Steep Slope exemption.
DPD has a handy “Tip”, they use to be called, “CAM”, client Assist Memo, I guess that sounds too official, now it is called a Tip. In this case Tip 327a.
Seattle has designated certain areas as Environmentally Critical Areas, ECA,s. They even created Seattle Municipal Codes to regulate their development. SMC Chapter 25.09
In-short to develop an area is designated by the city as a Geological Hazard you will need approval from the director. In the case of Steep Slopes you can get an exemption per SMC 25.09.180 A, and B2. The easiest exemption to receive is 25.09.180 B.2.d. Which to paraphrase states: if the steep slope was created by “right of way improvements” (when a road was built) you should get a steep slope exemption. SDOT even keeps records of slopes before and after roads were constructed in their “Vault”.
What is meant by “right of way improvements”? Think of a gentle slope and a road is built across the slope, some dirt is piled on the high side of the road, and some dirt is pushed down hill. Now both sides of the road have a steep slope, created by “right of way improvements”
Below is an excerpt of 25.09.180:
B. Impacts on steep slope areas
1. Development is prohibited on steep slope areas, unless the applicant demonstrates that the provisions of subsections 25.09.180.B.2 or 25.09.180.E apply.
2. Provided that all the provisions of this Chapter 25.09 and all applicable provisions of Title 23 and Chapters 22.800 through 22.808 are met, subsection 25.09.180.B.1 does not apply when the applicant demonstrates the development meets one of the following criteria. In determining whether these criteria are met, the Director may require a geotechnical report to verify site conditions and to evaluate the impacts of the development in the steep slope area and shall require such a report for criteria in subsections 25.09.180.B.2.c and 25.09.180.B.2.d. The geotechnical report is subject to the provisions for third party review in subsection 25.09.080.C.
a. Development is located where existing development is located, if the impact on the steep slope area is not altered or increased; or
b. Development is located on steep slope areas that have been created through previous legal grading activities, including rockeries or retaining walls resulting from rights of way improvements, if no adverse impact on the steep slope area will result; or
c. Development is located on steep slope areas that are less than 20 feet in vertical rise and that are 30 feet or more from other steep slope areas, if no adverse impact on the steep slope area will result; or
d. Development is located on steep slope areas where the Director determines that application of subsection 25.09.180.B.1 would prevent necessary stabilization of a landslide-prone area.
Links useful for research:
List of DPD Tips: http://web1.seattle.gov/dpd/cams/CamList.aspx
Entire Seattle Municipal Code can be found here: https://www.municode.com/library/wa/seattle/codes/municipal_code