1. Review of NPDES Permit Requirements for Low Impact
Development
2. Integrating LID into Sammamish’s Codes and Standards
o
Amendments to SMC 21A.85
o
Other Proposed Code Amendments
3. Next Steps/Resources
NPDES Requirements
2013-2018 Western Washington Phase II Municipal Stormwater
Permit
Section S5.C.4.f, requires:
•
No later than December 31, 2016, permittees shall review,
revise and make effective their local development-related
codes, rules, standards, or other enforceable documents to
BMPs vs Principles
•
LID BMPs achieved through the adoption:
o
King County Surface Water Design Manual
o
Sammamish Addendum to the KCSWDM
•
LID Principles achieved through the adoption:
o
SMC 21A.37 Development Standards - Trees
o
Public Works Standards
o
Amendments to SMC 21A.85 LID Code
BMPs vs Principles
•
LID BMPs achieved through the adoption:
King County Surface Water Design Manual
Sammamish Addendum to the KCSWDM
•
LID Principles achieved through the adoption:
SMC 21A.37 Development Standards - Trees
Public Works Standards
o
Amendments to SMC 21A.85 LID Code
LID Principles
Intent: To make LID the preferred and commonly-used
approach to site development.
Principles include minimizing:
•
Impervious surface coverage
•
Native vegetation loss
INTEGRATING LID INTO SAMMAMISH’S CODES
& STANDARDS
Integrating LID into Sammamish’s Codes and Standards
o
Amendments to SMC 21A.85
Challenges with Existing Code
SMC 21A.85 – Low Impact Development
–
Chapter is too complicated
–
LID techniques too difficult to achieve
–
Incentives are too low
Proposed Amendments to SMC 21A.85
Sections:
21A.85.010 Intent and goals 21A.85.020 Applicability
21A.85.030 Sammamish comprehensive low impact development design
21A.85.040 General low Impact Development approaches and standards
21A.85.050 Residential preferred LID approaches and standards 21A.85.060 Town center LID approaches and standards
21A.85.070 Preferred Low Impact Development incentives 21A.85.080 Review
Proposed Amendments to SMC 21A.85
Sections:
21A.85.010 Intent and goals 21A.85.020 Applicability
21A.85.030 Sammamish comprehensive low impact development design
21A.85.040030 General lLow Impact Development techniques
approaches and standards
21A.85.050 Residential preferred LID approaches and standards 21A.85.060 Town center LID approaches and standards
21A.85.070040 Preferred Low Impact Development incentives 21A.85.080050 Review
Proposed Amendments to SMC 21A.85
– Retention of Existing Forested Condition
– Restoration of Vegetated Area
– Restoration of Critical Area Buffer
– Increased Critical Area Buffer Width
Proposed Amendments to SMC 21A.85
– Retention of Existing Forested Condition
– Restoration of Vegetated Area
– Restoration of Critical Area Buffer
– Increased Critical Area Buffer Width
Proposed Amendments to SMC 21A.85
LID approaches eligible for incentives:
– Limited Site Disturbance
– Reforestation
Proposed Amendments to SMC 21A.85
LID techniques eligible for incentives
– Minimal Foundation Excavation
– Joint Use Driveway
– Hollywood Driveway
Proposed Amendments to SMC 21A.85
LID techniques no longer eligible for incentives
– Pervious Pavements/Materials*
– On Site Infiltration*
– Biofiltration Swales and Rain Gardens*
– Soil Amendments*
– Performance Guarantees for LID Approaches*
– Vegetated Roofs
– Drought Tolerant Landscaping
– Open Space
Proposed Amendments to SMC 21A.85
LID Incentives
– Increased Density
– Recognition by City
– Building Height Increase
– Increased Signage
– Attached Housing
Proposed Amendments to SMC 21A.85
Graduated Scale
– All or nothing approach limits use of techniques
– Adding a “graduated scale” of points awarded for some techniques
Example
Conventional Development
LID Development
Technique Points Retention of 30% Additional Trees 15 Total Points 15LID Development
