A.
General.
1.
Components of the drainage system. Drainage systems, including
all conveyances, inlets, conduits, structures, basins, or outlets
used to drain stormwater, must be designed and constructed to promote
the health, safety, and welfare of the property owner and the public.
2.
Management of stormwater runoff. Adequate provision must be
made for the acceptance, collection, conveyance, detention, and discharge
of stormwater runoff drainage onto, through, and originating within
the Subdivision.
3.
Maintenance responsibility.
(i)
The property owner or Property Owners’ Association, as
applicable, shall be responsible for maintaining detention and retention
ponds. The property owner shall be responsible for associated pond
maintenance costs, which the City may approve through an Improvement
Agreement if deemed appropriate by the City. For any facility serving
commercial or multifamily development, or multiple lots, a management
company or Property Owners’ Association capable of funding operation
and maintenance shall maintain such facilities.
(ii)
It is a violation for a detention/retention pond
or a structural control to be unable to operate for its intended purpose
due to lack of maintenance.
4.
Discharge of stormwater runoff. Stormwater discharge must not
have an adverse impact downstream; must be released in a manner that
does not alter existing drainage patterns onto neighboring properties;
and shall not endanger human life or public or private property.
5.
Drainage facilities. Drainage facilities shall be provided and
constructed by the Developer or Subdivider in accordance with the
requirements within this Section 7.2 Drainage and Stormwater and the
Engineering Technical Manual.
B.
Planning and construction.
1.
Plans, profiles, and specifications shall be prepared for stormwater
improvements to be constructed. All proposed stormwater improvements
shall conform to the standards established in the Engineering Technical
Manual.
(i)
Each sheet of the plans and profiles shall bear the seal and
signature of the Professional Civil Engineer licensed in the State
of Texas who prepared them.
2.
The Subdivider shall incur the cost of all drainage improvements
connected with development of the Subdivision and acceptance of current
upstream flows necessary to safely and adequately drain the Subdivision,
including any necessary off-site channels or storm sewers and acquisition
of any required easements.
(i)
The 100-year storm must be contained within the street Right-of-Way
or the drainage easement boundaries.
(ii)
Any necessary off-site channel or storm sewers
which are required to be within easements must have a separate instrument
easement filed with Travis County and a filed copy shall be submitted
to the City before Subdivision Construction Plans will be approved.
C.
Residential grading and drainage.
1.
Lot-to-lot drainage standards.
(i)
Lot design and grading for individual lots within a Subdivision
are required to conform to this Section 7.2 prior to occupancy of
a structure.
(ii)
Surface runoff from residential lots shall cross
no more than one additional lot before being directed toward the street
or a dedicated drainage system.
(iii)
When the flow reaches the second lot, an easement
will be required to convey the water from the original lot to the
street or to a dedicated City drainage system.
(iv)
Where lot-to-lot drainage occurs, the City Engineer
may require a drainage easement between the lots.
2.
Detailed standards. See the Engineering Technical Manual for
requirements for detailed standards and policies.
D.
Nonresidential grading and drainage.
1.
Lot-to-lot grading and drainage standards.
(i)
Grading and drainage plans shall ensure that surface runoff
from nonresidential individual lots cross no more than one (1) additional
lot before being directed toward a private regional stormwater system
or a dedicated City drainage system.
(ii)
When the flow reaches the second lot, side lot
swales may be utilized to direct the flows to private enclosed systems
or to a dedicated City drainage system within a dedicated easement
or in street right-of-way.
(iii)
Concentrations of stormwater shall not be discharged
to City Streets through driveways or flumes but shall be collected
into an enclosed system, either private or public, prior to reaching
the curb line of the roadway.
(iv)
Specific deviations from these guidelines may
be approved by the City Engineer on an individual basis.
2.
Detailed standards and design criteria. See the Engineering
Criteria Manual for detailed standards and policies.
E.
Materials.
1.
