Wednesday, July 11, 2007
LIDAR for Whidbey (NOTE N-S glacial grooves)
Seepage from Silver Ck.yields permanent VEGETATION
Silver Creek yields fault information
The photos above and below show two indications of faulting in the Mariner's Cove area of Whidbey Island, S36 T33N R2E
Silver Lake, which feeds the Creek, is near the highest elevation on W.I.(531 feet, south of the lake) and the creek exists near the 500 foot mark. Sea Level, where the hanging gardens and Mariner's Cove lie is some 2000 feet to the south. The orientation of Silver Creek is 120 degrees from north, as is a small creek, unnamed, near Strawberry hill area. This is known to be the Strawberry Fault of similar orientation- a left-lateral fault of unknown planar configuration at depth. Should the fault plane exist at the surface as Silver Creek and at sea level as the Strawberry fault, this would yield the planar dip of the discontinuity sloping downward to the SSW. It would have a slope of about 20-25 percent, where the high point of the island is rising as the ground surface at the lake sinks (there is a continual seepage into the lake from high ground to the south).
This, if true, should be of great interest to the property owners, since the slumping would be larger than normal with the wedging of the subsurface upward to the south. Polnell Point is part of this left-lateral system but parallel to it- probably a continuation of the Rocky Point fault reported last month in this BLOG, continuing on to Camano Island where large slumps are observed.
Island County could easily monitor this situation with the data they have accumulated in their well file (from testing of some 6000 wells in the county).
Whenever fracturing creates pathways at the ground surface, the acidic rainwater finds these openings moreso than for non-fractured areas. The entrance of acidic water reacts with the calcitic cement holding the soil and Pre-Stone together and weakens it- yielding bicarbonate HCO3 to nearby wells. This can be monitored by the county, to observe the change with time. Whenever there is a consistent increase, slumping and fracturing can be expected to increase.
This would be a WISE use of the County Hydro-geological manpower and data, rather than their present action to force property owners to drill new wells and to test them subsequently before granting permits for building (to prevent the possibillity of new sea water intrusion). The present well data can be used to eliminate areas from consideration for drilling, rather than the present wasteful practice of requiring the drilling of new wells which are later condemned after spending drilling and testing dollars (to present a water sample for couty rejection).
I recommend that the county initiate a program of testing present wells to determine whether, in doubtful areas, HCO3 is increasing (thereby indicating incipient slumping). Simultaneously, the county should do mapping of the lines of water chemistry (from well data in the already-existing files)anomalies in terms of faulting and fracturing.
See a previous BLOG relating saltwater intrusion to lines of anomalous potassium and flouride in the groundwater (on a map), found from water analyses in the present files- FREE. All of these data for analysis are in hydro-geological files, and should be used, what with the tremendous time and expense used to amass this water quality file.
If you are considering buying a property where neighbors have history of increasing salinity (salt taste) in their drinking water, ask to see the map of excessive K/Cl (potassium divided by Chlorides in ORIGINAL well water Chemistry). This map will show if there is high risk of encountering unusual water, which exists near faulting. YOU DON'T HAVE TO DRILL AN EXPENSIVE WELL, AND LATER PAY FOR EXPENSIVE COUNTY-REQUIRED TESTING TO DETERMINE IN ADVANCE WHETHER THE DRILLSITE SOULD BE AVOIDED (THIS WORK WILL COST YOU- the property owner and taxpayer- MORE THAN TEN THOUSAND DOLLARS).