Butte County Water and Resource Conservation

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1 Groundwater Status Report Appendix G Basin Management Objective Reports Available at the Department s website Butte County Water and Resource Conservation

2 BASIN MANAGEMENT OBJECTIVES ANGEL SLOUGH SUBINVENTORY UNIT Butte County Water Advisory Committee Member Catherine Cottle Contact Information Phone Number: Address: Description of the Angel Slough Sub-Inventory Unit The Angel Slough Sub-inventory Unit (SIU) covers an area of about 5400 acres in the southwest portion of the West Butte Inventory Unit. In summer, in a normal year, at least 70% of this area is supported by groundwater. To the northern and easterly directions it is bordered by the M&T sub-inventory Unit. The Llano Seco sub-inventory Unit borders it to the south and to the west it is bordered by the Sacramento River. In times of flooding, water flows directly from the river into Angel Slough. Known to many as "the dips on River Road, it is actually where Angel Slough crosses River Road. This results in flooding of orchard and row crops normally supported by surface water and groundwater and makes River Road impassable by vehicles. At these times, releases by Keswick Dam into the Sacramento River directly effect how long orchard and row crops remain flooded. Monitoring stations at Hamilton City (HMC) and Ord Bend (ORD) track river level data. This information can be found on the California Data Exchange Center (CDEC) website Angel Slough 2016 BMO 1

3 Management Objective It is the intent of this objective to maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply, and to assure a sustainable agricultural supply of good quality water now and into the future. The management objective is also to assure a sustainable groundwater supply of good quality from the alluvial aquifer system for all domestic users in the sub-inventory unit and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. Geologic Formations Identified In Sub-Inventory Unit: Geologic formations in the Angel Slough SIU, from youngest (shallowest) to oldest (deepest), include: Quaternary Alluvium Modesto Formation Tehama Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Angel Slough SIU are: Modesto Formation Tehama Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring SPRING Well ID First Aquifer Stage 1 Alerts Stage 2 Alerts Well Type Record System Elev. (ft) Elev. (ft) 21N01W23J Alluvium Irrigation N01W35K Alluvium Irrigation FALL Well ID First Aquifer Stage 1 Alerts Stage 2 Alerts Well Type Record System Elev. (ft) Elev. (ft) 21N01W23J Alluvium Irrigation N01W35K Alluvium Irrigation Groundwater Quality There are currently no wells being sampled for water quality within the Angel Slough SIU. Staff and stakeholders are hopeful that an appropriate water quality monitoring well will be located in the future. Angel Slough 2016 BMO 2

4 Land Subsidence Land subsidence will be monitored at the closest extensometers located in the M&T and Western Canal sub-inventory units. Angel Slough SIU Stakeholder Issues and Recommendations Future Monitoring Recommendations Efforts will be made to identify additional domestic wells that could be added to the existing monitoring well network in the sub-inventory unit to allow for development of additional management objectives for the alluvial aquifer system. Locate additional wells, either irrigation or domestic, with sufficient historical construction information to include in the water quality monitoring network. Stakeholders would like to revisit the chosen methodology for defining BMO alert stages in this SIU for comparison purposes. No abnormal well functions were reported in More acreage is devoted to Walnuts than in previous years with an estimated 200 acres recently planted. Supporting Data Hydrographs on the following pages depict yearly spring and fall groundwater level measurements with established alert levels. QM Questionable Measurement Angel Slough 2016 BMO 3

5 21N01W23J001M Angel Slough 2016 BMO 4

6 21N01W35K002 Angel Slough 2016 BMO 5

7 BASIN MANAGEMENT OBJECTIVES BIGGS/WEST GRIDLEY SUBINVENTORY UNIT Butte County Water Advisory Committee Member Eugene Massa Jr. Contact Information Phone Number: Address: Description of the Biggs/West Gridley Sub-inventory Unit The Biggs/West Gridley Sub-inventory Unit (SIU) covers an area of about 34,000 acres. It is bordered by the Richvale SIU to the north, Sutter County to the south, the Thermalito and Butte SIUs to the east, and the Butte Sink SIU to the southwest. The Biggs/West Gridley SIU corresponds roughly to the service area of the Biggs/West Gridley Irrigation District. Land use within the SIU is mainly agricultural, although portions of the cities of Biggs and Gridley fall within the eastern edge of the SIU boundary. Agricultural crops consist mainly of rice production, with small areas of orchard, grain, and field crops. A mixture of surface water and groundwater supports agricultural production. In a normal year, about 7% of the Biggs/West Gridley SIU is in summer agricultural production supported by groundwater. In a drought year, about 13% of the SIU is in summer agricultural production supported by groundwater. Management Objective To maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply. It is the intent of this management objective to assure a sustainable agricultural supply of good quality water now and into the future, and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. The management objective is also to assure an adequate groundwater supply of adequate quality from the alluvial aquifer system for all domestic users in the sub-inventory unit. Current Conditions- Due to statewide drought conditions, the Department of Water Resources notified the Joint Districts that it would impose full reductions under their diversion agreement. This resulted in a 50% reduction in the District s diversions. The last time the District was curtailed was in 1992, 23 years ago. A number of the District s landowners supplemented their curtailed supply by pumping their privately owned groundwater wells to irrigate rice, orchards, habitat and other crops. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Biggs/West Gridley SIU, from youngest (shallowest) to oldest (deepest), include: Biggs/West Gridley 2016 BMO 1

8 State Well Number Basin Deposits Modesto Formation Sutter Formation Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Biggs/West Gridley SIU are: Modesto Formation Laguna Formation Lower Tuscan (Formation Unit B) Aquifer System BMO Key Wells Selected for Groundwater Level Monitoring Alert levels established using the standardized Historic Range Method as defined in Chapter 33A. SPRING Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 17N01E10A01M 1953 Riverbank Domestic N02E16F01M 1947 Basin Deposits Irrigation N02E25M01M 1959 Modesto Irrigation N02E32H01M 2001 Riverbank/Modesto Domestic FALL Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 17N01E10A01M 1953 Riverbank Domestic N02E16F01M 1947 Basin Deposits Irrigation N02E25M01M 1959 Modesto Irrigation N02E32H01M 2001 Riverbank/Modesto Domestic N01E35L001M is a monitoring well installed in With this short period of record, no alert stages are assigned. However, groundwater levels are tracked to monitor changing conditions from year to year. BMO Key Wells Selected for Groundwater Quality Monitoring Annual Groundwater Temperature Measurement ( o C) NO2E35R01M Biggs/West Gridley 2016 BMO 2

9 Electrical Conductivity (µs) ph State Well Number Annual Groundwater ph Measurement NO2E35R01M State Well Number Annual Groundwater Electrical Conductivity Measurement (microsiemens/cm) NO2E35R01M Biggs-West Gridley EC=700 ph= ph= Year EC ph BMO Key Well(s) Selected for Land Subsidence Monitoring Land subsidence is continuously monitored by the Department of Water Resources and Butte County Water and Resource Conservation at the closest extensometers in Biggs West Gridley, Western Canal Water District and Richvale sub-inventory units. Biggs/West Gridley SIU Issues and Recommendations Future Monitoring Efforts will be made to identify additional domestic wells that could be added to the existing monitoring well network in the sub-inventory unit to allow development of management objectives for the alluvial aquifer system. Continued efforts will be made to gather all relative historical information on the existing water quality monitoring well. Stakeholders in the Biggs/West Gridley SIU will work with staff to locate additional wells, either irrigation or domestic, with sufficient historical construction information that may be included in the water quality monitoring network. Biggs/West Gridley 2016 BMO 3

10 Supporting Data Hydrographs on the following pages depict yearly spring and fall level measurements with established alert levels. QM Questionable Measurement 17N01E10A001 Biggs/West Gridley 2016 BMO 4

11 18N02E16F001 This well has long been a Key Well highlighted in the Butte Basin Water Users Annual report. The figures below and on the following page show the hydrographs for well 18N02E16F001M located in the north-central portion of the Biggs-West Gridley SIU. The area surrounding this well is characterized as rural agricultural. Agricultural cultivation in this area consists primarily of rice production supported by a combination of surface and groundwater. The well is an active irrigation well, constructed in the upper portion of the aquifer. Water elevations have been monitored since 1947 at this location. Groundwater levels in this well were monitored on a semi-annual basis until 1991, and on a monthly basis from 1991 to about Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly, April through October, due to drought conditions. The historical average depth to water, including 2015 data, is 6.1 feet below ground surface in the spring and 6.6 feet below groundwater surface in the fall. Water levels remain consistent with historical levels, with both spring and fall measurements remaining at or above the historical average. The figure shows that the spring to fall fluctuation of groundwater levels in the unconfined portion of the aquifer system averages only 1 to 2 feet during years of normal precipitation and years of drought. Close examination of the spring to summer fluctuations indicate that groundwater levels rise during the summer months as the upper aquifer recharges due to flood irrigation for rice production. Long-term comparison of spring-to-spring groundwater levels shows almost no change in groundwater levels associated with the , and or 1994 drought periods. Further long-term analysis of spring-to-spring groundwater levels indicates that there has been an increase of about 2 feet in groundwater levels since the late 1940s. Biggs/West Gridley 2016 BMO 5

