Friday, June 22, 2007

Does your Groundwater Taste Bad?

Expenditures to Eliminate Salt Water Intrusion

Whidbey Island, with its increasing population, has human-induced stress on its groundwater supply. This is a particular problem in coastal areas- where all want to live, because of the views of the Puget Sound (and its salt water).
The groundwater must remain in a steady state situation- where the precipitation must equal or surpass the usage- for inhabitants to depend upon a sufficient supply of fresh water. Groundwater existed before Man began to pump it, in a lens configuration. That is, a lens-shaped or elliptical layer of fresh water (which extends below sea level for part of the island) lay above the deeper brackish or salt water. The water-bearing layers (named aquifers) in an isolated lens occur within a portion of the island isolated by faults, on at least two sides. The other two edges of the lens generally exist at the beach, and the lens is the thinnest there. The lens is thickest in the center of the island. The faulting, which occurs every few miles on the island, acts as active slices or cuts in the layers containing the water, and these may isolate an area from neighboring lens. Water may move along the active fault, or cut, where it will create seeps or springs upon reaching the cliffs near the sea. This case is particularly obvious at Dugualla Bay, where an aborted ice lobe, from Glaciation times, has sliced the water-bearing layers to produce many springs (see the link labeled Bounty from the Earth to see one such spring bringing iron from the earth, at Penn Cove).
A proper analysis of the groundwater available for a particular neighborhood should first determine the lens and its boundaries of faulting and coastal saltwater. This costs the County time and Money, hence the workers are reluctant to undertake this requirement. Water should not be expected to cross the fault boundaries to recharge an adjoining lens. Whenever the permeable layers allow fresh water to cross from one lens to another, this is serendipity!
So long as Man used only spring water and cisterns, the natural lens configuration remained in a steady condition (or steady state in engineering notation). However, whenever man began to pump the fresh water, the equilibrium was disturbed. Several things then happened:
1. The lens became thinner (pressure dropped in the bottom of the well), causing the water table to lower, and the underlying mineralized water to rise to fill the bottom of the aquifer. In drastic cases, the underlying mineralized water forms a cone- rising to the level of the pump (smallest part of the cone pointing to the well);
2. Near the boundary or fault crossing the island, there is increased water movement as water pressure drops (due to loss of height or head);
3. The mineralized water, which exists along the fault and below the fresh water lens, moves toward the region of low pressure- this will be upward for the deeper non-fresh water and laterally for the case of faulting;
4. All of this causes a reduction of fresh water and an increasing content of mineralized water in the lens.
Faulting will exaggerate the influx of mineralized water, and if the fault connects with the sea, the water becomes more salty with time. It is not certain that the groundwater will become “salty” to the taste, since mineralized water from below may contain other objectionable minerals. This includes sulfate, which is attacked by bacteria to cause a stink. Iron will be associated with such deposits as the Esperance sand and the one causing the Penn Cove spring mentioned above. Other exotic ions cause strange tastes, and changes in Reduction potential and acidity or alkalinity create turbidity or precipitation of unsightly compounds in the water supply (most of which are measured in water quality tests).
