Submission and approval of a stormwater management plan will
comply with a comprehensive stormwater management plan review and
approval process administered by the Department that:
A.
Considers all aspects of project planning, design, and construction
from initial conception through final approval;
B.
Requires the submission, review, and approval of interim plans at
an increasing level of detail for specific stages of project development;
and
C.
Provides for coordinated input for all plans from all appropriate
agencies, departments or divisions, including, but not limited to,
Planning, Zoning, Public Facilities and the District.
A.
The owner/developer is responsible for submitting phased stormwater management plans for development projects according to the comprehensive review and approval process specified in § 274-28, Comprehensive plan review and approval process, and pursuant to the Environment Article, Title 4, Subtitle 2, Annotated Code of Maryland, 2009 Replacement Volume. Plans shall be submitted for the concept, site, and final stormwater management plan phases of project design. Comments from the County Engineer shall be addressed and approval received at each phase of project design prior to subsequent submissions.
B.
Concept stormwater management plan. The owner/developer shall submit
a concept stormwater management plan that provides sufficient information
for an initial assessment of the proposed project and whether stormwater
management can be provided according to this chapter and the Design
Manual. Plans submitted for concept approval shall include, but not
be limited to:
(1)
A drawing at a scale not to exceed one inch equals 50 feet, or as
approved by the County Engineer, showing site location, existing natural
features, water and other sensitive resources, topography, and natural
drainage patterns;
(2)
The anticipated location of all proposed impervious surfaces, buildings,
roadways, parking, sidewalks, utilities, and other site improvements;
(3)
The location of the proposed limit of disturbance, erodible soils,
steep slopes, and areas to be protected during construction;
(4)
Preliminary estimates of stormwater management requirements, the
selection and location of ESD practices to be used, and the location
of all points of discharge from the site; and
(5)
A narrative that supports the concept design and describes how ESD
will be implemented to the MEP.
C.
Site stormwater management plans. Following concept stormwater management
plan approval, the developer shall submit a site stormwater management
plan that addresses comments received during the previous review phase.
Plans submitted for site stormwater management plan approval shall
be of sufficient detail to allow development to be reviewed and include
but not necessarily be limited to:
(1)
All information provided during the concept stormwater management
plan review phase;
(2)
Final site layout, exact impervious surface locations and acreages,
proposed topography, delineated drainage areas at all points of discharge
from the site and stormwater volume computations for ESD practices
and quantity control structures;
(3)
A proposed erosion and sediment control plan that contains the construction
sequence, any phasing necessary to limit earth disturbances and impacts
to natural resources, and an overlay plan showing the types and locations
of ESD and erosion and sediment control practices to be used;
(4)
A report with sufficient calculations to support the design;
(5)
A narrative that supports the site development design, describes
how ESD will be used to meet the minimum control requirements, and
justifies any proposed structural stormwater management system;
(6)
Soils report, to include the soil boring and soil test results;
(7)
Any waiver requests with supporting information and calculations;
and
(8)
An adequate outfall study.
D.
Final stormwater management plans. Following site stormwater management
plan approval, the developer shall submit final erosion and sediment
control and the final stormwater management plans that reflect the
comments received during the previous review phases. Plans submitted
for final stormwater management plan approval shall be of sufficient
detail to allow all approvals and permits to be issued according to
the following:
(1)
Final erosion and sediment control plans shall be submitted according
to COMAR 26.17.01.05; and
(2)
Final stormwater management plans shall be submitted for approval
in the form of construction drawings and be accompanied by a report
that includes sufficient information to evaluate the effectiveness
of the proposed runoff control design.