12 18N02E16F001M Biggs/West Gridley 2016 BMO 6

13 18N02E25M001 Biggs/West Gridley 2016 BMO 7

14 18N02E32H001 Biggs/West Gridley 2016 BMO 8

15 18N01E35L001M Biggs/West Gridley 2016 BMO 9

16 BASIN MANAGEMENT OBJECTIVES BUTTE SUBINVENTORY UNIT Butte County Water Advisory Committee Member Mark Orme Contact Information Phone Number: Address: Description of the Butte Sub-inventory Unit The Butte Sub-inventory Unit (SIU) covers an area of about 21,400 acres. It is bordered by the Biggs/West Gridley and Thermalito SIUs to the north and west, the North Yuba Inventory Unit to the east, and Sutter County to the south. The Butte SIU corresponds roughly to the service area for the Butte Water District. Land use within the SIU is mainly agricultural, but also includes most of the urban area for the cities of Biggs and Gridley. Agricultural production consists mainly of orchard crops with smaller areas of rice and field crops. A mixture of surface water and groundwater supports agricultural production. In a normal year, about 29% of the Butte SIU is in summer agricultural production supported by groundwater. Groundwater is also used as the municipal water source for much of the urban area surrounding the cities of Biggs and Gridley. Current Conditions Numerous orchards in the Butte Water District are converting to micro-jet irrigation supported by NRCS irrigation efficiency programs. This often is accompanied by a conversion from surface water use to groundwater use for irrigation. As a result, surface water deliveries by the district have been declining over the past few years. Major crop changes have also occurred in the past couple years with walnuts largely replacing peaches. Also some rice acreage has converted to walnuts. In 2015, due to statewide drought conditions, the Department of Water Resources notified the Joint Districts that it would impose full reductions under their diversion agreement. This resulted in a 50% reduction in the District s diversions. The last time the District was curtailed was in 1992, 23 years ago. A number of the District s landowners supplemented their curtailed supply by pumping their privately owned groundwater wells. Management Objective To maintain the groundwater surface elevation at a level that will assure an adequate and affordable irrigation water supply from the Alluvial, Sutter Buttes Rampart, Lower and Upper Tuscan Formations aquifer systems. It is the intent of this management objective to assure a sustainable agricultural groundwater supply of good quality now and into the future, and to assure the water supply can be utilized to the maximum extent possible without injuring groundwater Butte 2016 BMO 1

17 quality or inducing land subsidence. The intent of this management objective is also to assure an adequate supply of groundwater from the alluvial aquifer system of suitable quality for all domestic groundwater users in the sub-inventory unit. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Butte SIU, from youngest (shallowest) to oldest (deepest), include: Quaternary Alluvium Modesto Formation Riverbank Formation Laguna Formation Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Butte SIU are: Quaternary Alluvium Modesto Formation Riverbank Formation Laguna Formation Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring Spring Well ID First Aquifer Stage 1 Alerts Stage 2 Alerts Well Type Record System Elev. (ft) Depth (ft) Elev. (ft) Depth (ft) 17N02E14A01M 1947 Modesto Formation Irrigation N02E14H01M 2000 Basin Deposits Domestic N03E16N01M 1953 Riverbank Formation Domestic Fall Well ID First Aquifer Stage 1 Alerts Stage 2 Alerts Well Type Record System Elev. (ft) Depth (ft) Elev. (ft) Depth (ft) 17N02E14A01M 1947 Modesto Formation Irrigation N02E14H01M 2000 Basin Deposits Domestic N03E16N01M 1953 Riverbank Formation Domestic BMO Key Well(s) Selected for Land Subsidence Monitoring Land subsidence is continuously monitored by the Department of Water Resources and Butte County Water and Resource Conservation at the closest extensometers in the Western Canal Water District, Biggs West Gridely, and Richvale sub-inventory units. Butte 2016 BMO 2

18 Butte SIU Issues and Recommendations The monitoring network will be reevaluated and adjusted as necessary, so if at all possible, monitoring groundwater levels in each aquifer at key locations can occur. If possible, data collection will be initiated for the development of groundwater quality management objectives in the future. Explore avenues to install an extensometer within the District to monitor for subsidence. Supporting Data Butte Water District Map included. Hydrographs on the following pages depict yearly spring and fall level measurements with established alert levels. QM Questionable Measurement Butte 2016 BMO 3

19 Butte Water District Base map BMO wells are 14A001, 14H001, and 16N001 Butte 2016 BMO 4

20 17N02E14A001 Butte 2016 BMO 5

21 17N02E14H001 ** Note: almost weekly monitoring during October 2013 and 2014 Butte 2016 BMO 6

22 17N03E16N001N This well has long been highlighted in the Butte Basin Water Users Annual report. Water elevations have been monitored at 17N03E16N001 since 1953, located in the southeast portion of the Butte sub-area. The area surrounding this well is characterized as rural agricultural. Agricultural cultivation in this area consists primarily of orchard crops supported by groundwater. The well is an active domestic well, constructed over the upper and middle portions of the aquifer. The groundwater levels in this well were monitored on a semi-annual basis until approximately 1991, and on a monthly basis from approximately 1991 to Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly, April through October, due to drought conditions. The hydrographs on the following page for well 17N03E16N001M show that the spring to fall fluctuation of groundwater levels in the unconfined portion of the aquifer system averages only 3 to 6 feet during years of normal precipitation and 1 to 3 feet during years of drought. The historical average depth to water, including 2015 data, is approximately 9.4 feet below ground surface in the spring and approximately 11.7 feet below ground surface in the fall. Long-term comparisons of spring-to-spring groundwater levels shows a small decline in spring groundwater levels associated with the , and 1994 drought periods, followed by recovery to normal levels. Further long-term analysis of spring-to-spring groundwater levels indicates very little change in spring groundwater levels since the 1950s with just a couple of feet decline in the last couple of years. Fall groundwater levels have declined approximately 3 feet over the period of record. Butte 2016 BMO 7

23 17N03E16N001M ** Note: almost weekly monitoring during October 2013 and 2014 Butte 2016 BMO 8

24 BASIN MANAGEMENT OBJECTIVES BUTTE SINK SUBINVENTORY UNIT Butte County Water Advisory Committee Member Vacant Contact Information Phone Number: Address: Description of the Butte Sink Sub-inventory Unit The Butte Sink Sub-inventory Unit (SIU) covers an area of about 10,300 acres, bordered by the Biggs/West Gridley SIU to the north and east, Sutter County to the south, and Butte Creek (the Colusa County boundary) to the west. Much of the Butte Sink area consists of waterfowl refuges and privately managed wetlands habitats. These habitats are primarily composed of native riparian vegetation and support aquatic, terrestrial and avian threatened and/or endangered species along with a diverse component of wetland dependent and associated species. A smaller portion of the SIU supports agricultural production of rice and grain crops. Waterfowl refuges, wetlands and agricultural land use in this area are supported by the application of a combination of surface and groundwater. The Butte Sink SIU is the lowest point of elevation in Butte County and thus receives a tremendous amount of storm runoff. The reduced rate of surface elevation drop in the Butte Sink especially south the Gridley-Colusa highway (collectively known as the lower Butte Sink) allows for prolonged periods of flooding. There is significant opportunity for ground water recharge during the fall application of surface water in the wetlands habitats and when weather events cause flooding. The southwestern most portion of the Butte Sink SIU has surface water rights and therefore uses little groundwater. Most of the groundwater pumping occurring within the Butte Sink SIU occurs at the Gray Lodge Wildlife Refuge, and outside of the Butte Sink SIU to the south in Sutter County. This surrounding groundwater pumping likely affects the groundwater levels monitored within the Butte Sink SIU. Land in the Butte Sink SIU receives extensive rice runoff and surface water from Biggs/West Gridley Water District, Richvale Irrigation District and Western Canal Water District. If surface water drainage or deliveries were cut to the Butte Sink SIU area, groundwater use would increase significantly. Current Conditions In 2014, fall measurements declined in most wells, as much as 6.7 feet. Spring groundwater level measurements remained comparable to those taken in the spring of Management Objective To maintain the groundwater surface elevation in all aquifer systems at a level that will assure the continued sustainability and health of the Butte Sink wetlands. It is also the intent of this management objective to assure a sustainable Butte Sink 2016 BMO 1

25 Well ID agricultural and wildlife management water supply of good quality for now and into the future, and to assure the water supply can be utilized without injuring groundwater quality or inducing inelastic land subsidence. The management objective also strives to assure an adequate supply of good quality groundwater for all users in the sub-inventory unit. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Butte Sink SIU, from youngest (shallowest) to oldest (deepest), include: Quaternary Alluvium Basin Deposits Modesto Formation Riverbank Formation Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Butte Sink SIU are: Modesto Formation Riverbank Formation Tuscan Formation Sutter Formation BMO Key Wells Selected for Groundwater Level Monitoring For the Butte Sink SIU the groundwater level objectives were chosen to support both groundwater levels that support wetland habitat and available groundwater in storage in the deeper aquifer systems. The spring groundwater level measurement is intended to reflect the change in groundwater in storage in the deeper aquifers and the fall measurements are intended to support the wetlands habitat. In 2007, a multi-completion dedicated monitoring well was installed by DWR Northern District within the Grey Lodge Wildlife Refuge, SWN 17N01E24A SPRING First Record Well Type Aquifer Stage 1 Alerts Stage 2 Alerts Elev. (ft) Depth (ft) Elev. (ft) Depth (ft) 17N01E17F001M 1992 Monitoring Riverbank N01E17F002M 1992 Monitoring Sutter Formation N01E17F003M 1992 Monitoring Sutter Formation N01E24A003M 2007 Monitoring Sutter & Tuscan 17N01E24A004M 2007 Monitoring Sutter Formation 17N01E24A005M 2007 Monitoring Sutter Buttes Rampart 17N01E24A006M 2007 Monitoring Sutter Buttes Rampart 17N02E19J001M 2000 Irrigation Sutter Formation Butte Sink 2016 BMO 2

26 Well ID FALL First Record Well Type Aquifer Stage 1 Alerts Stage 2 Alerts Elev. (ft) Depth (ft) Elev. (ft) Depth (ft) 17N01E17F001M 1992 Monitoring Riverbank N01E17F002M 1992 Monitoring Sutter Formation N01E17F003M 1992 Monitoring Sutter Formation N01E24A003M 2007 Monitoring Sutter & Tuscan 17N01E24A004M 2007 Monitoring Sutter Formation 17N01E24A005M 2007 Monitoring Sutter Buttes Rampart 17N01E24A006M 2007 Monitoring Sutter Buttes Rampart 17N02E19J001M 2000 Irrigation Sutter Formation The multi-completion monitoring well (SWN 17N01E24A ) was installed at the Gray Lodge Wildlife Refuge in Groundwater elevation data is presented but no Alert levels established until enough years of data have been collected for analysis. BMO Key Wells Selected for Groundwater Quality Monitoring There are currently no wells being sampled for water quality within the Butte Sink SIU. BMO Key Well(s) Selected for Land Subsidence Monitoring Land Subsidence is continuously monitored by the Department of Water Resources and Butte County Department of Water and Resource Conservation. The closest extensometer to the sub-inventory unit is in Biggs West-Gridley Water District (18N01E35L001M). Butte Sink SIU Stakeholder Issues and Recommendations Butte Sink would like to identify an appropriate well for water quality monitoring. Supporting Data Hydrographs on the following pages depict yearly spring and fall level measurements with established alert levels. QM Questionable Measurement Butte Sink 2016 BMO 3

