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Emergency no more?

What's the story with those "Emergency" wells in the Laguna de Santa Rosa? An O.W.L. Foundation White Paper explores the history and use of these "stand-by" wells and how they have been forced into full time production wells.

 


SCWA “Emergency Wells” and the WSA

History

Between 1975-1977, northern California experienced one of the most severe droughts of the century - remembered as the “76-77 drought.”  In 1977, the Sonoma County Water Agency (SCWA) predicted the Russian River would go dry in “the later part of October or November” (SCWA, 1977a). SCWA drilled the “emergency wells” after decision “to proceed on an emergency basis and bypass provisions of the California Environmental Quality Act” (SCWA, 1977a).  The Occidental Road, Sebastopol Road, and Todd Road emergency wells were drilled in the western Santa Rosa Plain near the Laguna de Santa Rosa east of Sebastopol (see Figure 1). Additionally, three deep wells were drilled in Rohnert Park - #14, #15, and #16 (SCWA, 1977b).

Figure 1: Map showing approximate location of SCWA “Emergency Wells” near City of Sebastopol, California.


After conducting 7 to 11 day pumping tests in 1978, SCWA concluded:

 “…use of the emergency wells does have an impact on some of the nearby private wells and some not so nearbyThe most significant effect occurred during pumping of the Occidental Road well.  Most of the monitored shallow wells within a mile radius and varying in depth from 70 feet to 250 feet experienced a drop in water levels ranging from 1.0 to 13.0 feet.”   (SCWA, 1978a)

 In 1979, analysis of a pump test where all three “emergency wells” were pumped simultaneously, SCWA concluded:

 “Impacts on water levels of the local wells followed the patterns experienced during earlier development and pump tests” (SCWA, 1979).

Obviously, SCWA has known for over 25 years that pumping from the “emergency wells” would impact neighboring private wells.

After the 76-77 drought, the “emergency wells” were not pumped much until 1998. The original Occidental Road and Sebastopol Road emergency wells had water quality issues (SCWA, 1979) and were re-drilled in 1998.  Pumping of the Todd Road emergency well resumed in 1998.  Incidentally, 1997-1998 was the wettest year of the century for Santa Rosa – hardly a drought-induced emergency! Regular pumping of the Sebastopol Road and Occidental Road emergency wells commenced in mid 2001 and mid 2003, respectively. By late 2003, the three “emergency wells” were pumping over 5 million gallons per day – more than the City of Rohnert Park ever pumped.  Figure 2 shows pumping rates according to SCWA data beginning in mid 2001 and ending in late 2003.

In the 2004 Rohnert Park Draft Water Supply Assessment (WSA) (Winzler & Kelly, 2004), water level data are presented for SCWA wells, but these data are shown only through 1996. Why? Perhaps because 1997 and later data would show downward water level trends that would contradict key conclusions of the WSA!  SCWA has monitored water levels in monitoring wells near the emergency wells since 1996. These data are presented below.


Figure 1: Pumping rates for Occidental Rd, Sebastopol Rd, and Todd Rd SCWA “Emergency Wells” from mid 2001 to late 2003.

Groundwater Elevation Monitoring Screened intervals for the emergency wells are:

Perforation Interval

Occidental Rd.

Sebastopol Rd.

Todd Rd.

Top (ft bgs)

313

410

650

Bottom of (ft bgs)

773

1020

800

Several monitoring wells were installed adjacent to the “emergency wells” at different depths:

Well I. D.

Total Depth

Screened Interval

 

(ft bgs)

(bgs)

Occ MW 1

830

na

Occ MW 2

90

60 - 80

Occ MW 3

92

67 - 87

Occ MW 4

830

na

Occ MW 5

50

30 - 50

Santa Rosa

40

20 - 40

Mattos

~ 58

38 - 58

Seb MW 1

1030

na

Seb MW 2

194

170 - 190

Seb MW 3

189

164 - 184

Seb MW 4

1035

na

Seb MW 5

80

60 - 80

Seb MW 6

50

30 - 50

Seb MW 7

90

70 - 90

Todd Red

80

na

Todd White

257

na

Todd Blue

570

na

For both the Occidental Road and Sebastopol Road emergency wells, “MW-1” and “MW-4” are screened in deep zones similar in depth to the production zones for the emergency wells.  Occidental Road monitoring wells “MW-2”,  “MW-3”, and “MW-5” are very shallow, screened at 60-80, 67-87, and 30-50 feet below ground surface. Sebastopol Road monitoring wells “MW-2” and “MW-3” are screened at 170-190 and 164-184 feet below ground surface and, thus, are in the “shallow zone” (less than 200 feet deep) according to the 2004 Rohnert Park Draft Water Supply Assessment (WSA). Sebastopol Road monitoring wells  “MW-5” and “MW-7” are very shallow at 60-80 and 70-90 feet below ground surface.