Nearby faulting may cause the analyst to conclude that there is salt water intrusion, when the water merely exhibits its exotic contents. The county has undertaken to solve the mineralization problem, by looking only for chlorinity or salinity, while ignoring the minerals brought by faulting. This is now done by requesting that the landowner pay for an independant 24 hour production test, where a significant increase in the chloride ion condemns the well. The owner has to pay not only for the drilling but the testing of the well (as well), and he is not given a permit to build, when the production test indicates unsuitable water.
The easiest way to avoid appraising the groundwater purity in advance is to cause property owners to make expenditures to find whether there is high salinity present, which deters drilling in unknown areas. Rather than analyze the movement of exotic ions, it is simplest to categorize all abnormalities as Sea Water Intrusion, thereby minimizing county work.
Here is a method which will determine whether mineralization is from the sea, or from deeper zones- which have higher concentrations of undesirable ions or minerals at their original depth (greater depths of a drill hole encounters increasing temperatures, which generally produces higher concentrations of almost all soluble minerals):
a. For aquifers near faulted areas, the deeper warmer zones cause Potassium and Fluoride to diffuse upward along the fault. This does not mean that water is moving upward, but that the minerals are moving toward a region of lesser concentration (this is the normal occurrence for dissolved minerals, either Cations- positively charged, such as K+, potassium, or anions such as Fˉ, fluoride).
b. Groundwater with original exotic ions should be scrutinized for the pattern which it creates on a map, in as many locations as possible.When there is a linear arrangement of abnormal concentration of K or F on a map of an area containing more than 20 water wells, this suggests a faulted zone
a. Whidbey Island has most of the dominant faults tracing northwest to southeast, NW-SE, so that if this lineation is found on the map, there is a great likelihood that an active fault exists in the mapped area. Sometimes, the faulting lineation can be noticed on a topographic map, just by finding a creek which orients in this direction, e.g. Silver Creek.
b. Island County has such a data base already present due to the excellent collection by a hydro-geologist. However, after taking great pains to collect the data from water wells and to determine by GPS where the wells are located on the map, the chemical analyses are ignored.
c. Major faults exist on Whidbey Island in at least 10 areas, but the location of faulting sometimes may be found by simply looking at a topographic map- e.g. for Honeymoon Bay, the indentation is caused by three or more creeks making exit at a coastline where faulting caused unusual erosion. I have seen this small normal fault, which is just south of the bay, in the first cliffs adjacent to the indentation. Harrington Lagoon (indentation) is another suspect, which could easily be “rounded up” by making a map of K/Cl (potassium/chloride ions), to determine whether there is the usual NW-SE anomaly.
d. Whenever there is a fault indication on the topographic or K/Cl or F map, the proposed well location could then be assessed as to whether money should be spent before drilling. Requesting that a landowner pay for a pumping operation (requiring several thousand dollars), where the result could negate the use of the finished well is an easy way out for the county, and this could be avoided by use of data and workers already available to make an appraisal beforehand.
e. See the link: for the original work done to establish this method. This work should be refined, to encompass the several thousand wells finished since the analysis was made 7 years ago. The work is referred to as Geochemical Mapping, K/Cl method, or Water well chemical analysis.
Note: 1 the original composition of the groundwater must be used for these analyses- since man can easily re-arrange the composition by pumping the well.
2. Ιt is normal for mineralized water to underlie the fresh water zone- the deeper one drills, the more exotic the water becomes.
More comments are to follow, in a subsequent Posting.