27 17N01E17F001 This has long been a key well highlighted in the Butte Basin Water Users Annual Report. The figures on the following page are hydrographs (spring and fall groundwater levels) for well 17N01E17F001M, in the northwestern portion of the Butte Sink Sub-area. The land use surrounding this well is characterized as native riparian and agricultural. Agricultural cultivation in this area consists of rice production supported primarily by surface water. Surface water is also used as the primary source for flooding of native riparian land for waterfowl habitat. This well is a dedicated monitoring well, constructed in the upper to middle portions of the aquifer, with a groundwater level measurement record dating back to The groundwater levels in this well were monitored on a monthly basis from 1992 to Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly, April through October, due to drought conditions. The figure shows that the spring to summer fluctuation of groundwater levels in the unconfined portion of the aquifer system averages only 3 to 5 feet during years of normal precipitation. Monitoring in this well began during the and 1994 drought period so it is not possible to fully determine the impact of this drought period on the water level in this well. All groundwater level measurements (spring, summer, and fall) have been within 14 feet of the ground surface. Over the 20 year period of record, there is not a significant trend for spring levels until the past few years in which they are declining. The fall 2015 level reached a new historical low for the second year in a row. Water elevations have been monitored since 1992 at this location and the historical average depth to water, including 2015 data, is approximately 2.4 feet below ground level in the spring and approximately 5.7 feet below ground level in the fall. Butte Sink 2016 BMO 4

28 17N01E17F001M Butte Sink 2016 BMO 5

29 17N02E17F002 Butte Sink 2016 BMO 6

30 17N01E17F003 Butte Sink 2016 BMO 7

31 17N02E19J001 Butte Sink 2016 BMO 8

32 17N01E24A (no Alert Level) Butte Sink 2016 BMO 9

33 Butte Sink 2016 BMO 10

34 BASIN MANAGEMENT OBJECTIVES CHEROKEE SUBINVENTORY UNIT Butte County Water Advisory Committee Member Gary Cole Contact Information Phone Number: (530) Address: Description of the Cherokee Sub-Inventory Unit: The Cherokee Sub-Inventory Unit (SIU) covers an area of approximately 14, 700 acres and is bordered on the north and east by the Foothill inventory unit. To the northwest are the Pentz and Esquon Sub-Inventory Units (SIU), to the southwest lies the Western Canal SIU, and due south is the Thermalito SIU. Larger capacity agriculture and business production wells tap into the Lower Tuscan Aquifer (Formation Unit B). The Lower Tuscan Unit B (Lower Tuscan) varies from approximately 700 feet deep from ground surface in the western portion of the Cherokee SIU and slopes upward to zero feet thick in some portions on the eastern edge of the Cherokee SIU. Underlying the Lower Tuscan are ancient marine layers, and salty waters exist. Some domestic wells of approximately feet in depth in the western part of the Cherokee SIU extract water from deposits overlying the Lower Tuscan aquifer. However, the majority of domestic wells in the SIU are pumping from the Lower Tuscan. In the easterly areas (Butte Valley), the potable water aquifer varies from zero feet to a few hundred feet as one travels westward. Drilling too deeply, through the Lower Tuscan, produces non-drinkable water from marine layers beneath the Lower Tuscan. Additionally, upper and lower boundary elevations of the Lower Tuscan slope upward to the east. The top of the Lower Tuscan goes from elevations of approximately 120 feet above sea level to the west and south to approximately 400 feet above sea level in the east and comes to the ground surface in some areas. The bottom of the Tuscan B formation slopes from approximately 500 feet below sea level in the west to 400 feet above sea level in the east and comes to the ground surface in some areas. The majority of water volume pumped from groundwater in the Cherokee SIU is for farmland irrigation. Domestic water supply usage from the aquifer is of smaller volume but equally critical. There are presently few other sources of water for domestic use in the Cherokee SIU. All residents are totally dependent on water from the aquifer system except for few who use water from natural springs near the eastern perimeter of the Cherokee SIU. Rural housing is increasing in numbers in Butte Valley and will increase demands for groundwater in the Cherokee SIU. Cherokee 2016 BMO 1

35 According to the Department of Water Resources (DWR) as of 2005, there are 183 wells total in the Cherokee SIU. There are 104 domestic wells (depth from surface: shallow to 260 feet). There are 62 irrigation wells (depth from surface: approximately feet). There are three wells for monitoring purposes only, and 15 additional wells classified as other, which could mean a number of things from stock animals supply to some other monitoring purpose. According to 1997 estimates, approximately 24,000 acre feet of water was being pumped from groundwater and used in the Cherokee SIU. Current Conditions- Some orchards use moisture sensing devices to better manage water application. In 2015, one smaller/shallower agricultural well had to be run at a reduced pumping rate since it broke suction at normal rpms. All wells appeared to have slightly less output than in 2014 but none went dry or had water levels fall below the pump settings. Management Objectives 1. To maintain upper groundwater elevations in the Lower Tuscan at affordable extraction elevations now and into the future. a. To maintain adequate groundwater elevations in our underlying aquifer, the Lower Tuscan, throughout the year at affordable and dependable elevations from the surface for farming and other larger volume users. b. To maintain adequate water elevations in the Lower Tuscan aquifer throughout the year for affordable and dependable domestic needs. 2. To maintain dependable and adequate supply (volume) throughout the year at affordable extraction elevations now and into the future. a. To maintain a volume of groundwater in the Lower Tuscan aquifer system that will insure adequate amounts at affordable extraction elevations for farming and other larger volume users throughout the year. b. To maintain a volume of groundwater in the Lower Tuscan at affordable extraction elevations for domestic needs throughout the year. c. To maintain sufficient volume and elevation of groundwater in the Lower Tuscan to prevent up-welling and excessive mixing of salt water from underlying marine layers. 3. Monitor for changes in water quality. Changes in groundwater parameters of temperature, ph and EC (electrical conductivity) can indicate impacts to the groundwater system. These parameters will be evaluated annually according to Chapter 33A of the Butte County Code. 4. Monitor for permanent land subsidence. If it is detected anywhere in Butte County where similar geological/aquifer structure and groundwater extraction conditions exist, then we will immediately review the Cherokee SIU conditions and take appropriate actions. Since permanent subsidence by definition has already permanently caused damage, our main goal will be to prevent additional subsidence/damage over a larger area or to a greater extent. Cherokee 2016 BMO 2

36 5. Monitor to avoid threats of environmental degradation. Degradation could cause additional management expenses from accessing water for overlying uses. 6. Monitor to avoid water levels dropping below historical operating ranges to insure pumps function adequately at designed pressures for irrigation systems in orchards, and to deliver designed pressure, volume, and coverage for maximum production of crops and prevent crop damage from less than adequate watering. 7. Sufficiently investigate practices within and around the Cherokee SIU when Alert Stages are reached in order to determine if they have been created by or accentuated by actions or forces from outside Cherokee SIU. Geologic Formations Identified In Sub-Inventory Unit: Geologic formations in the Cherokee SIU, from youngest (shallowest) to oldest (deepest), include: Quaternary Alluvium Basin Deposits Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Cherokee SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring Groundwater Levels Seven monitoring wells have been selected for establishing BMO levels as per the ordinance requirements of groundwater level monitoring. Three of those wells are located in the most heavily farmed areas, with one major business water user. Two additional wells, two in central Butte Valley and one on the northeasterly edge of the Cherokee SIU, were selected as primary monitoring wells. Both of the last two wells are in close proximity to the most populated areas of the Cherokee SIU. The agricultural wells selected are critical to our evaluation times because they are continuously monitored. Note, the newest well added to the BMO monitoring does not have sufficient historical measurements to establish Alert Stages. Those will be established when sufficient data has been recorded. Cherokee 2016 BMO 3

37 SPRING Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N02E24C01M 1999 Tuscan B Monitoring N02E24C02M 1999 Tuscan B Monitoring N02E24C03M 1999 Tuscan B Monitoring N03E31M01M 2001 Tuscan B Monitoring N03E33L01M 1999 Tuscan B Irrigation N03E22C01M 2001 Tuscan B Domestic N03E32B01M 1999 Tuscan B Irrigation N03E29J Tuscan B Domestic * * FALL Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N02E24C01M 1999 Tuscan B Monitoring N02E24C02M 1999 Tuscan B Monitoring N02E24C03M 1999 Tuscan B Monitoring N03E31M01M 2001 Tuscan B Monitoring N03E33L01M 1999 Tuscan B Irrigation N03E22C01M 2001 Tuscan B Domestic N03E32B01M 1999 Tuscan B Irrigation N03E29J Tuscan B Domestic * * *The domestic well (SWN 21N03E29J03) was added to the DWR monitoring network in the Cherokee Sub-Inventory Unit in the Fall of Groundwater elevation data will be presented in this report but will not have a corresponding BMO. BMO Key Wells Selected for Groundwater Quality Monitoring Groundwater Quality- Currently, Butte County Department of Water and Resource Conservation monitors two wells annually in the Cherokee SIU for water quality. One well was sampled for the first time in 2007, the other has been monitored since The newer well replaces a well previously monitored in the Butte Valley area that was discontinued from the monitoring grid because of new property owners that did not wish to participate in the program. The available results for the measured constituents of temperature, electrical conductivity and ph are included in this report. Note: The distance between the previously monitored Butte Valley well and the new one is approximately 2.4 miles. Cherokee 2016 BMO 4

