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HomeMy WebLinkAboutBLD2022-00277-09- hydrogeological evaluationBender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx April 6, 2022 Ms. Debbie Gussenhoven 423 Cormorant View Drive Brinnon, Washington 98320 HYDROGEOLOGIC EVALAUTION, GUSSENHOVEN WELL, BRINNON, WASHINGTON Dear Debbie, This letter presents our hydrogeologic evaluation of the groundwater conditions in the vicinity of your new well, recently installed at 423 Cormorant View Drive in Brinnon, Washington. This evaluation is required by Jefferson County Code JCC18.22.330 (8)(e)(iii)2 which requires that an evaluation be performed to demonstrate that use of the well will not cause detrimental interference with existing water rights, nor use that is detrimental to the public interest. Since your well is located within a High Risk Seawater Intrusion Protection Zone (SIPZ), this evaluation provides a safety measure to consider whether the anticipated use of your well could or could not degrade the water supply and quality at neighboring wells, nor move the saltwater/freshwater boundary inland. Background The property is located at 423 Cormorant View Drive in Brinnon, Washington. As shown in Figure 1 the site is located near the southwest corner of Black Point, where it abuts to the mainland just north of the Duckabush River delta. Figure 2 shows the location of the well in the southeast corner of the property. The well is located about 200 feet from the proposed drain field and about 230 feet from the new residence to be constructed. The surveyed ground elevation at the location of the wellhead is 224 feet. The well was drilled by Arcadia Drilling Inc. and was completed on March 4, 2022. The measured depth to water by the driller prior to performing a pumping test at the well was 213 feet; this equates to a groundwater level elevation of 11 feet above sea level. After performing a pumping test at the well, the depth to water rose to 211 feet, or a groundwater elevation of 13 feet. The proposed use of the well is for domestic purposes. Hydrogeologic Evaluation The following provides a description of the hydrogeologic evaluation items required by JCC18.22.930(2)(b). RECEIVED DCD 7/11/22 Letter to Ms. Debbie Gussenhoven April 6, 2022 Page 2 Bender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx (i) Description of the Hydrogeologic Setting of the Region The project site lies on the boundary of the Olympic Mountains and the Puget Sound Lowland which has a complex history of mountain building, volcanism, faulting, erosion, deposition of sedimentary rocks, and several periods of glaciations. Bedrock was mapped by Tabor and Cady (1978) along much of the east side of Black Point and to the west of the site toward the Olympic Mountains. Bedrock consists of Crescent Formation basalt. The depth to bedrock at the site is not known, but is in excess of 300 feet. During the Pleistocene (10,000 to 200,000 years ago), continental glaciation advanced into the Puget Sound Lowland at least four times. The Fraser Glaciation, particularly the Vashon Stade (last glacial advance about 13,000 to 19,000 years ago) has modified the project area to its present topography. As the glacial ice known as the Puget Lobe advanced into the project area, meltwater streams began depositing advance outwash deposits of silt, sand, gravel and cobbles over ancestral topography. At times, the Puget Lobe blocked the drainages of the outwash meltwater streams and formed ice dammed glacial lakes. In the relatively quiet waters of the glacial lake, glaciolacustrine deposits of sandy silts, silts, and clays were deposited at the bottom of the lake. As the Puget Lobe advanced into project area, the glaciolacustrine and outwash deposits were overrun by the advancing ice and a heterogeneous mixture of silts, sands, gravel, cobbles and boulders known as Vashon till were deposited in and under the advancing glacial ice. As the glacial ice retreated, the area experienced active ice margin deposition and later area ice stagnation. Deposits of ice contact stratified drift were deposited along the margins of the Vashon Stade glacial ice. As the glacier wasted and ice retreated, large blocks of ice were left in place (stagnant ice) and glacial Lake Leland began draining and releasing large volumes of water that flowed through the area and eroded the glacial deposits creating kame terraces and eskers consisting of coarsely bedded sands, gravelly sand, sandy gravel recessional outwash. There were likely intermittent pulses of glacier advance during the overall recessional period, and the ice likely moved back and forth over the site area multiple times. The large stagnant blocks of ice eventually melted and produced deep localized depressions known as kettles, many which are found on Black Point to the east of the site. As a result of these processes, the soils beneath the site consist of multiple layers of coarse sand and gravels that will transmit groundwater to wells, and fine-grained soils that