(Ordinance 2012-10 adopted 8/21/12)
This Chapter discusses the five-step development process. Local
governments will integrate these processes into their current process
by the addition of local provisions.
A formal integrated Stormwater Management Development Process
shall be implemented to meet the stormwater management goals and to
see that local stormwater guidelines and requirements are implemented.
The process shall include the steps, meetings, and documents that
must be met by the developer. The five-step process described herein
includes the following:
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The iSWM Plans: The iSWM Plans are the documents that summarize
the data collected in steps 1 and 2 and are shown on the conceptual/preliminary
and final plans that must be submitted to the municipality as part
of steps 3, 4, and 5. Each submittal must follow the criteria outlined
in Sections 14.2.0 and 14.3.0. Submittals shall include information
in accordance with the checklists that are included in Section 14.5.0.
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The iSWM Construction Plan: The iSWM Construction Plan is the document that uses data collected in steps 1 and 2 to protect water quality during construction. It is submitted to the municipality with the Final iSWM Plans in Step 4. An overview of the iSWM construction plan content is covered in Section 14.2.2. More detailed criteria for the iSWM Construction Plan are outlined in Section 14.4.0.
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The iSWM Plans and iSWM Construction Plan are a subset of the
overall development process that occurs throughout the planning and
development cycle of a project and then continues after construction
is completed via regular inspection and maintenance of the stormwater
management system.
In addition to these plans, stormwater master plans are an important tool used to assess and prioritize both existing and potential future stormwater problems and to consider alternative stormwater management solutions. Local governments may have individual watershed plans, or several governments may work cooperatively to develop a unified approach to watershed planning, development controls, permit compliance, multi-objective use of floodplain and other areas, and property protection. Refer to the Local Provisions in Step 1 under Section 14.2.2 where regional approaches (if any) are identified.
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Local Provisions: Conceptual,
preliminary, and final iSWM Site Plans and supporting technical data
will be submitted for review and approval to the City of Azle.
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(Ordinance 2012-10 adopted 8/21/12)
This section describes the typical contents and general procedure
for preparing iSWM Plans and the iSWM Construction Plan. The level
of detail involved in the plans will depend on the project size and
the individual site and development characteristics. Figure 2.1 lays
out the five-step process. Each of the following steps builds on the
previous steps to result in the Final iSWM Site and Construction Plans:
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Step 1 - Review Local Requirements and Municipality’s
Processes
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Step 2 - Collect Data and Perform Site Analysis
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Step 3 - Prepare Concept/Preliminary iSWM Plans
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Step 4 - Prepare Final iSWM Plans and iSWM Construction Plan
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Step 5 - Prepare Operation and Maintenance Plans
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Figure 14.2.1 iSWM Flowchart
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Local Provisions: Prior to Certificate
of Occupancy being issued, a Final Grading Certificate prepared by
an engineer or the contractor, as appropriate shall be submitted.
The Final Grading Certificate shall state that the site grading and
drainage improvements are constructed in substantial compliance with
the approved plans. If the improvements were not constructed in substantial
compliance with the plans, appropriate documentation shall be provided
to substantiate any changes. If changes were made to public facilities,
the City shall require an engineer to document field changes by submitting
certified as-built plans.
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Step 1.
Review Local Requirements and Municipality Processes
The site developer shall become familiar with the local stormwater
management, development requirements and design criteria that apply
to the site. These requirements include:
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iSWM Criteria Manual for Site Development and Construction (this
manual including all local provisions)
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Available online iSWM Program documents
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iSWM Technical Manual
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iSWM Tools
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iSWM Program Guidance
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State and Federal Regulatory Requirements
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Other Local Municipal Ordinances and Criteria
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Platting Procedures
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Zoning Requirements
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Development Codes and Procedures
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Tree and Landscape Requirements
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Special Use Permits
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Drainage Master Plans and Watershed Plans
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Erosion Control Plans
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Floodplain Ordinances
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Grading Plan Requirements
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Construction/Building Permit Notifications and Requirements
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Information regarding the above items can be obtained
from this manual or at a pre-submittal (or similar) meeting with the
municipality.
A critical part of any project involves the proposed development
working closely with various departments within the municipality.
Integrating the stormwater practices with other regulatory requirements
will promote a sustainable development.
Opportunities for special types of development (e.g., clustering)
or special land use opportunities (e.g., conservation easements or
tax incentives) must be investigated. In addition, there may be an
ability to partner with a local community for the development of greenways
or other riparian corridor or open space developments.
All applicable State and Federal regulatory requirements must
be met.