38 State Well Number Annual Groundwater Temperature Measurement ( o C) N02E24Q01M N03E29J03M N03E26E01M State Well Number Annual Groundwater ph Measurement N02E24Q01M N03E29J03M N03E26E01M State Well Number Annual Groundwater Electrical Conductivity Measurement (microsiemens/cm) N02E24Q01M N03E29J03M N03E26E01M BMO Key Well(s) Selected for Land Subsidence Monitoring Land subsidence is continuously monitored by the Department of Water Resources and Butte County Department of Water and Resource Conservation in the closest Sub- Inventory Unit at State Well number 20N01E18L03M, located within the Western Canal Sub-Inventory Unit. Cherokee SIU Stakeholder Issues and Recommendations 1. Philosophy of the Cherokee Sub-Inventory Unit Stakeholders Cherokee SIU stakeholders want to participate in the Butte County BMO process, and we want to have direct influence on the management of our underlying groundwater and aquifer systems. Because of the vital importance of the Lower Tuscan Aquifer underlying the Cherokee SIU for the existing environments and habitats, businesses, agriculture, domestic needs, recharge, plant and animal needs, economic value of our properties, and future residential growth and needs, we want to be proactive in its management. Our goals center on maintaining water levels and volume in the Lower Tuscan aquifer at economical levels to sustain and improve its functions for all overlying users. In the long chain of water users in California, we believe lands overlying aquifers have first rights for use of that groundwater for their needs. Stakeholders have Cherokee 2016 BMO 5

39 responsibilities to protect all aspects of the aquifers, overlying lands relating to the aquifers, and not pump more than is needed for those overlying lands. Groundwater is not a commodity to be sold if it causes harm to other stakeholders. It is a resource to be used wisely without harming other overlying stakeholders and environments. 2. Future Monitoring Recommendations and Goals for the immediate, on-going and long-term: a. Expand domestic well monitoring on the east side of Clark Road in Butte Valley. b. Add additional agricultural monitoring wells if stakeholders indicate presently selected wells do not accurately reflect the intent of the Cherokee SIU BMO. c. Continue to receive and accumulate well data from the production well being monitored on Butte College Campus so trends and alert levels can be established for better management of the Cherokee SIU. d. Keep the Lower Tuscan Aquifer a healthy system now and into the future so all overlying landowners have good water at an affordable pumping cost and adequate amounts for their overlying needs. Have an aquifer system that may be used by its stakeholders without doing harm to others by increasing extraction costs or decreasing extraction amounts needed by surrounding stakeholders. e. Work with Cherokee Watershed, Butte County, and other agencies to promote good management of the Cherokee watershed in groundwater related issues related to the Lower Tuscan Aquifer. f. Maintain adequate aquifer water levels and volume during fall and winter seasons for the tree farmers, business users, and domestic needs that exist year round. Supporting Data Hydrographs on the following pages depict yearly spring and fall groundwater level measurements with established alert levels. QM Questionable Measurement Note: In 2014 and 2015 monthly measurements were taken. The first of the two measurements (March) in the Spring graphs should be considered the BMO level. Cherokee 2016 BMO 6

40 20N02E24C001 Cherokee 2016 BMO 7

41 20N02E24C002 The key well 20N02E24C002M is part of a dedicated, multi-completion monitoring well set that was installed in The well is in the west central portion of the sub-area south of the original key well highlighted in Butte Basin Water Users Annual reports. Measurements in this well represent groundwater conditions between 336 to 377 foot depth in the semi-confined portion of the Lower Tuscan aquifer system. Water levels have been monitored since 2000 at this location and the historical averages for depth to water from ground surface, including 2015 data, are 36.6 feet in the spring and 44.2 feet in the fall. The relatively short period of record for this well makes analysis of long term trends difficult, but spring groundwater levels have generally declined since the spring of 2000, on the order of about 20 feet. Cherokee 2016 BMO 8

42 20N02E24C003 Cherokee 2016 BMO 9

43 20N03E31M001 Cherokee 2016 BMO 10

44 20N03E33L001M Cherokee 2016 BMO 11

45 21N03E22C001M Cherokee 2016 BMO 12

46 21N03E32B001M Cherokee 2016 BMO 13

47 21N03E29J003: spring and fall measurements *Note: not measured fall due to excessive time required of DWR to coordinate measurement. The Water and Resource Conservation now conducts this monitoring. Cherokee 2016 BMO 14

48 BASIN MANAGEMENT OBJECTIVES CHICO URBAN AREA Butte County Water Advisory Committee Member Vacant Contact Information Phone Number: Address: Description of the Chico Urban Area Sub-Inventory Unit The Chico Sub-Inventory Unit (SIU) covers an area of about 15,400 acres in the Greater Chico urban area and is split between the Vina and West Butte inventory units. The SIU boundary corresponds roughly to the municipal water service area for the City of Chico, which is operated by the California Water Service Company. The company supplies groundwater to the Chico area through the operation of about 66 groundwater wells. There are a number of private wells in the SIU that are utilized for domestic and irrigation purposes. Management Objective Basin Management Objectives for the Chico Urban Area reflect groundwater levels adequate to sustain municipal, agricultural and domestic use and the quality of streams and groundwater dependent vegetation. These groundwater levels reflect the natural seasonality of the groundwater systems. Basin Management Objectives for the Chico Urban Area is based on water quality measurements (temperature, ph, and electrical conductivity,) that represent water quality acceptable for human consumption and agricultural purposes related to saline intrusion. Basin Management Objectives for the Chico Urban Area reflect measurements that do not demonstrate inelastic land subsidence. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Chico Urban Area SIU, from youngest (shallowest) to oldest (deepest), include: Basin Deposits Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Chico Urban Area SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Chico Urban Area 2016 BMO 1

49 BMO Key Wells Selected for Groundwater Level Monitoring In the Chico Urban SIU a triple-completion Bureau of Reclamation monitoring well will be used to monitor water levels in the Upper Tuscan and the Lower Tuscan. The e-log for this well shows it to be screened in these aquifers. In addition to monitoring specific aquifers, there are seven California Water Service production wells to monitor for the continued health of the municipal and industrial (M & I) water supply. While these wells will not provide information about the specific aquifers underlying the Chico Urban Area since they are not screened in a single aquifer, the information will help track whether municipal supply is being sustained, as called for in the BMO objectives. Two dedicated monitoring wells measured for the Chico Nitrate Compliance Program provide groundwater level data for the shallow alluvial aquifer but do not have assigned alert stages. SPRING First Well ID Record Well Type Aquifer Stage 1 Alerts Stage 2 Alerts Elev. (ft) Depth (ft) Elev. (ft) Depth (ft) CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite N01E28J001M 1958 Monitoring Tuscan B N01E28J003M 1958 Monitoring Tuscan B N01E28J005M 1958 Monitoring Tuscan B Well ID FALL First Record Well Type Aquifer Stage 1 Alerts Stage 2 Alerts Elev. (ft) Depth (ft) Elev. (ft) Depth (ft) CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite CWSCH M&I Production Composite N01E28J001M 1958 Monitoring Tuscan B N01E28J003M 1958 Monitoring Tuscan B N01E28J005M 1958 Monitoring Tuscan B Chico Urban Area 2016 BMO 2

50 Wells measured and tracked but no alert stage assigned due to short period of record. First Well ID Well Type Aquifer Record 22N01E35E001M 2005 Irrigation Unassigned 22N02E30C002M 2002 Monitoring Unassigned BMO Key Wells Selected for Groundwater Quality Monitoring The Chico well selected for monitoring is 22N02E17 Groundwater Temperature in Celsius Sub-Inventory Unit State Well Number Chico Urban Area 22N02E NM 18.4 Groundwater ph Sub-Inventory Unit State Well Number Chico Urban Area 22N02E NM 6.9 Groundwater Electrical Conductivity (microsiemens/cm) Sub-Inventory Unit State Well Number Chico Urban Area 22N02E NM 214 BMO Key Well(s) Selected for Land Subsidence Monitoring State Well Number 22N01E35E01M. No inelastic subsidence has been detected. BMO Alert Stage Methodologies The Chico Urban Area Sub-Inventory Unit utilizes the BMO Alert Stage historic range method specified in Chapter 33A-5 of the Butte County Code. BMOs for Groundwater Level Summary - The Chico Urban Sub-inventory unit utilizes the Historic Range Method specified in the BMO Groundwater Elevation Criteria (Chapter 33A-5c1. of the Butte County Code). In the spring of 2015, seven wells (CWSCH01, CWSCH02, CWSCH03, CWSCH05, CWSCH06, CWSCH07 and 28J03) reached BMO Alert Stage 1. Two wells (28J01 and 28J05) reached an Alert Stage 2. All other measurements met BMOs for groundwater elevation. In the fall of 2015, three wells (CWSCH01, CWSCH03, CWSCH06) reached an Alert Stage 1. Three wells (28J01, 28J03 and 28J05) reached an Alert Stage 2. California Water Service Wells - Groundwater levels for the California Water Service (CWS) monitoring wells are measured static (non-pumping) groundwater levels, provided by California Water Service Company. Although the groundwater level measurements presented in the CWS hydrographs were collected when the wells were not pumping (static groundwater levels), it should be noted that effects from recent Chico Urban Area 2016 BMO 3

51 pumping of these production wells could result in groundwater level readings that are deeper than stable static conditions. Overall analysis of the seasonal fluctuation of groundwater levels in these California Water Service wells indicates a rather consistent seasonal fluctuation (spring to fall) of 8 to 20 feet during normal years. Analysis of seasonal groundwater levels during drought years shows a wide range of fluctuation depending upon the individual well. Some wells show little or no seasonal change between wet, normal and dry years, while other wells show large differences. The wide range of response to seasonal change in normal versus drought years is likely due to the wide range of operational scenarios that can be imposed upon these municipal wells. Overall, the hydrographs indicate that groundwater levels in the California Water Service area of the Chico Urban Area Sub-Inventory Unit have declined an average of about fourteen feet between 1988 and Spring levels have generally declined over the past five years over the course of the severe drought. However, 2015 fall levels in several of the Cal Water wells came up from where they were in fall The water savings achieved by residents in the Chico area as a result of the Governor s Order has resulted in slowing or reversing the downward trend in fall water levels in Chico Urban Area 2016 BMO 4

