Report on the Hydrogeological Investigation Conducted at the Black Diamond Parking Lot Artesian WellPrepared By:
Nadine L. Romero, Hydrogeologist
Date: September 10, 1997
The purpose of this hydrogeological investigation was to determine additional information about the condition of the Black Diamond Parking Lot artesian well including the well depth, the condition of the existing casing and the existence of clay or confining units above the aquifer per Department of Health requirements for source approval and protection under WAC 246-290-130 and 135.
The State Department of Health requires that a demonstration of aquifer confinedness be provided using the "DOH Simplified Method for Evaluating Confined Aquifers". This investigation used borehole geophysical methods, (gamma log) to determine the lithology and presence of clay and silt units above the ground water source. In addition, the hydrogeologic investigation also used a down-hole camera to determine the condition of casing, i.e. whether there were any cracks or broken joints which may create entry zones for water other than the artesian source.
The artesian well located on the 400 block of 4th Ave East next to Rich's Tire Store is a 1.8 inch diameter well which was constructed sometime between 1895 and 1915. The site was a former railroad ground according to the certificate of water right (Appendix). The well flows at approximately 10 gpm. During the hydrogeological investigation the actual well-head was found approximately 40 feet south of where the existing above ground fountain or 'cistern' is located and is at a depth of 2.5 feet below the paved asphalt parking surface.
Nothing is known about who constructed the well or the exact date of its installation. The author of this report has been conducting a separate historical study of how and when artesian wells were first constructed in Olympia. Due to high water taxes in 1895, local business owners decided to drive their own water wells. Early newspapers cite that the first successful well was constructed by Talcott Jewelers in April of 1895 followed by numerous other businesses, hence Olympia's "artesian legacy" and the drilling of over 90 artesian free flowing wells.
Artesian Well Geophysical Study Findings - "Depth to Confinedness" Determination
On July 17,1997 a borehole geophysical investigation was conducted on the Black Diamond Parking Lot artesian well using a gamma ray logger and a black and white video camera (Attachment A). Gamma logging and induction logging was conducted uphole as well as downhole. The artesian well was determined to be 90 feet deep with casing to the bottom of the borehole. The minimum diameter of the well is 1.7 inches and the maximum is 1.8 towards the surface. Distinct clay layers were found at the following intervals:
31 - 36 feet below ground surface
42 - 50 ft ""
56 - 58 ft ""
60 - 63 ft ""
In addition many silty-sandy-clayey intervals were also found between clay units. In general there is a gradual decrease in grain size towards the artesian ground water source at 90 feet below ground surface.
The depth to "confinedness" based on the gamma logging shows that there is a separation of around 60 to 70 feet from the artesian water potentiometric surface to the lowest clay unit and greater than a 40 feet separation for the nearest surface clay interval. Therefore, the criteria of static water level being greater than > 20 feet above the bottom of the lowest confining unit is met.
Furthermore, multiple layers of clay total 18 feet and this total thickness does not take into account the other large intervals of fine-grained sediments that were cited on the geophysical logs, as discussed above.
Local Hydrogeology and Hydrogeochemistry
There are few well logs for downtown Olympia and relatively little is known about the sediments below the city. One nearby well log reveals that sediments are greater than 500 feet thick. DNR studies by Gerstel show that the Capitol Campus hillside is Vashon Recessional (Qvr) and Vashon Advance (Qva) outwash. The Olympia subsurface stratigraphy from near surface to depth, is likely to be Kitsap (Qf) formation underlain by Quaternary Penultimate (Qc) deposits followed by the poorly understood Quaternary-Tertiary (?) Undifferentiated Deposits (TQu).
The Black Diamond Parking Lot Artesian well may have been driven into the undifferentiated sediments (TQu) and into what appears to be a fine "beach-sand", for example. The undifferentiated sediments are thought to be older than 35,000 years, however recent discussions with DNR geologists show latest research may place TQu even older.