will perch or confine groundwater. As such, the erosive and depositional stages throughout these glacial and interglacial processes have formed multiple aquifer systems that may or may not be continuous regionally. These may pinch out within the soil sequence, pinch out at the contact with bedrock to the west, or may be connected with Hood Canal to the east. RECEIVED DCD 7/11/22 Letter to Ms. Debbie Gussenhoven April 6, 2022 Page 3 Bender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx Hood Canal lies to the south and east of the site. Hood Canal is a saltwater body connected to Puget Sound. Groundwater discharge from the aquifers formed on the west side of Hood Canal, which abuts the Olympic Mountains, and groundwater discharge from Black Point ultimately flows to Hood Canal. As fresh water is less dense than sea water, fresh water will essentially float on top of the sea water boundary for some distance off of the shoreline. A general relationship of how deep the freshwater lens extends below the groundwater level is the Ghyben-Herzberg relationship, which states that for every foot of freshwater head above sea level, about 40 feet of fresh water will lie below sea level. As an example for the subject site, with a groundwater elevation of 13 feet above sea level, about 520 feet of fresh water may lie below sea level. This relationship is generally true in uniform aquifers; however, the soils beneath the site compose a layered aquifer system which leads to a more complex geometry of the fresh water/seawater boundary. (ii) Site Location, Topography, Drainage, and Surface Water Bodies The site is location in the southwest corner of Section 15, T25N R2W. The site is located on the southwest corner of Black Point, and lies west of Highway 101. Ground surface in the vicinity of the site slopes down to Hood Canal generally from north to south. The site elevation at the wellhead is 224 feet; elevations on Black Point can approach elevation 300 feet. Highway 101 runs along a lower elevation trough located between Black Point and the western slopes of the Olympic Mountains. The Duckabush River and delta lie to the west and southwest of the site, and forms a major drainage from the Olympic Mountain Range. The area at the site and north of the Duckabush River is hummocky, as shown in Figure 4. Figure 4 also shows minor streams and tributaries that flow from north to south toward the river and Hood Canal. (iii) Soils and Geologic Units Underlying the Site As discussed in Section (i) above, the soils underlying the site were formed during complex glacial and interglacial erosive and depositional processes. The traditional soils associated with the Vashon Stade, the last glacial advance in the area, consist of relatively pervious recessional outwash sand and gravel, low permeability till deposited below the advancing ice front, and pervious advance outwash sands. Glaciomarine clay and silt is typically found below the advance outwash, and this low permeability unit was deposited in the glacial lake formed in front of the advancing glacier. Underlying this low permeability soil lies interglacial soils, which are composed of both low permeability fine-grained soils and coarse grained sands formed in an environment similar to that present in our current interglacial period. The site is located in an area that has seen all of these processes; however, since a considerable amount of ice stagnated and formed a barrier of sorts during glacial retreat and re-advance, the traditional stratigraphy has been eroded and redeposited by meltwater streams. As such the RECEIVED DCD 7/11/22 Letter to Ms. Debbie Gussenhoven April 6, 2022 Page 4 Bender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx traditional stratigraphy presented above may not be regional and there may be some interconnection of aquifers on a large scale. Based on the Gussenhoven well log (Figure 3) we would believe that the upper 40 feet of soils encountered during drilling is till, underlain by reworked recessional and advance outwash soils to a depth of roughly 239 feet. Between depths of 239 feet and 313 lies about 74 feet of largely dry fine glaciomarine sand and silt. These soils are fine-grained interglacial soils that appear, based on the ‘dry’ description in the boring log, to represent an aquitard with a base elevation of about -89 feet. The well withdraws groundwater from underlying coarse grained pervious soils that lie to and below the bottom of the boring at 339 feet, or elevation -115 feet. To provide an example of the varying soil conditions in the vicinity of the site, the well previously owned by Mr. Gaul lies roughly 550 feet west of the Gussenhoven well. The water quality from that well has significantly elevated chlorides and is one reason that this area is designated a High SIPZ zone. The boring encountered 360 feet of low permeability sandy clay to elevation -219 feet; seven feet of pervious sand and gravel were then encountered below that level. The base of the low permeability