52 CWSCH01 Well CWSCH01 is located just southwest of the center of the California Water Service area. Water elevations have been monitored since 1988 at this location and the historical depth to water averages, including 2015 data, are; Spring = 71 feet and Fall=82 feet. It was discovered that the measurement recorded in April 2009 was inaccurate due to an equipment error and therefore the graph shows it as a questionable measurement. The record of fall water level measurements shows declining levels with the average of the last five years ( ) almost 14 feet lower than the average of the first 5 years on record ( ). Both of these time periods contain multiple drought years. Chico Urban Area 2016 BMO 5

53 CWSCH02 * Note: Fall 2012 was a questionable measurement, re-checked the depth to water was 65 feet (compared to 97 ). Chico Urban Area 2016 BMO 6

54 CWSCH03 Well CWSCH03 is located in the northeastern portion of the California Water Service area. Water elevations have been monitored since 1988 at this location and the historical depth to water averages (from static one-time measurements), including 2015 data, are feet in the spring and feet in the fall. Spring water levels recorded in the last five years represent a decline of approximately fourteen feet from average spring water levels recorded Chico Urban Area 2016 BMO 7

55 CWSCH04 Chico Urban Area 2016 BMO 8

56 CWSCH05 Chico Urban Area 2016 BMO 9

57 CWSCH06 Chico Urban Area 2016 BMO 10

58 CWSCH07 Chico Urban Area 2016 BMO 11

59 22N01E28J001-5M Well 22N01E28J001-5M is part of a dedicated multi-completion monitoring well set that was installed by the United States Bureau of Reclamation in The well is located in west Chico, north of West Sacramento Avenue and west of Nord Avenue. Water elevations have been monitored since 1958 at this location, in all three wells. Continuous data is available online for 28J01 with data since January The hydrograph of groundwater elevation is below. Chico Urban Area 2016 BMO 12

60 22N01E28J001 This monitoring well is screened from feet below ground surface. Chico Urban Area 2016 BMO 13

61 22N01E28J003 This monitoring well is screened from feet below ground surface. Chico Urban Area 2016 BMO 14

62 22N01E28J005 Measurements from 22N01E28J005M represent groundwater conditions within the confined portion of the Tuscan Formation aquifer system between 740 to 800 feet in depth below ground surface. Chico Urban Area 2016 BMO 15

63 Wells without Assigned Alert Stages 22N01E35E001M Chico Urban Area 2016 BMO 16

64 22N02E30C002M Chico Urban Area 2016 BMO 17

65 Chico Nitrate Wells Selected to Monitor the Shallow Alluvial Aquifer Two dedicated monitoring wells measured for the Chico Nitrate Compliance Program are selected based on location and length of historical data record to provide groundwater level data for the shallow alluvial aquifer. DMW-10 is north of Lindo Channel and has a well depth of 39 feet. 2-S1 is north of Big Chico Creek and has a well depth of 25 feet. Well data is obtained from the Chico Nitrate Compliance Program. Stakeholders recommend that a monitoring well near Little Chico Creek also be included. Chico Urban Area 2016 BMO 18

66 Chico Urban Area 2016 BMO 19

67 Chico Urban SIU Stakeholder Issues and Recommendations 1. Land Use Changes County service areas formerly with onsite sanitary septic systems are now connected to the City of Chico sanitary sewer system which conveys wastewater to the Chico Water Pollution Control Plant on the far west side of Chico. This change removed any appreciable recharge that occurred from the septic systems. 2. Monitoring the Alluvial Aquifer - Local stakeholders strongly recommend that the monitoring network include wells to monitor groundwater conditions in the shallow (alluvial) aquifer. A suggestion was made that several domestic wells could be added to the existing monitoring well network within the sub-inventory unit to allow development of management objectives for the alluvial aquifer system. Butte County staff is partnering with CSU Chico and the SIU representative to survey existing compliance monitoring wells by other entities to identify if any may be appropriate to add to the BMO monitoring network. In 2015, two nitrate compliance monitoring wells were added to the report. Additional existing monitoring wells could be added in the future. 3. Water Conservation Efforts On April 1, 2015, by Executive Order, the Governor required a statewide 25% reduction in potable urban water usage through February 28, Each urban area was given a target percent reduction by the State Board compared to the amount used in Chico s target percent is 32%. Residents have responded with water saving actions and have reduced their per capita use to gallons per day with a cumulative reduction since June 1 of 39.5% (as of September). In 2009, the California Legislature passed a law ( 20 by 2020 ) requiring water purveyors to reach a 20 percent reduction in per-person water use by the year The law included an interim required reduction of 10 percent by The To encourage its customers to conserve, the California Public Utilities Commission approved Cal Water s request for a tiered rate structure, which means when one uses above a certain threshold they pay more per unit of water. In addition, Cal Water s many drought related education and outreach efforts have focused on water conservation. Cal Water s demonstration conservation garden with drought-tolerant plants has been located at the southeast corner of Sheridan and East First Avenues since Cal Water s single-family residential customers can get a free conservation kit featuring a range of water saving plumbing retrofit fixtures including a high efficiency showerhead, hose nozzle, faucet aerators and toilet leak tablets. Commercial and residential Cal Water customers can also access conservation rebates and programs including free irrigation sprinkler nozzles, and rebates on a smart irrigation controller, on a high efficiency clothes washer and on high efficiency toilets. As a result, customers within the CalWater Chico service area have already exceeded water Chico Urban Area 2016 BMO 20

68 conservation targets: The per capita water demand of 224 gallons per capita per day (gpcd) in 2013 was 21.7 percent less compared to the baseline of 286 gpcd. Information about the rebates and programs for CalWater customers is accessible at 4. Urban Water Management Plan The California Water Code requires all urban water suppliers that provide water for municipal purposes either directly or indirectly to more than 3,000 customers (or supply more than 3,000 acre feet of water annually) to prepare Urban Water Management Plans (UWMP) at least every five years. On June 24, 2011 the California Water Service Company submitted to California Department of Water Resources the final version of its UWMP. The UWMP is a foundation document and source of information for a Water Supply Assessment and Written Verification of Water Supply. The UWMP also serves as: a long-range planning document for water supply; source of data for development of a regional water plan; source document for cities and counties as they prepare their General Plans; and key component to Integrated Regional Water Management Plans. The UWMP for the Chico District of California Water Service Company is available for review online at: The 2015 UWMP is under development and will be finalized in June Water Quality Although not specifically a component of the BMO program, the Chico Urban Area Sub-inventory Unit stakeholders have expressed an interest in groundwater contamination from toxins. Significant groundwater quality monitoring by multiple agencies is ongoing within the Chico Urban Area to track nitrate contamination and toxic plumes, including the Butte County Nitrate Compliance Program and the Department of Toxic Substances Control program for monitoring toxic chlorinated solvent plumes. California Water Service Company monitors water quality constituents important for drinking water supply for all of its water supply wells. Nitrate Compliance Monitoring The Butte County Environmental Health Division of the Public Health Department contracts to perform groundwater monitoring for the Chico Urban Area Nitrate Compliance Program. The nitrate compliance monitoring program has been prepared in response to the contamination of groundwater in the Chico Urban Area by nitrate, a form of nitrogen. The discharge from individual septic systems has been cited by the Central Valley Regional Water Quality Control Board as the primary source of groundwater nitrate contamination that exceeds drinking water standards set by the US EPA and the State Water Resources Control Board. Nitrate levels that exceed the standard have been established as a threat to public health and is subject to regulation. All monitoring reports associated with the Nitrate Chico Urban Area 2016 BMO 21

69 Compliance Program are available for public review at the Chico Branch of the Butte County Public Library and from the County s website, Volatile Organic Chemical Monitoring - The California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) is continuing its efforts to protect public health and oversee characterization and remediation of chlorinated solvents contamination in Chico Groundwater. The Chico Branch of the Butte County Library is the local information repository for investigation reports, monitoring reports and related documents. There are eight toxic chlorinated solvent plumes in the Chico area with the northernmost plume near the Chico airport and the southernmost plume near Hegan Lane and the Midway. DTSC is responsible for oversight of remediation activities at all eight plumes in the Chico area. One DTSC oversight program involves the Skyway Subdivision Groundwater Plume. Chlorinated solvents contamination of groundwater in the Skyway Homes Subdivision area of south Chico was discovered in November DTSC has determined that the most likely source of the contamination was the former CE Building Products operation on Speedway Avenue. ABB Inc., which purchased the parent company of CE Building Products in 1990, has been identified as a Responsible Party for investigating and cleaning up the Skyway Plume. ABB is cooperating fully with DTSC in investigating the contamination, and has agreed to fund connection of homes and other buildings within the affected area to the California Water Service Company public water system. Extension of the water main was completed by January Fact Sheets and other documents for the Skyway Subdivision Groundwater Plume are available at Another DTSC oversight program involves remediation of contamination in intermediate and deep zone aquifers in the central Chico area known as the Central Plume. Since July 1995 more than 1300 pounds of VOCs have been removed from the aquifers. A Remedial Action Plan (RAP) for the Central Plume was finalized in June 2007, to address a hot spot of contamination discovered in early The RAP provided for installation of three additional shallow zone aquifer (SZA) extraction wells and one monitoring well which have been installed. Source area in-situ chemical oxidation by injection of potassium permanganate has recently been implemented. The most recent fact sheets and reports for the Chico Groundwater Central Plume are available at cmd=community_involvement Additional documents related to the Central Plume are available at Chico Urban Area 2016 BMO 22