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Local Provisions: NONE
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Step 2.
Collect Data and Perform Site Analysis
Using field and mapping techniques approved by the municipality,
the site engineer shall collect and review information on the existing
site conditions and map the following site features:
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Topography
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Drainage patterns and basins
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Intermittent and perennial streams on-site and off-site waters
that will receive discharges from the proposed development
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Soil types and their susceptibility to erosion
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Ground cover and vegetation, particularly unique or sensitive
vegetation areas to be protected during development
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Existing development
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Existing stormwater facilities on-site and off-site facilities
that will receive discharges from the proposed development
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Property lines, adjacent areas and easements
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Wetlands and critical habitat areas
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Boundaries of wooded areas and tree clusters
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Floodplain boundaries
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Steep slopes
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Required buffers and setback along water bodies
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Proposed stream crossing locations
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Other required protection areas
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The site analysis shall be summarized in the conceptual/preliminary
iSWM Plans along with any other supporting documents. The data collected
and analyzed during this step of the development process shall be
used as the starting point for preparing the iSWM Plans and the iSWM
Construction Plan.
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Local Provisions: NONE
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Step 3.
Prepare Conceptual/Preliminary iSWM Plans
Conceptual iSWM Plan
Based on the review of existing conditions and site analysis,
the design engineer shall develop and submit a Conceptual iSWM Plan
for the project. The Conceptual iSWM Plan allows the design engineer
to propose a potential site layout and gives the developer and local
review authority a “first look” at the stormwater management
system for the proposed development. The following steps shall be
followed in developing the Conceptual iSWM Plan with the help of the
Checklist for Conceptual iSWM Plans found in Section 14.5.0 of this
manual:
1.
Use integrated Site Design Practices (Section 14.3.2.2) as applicable
to develop the site layout, including:
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Preserving the natural feature conservation areas defined in
the site analysis
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Fitting the development to the terrain and minimizing land disturbance
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Reducing impervious surface area through various techniques
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Preserving and utilizing the natural drainage system wherever
possible
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2.
Determine the credits for integrated Site Design (Section 14.3.2.2)
and water quality volume reduction (Section 14.3.2.3) as applicable,
to be accounted for in the design of structural and nonstructural
stormwater controls on the site.
4.
Perform screening and conceptual selection of appropriate temporary and permanent structural stormwater controls (Section 14.3.8 and Section 14.4.0) and identification of potential site locations.
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It is extremely important at this stage that stormwater system
design is integrated into the overall site design concept in order
to best and most cost-effectively reduce the impacts of the development
as well as provide for the most cost-effective and environmentally
sensitive approach. Using hydrologic calculations, the goal of mimicking
pre-development conditions can serve a useful purpose in planning
the stormwater management system.
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Local Provisions: Conceptual iSWM Site Plans shall be prepared and submitted to the City of Azle in the initial planning stages of a land development project with a Conceptual iSWM Site Plan. In general, the engineer and planner will follow the conceptual iSWM Site Plan guidelines as presented in Section 14.2.2 Step 3, as applicable to Azle. Water quality and streambank protection detention requirements are part of the City of Azle criteria. A conceptual drainage study and Conceptual iSWM Site Plan for any proposed development shall include at a minimum the information listed in the Engineer’s Checklist for Conceptual iSWM Site Plan shown in Chapter 5, Appendix A - City of Azle Detailed Checklists and Forms.
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A Grading Permit is required prior to any construction or grading
activity involving 0.1 acres or more of disturbed surface area, if
disturbed areas are located within Floodplain and/or drainage easement.
This Grading Permit will be approved for earthwork only, will be at
the risk of the owner/developer, and will require compliance with
any other required permits or approvals including floodplain and SWPPP,
as applicable.
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Preliminary iSWM Plans
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The Preliminary iSWM Plan ensures that requirements and criteria
are complied with and opportunities are taken to minimize adverse
impacts from the development. This step builds on the data developed
in the Conceptual iSWM Plan by refining and providing more detail
to the concepts identified. If no Conceptual Plan is submitted, it
shall be part of the Preliminary iSWM Plan. The checklist for Preliminary
iSWM Plan in Section 14.5.0 outlines the data that shall be included
in the preliminary iSWM Plan.
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The Preliminary iSWM Plan shall consist of maps, plan sheets,
narrative, and supporting design calculations (hydrologic and hydraulic)
for the proposed stormwater management system. The completed Preliminary
iSWM Plan shall be submitted to the local review authority for review
and comment.