Technique Points Retention of 30% Additional Trees 15 10% Reduction in Impervious Surface Coverage 6 Total Points 21LID Development
Technique Points Retention of 30% Additional Trees 15 10% Reduction in Impervious Surface Coverage 6 Joint Use Driveways 6LID Development
LID BMPs per the Surface Water Design Manual
LID Development
Technique Points Retention of 30% Additional Trees 15 10% Reduction in Impervious Surface Coverage 6 Joint Use Driveways 6LID Development
Technique Points Retention of 30% Additional Trees 15 10% Reduction in Impervious Surface Coverage 6 Joint Use Driveways 6Total Points 27
Other Proposed Code Amendments
•
SMC 16.15 – Clearing and Grading
•
SMC 21A.15 & 21B.15 - Technical Terms and Land Use Definitions
•
SMC 21A.30 – Development Standards – Design Requirements
•
SMC 21A.35 – Development Standards – Landscaping and Irrigation
•
SMC 21A.40 – Development Standards – Parking and Circulation
•
SMC 21B.25 – Development Standards – Density and Dimensions
•
SMC 21B.30 – Development Standards – Design Requirements
•
SMC 21B.35 – Development Standards – Landscaping and Irrigation
Other Proposed Code Amendments
Clearing and Grading
(SMC 16.15)
• Amendment to the definition of compaction for consistency with the KCWSDM
Technical Terms and Land Use Definitions
(SMC 21A.15 & 21B.15)
Other Proposed Code Amendments
Development Standards – Design Requirements
(SMC 21A.30)
• Cluster development open spaces to be located where existing stands of native vegetation exist
• Recreation space credits provided for stormwater runoff tracts that meet design criteria (as specified in Sammamish Addendum)
Other Proposed Code Amendments
Development Standards – Landscaping and Irrigation
(SMC 21A.35)
• Landscaping requirements for detention facilities as specified in the 2016 KCSWDM and Sammamish Addendum
• 10’ of Type I landscaping only required where slopes of pond exceed 3H:1V
• Landscaping standards for bioretention facilities within parking lot landscaping
Other Proposed Code Amendments
Development Standards – Parking and Circulation
(SMC 21A.40)
• Permeable pavement may be used for off-street parking without requiring Director approval
Development Standards – Density and Dimensions
(SMC 21B.25)
• Low Impact Development site planning principles/practices that minimize stormwater runoff are included for bonus commercial or residential capacity
Other Proposed Code Amendments
Development Standards – Landscaping and Irrigation
(SMC 21B.35)
• Replacement trees for removed deciduous trees will be replaced with a mixture of deciduous and coniferous trees, at a ratio of 2 coniferous trees for every 1 deciduous tree
– Example:
• Six 12” diameter deciduous trees are removed
• Four replacement trees are required for each removed tree, for a total of 24 replacement trees
• 16 coniferous trees and 8 deciduous trees would be required to be replanted
Other Proposed Code Amendments
Development Standards – Interim Stormwater Standards
(SMC 21B.85)
• Stormwater standards in the Town Center shall be in accordance to the adopted Surface Water Design Manual and Sammamish
Next Steps: Stakeholder Involvement
Open Houses
•
July 27th (1st Open House)
•
September 21st (2nd Open House)
Technical Stakeholder Meetings
•
August 9th (1st TSC Meeting)
•
August 24th (2nd TSC Meeting)
Next Steps: Adoption Phase
Planning Commission
•
September 1st (Work Session)
•
September 15th (Work Session)
•
October 20th (Work Session)
•
October 27th (Public Hearing and Deliberation)
City Council
•
November 8th (PC Handoff)
•
November 15th (Study Session)
Resources
Sammamish Stormwater Management Program website:
http://www.sammamish.us/departments/publicworks/Storm WaterManagement.aspx
Ecology’s stormwater website:
http://www.ecy.wa.gov/programs/wq/stormwater/index.html
Washington Stormwater Center LID portal:
