Permit Requirements for Landslide-Prone Areas in the City ......Slope Stability and Vegetative Soil Stabilization in the Puget Sound Region December 5, 2013 Permit Requirements for

Slope Stability and Vegetative Soil Stabilization in the Puget Sound Region

December 5, 2013

Permit Requirements for Landslide-Prone Areas in the City of Seattle


December 5, 2013

Landslide-Prone Areas Rob McIntosh, P.E., Senior Geotechnical Engineer

Department of Planning and Development (DPD)

Trees and Vegetation Seth Amrhein, Senior Environmental Analyst

Department of Planning and Development (DPD)

AGENDA


December 5, 2013

Definition of Landslide-Prone Areas in the Environmentally Critical Areas (ECA) Ordinance

– Known landslide areas

– Potential landslide areas

– Steep slopes

(at least 10 feet high and 40% or greater average slope)

• http://web1.seattle.gov/dpd/maps/dpdgis.aspx


December 5, 2013

Development Regulations for Landslide-Prone Areas in Seattle

– No grading/disturbance of steep slope areas is allowed. Limited exemptions include:

• Proposed development is located where existing development is located

• Proposed development is located on steep slope areas created by previous legal grading

• Proposed development is in an isolated steep slope less than 20 feet in height

• Proposed development is the minimum necessary to stabilize the slope

• See Client Assistance Memo (CAM) 327A.

– Permit required for any grading over 25 cubic yards


December 5, 2013

Development Regulations for Landslide-Prone Property in Seattle

– Permit required for all retaining walls

– Permit required for installation of drainage


December 5, 2013

Development Regulations for Landslide-Prone Property in Seattle • Getting a Building Permit

– Visit the Applicant Services Center on the 20th Floor of 700 5th Ave, Seattle to get started

– Call 206-684-8850 to get more

information or to schedule an

intake appointment

– Pre-application site visit (PASV)

– Plan review and corrections

– Expedited permitting for some landslide repairs

– Special Inspections


December 5, 2013

Don’t List

• Don’t direct storm or other water onto a slope.

• Don’t denude vegetation on slope without an approved re-vegetation plan.

• Don’t cut into the toe (or bottom) of a slope.

• Don’t remove tree stumps from slopes.

• Don’t install a permanent irrigation system in landslide-prone areas.

• Don’t put fill or yard debris on a steep slope.


December 5, 2013

Tree and Vegetation Overview SMC 25.09.320

• Removing, clearing, or any action

detrimental to habitat, vegetation or trees

is prohibited within the following areas:

landslide-prone critical areas, steep slope

buffers, riparian corridors, shoreline

habitat, shoreline habitat buffers, wetlands

and wetland buffers, except for…


December 5, 2013

Tree and Vegetation Overview (Tip 331)

Area of Work File Plan with

DPD

DPD Routed

Plan Review

SEPA review

required

Plan Type

Less than 750

sq. ft.

None

750 sq. ft. or

greater

YES Maintenance

plan

Normal and Routine Maintenance*

* Normal and routine maintenance includes practices that are necessary to maintain

existing pathways and landscaping, ensure the health of existing vegetation, or achieve

limited pruning to allow windowing, reduce tree mass or redirect tree growth. Removal

of trees and vegetation is not considered normal and routine maintenance.


December 5, 2013


Area of Work DPD Routed

Plan Review

SEPA review

required

Plan Type

Less than

1500 sq ft

YES NO Restoration plan as part of

plan set

1500 to less

than 9000 sq

ft

YES

NO Restoration plan as part of

plan set

9000 sq ft or

greater for

SFR

YES

YES

Restoration plan and SEPA

checklist as part of plan set

Approved as Part of an Issued Building or

Grading Permit


December 5, 2013


Area of Work* File Plan

with DPD

DPD Routed

Plan Review

SEPA review

required

Plan Type

Less than

1500 sq. ft.**

YES

Restoration plan,

ECA Restoration

plan application

1500 sq. ft. or

greater

YES

YES

Restoration plan,

SEPA checklist,

ECA Restoration

plan application

Vegetation Restoration Project-removing

invasive plants and noxious weeds by hand

* Area measured cumulatively over three years.

** In landslide-prone areas, when disturbance exceeds 750 square feet, the plan

shall be approved by a licensed geotechnical engineer or geologist.


December 5, 2013


Area of Work File Plan

with DPD

DPD Routed

Plan Review

SEPA review

required

Plan Type

All YES

Hazard Tree

Application (see

Tip 331B* for

information and

submittal

requirements.

Hazard Trees

*Hazard Tree Removal Application , Tree Risk Assessment report by

Tree Risk Assessment Qualified Arborist, photos, site plan


December 5, 2013

Vegetation Restoration (Tip 331A) Provides general information about creating a revegetation plan. Geared toward homeowners.

Vegetation restoration

projects need to be

designed to:

promote maintenance or

creation of a naturally

functioning condition that prevents erosion, protects

water quality, or provides diverse habitat


December 5, 2013

Vegetation Restoration (Tip 331A)

WHAT IS VEGETATION RESTORATION? • Vegetation restoration is the establishment of native

vegetation, including the removal of non-native or

invasive plants.

• Goal is “to promote maintenance or creation of a

naturally functioning condition that prevents erosion,

protects water quality, or provide diverse habitat” (SMC

25.09.320).

• Restoration should result in a densely vegetated area

with a significant diversity of native trees, shrubs and

groundcover


December 5, 2013


Examples of allowed restoration

include:

• re-establishment of a native ecosystem

in human impacted areas such as

paved surfaces, lawns or landscaped

areas

• replacing non-native, noxious and/or

invasive species such as English ivy,

Himalayan blackberry, or reed canary

grass, with native plantings


December 5, 2013


Examples of allowed restoration include

(continued):

• replacing previously topped trees with healthy native

trees

• replacing monocultural stands of deciduous trees like big

leaf maples and red alder with native conifers


December 5, 2013


Examples:


December 5, 2013


Examples (before and after maintenance):


December 5, 2013


Examples (established revegetation):


December 5, 2013


Examples (established revegetation):


December 5, 2013

Hazard Trees (Tip 331B)

Hazard trees must have a target

(infrastructure or people).

Large holding roots on Bigleaf maple


December 5, 2013

Selective Removal & Thinning For View Corridors

Tree removal is not permitted for views. Pruning is OK when done

using best practices to maintain tree health; topping is prohibited.

Removal only permitted if tree is hazardous or if necessary “to promote

maintenance or creation of a naturally functioning condition that

prevents erosion, protects water quality, or provide diverse habitat.”


December 5, 2013

Question & Answer

Documents

Permit Requirements for Landslide-Prone Areas in the City ......Slope Stability and Vegetative Soil Stabilization in the Puget Sound Region December 5, 2013 Permit Requirements for