70 6. Monitoring of Stream and Vegetation Chico Urban Area stakeholders expressed an interest to maintain groundwater levels adequate to sustain the quality of the area streams and the groundwater dependent vegetation. There is not, however, adequate research available to determine what those adequate levels are. The current BMO provides information about the quantity of groundwater as compared to previous years, but does not assess the status of the streams or of the groundwater dependent vegetation. There are some data available to measure stream quantity. DWR maintains streamflow information on both Big and Little Chico Creek. ( Big Chico Creek Watershed Alliance Stream Team Project collects stream flow and stream quality data for Big Chico Creek. These data have not, however, been correlated to the groundwater measurements developed for the BMO. There is no assessment of the relation of the two sets. The relationship between streamflow and groundwater needs much study. Although surface water and groundwater appear to be two distinct sources of water, they are not. Surface water and groundwater are basically one singular source of water connected physically in the hydrologic cycle ( m). Stakeholders suggest that piezometers could be used to measure depth to groundwater. Piezometers are inexpensive to purchase, use, and maintain and could be installed along all Chico Urban Area creeks. In fact, many piezometers have been installed at various locations bordering Big Chico Creek on the CSU, Chico campus center. Data have been recorded for many years. There should be an effort to correlate existing groundwater level data to existing piezometer data. Such an undertaking to correlate with BMOs and its cost effectiveness will need to be evaluated by the Technical Advisory Committee. Butte County has developed an Environmental Monitoring Plan as a component of the Integrated Water and Resources Plan. The funding to implement the Environmental Monitoring Plan has not been secured. The links to these documents are available on the department s website. Of further interest is the health of the flora and fauna dependent on stream flow and groundwater, particularly Quercus Lobata or Valley Oak. The methodology used to measure the health of orchard trees could be used to assess oak and sycamores. Tensiometers could be used to measure the soil moisture around oaks. Sycamore twig die off in August can be measured. The quality of the oak crowns can be observed. The pre-dawn xylem sap tension can be measured during the dry season using a pressure chamber device. Trees near flowing streams are measured to identify a healthy xylem sap tension. Trees distant from Chico Urban Area 2016 BMO 23

71 streams are measured to monitor connectivity with groundwater. All of these observations and data can be correlated to the BMO measurements. If further study is made of the relationship of groundwater quantity and quality to the health of the BMO Area environment, the objective of maintaining the health of the Chico Urban Area streams and their dependent flora and fauna can be met. These goals can be met if outreach is made to other resources in the Chico Urban Area. The City of Chico Urban Forester and the CSU, Chico Biology Department could be particularly helpful. It is the intention of the stakeholders of the Chico Urban Area SIU that all possible resources be used to further the study of the relationship of groundwater to our environment. 7. Monitoring of Conjunctive Use Projects Stakeholders expressed an interest in the need to monitor conjunctive water management projects that might have the potential to affect Chico urban area groundwater levels. 8. Fracking of Gas and Petroleum Wells- Stakeholders expressed interest in being updated about whether hydraulic fracturing ( Fracking ) of natural gas and petroleum wells is occurring in the region and the potential impact to Butte County groundwater resources. Chico Urban Area 2016 BMO 24

72 APPENDED DOCUMENTS FOR THE CHICO URBAN AREA BMO Some Key Dates in the Butte County Nitrate Compliance Plan: High groundwater nitrate concentrations discovered in area wells in the Chico Urban Area (see Chapter 1 & Chapter 2, Nitrate Compliance Plan) 1985/86 - Original scoping of nitrate problems by DWR and development of initial monitoring report County Service Area 114 (CSA 114) formed by the Butte County Board of Supervisors to fund technical studies and groundwater evaluations Prohibition Order No adopted by the Regional Water Quality Control Board (Redding) Initial characterization of 119 wells Nitrate study team assembled, representatives from: Butte County Admin Office (BCAO), Butte County Environmental Health, RWQCB, independent hydro-geologists, Dames & Moore (BCAO s consultant), and professors from UC Davis and CSU-Chico for peer review Groundwater Nitrate Study - Chico Urban Area Final Report (Dames & Moore) Technical Memorandum - Hydrologic and Soils Conditions (Dames & Moore) 1997/ Preparation of Chico Urban Area Nitrate Compliance Plan by Butte County and the Citizens Nitrate Advisory Committee Chico Urban Area Nitrate Compliance Plan adopted by the Butte County Board of Supervisors. Presented to the City of Chico, to the RWQCB-Redding, and the Central Valley RWQCB (Sacramento) as the County s official response to Prohibition Order Butte County continues to be on the list for State Revolving Fund (SRF) Loan application funding through the State Water Resources Control Board East Lassen Avenue sewer installed. Casa de Flores Mobile Home Park (300 units) and other high-density developments started connecting to sewer Draft and Final EIR for the Chico Urban Area Nitrate Compliance Plan Butte County receives Small Communities Grant from the SWRCB to do initial sewer feasibility study for connecting low income mobile home parks (located north of Eaton Rd) to sewer 2004/05 - Oversight monitoring program initiated by Butte County Environmental Health for units within CSA 114 that are proposed to remain on septic systems. New groundwater nitrate monitoring wells installed to replace lost/destroyed monitoring sites. Most recent sampling event conducted by Hanover Environmental Butte County and City of Chico Redevelopment Agency execute the Chico Urban Area Joint Powers Financing Authority (JPFA) to facilitate the financing for sewer construction 2006/07 - JPFA develops financial loan application for sewer construction. Several of the reports mentioned above are located in the public reserve section of the Chico Public Library, or the Meriam Library, Special Collections Section at CSU-Chico. Also, view the Chico Urban Area Nitrate Compliance Plan at Select Administration from the dropdown menu and then Chico Nitrate Compliance Program from the menu on the left. Chico Urban Area 2016 BMO 25

73 BASIN MANAGEMENT OBJECTIVES DURHAM DAYTON SUBINVENTORY UNIT Butte County Water Advisory Committee Member Fred Montgomery Contact Information Phone Number: Address: Description of the Durham Dayton Sub-Inventory Unit The Durham Dayton Sub-Inventory Unit (SIU) covers an area of about 40,000 acres in the heart of the West Butte Inventory Unit. It is bordered by Big Chico Creek to the north, Butte Creek and the Western Canal SUI to the south, foothills to the east, and the M&T and Llano Seco SIUs to the west. In a normal year, 67% of the Durham Dayton SIU in summer agricultural production is supported by groundwater. In addition, 18% of the SIU is within the California Water Service Company area and uses groundwater as a municipal water source. Management Objective To maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply and to insure that spring groundwater elevations return to historical levels. It is the intent of this management objective to assure a sustainable agricultural supply of good quality water now and into the future, and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. The management objective is also to assure an adequate groundwater supply of adequate quality from the alluvial aquifer system for all domestic users in the SIU. Current Conditions- Groundwater levels are dropping during these extreme drought years resulting in dropping pressures in wells in the sub-unit. More farmers have installed soil moisture monitors and other technologies to more closely manage water applications. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Durham Dayton SIU, from youngest (shallowest) to oldest (deepest), include: Basin Deposits Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Durham Dayton SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Durham Dayton 2016 BMO 1

74 BMO Key Wells Selected for Groundwater Level Monitoring SPRING Well ID First Record Aquifer System Well Type Spring Stage 1 Alert Elev. (ft) Spring Stage 2 Alert Elev. (ft) 20N01E10C002M 1947 Basin Deposits Irrigation N02E06Q001M 1947 Basin Deposits Irrigation N01E10B003M 1995 Upper Tuscan Irrigation N01E25K001M 1993 Modesto Domestic N01E26K001M 1993 Upper Tuscan Irrigation N01E27D001M 1946 Modesto Domestic N02E07C001M 1967 Upper Tuscan Irrigation N02E30L001M 1995 Lower Tuscan Domestic FALL Well ID First Record Aquifer System Well Type Fall Stage 1 Alert Elev. (ft) Fall Stage 2 Alert Elev. (ft) 20N01E10C002M 1947 Basin Deposits Irrigation N02E06Q001M 1947 Basin Deposits Irrigation N01E10B003M 1995 Upper Tuscan Irrigation N01E25K001M 1993 Modesto Domestic N01E26K001M 1993 Upper Tuscan Irrigation N01E27D001M 1946 Modesto Domestic N02E07C001M 1967 Upper Tuscan Irrigation N02E30L001M 1995 Lower Tuscan Domestic Additional monitoring wells have been added to the monitoring network in the Durham Dayton SIU. They are included in the data summary spreadsheets and hydrographs are provided in this report. However, a BMO has not yet been established for these wells since their period of record is not yet long enough for analysis. Well ID First Aquifer Record System Well Type 20N01E02H003M 2001 Unknown Monitoring 21N01E13L002M 2012 Lower Tuscan Monitoring 21N01E13L003M 2012 Lower Tuscan Monitoring 21N01E13L004M 2012 Upper Tuscan Monitoring 21N02E18C001M 2010 Unknown Monitoring 21N02E18C002M 2010 Unknown Monitoring 21N02E18C003M 2010 Unknown Monitoring BMO Key Wells Selected for Groundwater Quality Monitoring State Well Number Annual Groundwater Temperature Measurement ( o C) N01E15E02M NM 19.3 NM NM Durham Dayton 2016 BMO 2

75 State Well Number Annual Groundwater ph Measurement N01E15E02M NM 7.54 NM NM 7.49 NM 7.5 State Well Number Annual Groundwater Electrical Conductivity Measurement (microsiemens/cm) N01E15E02M NM 327 NM NM BMO Key Well(s) Selected for Land Subsidence Monitoring Land subsidence will be monitored at the closest extensometers located in the Western Canal sub-inventory unit. Maximum annual inelastic land subsidence shall not exceed 0.01 feet per year. Future Monitoring Recommendations Possibly secure funding for the installation of an extensometer to monitor land subsidence in the Durham Dayton Sub-Inventory Unit. Explore options for installing multi-completion monitoring wells to more accurately measure aquifer-specific water quality and levels. Supporting Data Hydrographs, on the following pages, depict yearly spring and fall groundwater level measurements with established alert levels. QM Questionable Measurement Note: In 2014 and 2015 monthly measurements were taken. The first of the two measurements (March) should be considered the BMO level. Durham Dayton 2016 BMO 3

76 20N02E06Q001M 20N02E06Q001M has long been a Key Well in the Butte Basin Groundwater Users Annual report and is also a BMO well. The figure below is a hydrograph for well 20N02E06Q001M, located about two miles south of Durham. This area marks a change in agricultural water uses from groundwater to the north and surface water use to the south. The well is a deep irrigation well with shallow casing, and a groundwater level measurement record dating back to Groundwater levels in this well represent a mixture of the unconfined and confined portions of the aquifer system. The groundwater levels were monitored on a semi-annual basis until 1991, on a monthly basis from 1991 to about Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly April through October due to drought conditions. The figure shows a seasonal fluctuation (spring to fall) in groundwater levels of about 10 to 15 feet during years of normal precipitation and less than 5 feet during years of drought. Long-term comparison of spring-to-spring groundwater levels shows a decline of approximately 15 feet associated with the , and 1994 drought periods. Water levels have dropped below previous historical lows during the past couple years of severe drought. Water elevations have been monitored since 1947 at this location and the historical average depth to water, including 2015 data, is approximately 12.5 feet in the spring and 20.6 feet in the fall. However, over the past decade, the depth to groundwater has declined by about 14 feet. In 2015, groundwater level measurements occurred on a monthly basis through the summer. The March and April measurements are both about 28 feet below ground surface and plot on top of each other in the graph. The March measurement is considered the Spring BMO level. Durham Dayton 2016 BMO 4