Thursday, June 21, 2007

Whidbey- the "Soft" Island, compared to the San Juans

This Temporary Island

“Every Island is manned” could be the Logo for Whidbey and other significant Puget Sound Islands, since all of these water-surrounded bits of terra firma are considered refuges for some portion of society- due to the desire to escape from the problems of everyone else. An island represents a kind of Nirvana, where man can feel that he is distant from the artificialities of his culture. After all, there is sufficient water, agriculture land, and game to survive temporarily any artifice or arbitrary creation which the “others” can originate. He can feel “Free” to live by his own code, and indeed Whidbey seems to have many of these escapist subcultures.
Although Whidbey was named by the English sea captain Vancouver, it was actually first noticed by the Spanish explorers, after being manned by pre-historic Asians for some few thousands of years (Spanish nomenclature is still in use for some of the locations, e.g. San Juan de Fuca, Lopez, Port Angeles, and Sucia). Native middens can be seen today on some protected shorelines, which exhibit shells and artifacts discarded by ancient cultures. The mussel and clam shells were thrown down by the midden shuckers with their concave side up- where the meat was scraped and the residual shell was dropped from that meat-side-up position. A historic culture still resided on part of the island, near Coupeville and Penn Cove- called Salish at Snakelum Point, after the arrival of Caucasians. A backwater protective cove also exists at the end of Monroe Landing Road, where natives docked their canoes for protection from the winter storms. There is a peninsula at the same location (probably man-made), which blocked the SW winds from their idle canoes. Penn Cove runs counter to the normal north-south waterways about the island, since it exhibits a movement of an ice lobe (one of the last) which moved at an angle of 250 degrees from north- unlike the other glacial movements which generally moved south, leaving great scrapes and waterways on most of the island. With this abnormal movement of the ice (evidently downhill from such mountains as Glacier Peak) one can see features not noticeable on the other parts of the island- which generally are exhibited along a north-south axis. One can look into ancient canyons from fossil waterways along this E-W excursion, which are now filled with gravels and river-brought debris.
I have generally noticed that the western beaches and coastline of Whidbey Island recede yearly, so I undertook to measure the annual retreat. This was most noticeable, for the case of a newly built house near Ledgewood. Since I was there for its inception, I noticed over the period of ten years the amount of movement of the high tide line eastward. This was abnormal, since the lot owner disturbed the normal erosion of the beach. He undertook to place hewn granite stairs on the slope for easy access to the beach. In addition, he placed large boulders to block the sea’s advance. After the first year of emplacement, all trees had been uprooted and the stairs had been moved to the east by winter storms. There was about a three foot retreat of the cliffs, even with the boulder reinforcement. The operator had a good budget, and reset the boulder line to match the new beachhead, presenting an obvious recess into the cliffs, compared to his neighbors. Over seven years, his arrangement has now created a seven foot “bay” compared to neighbors’ coastlines, and he has a somewhat stable beachfront. The stairs mostly became covered by sand, but he has retrieved some of these to be emplaced further to the east, and now he has only to wait for the neighbor’s coastline to catch up with his accelerated erosion.
Finding an average erosion of the west beaches requires a measurement of the movement of old trees, where the trunks can be seen to partly slant (over the previous cliffs as the cliffs slumped). Looking at trees which are over the age of thirty years, one can see where they have leaned over the cliffs and then restarted to grow vertically. Using the diameter of existing two-angle slanted trees, and the fact that the whole tree would have leaned over the cliff at the time of slumping, one can calculate the rate of erosion. Measure the distance from the cliff face now to the tree base for the distance that slumping has proceeded since the tree leaned over the cliff (due to slumping). Then estimate the age of the vertical portion of the tree above the slanted portion, which determines the number of years since the last slumping. Assuming that slumping proceeds at the same rate as cliff retreat, the rate of retreat may be calculated: 12 feet/18 years yields 8 inches retreat yearly. There were two different trees which calculated this annual retreat, and the number may be considered useful for that particular location. However, the nearby location of a spit, point, bay, or other feature has a large bearing on the annual erosion by storms, so that one must consider aggravating features for any particular location. My opinion is that after watching Baby and Smith Island- just offshore from Whidbey- erode rapidly, that the main part of the island will wash into the Puget Sound within 1000 years. One can relate this to the width of channels between Whidbey and the Olympic peninsula (or to separation from Camano island or the Washington mainland), and speculate that these channels have been created by NW-SE faulting in the 14,000 years since the last glaciation. These distances approximate the width of Whidbey, and this gives some confidence to the calculation of annual retreat.
This average annual retreat of Whidbey’s western coastline is somewhat less than a foot yearly, so give yourself a foot of insulation from the sea for each expected year of your remaining life, to remain HIGH and DRY!

Wednesday, June 20, 2007

Thrusting from Ice? or from Below?

The above photos were taken from parts of the cliffs, both south and north of Ebby's Landing- near Coupeville. This represents a portion of the island where melt water flowed west from Penn Cove glacier, created a drainage which remains today. Later, the sand which washed westward towards the present Admiralty Passage was picked up by the wind and deposited along the ancient beaches. This action allowed Dunes to form above the beachline (similar to that on the Oregon coast today), and to form coastal dunes just above the waterline. These dunes are now stabilized by vegetation, and can be seen by walking the trail above the Ebby's Preserve, where the stabilized sands "Lip Over' the farmland- remaining higher than the tilled soil.
Ignore the cross-bedding shown in the layers- which is old dune markings. Look for parallel fractures in the sands, where the beds have slid along the newer discontinuities. The fractures allow movement of both the sands and water which percolates through them. The tubular outlet indicates seepage from such fractures or faulting. A buckle, which occurs in one of the cross-beds, is unmistakenly a result of thrusting. This could be from the later glaciers sliding southward over the beds or the underlying bedrock sliding northward under them.

