HomeMy WebLinkAboutBLD2020-00537-09- GEOTECH WAIVERTO: Patty Charnas, Director / UDC Administrator
FROM: Amanda Hunt, Assistant Planner
DATE: January 28th, 2021
RE: 531 Seamount Dr, Brinnon, Washington, Geotechnical Report Waiver Request –
Approval Recommendation
Roberta Mark applied for a geotechnical report waiver during the course of a BWOP –
Workshop/Satellite Bedroom with bathroom application (BLD20-00537). They plan to contine
the current use of the structure. Their property is mapped as a Shoreline Slope Stability Area –
Unstable Slope, with a Moderate Landslide Hazard Area located down slope. I have reviewed the
waiver request submitted by Roberta Mark, available map and data, and completed the attached
geohazard checklist. The property owner will plant several trees in the less vegetated areas of the
slope as a condition of waiver approval. The existing structure area has a slope of 16% , the steep
slope has an approximate slope of 73%, and the overall parcel has a slope of 11%. Based on our
available data, the Mark property, the existing developed area, and analysis from the geohazard
checklist, I find that the standards for a geotechnical report waiver, under Jefferson County Code
18.22.910, have been satisfied.
_X__ Approved
___ Denied
______________________________________________
Patty Charnas, Director / UDC Administrator
Attachments:
Supplemental application waiver from special reports
Geohazard Checklist
Site Plan
Geohazard Checklist
1. Which of the following are mapped on-site?
Land Slide Hazard: Moderate __X__ High ____ Recent Landslide ____ Old Slide ____
Erosion: ____
Seismic: ____
Shoreline Slope Stability: Unstable _X___ Landslide ____ Modified ____
Two or more? Yes _X___ No ____
2. Existing Development? Yes _X__ No ___ Evidence of geohazard? Yes___ No _X__
3. Is the slope greater than 15 %? (rise/run = %) Yes __X__(approx. 73%)__ No ___
4. Will the development be less than 35 feet from the top or toe of slope? Yes _X_(approx. 10 ft)_
No ____
5. Does the site have a less stable slope form? Yes ____ No _X___
Divergent ____ (most stable) Planar __X__ (more stable) Convergent ____ (less stable)
6. Is there any information regarding stability of the soil e.g. septic soil logs, NRSC soil survey etc.
Yes ____ No__X___
7. What type of vegetation on-site?
Heavily Vegetated with Native (most stable) _X___ Not well vegetated (less stable) ____ Recent
Timber Harvest ____ (least stable)
8. Site Visit recommended on moderate or greater risk areas to look for indicators (see list) – Any
indicators? Yes ____ No _X___
Site Visit (1/28/2021) Finding(s):
- The property sits on gravel/glacial till soils, which are considered very stable.
- There was only 1 jack-strawed tree on the steep slope. All other trees are over 50 years old
and show no signs of land movement.
- The Workshop disperses stormwater directly off the slope. There were no topographic
indicators that stormwater runoff was creating a hazard on the steep slope (e.g. no ground
disturbance present where runoff is dispersed).
9. Were there any other Geotechnical Report’s done on adjacent properties? Yes ____ No __X__
If yes, did the Geotech indicate a geohazard or unstable slope? Yes ____ No ____
* 4 of the 9 questions were checked “yes”, indicating that a geotechnical report is not required*