77 Durham Dayton 2016 BMO 5

78 20N01E10C002 Durham Dayton 2016 BMO 6

79 21N01E10B003 Durham Dayton 2016 BMO 7

80 21N01E25K001 Durham Dayton 2016 BMO 8

81 21N01E26K001 Durham Dayton 2016 BMO 9

82 21N01E27D001 Durham Dayton 2016 BMO 10

83 21N02E07C001 Durham Dayton 2016 BMO 11

84 21N02E30L001 Durham Dayton 2016 BMO 12

85 21N02E18C *Note all data including summer measurements shown, beginning in summer 2010 Durham Dayton 2016 BMO 13

86 21N01E13L002-4 *Note measurements began in 2012 Durham Dayton 2016 BMO 14

87 Durham Dayton 2016 BMO 15

88 20N01E02H003 * Note measurements began in 2001 Durham Dayton 2016 BMO 16

89 BASIN MANAGEMENT OBJECTIVES ESQUON SUBINVENTORY UNIT Butte County Water Advisory Committee Member Rick Ponciano Contact Information Phone Number: (530) Address: Description of the Esquon Sub-Inventory Unit The Esquon Sub-Inventory Unit (SIU) covers an area of about 11,600 acres in the northern portion of the East Butte Inventory Unit. It is bordered by the Pentz SIU to the north, Western Canal SIU to the south, Cherokee SIU to the east, and Durham Dayton to the west. The Esquon SIU almost corresponds to the water service areas associated with the Durham Mutual Water Company. Agricultural land use within the SIU includes production of orchards, rice, and grain crops supported by both surface water and groundwater. In a normal year, about 27% of the Esquon SIU is in summer agricultural production supported by groundwater. Butte Creek supports a generally declining population of spring run Chinook salmon. In 1998, Rancho Esquon worked with Ducks Unlimited to install a state of the art fish ladder and screen on an existing diversion. This project was designed according to California Department of Fish and Game standards to help with the passage of spring run Chinook salmon. The biological benefits of the project are improved passage of juvenile and adult fish, and a curtailment of juvenile fish in the diversion. The water from the Rancho Esquon diversion supplies water to the orchards, rice and state, federal and private wetlands within the Esquon sub-inventory unit. The water diverted from Butte Creek is believed to help recharge groundwater in the Durham/Nelson area according to the Department of Water Resources, Northern District. Current Conditions Rancho Esquon fallowed approximately 800 acres in 2014 and is converting 700 acres of rice into almonds in 2015 and Land use changes primarily involve orchards with approximately 900 acres of additional almonds and walnuts. Rancho Esquon continuously updates their wells with variable speed drives and moisture probes in all their orchards and other areas to support precise irrigation. Interactions with stakeholders in the sub-unit occurs throughout the year. From these interactions, we are aware of approximately three ag wells that ran out of water in June and July of Management Objective To maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply. It is the intent of this management objective to assure a sustainable agricultural supply of good quality water now and into the future, and to assure the water supply can be utilized without injuring groundwater quality or inducing land Esquon 2016 BMO 1

90 subsidence. The management objective is also to assure an adequate groundwater supply of adequate quality from the alluvial aquifer system for all domestic users in the SIU. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Esquon SIU, from youngest (shallowest) to oldest (deepest), include: Basin Deposits Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Esquon SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring SPRING Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N02E09G01M 2001 Lower Tuscan Monitoring N02E09L01M 1953 Lower Tuscan Irrigation N02E20P01M 1995 Upper Tuscan Irrigation FALL Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N02E09G01M 2001 Lower Tuscan Monitoring N02E09L01M 1953 Lower Tuscan Irrigation N02E20P01M 1995 Upper Tuscan Irrigation An additional domestic well (SWN 20N02E08H03) was added to the DWR monitoring network in the Esquon Sub-Inventory Unit in Its hydrograph is included in this report although the period of record is not yet long enough to establish a BMO for it. BMO Key Wells Selected for Groundwater Quality Monitoring State Well Number Annual Groundwater Temperature (degrees Celsius) N02E09M02M Esquon 2016 BMO 2

91 State Well Number Annual Groundwater ph N02E09M02M State Well Number Annual Groundwater Electrical Conductivity (microsiemens/cm) N02E09M02M BMO Key Well(s) Selected for Land Subsidence Monitoring State Well Number 20N01E18L001M located in the Western Canal Water District. Subinventory Issues and Recommendations Monitoring Recommendation - Continue to explore options for installing multi-completion monitoring wells to more accurately measure aquifer specific water quality and levels. Supporting Data Hydrographs depicting yearly spring and fall level measurements with established alert levels. QM Questionable Measurement Note: In 2014 and 2015 monthly measurements were taken. measurements (March) should be considered the BMO level. The first of the two Esquon 2016 BMO 3

92 20N02E09G001M Esquon 2016 BMO 4

93 20N02E09L001M This well has long been a Key Well highlighted in the Butte Basin Groundwater Users Association Annual report. 20N02E09L001M is an active irrigation well, in the southern portion of the Esquon SIU. The area surrounding the well consists primarily of rice production using both surface and groundwater. The well is a deep irrigation well with shallow casing, and a groundwater level measurement record dating back to the 1950s. Groundwater levels in this well represent a mixture of the unconfined and confined portions of the aquifer system. The groundwater levels in this well were monitored on a semi-annual basis until 1991, and on a monthly basis from 1991 to about Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly, April through October, due to drought conditions. The figure shows that the historical spring to fall fluctuation in groundwater levels ranges 3 to 8 feet during years of normal precipitation and drought periods. Long-term comparison of spring-to-spring groundwater levels shows about a 10 foot decline in groundwater levels associated with the drought, followed by a similar decline between 1990 and 1994, perhaps associated with the and 1994 drought periods. The last few years show another drought related decline in elevations. Although groundwater levels in this well recovered from the drought to groundwater levels similar to those of the early 1980s, they have declined about 16 feet since the late 1950s compared to the last several years. The last several years of severe drought have resulted in dropping spring levels each year. Water elevations have been monitored since 1953 at this location and the historical average depth to water, including 2015 data, is approximately 9.8 feet in the spring and 17.3 feet in the fall below ground surface. Hydrographs of spring and fall groundwater levels are on the following page. Esquon 2016 BMO 5

94 Esquon 2016 BMO 6

95 21N02E20P001M Esquon 2016 BMO 7

96 20N02E08H003 This is a domestic well added to the network in BMOs have not yet been established for this well due to its short record. Esquon 2016 BMO 8

97 BASIN MANAGEMENT OBJECTIVES LLANO SECO SUBINVENTORY UNIT Butte County Water Advisory Committee Member Nickie Hughes Contact Information Phone Number: Address: Description of the Llano Seco Sub-Inventory Unit The Llano Seco Sub-Inventory Unit (SIU) covers an area of about 18,400 acres in the southwestern portion of the West Butte Inventory Unit. It is bordered by the M&T and Angel Slough SIUs to the north, Durham Dayton and Western Canal SIUs to the east, Glenn County to the south, and the Sacramento River to the west. This SIU corresponds roughly to the water service area associated with Rancho Llano Seco. Land uses within the Llano Seco SIU consist of a mixture of row crops, grain, pasture and native riparian supported by both surface water and groundwater. In a normal year, about 6% of the Llano Seco SIU is in summer agricultural production supported by groundwater. Current Conditions Expansion of orchard acreage is expected in the coming years, served by a mix of existing wells and a new well. In 2010, a field previously used for dry land grazing was converted to irrigated pasture using surface water. In 2013, 300 acres of walnuts were planted and used groundwater to irrigate (using one well in 2014 and two wells in 2015). In 2016 another 440 acres of almonds will be planted also using groundwater and a couple of existing wells, one of which has not been used for a long time. The new almond orchard will be irrigated using drip tape. Management Objective Observe and maintain the current and future groundwater surface elevation at a level which will provide an economical and adequate water supply to this area s crops and homes. This basin management objective is intended to be flexible to future land and water uses in this relatively undeveloped portion of Butte County. We began monitoring a well, located fairly close to the Sacramento River for water levels and water quality in 2008 which should give us an even better understanding of groundwater levels and quality in this area of Butte County. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Llano Seco SIU, from youngest (shallowest) to oldest (deepest), include: Quaternary Alluvium Basin Deposits Tehama Formation Tuscan Unit C (Upper Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Llano Seco 2016 BMO 1

98 Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Llano Seco SIU are: Tehama Formation Tuscan Unit C (Upper Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring Alert levels are calculated using the standardized historic range method defined in Chapter 33A. SPRING Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N01E18L01M 2000 Lower Tuscan Monitoring N01E18L02M 2001 Upper Tuscan Monitoring N01E18L03M 2001 Alluvial Monitoring N01W35K02M 1994 Alluvial Irrigation FALL Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N01E18L01M 2000 Lower Tuscan Monitoring N01E18L02M 2001 Upper Tuscan Monitoring N01E18L03M 2001 Alluvial Monitoring N01W35K02M 1994 Alluvial Irrigation Well ID Aquifer System Well Type Total Depth (ft) Top Perf (ft) Bottom Perf (ft) Geologic Formation at Top Perf. Geologic Formation at Bottom Perf. Aquifer Type 20N01E18L01M 20N01E18L02M Lower Tuscan Upper Tuscan Monitoring Tuscan B Tuscan B Confined Monitoring Tuscan C Tuscan C Confined 20N01E18L03M Alluvial Monitoring N01W35K02M Alluvial Irrigation Basin Deposits/ Tuscan C Basin Deposits Tuscan C Tuscan C Semi- Confined Semi- Confined Additional monitoring wells have been added to the monitoring network in the Llano Seco SIU. They are included in the data summary spreadsheets and hydrographs are provided in this report. However, a BMO has not yet been established for these wells since their period of record is not yet long enough for analysis. Well ID First Aquifer Record System Well Type Well Depth 20N01W04J01M 2008 Unassigned Irrigation Shallow 20N01W11N02M 2008 Unassigned Irrigation Shallow Llano Seco 2016 BMO 2

