Attachment_7_Construction_and_Testing_of_Two_Wells_at_Kalaloch_Final_Report.pdf

Construction and Testing of Two Wells at Kalaloch, Olympic National Park

Larry Martin, Hydrogeologist

Water Resources Division, National Park Service

Ft. Collins, Colorado

April 2014

Two water-supply wells were constructed at Kalaloch in late-winter 2014. Groundwater from the wells is intended to replace surface water diversion from Kalaloch Creek as the source for potable water for National Park Service facilities in the Kalaloch area. Water use in the area includes a campground, lodge and restaurant, employee housing, and the NPS maintenance area.

The wells are located on the east side of the employee housing area as shown in Figure 1. The wells are about 1,500 feet from the Pacific Ocean

Figure 1. Location of wells at Kalaloch

South Well

North Well

Water treatment plant and storage tank

Well Construction

The South Well was constructed from February 18-21, 2014. The well was drilled to a total depth of 123 feet as it was the first well drilled in this area and we wanted to explore the local geologic conditions. The South Well was subsequently backfilled to 66 feet with clean gravel.

Bentonite plugs were placed at 70 and 75 feet. The well was constructed with 6-inch steel casing.

The static water level is 35½ feet below ground surface. The finished well casing rises 1½ feet above ground surface.

Well screen was placed from 53-63 feet below ground surface, in the sand and gravel layers. The bottom five feet of screen from 58-63 feet has 0.010” openings (No. 10 slot). The upper five feet of the screen from 53-58 feet has 0.020” openings (No. 20 slot). The well was developed by air jetting for two hours. Figure 2 shows a construction diagram of the well.

Drillers log, South Well, depth is feet from ground surface

0-1 topsoil

1-5 sand and gravel up to 2 inches

5-10 sand, gravel, clay

10-15 sand, gravel, more clay

15-22 sand, gravel, increasing percentage of clay

22-24 clay and peat

24-43 clay and silt, some peat

43-50 sand and fine gravel, mostly less than ½ inch

50-55 fine sand

55-60 sand and gravel, mostly less than ½ inch

60-63 black sand, fining downward

63-70 clay and silt, wood fragments

70-75 clay

75-78 fine sand

78-81 clay, wood fragments

81-123 dense, hard clay with occasional wood fragments

The South Well has a WA Department of Ecology tag number BBS162.

A copy of the Department of Ecology Water Well Report is attached.

Elevations at the South Well were determined by performing a differential level loop survey beginning and ending with National Geodetic Survey benchmark # D475 benchmark near the visitor center. The elevation of the top of the casing is 49.88 feet (NAVD88). The lat/long location of the well was determined from high resolution aerial/satellite photos. The latitude is

47.60291ºN and the longitude is 124.36792ºW (NAD83).

Figure 2. Construction diagram of the South Well at Kalaloch.

North Well

The North Well was constructed from February 26-28, 2014. The North Well was drilled to 67 feet, stopping after the borehole had passed through the sand and gravel aquifer and continued 3 feet into the underlying clay and gravel sediments. The well was constructed with 6-inch steel casing. The static water level is 33 feet below ground surface.

Well screen was placed from 57-67 feet below ground surface, opposite the sand and gravel deposits. The bottom five feet of screen from 62-67 feet has 0.016” openings (No. 16 slot). The upper five feet of the screen from 57-62 feet has 0.014” openings (No. 14 slot). The well was developed by air jetting for about two hours. A construction diagram of the well is provided in

Figure 3.

Drillers log, North Well, depth is feet from ground surface

0-1 topsoil

1-25 brown clay

25-35 grey sand and gravel

35-43 blue sandy clay with gravel

43-52 grey sand and gravel

52-64 grey fine sand and gravel, water bearing

64-67 brown clay and gravel

The North Well has a WA Department of Ecology tag number BBS163.

A copy of the Department of Ecology Water Well Report is attached.