(a)
All the information supplied at the concept and the site phase
of the project;
(b)
Drainage area maps depicting predevelopment and post-development
runoff flow path segmentation and land use;
(c)
A vicinity map;
(d)
Existing and proposed topography and proposed drainage areas,
including areas necessary to determine downstream analysis for the
proposed stormwater management systems;
(e)
Any proposed improvements, including the location of buildings
or other structures, impervious surfaces, storm drainage facilities,
and all grading;
(f)
The location of existing and proposed structures and utilities;
(g)
Any easements and rights-of-way;
(h)
The delineation, if applicable, of the one-hundred-year floodplain
and any on-site wetlands;
(i)
Structural and construction details, including representative
cross sections for all components of the proposed stormwater management
systems;
(j)
All necessary construction specifications;
(k)
A sequence of construction;
(l)
Data for total site area, disturbed area, new impervious surface,
and total impervious surfaces;
(m)
A table showing the ESD and unified sizing criteria volumes
required in the Design Manual;
(n)
A table of materials to be used for stormwater management system
planting;
(o)
All soil boring logs and locations;
(p)
An inspection and maintenance schedule;
(q)
Certification by the owner/developer that all stormwater management
construction will be done according to this plan;
(r)
An as-built certification signature block to be executed after
project completion;
(s)
Structural details for nonstandard items or detail numbers for
standards;
(t)
A table of all stormwater management structures with numbers;
(u)
A list of all nonstructural stormwater management systems with
locations employed (i.e., lot numbers);
(v)
Nonstandard construction specifications; and
(w)
Other notes applicable to construction, inspection and maintenance
of all stormwater management systems.
E.
Reports submitted with stormwater management plan approval shall
be formatted per Plan Preparation Package requirements and include:
(1)
A complete narrative describing the project that supports the final
stormwater management design with a summary of stormwater management
requirements;
(2)
Drainage area maps if required;
(3)
Hydrologic computations of the applicable ESD and unified sizing
criteria according to the Design Manual for all points of discharge
from the site;
(4)
Hydraulic and structural computations for all ESD practices and structural
stormwater management measures to be used;
(5)
Unified sizing criteria calculations;
(6)
Calculations supporting waivers or the existence of an adequate outfall;
(7)
Pictures of the site and the outfalls; and
(8)
Copies of any previous studies to support the on-site improvements
The stormwater management plan and all supporting documents
shall be signed and sealed by a professional engineer or other licensed
professional as allowed under Maryland law. If the BMP requires either
a dam safety permit or small pond approval, then the design shall
be prepared by a professional engineer.
The following additional information may be required at any
stage (concept, site and/or final) of the stormwater management plan
reviews:
A.
Site characteristics:
(1)
Intended use of the structures, including design criteria, trade-off
conditions and/or areas not managed (NRCS Engineering Field Manual,
Chapter II).
(2)
Structure classification (NRCS Pond Standard Code 378).
(3)
Soils investigations for construction of small ponds, infiltration
facilities and any other stormwater management system per the Design
Manual for review by the District and the Department.
(4)
Topographic survey, including the area necessary to determine the
downstream effect from any proposed stormwater management structure.
(5)
Topographical information of the contributing watershed based upon
United States Geological Survey (USGS) topographic quadrangles with
a field-verified drainage area and acreage noted on the plan or County
topographic maps at one inch equals 200 feet.
(6)
Geotechnical investigations, including soils maps, borings, site-specific
recommendations, and any additional information necessary for the
proposed stormwater management plan design.
(7)
Descriptions of all watercourses, impoundments, and wetlands on or
adjacent to the site or into which stormwater directly flows.
B.
Computations:
(1)
Hydrology;
(2)
Hydraulic;
(3)
Structural;
(4)
Unified sizing criteria volume computations according to the Drainage
Manual;
(5)
For development proposed in the IDZ within the County critical area,
the predevelopment and post-development pollutant loadings; and
(6)
Any other information as required by the County Engineer in a format
as approved by the Department.
D.
Construction cost estimate.
E.
Maintenance schedule.
F.
If the plans include precast structures, then the developer shall
be responsible to submit shop drawings (approved by the design engineer)
to the County prior to the placement of the precast structure. The
information required on the shop drawing is as outlined in the Plan
Preparation Package.
G.
Adequate outfall study. The developer's study of the downstream
conditions shall extend to the point where an adequate outfall exists
as determined by calculations or to the point as determined by the
design engineer and as approved by the County Engineer.
H.
Standards and specifications. Stormwater management plans must be
prepared in sufficient detail, with reference to appropriate standards
and specifications, to ensure understanding by those responsible for
review, installation, and inspection.
I.
The developer will certify on the drawings that all clearing, grading,
construction and development will be accomplished strictly in accordance
with the final stormwater management plan. Changes made during the
construction process will not be permitted without prior written approval
of the Department and, where a small pond is involved, the District.
The licensed professional will certify on the drawings that the plan
meets all applicable, County, state and federal laws.
J.
In the case of a small pond, the developer shall retain a licensed
professional to inspect the construction of the pond. The licensed
professional shall submit routine inspection reports with test results
at time intervals established by the County Engineer. The licensed
professional shall not accept any work not in compliance with state
or County requirements and shall notify the County immediately when
work is not in compliance.