Coastal Dunes, after Glacial Melting
Ebby’s Landing is an excellent location to view the effects left by the last lobe of the Ice Age- where it traveled towards the west (probably from Glacier Peak to the east, through Penn Cove). This area is just west of the picturesque town of Coupeville, which sits next to Penn Cove- which was formed by the push by gravity of ice from mountains to the east about 14,000 years ago.
Coastal dunes form from wind-driven sand, which is delivered to the beaches by rivers as the ice melts. The sand is worked by the offshore currents, to be moved along the beach by daily tidal and storm currents. At some parts of the day, the sand is above the waterline, and subject to drying and aerial movement by onshore breezes. The winds are normally from the southwest, but heating of land during the day causes the air to ascend- bringing in wind from the beach and sea below the rising air. This sand-laden air dumps the sand as it climbs the beach, forming coastal dunes. These dunes are trapped by any hills or vegetation, forming wandering sand deposits which oscillate along the beaches. Consequently, there are many cross-bedded sand deposits seen in the now eroded cliffs. The deposits may be thin, since they form daily; varying direction winds create the cross-bedding as the temperature changes with the Sun’s elevation (nights bring off-shore breezes, when the seawater has warmer temperatures than the land). When one looks vertically, the dunes may have inter-dunal intervals which appear as discontinuities. These inter-dunal features may look like fractures, but they do not have paths for water flow similar to fractures- their permeability is usually less, since they have a fine layer of dust in the discontinuity.
Look at the accompanying photos, above and below this blog, to determine whether you can discriminate between fractures (at least two non-horizontal parallel lines in the sands, ignoring the bedding planes) and inter-dunal intervals.

Active Tectonics at Whidbey Island

Thrust Faulting on Whidbey Island

There are thrust faults on the island- those that are well-known include the NW-SE trending left-lateral faults. But, first for memory:

