Item WS-4 - 480-VVVVWork Session Item 4
Amendments to Ordinance No. 480 to add regulations for streamway buffer and permeable pavement
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Sustainability Plan
Adopted in 2014 (Ord. No. 1104)
Part of City’s Comprehensive Plan, Southlake 2030.
Contains prioritized recommendations to maximize efficient use of public resources.
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Background
Citizens Survey Strategy Map Southlake 2030 Plan
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Amendment Details – Creek Buffer
A Tier 1 recommendation of the 2015 Sustainability Master Plan is the implementation of a stream/creek/ floodplain buffer.
The intention of the buffer is to reduce erosion, preserve
habitat, increase open space, and minimize impacts from site development and increases in impervious coverage.
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Benefits of Creek Buffer
Can be used as nonstructural stormwater filtering and infiltration zones;
Keeps structures out of the floodplain and provides a right-of-way for large flood events;
Per Environmental Resource Protection Plan mapping data, Southlake has 57.74 linear miles of stream adjacent to at least some tree cover.
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Benefits of Creek Buffer
Helps to preserve riparian ecosystems and habitats. (From iSWM Technical Manual, rev. 9/14)
Per Environmental Resource Protection Plan mapping data, Southlake has 57.74 linear miles of stream adjacent to at least some tree cover.
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Sustainability Master Plan – Goals and Objectives
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Sustainability Master Plan Water Resources Recommendations
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Sustainability Master Plan – Water Resources
“(S)imply providing a buffer area adjacent to streams, creeks, and floodplains can protect water quality by allowing the ecosystem to naturally collect and treat pollutants in runoff
before they reach surface waters. Buffer areas can also reduce erosion, preserve habitat, increase open space, and reduce flooding.”
- Pg. 18
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Sustainability Master Plan Water Resources Recommendations
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iSWM
The adopted Integrated Stormwater Management (iSWM) Manual assists cities in meeting TCEQ stormwater requirements, in part by preserving certain natural site features conducive to abatement.
Preserv
ation and conservation of existing stream and riparian areas within a site listed as “Integrated Site Design Practice”s in the iSWM Technical Manual
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Visual Examples
(From iSWM Technical Manual, PL14)
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Visual Examples
(From iSWM Technical Manual, PL15)
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Sustainability Master Plan – Built and Natural Environment
Pg. 39
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Sustainability Master Plan Built and Natural Environment Recommendations
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Typical Creek Buffer Profile
(From iSWM Technical Manual, rev. 9/14)
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Proposed Amendment to Ord. No. 480
Allow bufferyard credit on property boundary containing buffer or on boundaries parallel to the buffer
Allow 1 for 1 tree credit for saving native trees within the buffer
Area measured 25ft from top of bank or 50ft from the creek centerline
No disturbance within stream buffer except for uses allowed in bufferyards
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STREAM ON PROPERTY BOUNDARY
Off-street parking
Building
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STREAM INTERIOR TO SITE
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Consider incentivizing use of pervious pavement (such as with credits towards impervious coverage limitations)
Amendment Details – Permeable Pavement
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Sustainability Master Plan
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Reduces surface temperatures by absorbing more heat than impervious paving;
Reduces pooling of water during rain events
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Permeable Pavers at DPS North
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Permeable vs. Conventional Surfaces
* Installed costs accounts for associated drainage structures and base aggregate costs, but does not account for maintenance or any land value factors.
Proper installation requires soil survey, base aggregate layers which allow for stability and water storage. Initial costs may be balanced out by a reduction or elimination in the need
for on-site detention, which frees land for other uses.
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Permeable vs. Conventional Surfaces
* Installed costs accounts for associated drainage structures and base aggregate costs, but does not account for maintenance or any land value factors.
Wide range of prices reflects the range of studies, applications, intended uses and type of materials.
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Proposed Amendment to Ord. No. 480
Permeable Concrete and Asphalt may be used to offset a limited increase in impervious coverage.
Definition added for permeable pavement.
Permeable pavers may be approved on a case by case basis.
Systems utilizing grass or gravel would not qualify as a permeable all-weather surface.
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Typical Development Site
Increased impervious coverage allowed with minimum area of permeable pavement.
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Anticipated Schedule
July 26th – SPIN Meeting
August 18th – Planning and Zoning Commission
September 6th – Council 1st Reading
September 20th – Council 2nd Reading
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Questions?