K.
The design plans will indicate the one-hundred-year floodplains,
backwaters, ponding for streams, culverts, storm drain systems, and
the maximum impounded water surface elevation of the stormwater management
structure during ultimate emergency spillway operation. The resultant
inundated area at this elevation shall be accurately delineated and
recorded on the site plan or plat as a perpetual stormwater management,
floodplain, backwater, or drainage easement, as applicable. Additional
buffer easements may be necessary or required for maintenance, access,
and/or safety purposes. No existing or proposed building structures
will be allowed within these easements without prior approval of the
Department. Peripheral construction may be granted, provided that
all floor elevations are at least one foot higher than the maximum
water surface elevation.
A.
The "as-built" plans shall be submitted to the Department following
the procedures established in the Plan Preparation Package. "As-built"
plans and certifications shall be submitted by a licensed professional
to ensure that ESD planning techniques, treatment practices, and structural
stormwater management measures are in compliance with the specifications
contained on approved plans. At a minimum, "as-built" certification
shall include a red-lined set of drawings comparing the approved stormwater
management plan with what was constructed. Other information shall
be submitted if required by the County Engineer as established in
the Plan Preparation Package. Final completion acceptance will not
be given until all final inspections and "as-built" plans have been
approved.
B.
In the case of small ponds, the developer shall also submit "as-built"
plans to the District. The "as-built" plans shall be certified by
a licensed professional as meeting or exceeding the requirements of
the approved plans and specifications. Procedures for "as-built" plans
submitted to the County are outlined in the Plan Preparation Package.
The Department will require stormwater management systems to
be protected by public or private easements or private inspection
and maintenance agreements. All inspection and maintenance agreements,
easement documents, and record plats shall be recorded prior to permit
issuance.
A.
In residential developments, the stormwater management and access
easements shall be located on properties of those responsible for
maintenance of such easements and facilities. Unless allowed by the
County Engineer, all easements shall be located outside the limits
of residential lots.
B.
In the case of publicly maintained facilities, the easements shall
be located in open space or public use lots unless otherwise approved
by the County Engineer.
A.
If a plat is not associated with a commercial, industrial or institutional
development, the owner will submit a completed signed and recorded
copy of the stormwater management inspection and maintenance agreement
prior to the issuance of the permit.
B.
Stormwater management areas subject to a stormwater management inspection
and maintenance agreement shall be shown, labeled and dimensioned
on the stormwater management plans.
C.
Access to the stormwater management systems shall be from a public
right-of-way.
Unless approved otherwise by the County Engineer, stormwater
management for private residential, private commercial, private industrial
or institutional developments shall be located outside of County-owned
rights-of-way, properties and public easements.
A.
Residential subdivisions. Structural stormwater management located
in residential developments shall be located outside residential lots
and shall be maintained by a homeowners' association. Nonstructural
stormwater management designed to address the stormwater management
requirements may be located on the lot if the stormwater management
measure is to address the lot development and not the infrastructure
development.
B.
Nonresidential development. Stormwater management measures located
in nonresidential areas such as commercial, industrial and institutional
development shall be located on the developer's property or an
approved off-site property and shall be maintained by the owner of
the property.
C.
Public development and maintenance. The County will maintain any
stormwater management system located in public rights-of-way or within
public easements dedicated to and accepted by the County.
Stormwater management and development plans shall be consistent
with adopted and approved watershed management plans or flood management
plans as approved by the Department in accordance with the Flood Hazard
Management Act of 1976 (Environment Article, Title 5, Subtitle 8,
Annotated Code of Maryland).
An operation and maintenance plan for all stormwater management
systems shall be required as a condition of final stormwater management
plan approval and shall be included on the stormwater management plan
sheets. A copy of the operation and maintenance plan shall be provided
to the parties responsible for the maintenance of the stormwater management
system.
If a project involves the discharge of some or all of the stormwater
runoff from the site in a manner that alters the water quality or
the flow characteristics of depth, velocity, width, rate, or volume
from that which exists in the pre-developed condition, the developer,
prior to the issuance of a permit, shall obtain from abutting property
owner(s) any necessary easement, right-to-discharge, or other property
interest concerning flow of water. Approval of a stormwater management
plan does not create or affect any right to direct runoff onto adjacent
property without that property owner's permission.