Dion and others compiled a report on Thurston County hydrology and discuss hydrostratigraphic units as well as water quality for the area wells. Potentiometric maps from the report show flow directions for the Penultimate, Vashon Advance and undifferentiated deposits trend southeast to northwest (towards Olympia) with a ground water divide between Chambers lake and Hicks lake. Each of the major peninsulas and the higher topography in southern part of Thurston County may serve as major recharge areas for the Penultimate and undifferentiated deposits of the region. The recharge area for Black Diamond Parking Lot artesian well is likely to be off in the southeast in the vicinity of Ward, Smith and Hewit lakes, for example. Travel times may be on the order of 25 years or more, however additional research is needed in this area and very little is know about the recharge of deeper aquifer systems in Thurston county.
A comprehensive water sample was taken at the Black Diamond Parking Lot artesian well on April 23, 1997 which included analyses for: inorganic chemicals (nitrate, major cations and anions, metals, cyanide); volatile organic chemicals (chlorinated hydrocarbons); pesticides and PCB's. With the exception of manganese at 290 parts per billion no other federal or state water quality action levels were exceeded. Manganese is considered a secondary standard or aesthetic standard versus a health criteria. A cation-anion balance was also performed on the sample (Appendix) to determine the laboratory accuracy in accounting for key ionic controls on water chemistry. A 4% difference in anions versus cations was found indicating that key or predominant cations and anions were accounted for in the chemical analyses (Ca, Mg, Na, K, HCO3, SO4, Cl). Bicarbonate was the predominant control on the water chemistry followed by magnesium, calcium and sodium. Many of the ground waters of Thurston county are calcium-magnesium/bicarbonate dominant and are very typical for glacial deposits due to the water-rock "interactions of slightly acidic recharge water with aluminosilicates". The high manganese concentration appears to be a classic chemical signature for ground waters from the TQu or undifferentiated deposits.
Overall, the present water quality for Black Diamond Parking lot artesian well is good and typical of waters in the undifferentiated deposits of Thurston county. Comprehensive water quality sampling should be conducted on the well at least yearly.
The costs for a comprehensive sampling conducted in this investigation was around $700.00 for the analyses alone (this includes VOCis, Pesticides and PCBis). Colliform and field indicator parameters should be performed at least quarterly. Other water parameters should be done yearly.
Down hole Camera Findings
A downhole camera survey was also conducted on July 17,1997 using a Hack and white camera. Fortunately PVC attachments were put on the camera to guide it down the well casing. A VCR tape was made of the journey up and down the borehole. Due to the removal of small zone of clay, which was installed inside the well-casing to hold a small sand filter in place the water was cloudy going down the borehole. However, coming up out of the casing, the well began to clear up and there was better film resolution. There were no visible problems with well casing or evidence of water percolating from joints or other areas of the well. In the last 6 inches of the casing, however (at the open bottom of the borehole), there appeared to be some holes which were probably due to the casing being driven into the ground in the early part of the century. The remaining 89 feet of casing (toward the surface) appeared to be in very good condition. Furthermore, very little build up appeared on casing walls. The film footage at the bottom was very interesting as one can see the upwellmg of artesian water from a fine sand 90 feet below sea-level. This film will be made available for the public on TCTV later this year.
This report represents a culmination of work performed over the last 10 months on the Black Diamond Parking lot artesian well, including a series of meetings, water sampling, research and a field investigation of the actual well.
Comprehensive water quality sampling as outlined above should be continued on a regular basis. I think that for the next few years the Black Diamond well can continue being used as drinking water source by the public/However, careful water quality monitoring as noted above and periodic checks of the casing should be done (perhaps every 5 to 7 years). It is important for the public to understand that anthropogenic impacts to the well are still possible in the future and that this well may perform as an environmental indicator of our aquifers in the Olympia area. Certainly other issues about liability and ownership will need to be considered.
Finally, the question about whether this well should continue to be a free-flowing well is a difficult one to answer. Olympia itself is part of a discharge zone where there are many natural springs found in the area. Water in these lower aquifers appear to discharge towards Bud Bay as indicated by the potentiometric maps of the area. Furthermore, it is unclear what the effect of capping an artesian well would be, i.e. whether springs would occur below foundations in the downtown vicinity or around the well head itself. These questions would certainly take a team of experts to resolve, some ground water modeling and field tests.