HomeMy WebLinkAboutPlanning 2016-10-27 ITEM 4 - LOW IMPACT DEVELOPMENT / TMC TITLES 18 AND 8.25 AMENDMENTS - STAFF REPORTCity of Tukwila
Department of Community Development - Jack Pace, Director
STAFF REPORT
TO THE PLANNING COMMISSION
Prepared October 10, 2016
FILE NUMBERS: L16 -0050 Low Impact Development Code Amendments
E16 -0008 SEPA Checklist
REQUEST:
Allan Ekberg, Mayor
Public Hearing regarding the proposed low impact development code
changes to the Zoning and Vehicle Parking Storage regulations. Based on
direction from the Planning Commission staff will revise the ordinances and
then the Planning Commission's recommendations will be forwarded to the
City Council for review.
PUBLIC HEARING: October 27, 2016
LOCATION: City wide
STAFF: Moira Bradshaw, Senior Planner
ATTACHMENTS: Titles 8.25 and 18 Draft Ordinance
Bioretention Plant List
Introduction
The National Pollutant Discharge Elimination System (NPDES) permit program, created in 1972 by the
Clean Water Act (CWA), helps address water pollution by regulating point sources that discharge
pollutants to waters of the United States. Due to recent regulatory changes at the Federal and State
levels Tukwila needs to modify its regulations to better control water pollution.
The City's NPDES Phase II permit allows the City to drain the collected surface water from its system
into the Green River. The permit is conditioned upon the City reviewing, revising, and making
effective changes to the City's development related codes, standards, and other enforceable
documents. The stipulation is that the City incorporate into its development codes the low impact
development (LID) principles and LID Best Management Practices no later than December 31, 2016.
LID is a stormwater and land use management strategy that strives to mimic pre- disturbance natural
hydrologic processes of infiltration, filtration, storage, evaporation and transpiration. It emphasizes
conservation, use of on -site natural features, site planning, and distributed stormwater management
practices that are integrated into a project design.
Tukwila City Hall • 6200 Southcenter Boulevard • Tukwila, WA 98188 • 206 -433 -1800 • Website: TukwilaWA.gov
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BACKGROUND
The Tukwila Planning Commission advises the Mayor and City Council on matters relating to land use,
comprehensive planning and zoning (TMC2.36.o3o.) Additionally, all code cities are required to adopt
development regulations that are consistent with and implement the City's Comprehensive Plan.
(RCW 35A.63.105)
The Tukwila Comprehensive Plan has the following policies regarding surface water management and
design. Any proposed regulation must implement and be consistent with these policies.
Natural Environment Element 4.1.5 Develop and implement
programs that encourage Tukwila residents and businesses to take
active measures to protect and enhance Tukwila's natural environment.
Such measure could include the use of Low Impact Development (LID)
techniques, natural stream bank restoration, non -toxic lawn care,
composting and recycling, among others.
Natural Environment 4.8.1 Demonstrate implementation of low
impact development techniques through grant funded public projects.
Where feasible incorporate such techniques into City Capital facilities
projects. Provide technical assistance to developers, and encourage the
use of such techniques for storm water management.
Natural Environment 4.8.2 Require that all proposed development
applications identify hydrologic features, both on and off -site, that
could be impacted by the project. Evaluate and prevent project impacts
on on -site and off -site watercourses, wetlands, drainage features and
springs to avoid adverse impacts to existing sensitive area hydrology.
Shoreline 5.10.1 Design, locate and manage shoreline development
including streets, flood control projects, surface water drainage and
sewer systems, clearing and grading activities, and landscaping in a
manner that minimizes opportunities for pollutants to enter the river,
provides erosion control, and otherwise protects water quality.
Utilities Element 12.1.26 Apply an adopted surface water design
manual as the minimum requirement for all development projects and
other actions that could cause or worsen flooding, erosion, water
quality and habitat problems, for both upstream and downstream
development.
Utilities 12.1. 29 Encourage the retention and planting of trees for
their beneficial effects on surface water runoff, including flow
attenuation, water quality enhancements and temperature reduction.
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DISCUSSION OF PROPOSED CHANGES
The draft ordinance (Attachment A) contains proposed changes to the City's Vehicle Parking and
Storage Section of the Tukwila Municipal Code (TMC) as well as a variety of changes to the Zoning
Code. Below is a summary of each section of the draft ordinance.
Section 1.
Vehicle Storage and Parking on Single- family Residential Property (TMC8.25) is being moved into the
Zoning Code. Three chapters of the Zoning Code will be changed to include the items being moved -
the Definitions, Low Density Residential — Basic Development Standards, and Off - street Parking
Chapters. The existing standard is that no more than 10% of a lot's surface or 1,200 square feet,
whichever is greater, be covered with a durable uniform surface (TMC 8.25.o2o(D).) That is proposed
for replacement with the development coverage standard of 75% for single family homes. See the
definition of "development area" below. See Sections 3, 7, and 14 below for how the other elements
of existing TMC 8.25 are being carried over into the Zoning Code.
Section 2.