Swales on residential lots. Swales on residential lots shall
be fully sodded, unless an equal alternative design is approved by
the City Engineer.
2.
Swales on nonresidential lots.
(i)
Swales on nonresidential lots must meet criteria of the engineering
technical manual or alternative designed approved by the City Engineer.
(ii)
Swales within the parking and private driving
lanes of nonresidential properties shall be constructed of natural
materials such as sod, plants, hardwood mulch, and rock that are suitable
to accept, dissipate and filter runoff.
3.
Enclosed systems on residential lots. Enclosed systems may be
designed in accordance with the Engineering Technical Manual or as
approved by the City Engineer.
4.
Enclosed systems on nonresidential lots. Enclosed systems on
nonresidential lots that will be dedicated to the City shall be designed
utilizing concrete pipe and collection inlets.
(i)
Private enclosed systems on nonresidential lots shall be designed
in accordance with the Engineering Technical Manual or as approved
by the City Engineer.
F.
Maintenance responsibility.
1.
Maintenance responsibility of all privately dedicated drainage
systems, including mowing, cleaning and repair, shall be specified
in the maintenance manual as the property owner, Property Owners’
Association or other entity as approved by the City Engineer.
2.
Maintenance responsibility of all publicly dedicated drainage
systems, including mowing, cleaning and repair, shall be the responsibility
of the City.
G.
Roof drains. All roof drains of residential structures shall be designed
to promote infiltration of stormwater within the lot (e.g. disconnected
downspouts) prior to stormwater draining toward the street or a rear
or side lot swale.
H.
Preliminary drainage plan.
1.
Applicability and purpose.
(i)
A Preliminary Drainage Plan shall be prepared for the following
developments:
(1)
New nonresidential construction or subdivision.
(2)
New multi-family subdivision or construction (3+
units),
(3)
New single-family residential subdivision or construction,
or
(4)
Any development or construction if impervious surface
is increased unless exempted by the City Engineer.
(5)
Any development or construction requiring Preliminary
Plat.
(ii)
The Preliminary Drainage Plan shall depict the
watershed(s) that the property or development will impact and how
the runoff from the fully-developed watershed will be conveyed to,
through, and from the development.
(1)
The Preliminary Drainage Plan must comply with
the standards outlined in this UDC, Engineering Technical Manual,
and other City codes.
(iii)
The Preliminary Drainage Plan shall demonstrate
the intent of the Developer or Property Owner with regard to conveyance
and proper handling of stormwater runoff. The preliminary drainage
plan shall show preliminary inlet and storm drain placement and sizing,
preliminary water quality/detention pond location and sizing, and
any necessary open channels that are required for the conveyance of
stormwater runoff.
(iv)
The Preliminary Drainage Plan may satisfy the
stormwater management portion of the Storm Water Pollution Prevention
Plan (SWPPP) that is required for construction activities; however,
the Preliminary Drainage Plan is not a substitution for the SWPPP.
(v)
The review of the Preliminary Drainage Plan does not constitute
final drainage plan approval or authorize a waiver to any of the Subdivision
Regulations and Development Standards.
2.
Plan required and previous plans.
(i)
A Preliminary Drainage Plan shall be provided, at the Applicant’s
expense, for the area proposed for development. The Preliminary Drainage
Plan shall depict any property impacted by the development, including
those not planned for earth disturbance.
(ii)
For property with a previously accepted Preliminary
Drainage Plan, the accepted Preliminary Drainage Plan may be submitted
and enforced unless a revised Preliminary Drainage Plan is required
by the City due to lot reconfiguration or other conditions created
by the new development.
3.
Submittal.
(i)
A copy of the Preliminary Drainage Plan shall be submitted in
a format specified by the City with the submittal of a Preliminary
Plat or Replat for review and acceptance.
(ii)
The Preliminary Drainage Plan shall be labeled
as "Preliminary."
(iii)
The Preliminary Drainage Plan shall be sealed
by and dated by the engineer.
(Ordinance 475 adopted 6/28/22)