TERMS: a fault is a slice into the earth, with obvious movement (displacement) either along the slice, up or down the slice or a combination of these two possibilities. Normally the slice creates a straight line along the surface of the Earth, but over a significant distance the slice may be curved, jagged, or irregular:
a. A normal fault is the most likely occurrence, and it is characterized by movement down into the earth (relative to the upthrown block). It is a result of a stretching of the earth’s crust, so that gravity causes the block to fall into the void created by the tension. The angle of dip of the fault plane may be 45 degrees to the earth’s surface up to almost vertical. This type of fault will drag along the opposing wall or plane, sometimes creating slickensides.
b. A reverse or thrust fault is less likely, being a result of compression of the earth’s crust- which occurs with great tectonic events, such as mountain building, salt domes, vulcanism, or subduction. However, I have seen small thrusts occurring over sinkholes, caused by prying of the roof as it is dropped into the earth.
The photos above show thrusting on a small scale, due to part of the crust being dragged horizontally. The fault plane angle may be almost horizontal, up to vertical.
c. A lateral fault is one which slices along the earth’s crust, due to the underlying sediments being moved by two separate forces (or directions); This is the type common to regions where large sections of the earth’s crust are moving at angles to each other, as with the Continental block moving west on Whidbey Island while the southern part of the island is moving northward (being in a separate Pacific block). Standing on either side of the fault line, it is left-lateral if the block across from the observer moves left.
d. There are other categories of faults, but it is best not to over-classify this slicing due to earth movements. These three types listed fit in with a physical categorization of mechanics, where there occurs Tension, Compression, or Shear (or combinations of these strains). Rock samples may be investigated with testing machines, by compressing, stretching or torsion, to yield numerical measurements such as moduli or strain/stress under Compression, Tension, or Shear, and failure end points for crushing, stretching, or shear. Classification does not increase understanding, and may cause confusion when it becomes voluminous- which is the usual case with geological categorization (which could be accused of creating terminology to suppress layman’s interference).
Large-scale movements on Whidbey Island The extreme northern end of W.I. has an obvious junction of the westward moving Continental plate (at Deception Pass), against the younger movement of the rest of the Island. This is noted, by merely looking at the hard green rock at the pass, compared to the young till and other glacial deposits dumped to the south by the glaciers of the last million years. When you drive over the bridge, notice the hard rock of Mesozoic age (greater than 65 m.y.). You cannot carve these metasediments with a knife, while anything south of these outcrops may be scratched with the fingernail.
All of this is known and well-documented, but what is not known is the influence of the Pacific plate as it interferes with Whidbey Island- which is well within the continental deposits. Although the Pacific plate occurs west of Vancouver Island (evidenced by soundings offshore), there is some evidence that it lurches occasionally into the border zone, which is Cascadia. This would be northward movement towards Alaska, as opposed to the general trend of most evidence as NW-SE (as is the trend of the shape of Vancouver Island, the California coast, and many large-scale geological features in the western USA.
So what is the evidence for north-south thrusting, on Whidbey Island? The first photo above shows large displacement (in a west facing cliff of 100 meters displacement or so) along a plane- almost horizontal- south of Hancock Lake. When one looks at the evidence, it is not clear whether the overlying sediments moved southward over the deeper, or whether the underlying moved northward under the shallower. This could be sorted out by using the following rules:
1. When the thrust dies out with depth, it can be assumed to have originated from the top- this would be the case for a sheet of ice from the young Glaciation sliding south (which actually happened- from independent studies). The thick layer of ice, being some thousands of feet thick, would drag the immediately underlying layers (being soft and lubricant-like) along with it- causing the simplest type of thrust.
2. When the thrust dies out toward the surface of the ground, it likely originated at depth. This would be the case of a plate of rock being moved at great depth, dying out as it reached soft sediments which do not show the sliding planes.
A large vertical section of cliff is necessary, for the above rules to indicate the correct analysis. This rarely occurs in nature, since one only finds an expression of thrusting in canyons, road cuts, or in vertical drill holes (with pictures for viewing). The vertical wall necessary usually slopes away from the feature of interest, also. I tend to think that the Hancock thrusting occurred mostly from glaciation, but it may have masked a simultaneous North-to-Alaska movement of Pacific crust.
Small Thrusting at Ebby’s Landing cliffs
The photos below the Hancock thrust are not as graphic, but they show small thrusts parallel to each other, with a seep occurring below them. There is also an obvious buckle, where the sediments rode over their deeper location. All three of these features together strongly indicate a thrust fault. Again, does the layer move from below toward the north, or is it the reverse (upper toward the south)? The first possibility would indicate a non-glacier action. Some subtle facts help the analysis;
The small seep indicates that a fluid path is open, and has not been sealed since glaciation time. This hints that stress operates now, not just when the glaciers were sliding.
Secondly, there are orthogonal fractures in the cliff, and this occurs with a large-scale tectonic action (such as is noted all over the west USA). This feature is not definitive, however.
Thirdly, there is an inflection in the bedding above the seep, and this is indicative of thrusting overall. This feature is at the bottom of the fault lanes, hinting that it is of non-glacial origin.
Overall, there is some evidence that Whidbey Island has some shear occurring from south to north, which would not be of glacier origin, but likely from a lurching of the northward Pacific plate influencing the island far to the east of the plate proper. But this is overwhelmed by evidence that the main faults occur due to interference of the westward-moving North-American plate and the transition zone to the west, short of the Pacific plate.
Make your own analysis from the photos, and then hike south from Lagoon Point County Park about a mile, to see the cliffs just short of the Hancock Lake.

Tuesday, June 19, 2007

Glaciers make Till last!

Till, we meet Again!

Whidbey Island has many Till layers, from the Ice Ages, at least 14,000 years ago. Till is an unsorted glacial deposit, which was dumped under the ice or left as uneroded sediments after the ice was completely melted. It has never been subjected to stream working, and rock roundness is due to the individual cobbles having been transported by water before they were dumped onto the ice.

Notice that there are many sizes of rocks, generally grey in appearance- due to coating with rock dust. They make poor soil, since they have little organic material entrained; weeds hardly grow in this type of surface. The easiest feature for identification is that of lack of stratification- water never having sorted the mix.