8003 LARIMER RD 2016-01-01 MF Import

TO: ADDRESS FILE 8003 FROM: DAN MATHIAS DATE: September 23, 1987 SIIBJECT: WOOD CREER DRAINAGE MEMORANDUM LARI;•iER ROAD PROBLEM �� � t� Sp� � In response to a concern expressed by Mrs. Spane at so03 Larimer Road, I inspected Wood Creek in :,outh Everett on September 21, 1987. Wood Creek has been running quite turbid in the last few days according to Mrs. Spane even though it has not rained since September 14, 1987. The Creek was in3eed running quite turbid, so I attempted to determine the source of the sediment. I walked up the creek from Larimer Road approximately 1000 feet until the brush got very thick. The water was still rur�ning very turbid 1000 feet upstream of Larimer Road. Na source oP sediment (eg. channel bank erosion) was noted in this 1000' r.each of Wood Creek. Approximately 2 years ago, the Department of Transportation rapaired a storm drain outfall washout adjacent to I-5. This area drains to Wood Creek and washed tons of sediment onto the Spaae property in 1985. I inspected the repaired outfall on September 21, 1987 and found it to be functioning properly. In fact, the stream was running very clear as far as I walked downstream (which was approximately 200' downstream of the confluence of the north and soutti forks of Wood Creek). Two sites which currently have Public Works Permits were also inspec�ed. These were the Eastmont Shc�:ping Center and the logging and clearing operation near Shadow Wood Drive. No sediment was being generated at either of these sites. The source or cause of t.he problem, therefore, is within the approximately 3000 feet rea.ch of the stream that I did not walk because of heavy brush. The problem could be a natural wash out from stream cut or mobilization of the sand bottom of the stream channel. The sand �ras deposited during the I-5 storrt, drain outfall washout two years ago. The most recent rainfall on Sep'.ember 14, 1987 was a small event (.25" of rain), but may have been large enough to increase stream velocity above tt�.e non-erodible velocity of the sand. It was noted that the upper reaches of t.he stream where the water was running clear, the channel bottom was mostly gravel and iree of sar.d dep�sits. It may just take a while (several years) before the sand is £ully flushed £rom the stream system.