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Other Cities
The following Cities have created stream buffering requirements:
Frisco (All major creeks must be maintained in an open, natural condition with buffer zones dedicated as an HOA lot
or City property §8.03)
Denton (Land disturbing activity restricted within 50-100 ft of stream centerline based on drainage basin area §35.17.8)
Mansfield (Property owner must maintain
existing vegetation adjacent to watercourses §52.24)
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Other Cities
Austin, TX (Land disturbing activity restricted within 100-300 ft of stream centerline based on drainage basin area §25.8)
Laredo, TX (50-200 ft buffer from Ordinary High Water Mark
depending on stream classification and features §24-57)
Georgetown, TX (Land disturbing activity restricted within 75-300 ft of stream centerline based on drainage basin area Ord. 2013-59
Sec. 7)
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Typical Components of Stream Buffer Ordinance
Purpose statement & Definitions
Delineation of affected areas (can be determined by factors such as drainage area or by stream classification)
Extent of buffer (measure from centerline
to top of bank or OHWM out to a certain distance or to extent of floodplain.)
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Uses or activities allowed within buffer (selective clearing, footpaths, passive rec equip, aerial utility crossings or bridges)
Means of protection during and after construction (fencing,
monuments, dedication to City or HOA tract)
Procedure for replacing removed vegetation within buffer
Road or utility crossing allowances and specifications
Variance criteria
Typical Components of Stream Buffer Ordinance
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Current Chapter 9.5 - ENVIRONMENT
Sec. 9.5-82. - Natural channels.
With no improvements: Natural creek channels may be approved without channel improvements provided that:
(1) Serious erosion is not expected (i.e. velocities
less than six fps unless an approved soils test indicates that a higher velocity would be acceptable);
(2) Sufficient easements are dedicated to provide protection of adjacent properties
or facilities;
(3) Floodway easements are determined in accordance with this article;
(4) Arrangements have been made for perpetual maintenance by the adjacent property owners and/or
the creek channel has been dedicated and accepted by the city; and
(5) In the judgment of the director of public works, the appropriate use of the neighboring property or the health
and safety of such persons affected will not be substantially injured.
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Sec. 9.5-82. - Natural channels.
(b) Erosion control: Such creeks may be modified by cutting and filling, or to provide for erosion and flood control facilities, in accordance with
plans approved by the director of public works.
All erodible areas shall be protected by laying the slopes back to a maximum slope of three feet horizontally to one foot vertically
with grass sod cover; or by installing concrete, rock, masonry, or retaining walls to an elevation at least one foot above mean water elevation.
(Ord. No. 605, § 1, 6-21-94)
Current Chapter 9.5 - ENVIRONMENT
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Current Chapter 9.5 - ENVIRONMENT
Sec. 9.5-309. - Methods of reducing flood losses.
In order to accomplish its purposes, this article uses the following methods:
(1)Restrict or prohibit uses that are dangerous to health,
safety or property in times of flood, or cause excessive increases in flood heights or velocities;
(2)Require that uses vulnerable to floods, including facilities which serve such uses,
be protected against flood damage at the time of initial construction;
(3)Control the alteration of natural flood plains, stream channels, and natural protective barriers, which are
involved in the accommodation of flood waters;
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Current Chapter 9.5 - ENVIRONMENT
Sec. 9.5-309. - Methods of reducing flood losses.
In order to accomplish its purposes, this article uses the following methods:
(4)Control filling, grading, dredging and other development
which may increase flood damage;
(5)Prevent or regulate the construction of flood barriers which will unnaturally divert flood waters or which may increase flood hazards to other lands.
(Ord.
No. 641-B, Art. 1, § D, 3-29-2011)
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Proposed Amendment to Ord. No. 480
Proposed Addition to Section 42
42.2 DEFINITIONS
g. Streamway: A naturally occurring watercourse and associated riparian corridor as measured 25 feet from top of bank or 50 feet from
a creek or stream centerline, or the boundary of the 100 year floodplain, whichever is greater, and which contains native growth such as canopy trees, understory trees, shrubs and groundcover
of the woody and herbaceous variety which are conducive to the protection and stabilization of the stream bank from the effects of development and water runoff.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
h. Streamway Buffer Credit: Bufferyard requirements may be completely or partially waived on any boundary of a site or portion thereof
which lies within a naturally-occurring stream corridor as defined in Section 42.2.g and in accordance with Section 9.5-82, “Open Channel Policy.” To qualify for credit, the streamway
buffer must meet the following:
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
The streamway buffer must be placed within a conservation easement and filed on the plat or by appropriate instrument in the County records.
The plat or easement must clearly state that no activity or clearing of vegetation shall take place without prior authorization from the City of Southlake, except in the case of an imminent
threat to life or property. Monuments shall be set on the property to delineate the boundary of the conservation easement.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
2. For developments with multiple lots under an owner’s association, it shall be the option of the developer to designate the buffer as
a separate lot under common ownership in lieu of a conservation easement. The lot must be deed restricted to prevent clearing or development in a way which achieves the intent of the
conservation easement. If the developer elects this option, bufferyard credit will apply to the side(s) of the lot(s) which directly abuts the buffer lot.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
3. The extent of the buffer and the existing trees therein shall be documented as part of a required tree survey, and the limits of the
buffer shall be clearly shown on all site and civil plans.