All references to depth zones are given for correspondence to the Rohnert Park WSA depth-based method of categorizing water level interpretation, which is not known to relate to any hydrogeologic structure in the Santa Rosa plain. The “shallow zone” is defined between 0 and 200 feet deep, the “intermediate zone” is defined between 200 and 600 feet deep, and “deeper zones” are below 600 feet deep. 

The original Todd Road emergency well has three monitoring wells: “Red”, “White”, and “Blue.”  The “White” well is 257 feet deep (shallow to intermediate?), the “Red” well is 80 feet deep (very shallow), and the “Blue” well is 570 feet deep (intermediate).

Through PRA requests by the Sebastopol Water Information Group (SwiG) and the Open Space, Water Resource Protection, and Land Use Foundation (O.W.L.),groundwater elevation monitoring and well production data were obtained from SCWA.  SCWA used automated transducers to obtain water level data between 2001-2004 at hourly intervals.  The data files span various time periods in various formats and add up to hundreds of thousands of water level elevation measurements. O.W.L. reduced the data into a common format for plotting. Figure 9 of the WSA shows the location of the Occidental Road and Sebastopol Road sites as wells “SCWA_06” and “SCWA_05” respectively and the Todd Road site as “SCWA_01, SCWA_02, SCWA_03, SCWA_04.”

Figure 3 shows 2001-2004 water level elevations for the Occidental Road emergency well. Monitoring wells MW-1 and MW-4 are screened in the deeper zone production interval.  Water levels in MW-1 and MW-4 plunge to about sea level after pumping begins in the Sebastopol Road emergency well in 2001 (see Figure 2). The Sebastopol Road emergency well is located about 1.5 miles to the southeast of the Occidental Road emergency well (see Figure 1). The impact of Sebastopol Road emergency well pumping on Occidental Road site water levels indicates emergency well pumping causes a broad cone of depression beneath the deep and intermediate depths of the western Santa Rosa Plain groundwater subbasin.    In mid 2003, water levels plunge to about 40 to 80 feet below sea level. This water level drop corresponds to commencement of pumping in the Occidental Road emergency well (see Figure 2). 

In Figure 3, the water levels in the Occidental Road monitoring wells MW-2 and MW-3 show decline since commencement of pumping at the Sebastopol Road emergency well. Thus, the SCWA data show that pumping from a deep well can affect very shallow zone water levels over 1.5 miles away. As pumping commences at the Occidental Road emergency well in mid-2003, water level decline becomes more severe in the very shallow zone. The water level in the very shallow well MW-5 shows seasonal variation, suggesting local recharge.

Figure 4 shows 2001-2004 water level elevations for the Sebastopol Road emergency well. Monitoring wells MW-1 and MW-4 indicate water level decline in the intermediate(?) and deeper zone from +25 above sea level before pumping to between 40 and 100 feet below sea level after commencement of pumping in the Sebastopol Road emergency well in mid 2001.   A sharp water level decrease for Sebastopol Road MW-1 in mid-2003 corresponds to commencement of pumping in the Occidental Road emergency well (see Figure 2). Sebastopol Road monitoring wells MW-2 and MW-3 in the shallow zone show a corresponding water level decline with some seasonal variation superposed on a long-term downward trend. Again, these data indicate that deeper and intermediate zone pumping affects the “shallow zone.”  Water level records for the very shallow zone wells MW-5 and MW-7 are too short in time duration to decipher long-term trends, but seasonal variations are evident.  A possible long-term downward trend could be interpreted for MW-5.

Figure 5 shows 1997-2004 water level depths for the Todd Road emergency well.  Presentation of data for the Todd Road emergency well are different here because (1) the Todd Road emergency well has been pumping since 1998, (2) SCWA did not provide a water level elevation information (only water level depth) and (3), the transducer data begin in 2004. Year 2004 transducer data are tied to conventional water level depth measurements since 1997. 