Elevations at the North Well were determined by performing a differential level loop survey beginning and ending with National Geodetic Survey benchmark # D475 benchmark near the visitor center. The elevation of the top of the casing is 48.38 feet (NAVD88). The lat/long location of the well was determined from the high resolution aerial/satellite photos. The latitude is 47.60359ºN and the longitude is 124.36818ºW (NAD83).

Figure 3. Construction diagram of the North Well at Kalaloch.

Well Testing

Both wells were tested by initially conducting a step-drawdown test to determine the maximum sustainable pumping rate while maintaining the water level in the well above the well screen.

The test pump was a Goulds 25GS15412 pump, which would be capable of pumping 33 gpm from a depth of 50 feet.

A step-drawdown test was conducted at the South Well on February 22 to determine the maximum sustainable pumping rater for a 24-hour test (Figure 4). The well was pumped at 10, 15, 20, 25, and 30 gpm. The water level recovered to within 1½” of the static water level within

15 minutes of shutting off the pump for the step-drawdown phase of the test.

Figure 4. Water level response in the South Well at Kalaloch during the pumping tests.

The 24-hour pumping test was started immediately following water level recovery from the step-drawdown test. The well was pumped at 25 gpm for 24 hours, resulting in about 10 feet of drawdown. Water level in the well stabilized at about 45 feet below ground surface; 8 feet above the top of the well screen. The water level recovered to within 2½ inches of the static water level within 10 minutes after pumping stopped.

The transmissivity of the aquifer is calculated using the slope of a line drawn through the drawdown data on a semilog plot of drawdown vs. time (Figure 5). Except for the first 4 minutes of the test, most of the data fall on a straight line. There is an offset in the data at 150 minutes into the test when there was a change of personnel making the measurements. However, the slope of the line is the same before and after the offset.

Figure 5. Semi-log plot of drawdown vs. time, South Well.

The transmissivity is calculated using a form of the Theis equation with the pumping rate (Q) in units of ft /day (25 gpm ≈ 4,800 ft

/day);

𝑇 =

2.3 𝑄

4 𝜋 ∆𝑠

2.3 (4,800 ft3 day⁄ )

4 𝜋 0.9 ft ≈ 980 ft2/day

The aquifer is about 20 feet thick, based on interpretation of the geologic log for the well. Thus the calculated hydraulic conductivity is 49 feet/day, which is within the range of expected values for a sand and gravel aquifer.

A storage coefficient for the aquifer could not be calculated because there are no observation wells; only the pumped well. The static water level is a few feet higher than the top of the aquifer, indicating the aquifer is under confined (artesian) conditions. The fast recovery to the static water level following cessation of pumping provides further evidence that the aquifer is confined.

There was no evidence of tidal influence on water levels in the well.

Given the large distance from the well to the ocean (1500 feet) and the low pumping rate (25 gpm), saltwater intrusion is not expected to be a problem. The specific conductivity of water pumped from the well was checked on a regular basis as a test for saltwater intrusion. Specific conductivity remained constant throughout the test (Figure 6), indicating that there had been no saltwater intrusion.

Figure 6. Specific Conductivity of water pumped from the South Well during the 24-hour test.

A step-drawdown test was conducted at the North Well on March 3 to determine the maximum sustainable pumping rate for a 24-hour test (Figure 7). The well was pumped at 10, 15, 20, and

17½ gpm. At 20 gpm, the water level was being drawn down toward the well screen too quickly.

The pumping rate was reduced to 17½ gpm and a stable pumping rate was maintained just above the top of the well screen. The water level recovered to within 1¼” of the static water level within 10 minutes of shutting off the pump for the step-drawdown phase of the test.

Figure 7. Water level response in the North Well at Kalaloch during the pumping tests.

The 24-hour pumping test was started at 9:25 on March 4 and continued until 9:45 on March 5.

The well was pumped at 15 gpm for 24 hours, resulting in about 17 feet of drawdown. Water level in the well stabilized at about 50 feet below ground surface; 7 feet above the top of the well screen. The water level recovered to within 1½ inches of the static water level within 15 minutes after pumping stopped.