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Local Provisions: A Preliminary Drainage study and iSWM Site Plan for any proposed development must accompany a preliminary plat submitted for development review, and shall include at a minimum the information listed in the Engineer’s Checklist for Preliminary iSWM Site Plan shown in Chapter 5, Appendix A - City of Azle Detailed Checklists and Forms. The study will include a downstream assessment of properties that could be impacted by the development. These studies will include adequate hydrologic analysis to determine the existing, proposed, and fully developed runoff for the drainage area that is affected by the proposed development and will include hydraulic studies that define the “adequate outfall.” The study, as part of the development of the iSWM Site Plan, shall address existing downstream, off-site drainage conveyance system(s) and define the discharge path from the outlet of the on-site stormwater facilities, to the off-site drainage system(s) and/or appropriate receiving waters. It will include a capacity analysis of all existing constraint points such as pipes culverts/bridges, or channels from the point of stormwater discharge of the development downstream to an “adequate outfall.” For drainage areas of 100 acres or less, the downstream assessment will be limited to an “adequate outfall point,” determined by the study, or the 10% rule (see the iSWM Hydrology Technical Manual, Section 2.4). For drainage areas larger than 100 acres, the “adequate outfall point” will be defined by the detailed hydrologic and hydraulic analyses. This preliminary drainage study and Preliminary iSWM Site Plan will include:
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1. A topographical map of the entire watershed (not just the
area of the proposed development) generally not smaller than 1" =
200' (or other such scale approved by City of Azle), delineating the
watershed boundary(s) and runoff design point(s), existing and proposed
land use and zoning, and the size and description of the outfall drainage
facilities and receiving streams.
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2. Computation tables showing drainage areas, runoff coefficients,
time of concentration, rainfall intensities and peak discharge for
the required design storms, for both existing and proposed (ultimate
development) conditions, at all design points for each component of
the stormwater system (streets, pipes, channels, detention ponds,
etc.).
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3. Any proposed changes to watershed boundaries (i.e. by re-grading,
where permissible by Texas Water Code). If significant changes to
watershed boundary are made, more extensive analyses of downstream
impact and mitigating detention will be required and a variance obtained
from the Storm Water Manager.
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4. FEMA Flood Hazard Areas, if applicable.
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5. In addition any required Corps of Engineers’ Section
404 permits, Conditional Letters of Map Revision (CLOMR), Letters
of Map Revision (LOMR) or other permits relating to lakes and streams
required by any federal, state or local authorities. These must be
documented in the Drainage Study.
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6. Detailed off-site outfall information. This shall include
the presence of existing or proposed drainage structures, bridges
or culverts; documentation of existing versus proposed developed site
as well as ultimate runoff, identification of downstream properties
which might be impacted by increased runoff, and proposed detention
or other means of mitigation. Downstream impacts shall generally be
delineated identified to a point where the drainage from the proposed
development has no impact on the receiving stream or on any downstream
drainage systems within the “zone of influence.”
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7. Report with technical documentation.
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8. A Grading Permit is required prior to any construction or
grading activity involving 0.1 acres or more of disturbed surface
area and if disturbed surface areas are located within floodplain
or drainage easement. This Grading Permit will be approved for earthwork
only[,] will be at the risk of the owner/developer, and will require
compliance with any other required permits or approvals including
floodplain and Landscaping (Section 29 [of the zoning ordinance])
and SWPPP, as applicable.
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Step 4.
Prepare Final iSWM Plans and iSWM Construction Plan
The Final iSWM Plans and iSWM Construction Plan shall be prepared
together and submitted to the local review authority for approval
prior to any soil disturbance or other construction activities on
the development site. The Final iSWM Plans add further detail to the
Preliminary iSWM Plan and reflect changes that are requested or required
by the local review authority.
The Final iSWM Plans and iSWM Construction Plan, as outlined
in the final iSWM Plan checklist in Section 14.5.0, shall include
all of the revised elements of the Preliminary iSWM Plans as well
as a landscape plan, operation and maintenance plan, and any permits/waiver
requests.
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Local Provisions: A Final Drainage Study and iSWM Site Plan for development of all or a portion (i.e. phase one or phase two, etc.) of the overall development shall be prepared and submitted to the City of Azle. This submittal shall include at a minimum the information listed in the Engineer’s Checklist for Final iSWM Site Plan shown in Chapter 5, Appendix A - City of Azle Detailed Checklists and Forms, including:
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1. Conformance with the Preliminary iSWM Site Plan and Study.
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2. Submission of detailed drainage calculations and detailed
design plans.
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3. The submission of a cover sheet signed by the Storm Water
Manager indicating the approval of the detailed construction drawings
for the proposed development is sufficient to clear a plat drainage
study comment.