soils, or aquitard, was at elevation -89 feet at the Gussenhoven well, but at the Gaul well the base of aquitard elevation was -219 feet; 130 feet deeper. This suggests that the aquifer that the Gussenhoven well taps is truncated to the west of their well, and the two wells withdraw water from different water bearing zones. We would believe that the deep soils at both the Gussenhoven and Gaul well locations originally consisted of low permeability glaciomarine soils, but during glacial retreat ice-marginal streams eroded the silt and clay at the Gussenhoven site and deposited sand and gravel near the base of the well; this fits well when one considers the block(s) of stagnant ice that dammed the drainages during glacial melt. We do not consider a 130 foot change in aquifer elevation between the two sites to be reasonable (i.e. the two wells do not share the same aquifer). (iv) Groundwater Characteristics of the Area, including Flow Direction and Gradient, and Existing Groundwater Quality. The aquifer that the Gussenhoven well withdraws water from is confined. This means that since the static water level in the well is above the top of the aquifer, groundwater in the sands is under pressure. Pumping from a well completed into a confined aquifer can produce considerable amounts of water with limited well drawdown, and does not produce the traditional cone shaped drawdown curve typically found in unconfined aquifer conditions. This aquifer response is ideal when proximate to a saltwater body such as Hood Canal, for it does not have an expanding unconfined cone of depression that could extend to the saltwater interface. A short-term pumping test was performed by the driller after the installation of the Gussenhoven well. The well specific capacity, or the gallons per minute per foot of water level drawdown was 2 gpm/ft; this is a good well with moderate pumping capacity. Analysis of the water recovery data suggests a RECEIVED DCD 7/11/22 Letter to Ms. Debbie Gussenhoven April 6, 2022 Page 5 Bender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx soil permeability of 0.005 ft/min, which is a moderate permeability. We regard this as a minimum soil permeability at the well based on the short duration of the test (38 minutes). To provide an example of the estimated well performance given the above hydrogeologic parameters; if 300 gallons were pumped from the well over a period of four hours, the drawdown at the well would be about 0.5 feet, and there would be no measurable drawdown at a distance of 200 feet from the well. We have performed a considerable amount of testing and analysis of the Black Point aquifer as a part of our work for the Pleasant Harbor Resort, which will be constructed on Black Point to the east of the site. That work has shown that the sea level aquifer on the point is recharged by subsurface flow from the ‘mainland’ soils to the west of Black Point, and by recharge of precipitation on Black Point itself. If the Gussenhoven well was connected to that aquifer, based on our work for Pleasant Harbor the hydraulic gradient would be about 0.005 ft/ft to the south. Given the depth of the aquifer supplying the Gussenhoven well, and that the sea level aquifer thickens considerably to the east, we suspect that some of the recharge to the site also comes from the west and northwest; there is insufficient data to calculate the hydraulic gradient for this scenario though we would believe it would be steeper than for the Black Point sea level aquifer. Following the pumping test a water quality sample was collected from the Gussenhoven well. The chloride result was 2.8 mg/l. This indicates good water quality with respect to chlorides and indicates that sea water intrusion is not present at this site. (v) The Location and Characteristics of Wells and Springs within 1,000 feet of the Site We are not aware of any springs in the vicinity of the site. The depth to water (see below) is generally 30 feet or more in vicinity wells; as such the presence of nearby springs is unlikely. Springs may be present to the west and northwest of the site along the hillslopes. The closest well to the Gussenhoven well is about 250 feet to the west. This well was drilled for a Mr. Swan but is now owned by Mr. Petroski and is 268 feet deep. After drilling the well was air tested with a yield of 22 gpm. We understand this well is used solely for domestic purposes. Given the hydraulic properties discussed in section (iv) above we do not believe there would be any impact to the Petroski well from domestic uses of the Gussenhoven well. As part of the Pleasant Harbor Resort water right application process, Ecology (Pearch, 2010) performed a significant study of the domestic wells in the vicinity of the proposed resort. At least six wells from that study are in the immediate vicinity of the Gussenhoven well. Two of those wells, as shown on Figure 4, were the Gaul well (previously discussed) and the Wysenberger well that had very high chloride concentrations, and those wells are the