Lot coverage and development area are interchangeable terms and both are defined in the Zoning
code. Development area is more prevalently used. "Lot coverage" is therefore being deleted and
where it was used (See Section 15,) "development area" is substituted.
Section 3.
The definition of "Development area" is being modified to distinguish between pervious and
impervious surfaces and provide an incentive to use pervious surfaces. The goal of low impact
development is to preserve native soils and vegetation, hence the allowance for only 75% of new
pervious surfaces /area. The exception for pedestrian and recreation space in MDR and HDR is being
moved out of the Definition to the Supplemental Development Standards section (TMC 18.50.) See
Section 10.
Section 4.
The definition for "native vegetation" is proposed for modification to allow a wider range of materials
that may be used in planting plans.
Section 5.
The "durable uniform surface" definition is being moved from the Vehicle Parking and Storage
Chapter (TMC8.25) to the Zoning Code and updated to reflect the goal of using pervious (or
permeable) surfaces.
Section 6.
A "pervious surfaces" definition is being added in order to encompass low impact development
materials. The Appendix shows images of pervious surfaces.
Section 7.
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A "development area" standard is being proposed for single family development. Single family lots
are divided into two categories: 75% on lots less than 13,000 square feet up to a maximum of 5,85o
square feet and 45% for those equal to and larger than 13,00o. A 5o% standard currently exists for
multi - family and 75% exists for townhomes.
Below is a table showing the development area coverage for single family homes permitted in 2015.
Permit #
Lot size
Structure
coverage
amount of site
impervious area -
other than
structures
D15 -0021 6,780 2276 710
D15 -0157 98,446 1694 2345
D15 -0161 9,459 1274 1308
D15 -0163 9,400 2451 1279
D15 -0285 15,387 3907 1455
D15 -0302 6,635 1870 1765
D13 -179 4,218 1315 338
amount of
pervious
improvements
Lot coverage
2,986 0.44
4,039 0.04
2,582 0.27
0.40
0.35
0.55
192 1653 0.39
total
impervious
area
r
r
2643
3,730
5,362
3,635
Section 8.
In the chapter for Residential Commercial Center Zone (RCC,) the development standards table has a
description of what may be included in landscape areas. Bioretention facilities are being proposed for
addition as they are a low impact development technique for landscape areas. Bioretention is defined
in the 2016 Surface Water Design Manual, which is being adopted by the City as part of its update to
the Surface Water Management Section of the TMC. It means, "A stormwater best management
practice consisting of a shallow landscaped depression designed to temporarily store and promote
infiltration or stormwater runoff. Standards for bioretention design, including soil mix, plants, storage
volume and feasibility criteria are specified in the Design manual." Biorretention area use plants and
soils to retain surface water and slowly absorb this water into the ground instead of into man -made
pipes and area streams and the River. The proposed Biorretention Plant list is attached. Images of
Biorretention facilities are contained in this Report's Appendix.
Section 9.
The proposed amended language is to update the code with respect to structural soils and to ensure
that the standards reflect the best available science with respect to landscape health.
Section 10
This section repeats the standards for development area that was noted in Section 7 above and
includes the exception from the development area standard for pedestrian, landscape and recreation
facilities in MDR and HDR. It also provides a reference to the Surface Water Design Manual for
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L16 -oo5o Low Impact Development Code Changes
evaluation of low impact development proposals. Minor changes in wording are incorporated to clarify
standards without changing the substance for senior housing and townhouse developments.
Section 11 and 12.
Proposed language to allow Biorretention as a viable landscaping technique and references a City of
Tukwila biorretention plant list. (See also Attachment B.)
Section 13.
Proposed language clarifies the off - street parking standards for low density residential development,
references "pervious pavement" as the preferred surface for parking areas and adds a stipulation that
any "additional" parking —that is any additional stalls greater than the minimum numbers - shall use
pervious surfaces.
Section 14.
The Residential Parking Requirements section of the Zoning Code is being updated to:
• Delete the reference to the number of stalls required as that exists in Figure 7 — "Required
Number of Parking Spaces for Automobiles and Bicycles."
• Include the standards from "Vehicle Parking and Storage Chapter of TMC (8.25.) See Section 1
above.
• Eliminate a standard from TMC 8.25 that limits the amount of durable uniform surfaces to io%
of a lot's area. The development area standard is being substituted for this requirement. See
Section 7 above.
• Eliminates the reference to "Vehicle Parking and Storage Section of the Public Peace and
Morals Chapter (TMC 8.25) because that has all been brought into the Zoning Chapter.
Section 15.
Substitutes the term "development area" for "lot coverage."
Section 16.
Eliminates the largest size parking stall in order to minimize the amount of impervious surface that is
allowed for automobile parking.
REQUESTED ACTION
Hold the public hearing on the proposed changes, deliberate and make a recommendation to the City
Council.
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Appendix
Bio- retention Images
Pervious Concrete Demonstaration
Asphalt paving half pervious half impervious
Commercial example of bioretention facility.
Pervious Asphalt — Notice voids b/w rocks
Access street using pervious material
Residential scale bioretention facility. Catch basin in place to drain
overflow.
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