The transmissivity of the aquifer is calculated using the slope of a line drawn through the drawdown data on a semilog plot of drawdown vs. time (Figure 8). After the first 10 minutes of the test, most of the data fall on a straight line until about 900 minutes into the test. From 900-

1500 minutes, the data points fall slightly below the trendline, indicating that drawdown is greater than would be predicted. There are not enough data points to determine the slope of a line through the late-time data. The change of the slope of a line through the late-time data may indicate a boundary in the aquifer. The arithmetic plot of the data (Figure 7) seemed to indicate a fairly stable water level throughout the duration of the 24-hour test.

Figure 8. Semi-log plot of drawdown vs. time, North Well.

The transmissivity is calculated using a form of the Theis equation with the pumping rate (Q) in units of ft /day (15 gpm ≈ 2,900 ft

/day);

𝑇 =

2.3 𝑄

4 𝜋 ∆𝑠

2.3 (2,900 ft3 day⁄ )

4 𝜋 0.5 ft ≈ 1,000 ft2/day

The aquifer is about 20 feet thick, based on interpretation of the geologic log for the well. Thus the calculated hydraulic conductivity is 50 feet/day, which is within the range of expected values for a sand and gravel aquifer.

A storage coefficient for the aquifer could not be calculated because there are no observation wells; only the pumped well. The static water level is a few feet higher than the top of the aquifer, indicating the aquifer is under confined (artesian) conditions. Additionally, the fast recovery to the static water level following cessation of pumping provides further evidence that the aquifer is confined.

Given the large distance from the well to the ocean (1500 feet) and the low pumping rate (15 gpm), saltwater intrusion is not expected to be a problem. The specific conductivity of water pumped from the well was checked on a regular basis as a test for saltwater intrusion; four times during the 4-hour step-drawdown test and 8 times during the 24-hour test. The conductivity remained constant at 116 umhos/cm throughout the pumping tests, indicating that there was no saltwater intrusion.

Potential for Saltwater Intrusion

The specific conductivity of water pumped from both wells was periodically tested during the step-drawdown and 24-hour tests. The conductivity remained constant at 140 and 116 umhos/cm at the South and North Wells respectively throughout the tests, showing that there was no saltwater being drawn into the wells.

The potentiometric surface for the aquifer in the vicinity of the wells was determined by subtracting the depth to the static water level in the wells from the ground surface elevation. At the South Well, the potentiometric surface was 12.7 feet above mean sea level. At the North

Well, the potentiometric surface was 13.1 feet above mean sea level. Both wells are screened in a confined aquifer, drawing groundwater from a sand and gravel layer that is overlain and underlain by thick clay beds.

There was no evidence of tidal influence on water levels in the well.

Given the relatively large distance to the ocean, the low pumping rate, and the potentiometric surface being significantly above sea level; no saltwater intrusion is anticipated at these wells during normal operations.

Water Chemistry

Water samples from both wells were collected near the end of the 24-hour pumping test. Samples were sent to Twiss Analytical Lab for inorganic analyses and Edge Analytical Lab for organic analyses. Copies of the lab reports are attached.

Groundwater from both wells had high concentrations of iron and manganese. Iron concentrations are 15.6 mg/l in the South Well and 12.2 mg/l in the North Well. The MCL

(maximum contaminant level) for iron is 0.3 mg/l. Manganese concentrations are 0.194 mg/l in the South Well and 0.132 mg/l in the North Well. The MCL (maximum contaminant level) for manganese is 0.05 mg/l. Iron and manganese are secondary contaminants, meaning that the standards are usually for aesthetic reasons and are not an absolute requirement. However, because these wells are a new source for the Kalaloch water system, they may be regulated for secondary contaminants also. The following excerpt is from the WA-DOH Water System Design

Manual (2009):

7.2.2 Secondary Contaminants

Secondary contaminants, such as iron and manganese, are regulated for aesthetic reasons such as adverse taste and odor, or staining plumbing fixtures. In general, source(s) must meet the water quality standards of WAC 246-290-310. New community and nontransient, noncommunity water systems without active customers must treat if secondary contaminants exceed the MCL (WAC 246-290-

320(3)(d)). However, existing water systems may install treatment consistent with the degree of consumer acceptance of the water quality and their willingness to bear the costs of meeting the secondary standard. See Appendix B for additional guidance on secondary contaminants.