reason the Gussenhoven site is within a high SIPZ protection zone. The Gaul well is very deep and likely in a separate aquifer from the Gussenhoven well; given its depth and high chloride concentrations (3,500 mg/l), we believe this well RECEIVED DCD 7/11/22 Letter to Ms. Debbie Gussenhoven April 6, 2022 Page 6 Bender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx was likely completed near the saltwater interface and up-coning of seawater was responsible for the high chloride concentrations. We do not believe this well is hydraulically connected nor will have any impact to the Gussenhoven well. The Wysenberger well is only 25 feet deep, proximate to the shoreline, and was used for irrigation purposes; the shallow depth, proximity to Hood Canal, and high pumping rates are responsible for sea water intrusion occurring in that well. As shown by the Gussenhoven well log in Figure 3, the Wysenberger well is not hydraulically connected to the Gussenhoven well nor will have any impact on the water quality of that well. Four other wells in the Ecology evaluation were proximate to the Gussenhoven well; these were the Boiling/Porter, Black Point Community, Evans, and Beattie wells. The base elevation of these wells was between -47 and -69 feet; the chloride concentrations in these wells was between 2.1 and 2.6 mg/l and were similar to the Gussenhoven water quality result. The base of well elevations were above, but close to the elevation of the top of aquifer at the Gussenhoven well (elevation -89 feet). We would believe that these wells represent the typical groundwater quality of the wells in the vicinity. (vi) An Evaluation of Existing Groundwater Recharge We performed an extensive recharge evaluation as part of our work for the Pleasant Harbor Resort. That work indicated that the Brinnon area receives an average of about 55 inches of precipitation. The aquifers in the vicinity of the site are recharged by the infiltration of precipitation, and possibly from some infiltration from upgradient streams. The presence of the Duckabush River likely also provides a positive recharge boundary to the aquifer. Based on our evaluation, the Black Point aquifer receives about 28.6 inches or about 1,500 acre feet of recharge annually; as such there is ample recharge to that aquifer. In addition, water balance calculations for the operation of the resort indicate that an increase in aquifer recharge should occur due to the Resort’s water use and infiltration planning; the resort will not have a negative impact on aquifer supply or quality. Since the other component of recharge to the Gussenhoven property will be from infiltration of precipitation and from subsurface seepage from the hillslopes to the west rising to the Olympic Mountains, there will be an ample source of recharge to the subject aquifer. The relative low density of existing domestic groundwater users in the area should not provide a threat to diminishing supply to the well in the future. Closure In our opinion, the Gussenhoven well has suitable supply for at least domestic uses and poses no threat to inducing seawater intrusion to the aquifer the well is completed in. Based on the measurements collected by the driller during testing of the well, the groundwater elevation at the well is 13 feet above mean sea level; this suggests a non-stressed aquifer with suitable supply potential. The quality of water the well will pump will not be impacted by other wells in the vicinity that have RECEIVED DCD 7/11/22 Letter to Ms. Debbie Gussenhoven April 6, 2022 Page 7 Bender Consulting, LLC 2213-01 C:\Users\Scott Bender\Documents\2213-01 Gussenhoven\Gussenhoven Hydrogeologic Evaluation.docx documented sea water intrusion. The well is located in what may be a separate aquifer than what some of the other nearby wells are completed in; even if not, all of these wells are completed in an aquifer that receives high annual recharge and those wells will continue to produce high quality water, and will not adversely impact each other while used for domestic purposes. Thank you for the opportunity to be of service. Please call us at (360) 631-5600 should you have any questions or comments. Sincerely, Scott F. Bender L.H.G., C.G.W.P. RECEIVED DCD 7/11/22 Figure 1 Site Location Project Number 2213-01Hydrogeologic Evaluation Gussenhoven Well Brinnon, Washington RECEIVED DCD 7/11/22 Figure 2 Gussenhoven Site Plan Project Number 2213-01Hydrogeologic Evaluation Gussenhoven Well Brinnon, Washington Well Location RECEIVED DCD 7/11/22 Figure 3 Gussenhoven Well Log Project Number 2213-01Hydrogeologic Evaluation Gussenhoven Well Brinnon, Washington Salguero Property RECEIVED DCD 7/11/22 Figure 4 Site Location, Topography, and SIPZ Project Number 2213-01Hydrogeologic Evaluation Gussenhoven Well Brinnon, Washington Well Location RECEIVED DCD 7/11/22 Figure 5 Gussenhoven Groundwater Quality Analyses Project Number 2213-01Hydrogeologic Evaluation Gussenhoven Well Brinnon, Washington RECEIVED DCD 7/11/22 RECEIVED DCD 7/11/22 RECEIVED DCD 7/11/22