The Todd Road emergency well has three monitoring wells: “Blue” (intermediate), “Red” (very shallow), and “White” (intermediate to shallow?).   The water level depths in Figure 5 indicate that pumping from the Todd Road emergency well induced water level decline in the intermediate zone of up to 100 feet in 1999 and 140 feet in late 2004. Thus, a long-term decline in the intermediate zone water levels is evident in the Todd Road “Blue” monitoring well.  Alternatively, the downward water level change in 2001 could be attributed to commencement of pumping from the Sebastopol Road emergency well. In that case, the three emergency wells appear to produce an expansive cone of depression at least 4 miles long in the deeper and intermediate zones beneath the Laguna de Santa Rosa in the western Santa Rosa Plain groundwater basin between Sebastopol, Santa Rosa, and Rohnert Park. The Todd Road “Red” monitoring well shows downward water level trends in response to the Todd Road pumping. Thus, the Todd Road well appears to impact very shallow zone water levels. The intermediate to shallow(?) “white” monitoring well also shows a slight water level decline that mirrors the intermediate zone water levels. The Todd Road monitoring well data collectively indicate that the “deep” Todd Road emergency well pumping affects all depth intervals from deep to very shallow zones. 

Conclusions

A Public Records Act release of water level data for monitoring wells adjacent to the SCWA “emergency wells” (which SCWA may now refer to as “groundwater wells”; see SCWA, 2004) reveals continuing long-term water level declines in the western Santa Rosa Plain groundwater subbasin. These water level declines occur in shallow, intermediate, and deeper depth zones as defined by the 2004 Rohnert Park Draft Water Supply Assessment. The data show that water level declines are laterally expansive in all depth-related zones. Water levels have not shown full recovery in spring season in any zone except, possibly, the very shallow zone (less than 100 feet deep). These water level data indicate commencement of an overdraft condition corresponding with the commencement of pumping by each of the Sonoma County Water Agency’s “emergency wells” in 1998, 2001, and 2003.  These data indicate overdraft conditions exist in the Santa Rosa plain groundwater basin outside the City of Rohnert Park’s city limits, contrary to the following claim of the 2004 Rohnert Park Draft Water Supply Assessment (p. 2-14):

“…there is no corresponding indication of prolonged declining groundwater elevations elsewhere in the subbasin in any zone, e.g., there is no indication that overdraft has occurred at the subbasin scale.” (Winzler and Kelly, 2004)

Notably, the “emergency wells” now contribute to Rohnert Park’s water supply through Rohnert Park’s water supply contract with SCWA.  Given that SCWA has not announced any plans to cease pumping of the “emergency wells,” a projected overdraft condition is expected to persist indefinitely in the western Santa Rosa Plain subbasin. The recent upsurge in production from the “emergency wells” indicates that a water shortage emergency exists in Sonoma County . Why? According to SCWA:

Water produced from the emergency wells …shall be available for use only during a water shortage emergency…” (SCWA, 1977a)

References

SCWA 1977a, Memorandum from Gordon W. Miller, Chief Engineer, to SCWA Board of Directors, August 1, 1977. Subject: Operation of Emergency Wells.

SCWA 1977b, Memorandum from Gordon W. Miller, Chief Engineer, to SCWA Board of Directors, September 12, 1977, Subject: Agency and Rohnert Park emergency well drilling programs.

SCWA 1978a, Memorandum from Gordon W. Miller, Chief Engineer, to SCWA Board of Directors, February 15, 1978, Subject: Impacts observed on groundwater levels by pumping Agency’s emergency wells.

SCWA 1979, Memorandum from John Kunselman to Richard W. Norton, December 16, 1979, Subject: October 1979 pump test of Agency’s three emergency wells.

SCWA 2004, “Water Supply Workshop”, Sonoma County Water Agency Staff Report, November 1, 2004.

Winzler & Kelly 2004, Draft Water Supply Assessment, City of Rohnert Park , October 2004.


Figure 3: Water level elevations in SCWA’s Occidental Road emergency well monitoring wells.


Figure 4: Water level elevations in SCWA’s Sebastopol Road emergency well monitoring wells.


Figure 5: Water level elevations in SCWA’s Todd Road emergency well monitoring wells.

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