4. For developments with multiple lots under an owner’s association, it shall be the option of the developer to designate
the buffer as a separate lot under common ownership in lieu of a conservation easement. The lot must be deed restricted to prevent alteration or development in a way which achieves the
intent of the conservation easement. If the developer elects this option, or if the buffer lot is dedicated to the city of Southlake, bufferyard credit will apply to the side(s) of the
lot(s) which directly abuts and runs parallel to the buffer lot.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
5. Adequate protection of the buffer shall be maintained throughout construction. If any damage is done to or within the buffer during construction,
the damaged area shall be restored to the maximum extent practicable with native plantings and ground cover. Such restoration shall be completed and new vegetation put in place prior
to issuance of a Certificate of Occupancy for the associated building(s).
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
6. A streamway buffer may only be used for passive recreation in conjunction with a Site Plan approved by the City, and only where topography
and considerations of stream bank stability and the integrity of the riparian area allow for such activity. Allowable uses include pedestrian, bike, or equestrian trails, provided that:
(a) any native plant material that is eliminated shall have a minimal impact and shall be replaced elsewhere within the buffer; (b) the total width of the streamway buffer is maintained;
and (c) all other regulations of this ordinance are met. In instances where such approved facilities are put in place, limited trimming and maintenance may be performed to keep the facilities
usable, so long as no additional clearing of vegetation is performed beyond what existed at the time the trail was completed. In no event shall the following uses be permitted in a streamway
buffer: playfields, stables, swimming pools, tennis courts or similar facilities, accessory buildings, parking facilities, or trash dumpsters.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
7. Additional plantings and/or restoration of the streamway buffer including replacement of invasive species with native species is encouraged
provided that such activity results in the planting of native species approved by the Landscape Administrator. Any approved landscaping placed within the buffer area will count toward
front or side yard landscaping as required in the Landscape Ordinance, Section 3.3.d.
8. For single lots which contain a stream corridor running within their boundaries rather than along
their boundaries, fifty percent (50%) credit shall be given towards plantings and width to the bufferyard required along the lot boundaries roughly parallel to the banks of the preserved
stream or the shortest linear site boundaries on either side if the stream meanders or runs diagonally through the site. Fencing requirements shall not be altered as part of the foregoing
bufferyard credit.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
On non-single family residential development, credit for existing trees within the stream corridor may be granted in the following instances:
The
trees within the stream corridor which are used as credit are native species in healthy condition and are within 2” to 6” caliper.
The trees used as credit are clearly tabulated and
marked on the approved Landscape Plan by species and caliper inch size.
Credit may be granted on a one for one basis towards any required planting within the interior of the site, other
required bufferyards, or the parking lot; provided, however, that the required plantings within these areas individually are not reduced by more than twenty percent (20%) of the minimum
requirements for any lot, building, or off-street parking area. All other requirements such as fencing type and height, irrigation, and parking lot island width shall be unaffected by
this provision.
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Proposed Amendment to Ord. No. 480
42.4 DETERMINATION OF BUFFERYARD REQUIREMENTS
4. On commercial developments with multiple lots or zero lot line buildings with common parking and amenities, or on sites where the developer
elects to parcel off or dedicate the buffer lot, credit toward required plantings shall be given only for the lot(s) which contains or abuts the stream corridor.
5. An applicant who
elects to preserve a streamway buffer for credit against bufferyard and tree planting requirements shall still be required to preserve the minimum percentage of existing tree coverage
as required in the Tree Preservation Ordinance No. 585-D.
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Pervious Pavement vs. Pervious Pavers
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Proposed Amendment
PROPOSED CHANGES TO SECTION 4 - DEFINITIONS
ALL WEATHER SURFACE – A dust free surface constructed of cement, asphalt, brick or other commonly accepted pavement which may be approved
by the Administrative Official. Not to include Permeable Pavement such as porous concrete or asphalt, as defined in this section.
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Proposed Amendment
PROPOSED CHANGES TO SECTION 4 - DEFINITIONS
PERMEABLE PAVEMENT – Also known as porous or pervious pavement, shall consist of cement or asphalt which meets the minimum load bearing specifications
utilized for an equivalent impervious all weather parking surface. A surface will be considered permeable if it is engineered and installed to current industry standards upon soil which
is appropriate to receive and abate the intake of water from the permeable surface (0.5 inches or greater of penetration per hour). The performance of the permeable surface must be maintained
at regular intervals and as needed through cleaning and/or sweeping. Damaged areas must be replaced with like materials when permeable pavement is used as credit for required open space
under the provisions of this ordinance. (CONT.)
