently used, were used in the past, or may be susceptible
to use in interstate or foreign commerce, including all waters
which are subject to the ebb and flow of the tide, including
wetlands. Groundwater is not considered a Waters of the United
States. |
| Watershed
— (1) An area that, because of topographic slope, contributes
water to a specified surface water drainage system, such as a
stream or river. (2) All lands enclosed by a continuous
hydrologic drainage divide and lying upslope from a specified
point on a stream; a region or area bounded peripherally by a
water parting and draining ultimately to a particular water
course or body of water. |
| Wetlands -
Wetlands are those areas that are inundated or saturated by
surface or ground water at a frequency and duration sufficient
to support, and that under normal circumstances do support, a
prevalence of vegetation typically adapted for life in saturated
soil conditions (U.S. ACE 1987). Wetlands generally include (1)
swamps, marshes, bogs, and similar areas; (2) lands that are
transitional between terrestrial and aquatic systems where the
water table is usually at or near the surface of the land and is
covered by shallow water. For purposes of this classification,
wetlands must have one or more of the following attributes: (1)
at least periodically, the land predominantly supports
hydrophytes (plants dependent on saturated soils or a water
medium); (2) the substrate is predominantly undrained hydric
soil; and (3) the substrate is non-soil and is saturated with
water or covered by shallow water at some time during the
growing season of each year. |
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| Z-Points
– An identification system for survey monuments established by
the District’s Surveyors. When a control point is established in
the field, the District Surveyor’s place a survey monument and
assign the monument a “Z” number, usually in the form of
“Z-4532”. This number is logged in a database maintained by the
District so that the surveyors can quickly retrieve information
about the location and coordinates of the monument at a future
date. District orthophoto and design maps generally show
locations and coordinate data for survey monuments established
by the District. |
| Zone
– The District is divided into seven geographical zones with
each zone being taxed separately. Monies raised in one zone must
be spent in only that zone. Each zone is represented by three
Zone Commissioners appointed by the District's Board to advise
the Supervisors and District staff. |
| Zone Commissioners
– Each zone is represented by three zone commissioners appointed
by the District's Board to advise them and District staff.
Commissioners represent their respective areas within the Zone.
The Commissioners preside over their Zone’s Budget Hearings and
Workshops, where they receive input from the public and discuss
construction project priorities. |
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