HomeMy WebLinkAboutRR-31 JeffersonTwanaRathvonRoadGradients8.15.25PO Box 2546, Bellingham, Washington 98227
Phone: (360) 714-9409
August 15, 2025
Richard Rathvon
20 Liberty Knoll
Colts Neck, NJ 07722
rrathvon@gmail.com
Re: Assessment of Twana Road Grade
I visited Twana Way to directly measure the road gradients on the road to so that a better
understanding of the road grade could be provided. The grades on multiple road sections were
measured directly using a Brunton compass with level bubble and using an electronic
inclinometer. The grade measuring locations and the grades are marked on the attached lidar bare
earth image of the Twana Way area.
The steepest gradient measured was 25%. This 25% gradient was approximately 50 feet in length
with gradients of 10 percent or less above and below.
I also noted that the road is appears to be full bench cut throughout its length. That is the road
has been cut into the slope such it not on constructed on any fill slopes. Cut slopes are within
very dense and/or hard glacial drift that is generally sandy with some areas that are silty. Some
minor slope ravel was observed on a limited steeper cuts. One indentation was observed in one
CA received 085/15/25
EXHIBIT RR31
cut that is consistent with a root throw – soil pulled out when a tree tipped over in the past.
Slopes above cut slopes are moderate to moderately steep and no areas of potential landslides
were identified on the slops above the road cuts or on the slopes below the road, other than
steeper slopes well away from the road associated with the shoreline bluff.
Stratum Group appreciates the opportunity to be of service to you. Should you have any
questions regarding this assessment please contact our office at (360) 714-9409.
Sincerely yours,
Stratum Group
Dan McShane, L.E.G., M.Sc.
Licensed Engineering Geologist
CA received 085/15/25
EXHIBIT RR31