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PROPOSED CHANGES TO SECTION 4 - DEFINITIONS
(CONT.) Permeable asphalt and concrete are not appropriate in areas of high traffic or on sites where toxic chemicals are routinely handled
or transported, where heavy machinery or trucks larger than one (1) ton routinely traverse, or on sites with gas or fueling stations, whether private or retail. Modular pavers which
allow for water infiltration shall be considered permeable pavement on a case by case basis if the pavers are made of load bearing masonry material and contribute to the aesthetics of
the site. For the purposes of this ordinance, in no case shall the use of grass pavers, grasscrete, honeycomb or grid systems, non-masonry tiles or pavers, or any system utilizing exposed
grass, vegetation, gravel, sand, or equivalent material as a parking surface constitute permeable pavement, a pervious surface for the purposes of calculating impervious coverage, or
an all weather surface as defined in this section.
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Proposed Amendment
PROPOSED CHANGES TO MAXIMUM IMPERVIOUS COVERAGE STANDARDS WITHIN SECS. 8,16,17,18,20,21,22,23,24,25,26,27,28
Allow for up to 5% increase in impervious coverage in exchange for use of
a minimum amount of permeable pavement on site in the following zoning districts: CS, MF-1, MF-2, O-1, O-2, C-1, C-2, C-3, C-4, B-1, B-2, I-1, I-2, HC
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Proposed Amendment
SECTION 21.5 DEVELOPMENT REGULATIONS (“C-2” Commercial District)
k. Maximum Impervious Coverage: The maximum impervious coverage shall not exceed seventy (70%) percent of the total lot
area; provided, however, that up to 5% of additional impervious coverage shall be permitted by utilizing an area of permeable concrete or permeable asphalt, as defined, within the required
off-street parking area which is equivalent to 400% of the overall area of increase in impervious coverage beyond the maximum allowed. Permeable pavement used for credit shall conform
to all requirements of this ordinance and shall be located on the same property on which impervious coverage is allowed above the maximum percentage. Subsequent removal of all or a part
of the permeable pavement shall require impervious coverage to decrease on the site by an equivalent amount.
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Proposed Amendment
Proposed Addition to Section 33
SECTION 33.22 USE OF PERMEABLE PAVEMENT TO OFFSET IMPERVIOUS COVERAGE
In the following districts, impervious coverage may be increased by 5% above the
maximum allowed provided a minimum area of permeable pavement is utilized as elsewhere specified: CS, MF-1, MF-2, O-1, O-2, C-1, C-2, C-3, C-4, B-1, B-2, I-1, I-2, HC
Permeable pavement
used for credit shall conform to all requirements of this ordinance and shall be located on the same property on which impervious coverage is allowed above the maximum percentage. Subsequent
removal of all or a part of the permeable pavement shall require impervious coverage to decrease on the site by an equivalent amount.
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Proposed Amendment
Proposed Addition to Section 35.4
TYPE OF PARKING SURFACE REQUIRED – All parking and vehicle use areas shall be of an all weather surface material and constructed in accordance with
applicable codes. Permeable pavement such as permeable asphalt, concrete or equivalent shall be considered an all weather surface if it is designed by a licensed engineer experienced
in the design of permeable pavement, is installed to industry standards, and meets the definition of permeable pavement in Section 4.
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Section 4 and Section 34 do not agree on number of garage sales allowed
Amendment Details – Garage Sales
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Section 4 and Section 34 do not agree on number of garage sales allowed
Amendment Details – Garage Sales
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Option 1 - Proposed Amendment to Section 4
GARAGE SALES – Occasional sales (garage sales and patio sales only) at retail, not to exceed two (2) three (3) in number on the same premises in any one calendar year, by a person who
does not hold himself out as engaging in, or does not habitually engage in, the business of selling such property at retail; provided that (1) the sale shall be confined to the garage
and/or patio of the premises; (2) no new merchandise acquired solely for the purpose of resale on the premises shall be sold at such occasional sale; (3) the duration of each such sale
shall not exceed three (3) consecutive calendar days; (4) a permit shall be secured at least 72 hours prior to and shall be prominently posted on such premises during such sale; (5)
the permit fee amount shall be as established by the City Council; (6) only one sign shall be permitted, not to exceed two (2) square feet in area, upon the premises where and when the
sale is taking place. All other signs relating to the sale, either on or off the premises, shall meet the requirements of all sign regulations adopted by the City.
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Option 2 - Proposed Amendment to Section 34
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