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4. Final drainage studies shall be approved based on the submission
of a signed cover sheet and drainage map with calculations from the
approved engineering construction drawings. Where City approval of
construction plans is not required, the above information required
for preliminary drainage studies, as well as construction plans for
any drainage improvements, shall be submitted.
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5. Note that unless specifically approved in a Grading Permit
issued by the Storm Water Manager, no work may be performed in the
FEMA regulatory floodway without a FEMA-approved Conditional Letter
of Map Revision (CLOMR).
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6. An iSWM Construction Plan must be prepared by an engineer;
such plan shall provide for erosion and sediment control during construction,
and must be submitted as an integral part of the final engineering
documents.
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7. A Storm Water Pollution Prevention Plan (SWPPP) must be prepared
by the engineer or another qualified professional prior to construction
in accordance with TCEQ and EPA requirements. The iSWM Construction
Plan submitted with the final engineering documents should normally
be incorporated into the SWPPP as its erosion and sediment control
plan component.
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8. A Grading Permit is required prior to any construction or grading activity involving 0.1 acres or more of disturbed surface area and if disturbed surface areas are located within floodplain and/or drainage easement. A Final Grading Permit will be required prior to the issuance of a building permit. See the Final Grading Permit (Form CITY OF AZLE-10) in Appendix A for submittal information. This Final Grading Permit will be required, even if a Grading Permit was obtained at an earlier stage.
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Construction Phase
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1. Pre-construction Meeting - Where possible,
a pre-construction meeting shall occur before any clearing or grading
is initiated on the site. This step ensures that the owner-developer,
contractor, engineer, and inspector can be sure that each party understands
how the plan will be implemented on the site.
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2. Periodic Inspections - Periodic inspections
during construction by City of Azle representatives. Inspection frequency
may vary with regard to site size and location; however, monthly inspections
are a minimum target.
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3. Final Inspection - A final inspection
is needed to ensure that the construction conforms to the intent of
the approved design. Prior to accepting the infrastructure components,
issuing an occupancy permit, and releasing any applicable bonds, the
City of Azle will ensure that: (a) temporary erosion control measures
have been removed; (b) stormwater controls are unobstructed and in
good working order; (c) permanent vegetative cover has been established
in exposed areas; (d) any damage to natural feature protection and
conservation areas has been mitigated; (e) conservation areas and
buffers have been adequately marked or signed; and (f) any other applicable
conditions have been met.
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4. Record Drawings - Record drawings
of the structural stormwater controls, drainage facilities, and other
infrastructure components will be provided to the City of Azle by
the developer.
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5. Final Grading Certificate - (Form
CITY OF AZLE-11) must be prepared by an engineer or the contractor
which certifies that grading and stormwater infrastructure have been
completed in substantial compliance with the Grading Permit, the iSWM
Site Plan, and the SWPPP including re-vegetation and filing of Notice
of Termination (NOT).
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Step 5.
Complete Operations and Maintenance Plan
An Operations and Maintenance Plan shall be developed in accordance
with this section. The plan shall be included in the Final iSWM Plan.
It needs to clearly state which entity has responsibility for operation
and maintenance of temporary and permanent stormwater controls and
drainage facilities to ensure they function properly from the time
they are first installed.
The Operations and Maintenance Plan shall include but is not
limited to:
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Responsible party for all tasks in the plan
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Inspection and maintenance requirements
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Maintenance of permanent stormwater controls and drainage facilities
during construction
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Cleaning and repair of permanent stormwater controls and drainage
facilities before transfer of ownership
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Frequency of inspections for the life of the permanent structures
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Funding source for long-term maintenance
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Description of maintenance tasks and frequency of maintenance
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Access and safety issues
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Maintenance easements
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Reviewed and approved maintenance agreements
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Testing and disposal of sediments
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Life span of structures and replacement as needed
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Guidance for development of Operations and Maintenance
Plans has been provided with each temporary and permanent Best Management
Practice (BMP) included in the iSWM Technical Manual.
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Local Provisions: A Stormwater
Facility Maintenance Agreement must be prepared by the engineer for
each stormwater control that will not be wholly maintained by the
City of Azle. This agreement must outline both preventive maintenance
tasks as well as major repairs, identify the schedule for each task,
assign clear roles to affected parties, and provide a maintenance
checklist to guide future owners including an annual self-inspection
to be provided to the City of Azle.
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For additional information, see Section 14.5.5, Stormwater Facility Maintenance Agreements.
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(Ordinance 2012-10 adopted 8/21/12)