There were no detections of volatile organic compounds in water from the North Well. The

South Well had a detection of toluene at 0.7 ug/l. The trigger level for toluene is 0.5 ug/l.

Additional sampling may be needed to determine whether detectable concentrations of toluene persist. Additional pumping and flushing water from the aquifer may result in the reduction to below detection limits as was the case for all other volatile organic compounds at both wells.

Trihalomethanes (in the form of chloroform) were detected in water from the South Well.

Trihalomethanes are a by-product of using chlorine to disinfect water. They result from the reaction of chlorine with organic matter in the water being treated. The total trihalomethane concentration in the water sample was 5.9 ug/l, well below the trigger level and MCL of 60 and

80 ug/l respectively. The detection of chloroform may be an artifact of overdosing the well with chlorine to disinfect it followed by insufficient flushing of water from the well prior to sampling.

Trihalomethanes in the North Well were below the detection limit of 0.5 ug/l.

Hydrogeology

Figure 9 is a geologic map of the Kalaloch area. The wells are located in an area that is mapped as continental glacial and non-glacial deposits of Pleistocene age (PEgdc). The description of this unit is (NPS, 2009):

These deposits consist of stratified fluvial cobbles and gravel exposed in sea cliffs of the marine terraces near Kalaloch Creek. Unit PEgdc deposits are generally oxidized to 1–3 m and capped with 1–2 m of loess. They are probably reworked from units PEapo and PEapwo(2) and alluvium from Kalaloch Creek. Deposits are gently dipping and laterally continuous, suggesting deposition in a beach environment and reworking by coastal waves. Some cut-and-fill structures and foreset beds exist.

The unit is essentially an accumulation of sediment that was transported down Kalaloch Creek and deposited in the near-shore and beach environment at the mouth of the creek. It is impossible to determine the areal extent of sand and gravel beds that are the source of groundwater for the wells. Stable water levels were obtained quickly during the test pumping, indicating that the aquifer has a large areal extent.

The two wells that were drilled at Kalaloch in late-winter 2014 are the only wells within several miles. There is not sufficient information to allow drawing a hydrogeologic cross-section that would have any credibility.

Summary

1. Two wells were constructed at Kalaloch to replace surface water diversions from

Kalaloch Creek as the source for the public water supply in the area. The wells are capable of providing a sustained yield of 15 gpm (North Well) and 25 gpm (South Well).

2. The source of groundwater for the wells is a sand and gravel aquifer from about 40-60 feet below ground surface. Sediments comprising the aquifer are probably old beach deposits. The lateral extent of the sand and gravel aquifer is unknown. The aquifer is confined by clay beds overlying and underlying the sand and gravel sediments.

3. There was no evidence of tidal influence on water levels in the wells during test pumping.

4. There was no evidence of saltwater intrusion during the test pumping.

5. Water quality tests of samples from both wells show that the water is generally good quality, except for high concentrations of iron and manganese.

6. There are no other water-supply wells within several miles of Kalaloch. There is no record of other water users or water rights for this local aquifer.

References

NPS Geologic Resources Inventory Program, 2009, Digital Geologic Map of Olympic National

Park and Vicinity, Washington, NPS Geologic Resources Inventory Program, Lakewood, CO, Geospatial Dataset-1048337.

Washington Department of Health, 2009, Water System Design Manual, DOH 331-123 (rev.

12/09), 325 pp.

Figure 9. Geologic map of the Kalaloch area. (NPS, 2009)

Well locations

Water well construction report – South Well, Kalaloch, Olympic National Park

Water well construction report – North Well, Kalaloch, Olympic National Park

Water Chemistry Analytical Results

South Well – 4 pages

North Well – 4 pages