99 Electrical Conductivity (µs) ph BMO Key Wells Selected for Groundwater Quality Monitoring Butte County Department of Water and Resource staff began sampling ph, temperature and EC on a well located in the Llano Seco SIU beginning in State Well Number Annual Groundwater Temperature Measurement ( o C) Unknown Annual Groundwater ph Measurement State Well Number Unknown State Well Number Annual Groundwater Electrical Conductivity Measurement (microsiemens/cm) Unknown Llano Seco EC=700 ph= ph= Year EC ph BMO Key Well(s) Selected for Land Subsidence Monitoring Land subsidence is continuously monitored by the Department of Water Resources and Butte County Water and Resource Conservation at the closest extensometer in the Western Canal Water District. Stakeholder Interaction Llano Seco interacts with its neighbors regarding pertinent water issues as they come up and we are always available to discuss issues that reach beyond the borders of the Llano Seco SIU. Llano Seco is working with M&T regarding surface water issues. Llano Seco 2016 BMO 3

100 Future Monitoring Recommendations None at this time. Supporting Data Hydrographs on the following pages depict yearly spring and fall level measurements with established alert levels. QM Questionable Measurement Llano Seco 2016 BMO 4

101 20N01E18L001 Llano Seco 2016 BMO 5

102 20N01E18L002 Well 20N01E18L002M was chosen to replace the original key well (formerly highlighted in the Butte Basin Water Users annual report) in the Llano Seco SIU. This new well is part of a dedicated, multi-completion monitoring well set that was installed in The well is along the eastern margin of the sub-area, due east from the original key well. Measurements in this well represent groundwater conditions between feet in the confined portion of the Upper Tuscan aquifer system. This well data is also utilized by both the Llano Seco and the Western Canal SIUs in the annual BMO document (although their alert stages are different as they use different methods for establishing the alert level). Water elevations have been monitored since 2001 at this location and the historical average depth to water, including 2015 data, is approximately 4 feet in the spring and approximately 7.5 feet in the fall feet below ground surface. The limited period of record for this well makes trend analysis difficult, but the available data does show a slight decline during recent drought years. Llano Seco 2016 BMO 6

103 20N01E18L003 Llano Seco 2016 BMO 7

104 21N01W35K002 Llano Seco 2016 BMO 8

105 20N01W04J001M For information only, no alert stage 20N01W11N002M For information only, no alert stage Llano Seco 2016 BMO 9

106 20N01W26H002M For historic purposes, information is presented on previous monitoring activities at well 20N01W26H002M. The figure below is a hydrograph for well 20N01W26H002M, located in the southern portion of the Llano Seco SIU. The area surrounding this well is characterized by rural agricultural land use, supported primarily by the application of surface water. This well is an unused irrigation well constructed in the unconfined portion of the aquifer system, with a groundwater level measurement record dating back to the early 1940s. The groundwater levels in this well were monitored on a semi-annual basis until 1991 and on a monthly basis from 1991 to about 1994, when monitoring of this well was discontinued. The figure shows that the average seasonal fluctuation (spring to fall) in groundwater levels was about 1 to 5 feet during normal and drought years. Long-term comparison of spring-tospring groundwater levels show little, if any, decline in groundwater levels associated with the , and 1994 drought periods. Overall comparison of spring-to-spring groundwater levels from 1976 to 1993 showed very little change in the unconfined aquifer system within this portion of the Llano Seco SIU. Groundwater level monitoring was discontinued in this well in Llano Seco 2016 BMO 10

107 BASIN MANAGEMENT OBJECTIVES M & T SUBINVENTORY UNIT Butte County Water Advisory Committee Member Lee Heringer Contact Information Phone Number: (530) Address: leeheringer@gmail.com Description of the M&T Sub-Inventory Unit The M&T Sub-Inventory Unit (SIU) covers an area of about 8,200 acres in the northwestern portion of the West Butte Inventory Unit. It is bordered by Big Chico Creek to the north, the Llano Seco and Durham Dayton SIUs to the south and east, and the Sacramento River and Angel Slough SIU to the west. The M&T SIU corresponds roughly to the water service area of the M&T Chico Ranch. Agricultural land use includes orchards, rice, and row crops supported by groundwater and surface water. In a normal year, about 27% of the M&T SIU is in summer agricultural production supported by groundwater. The M&T Ranch, located within the SIU, gets its surface water from two different sources. The Ranch diverts water out of Butte Creek east of Chico and allows it to flow down Edgar Slough/Comanche Creek where it runs through south Chico and then west to the Ranch. Once it reaches the Ranch, it then flows south to the Llano Seco Ranch. The Butte Creek diversion supplies water to the M&T Ranch, the Llano Seco Ranch, and Dayton Mutual. The diverted Butte Creek water, according to the California Department of Water Resources, helps recharge the groundwater in south Chico, the Hegan Road area, and the Stanley Avenue/Rodgers Road area. The M&T Ranch and the Llano Seco Ranch also jointly own a pumping plant on the Sacramento River, west of Chico. This surface water source helps supply the irrigation water needs for orchards, row crops, rice and federal, state and private wetlands. This river water also helps recharge the groundwater in the Ord Ferry Road, Seven Mile Lane and Dayton West Road area. The northeast part of the ranch, just south of Big Chico Creek, is primarily orchards and is supplied solely by groundwater. Our groundwater and surface water supplies are all an integral part of the M&T Ranch and provide us with vital irrigation water supplies. Management Objective To maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply. It is the intent of this management objective to assure a sustainable agricultural supply of good quality water now and into the future, and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. The management objective is also to assure an adequate groundwater supply of adequate quality from the alluvial aquifer system for all domestic users in the sub-inventory unit. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the M&T SIU, from youngest (shallowest) to oldest (deepest) include: Quaternary Alluvium Basin Deposits Modesto Formation M&T 2016 BMO 1

108 Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the M&T SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring Until 2009, M&T SIU used the specific depth method to determine the BMOs. In 2009, M&T began utilizing the standard historic range methodology described in Butte County Code, Chapter 33A. SPRING Well ID First Aquifer Spring Stage 1 Spring Stage 2 Well Type Record System Alert (ft) Alert (ft) 21N01W24B001M 1995 Lower Tuscan (B) Monitoring N01E29R001M 1947 Upper Tuscan (C) Irrigation N01E32E004M 1992 Modesto Formation Domestic FALL Well ID First Aquifer Fall Stage 1 Fall Stage 2 Well Type Record System Alert (ft) Alert (ft) 21N01W24B001M 1995 Lower Tuscan (B) Monitoring N01E29R001M 1947 Upper Tuscan (C) Irrigation N01E32E004M 1992 Modesto Formation Domestic Note: A multi-completion well, 21N01W11A , was added to the network in 2010 and another one, 21N01E13J001-3, was added in These wells are not assigned alert stages because of their short period of record. BMO Key Wells Selected for Groundwater Quality Monitoring State Well Number Annual Groundwater Temperature Measurement ( o C) N01E15D02M NM NM 17.1 State Well Number Annual Groundwater ph Measurement N01E15D02M NM NM 7.4 M&T 2016 BMO 2

109 Electrical Conductivity (µs) ph State Well Number Annual Groundwater Electrical Conductivity Measurement (microsiemens/cm) N01E15D02M NM NM 362 M & T EC=700 ph= ph= Year EC ph BMO Key Well(s) Selected for Land Subsidence Monitoring Land Subsidence is continuously monitored by the Department of Water Resources and Butte County Department of Water and Resource Conservation from State Well number 21N01W24B01M, which is within this Sub-Inventory Unit. M&T SIU Stakeholder Issues and Recommendations Being that this is a rural SIU, it is hard to disseminate information. We do not have a town or community within our boundaries, so the readings gathered in our SIU are used both for monitoring purposes, and internally to make sure we have as little impact on groundwater levels as possible through responsible usage. In 2014 rice acreage was removed and converted to trees. Additionally, more rice ground was taken out of production in 2015 in preparation for a 2016 tree planting. Improvements have continued in irrigation efficiency on the ranch through the utilization of both plant and soil moisture monitoring to determine irrigation scheduling, as well as replacement of dated irrigation systems with modern, efficient, water saving systems. The NRCS annually performs an irrigation evaluation and we alter our irrigation model based on their findings. Due to drought conditions, there were some reports of neighboring landowners wells going dry and/or the need to lower bowls. In 2015 we decided to lower the bowls of numerous ranch wells after pump pressure issues arose in two of our wells. The problem seemed to be limited to very old wells, which were set much shallower than modern wells. Future Monitoring Recommendations Efforts will be made to identify any suitable domestic wells that could be added to the existing monitoring well network in the subinventory unit to allow development of management objectives for the alluvial aquifer system. Although not a domestic well, the multi-completion monitoring well, 21N01W11A , was added to the network in 2010 and has two of its three nested wells screened in the alluvial aquifer system (30-50 ft bgs and ft bgs) and is near the Sacramento River. M&T 2016 BMO 3

110 Supporting Data Hydrographs on the following pages depict yearly spring and fall groundwater level measurements with established alert levels. QM Questionable Measurement Note: In 2014 and 2015 monthly measurements were taken. The first of the two measurements (March) should be considered the BMO level. M&T 2016 BMO 4

111 21N01W24B001M M&T 2016 BMO 5

112 22N01E29R001M This well has long been a Key Well in the Butte Basin Water Users Annual Report and is also a BMO well. The figure on the following page is a hydrograph for well 22N01E29R001M, located just south of Big Chico Creek in the northern portion of the M&T SIU. The well is surrounded by agricultural orchard production, supported by groundwater extraction. This well is an inactive irrigation well of intermediate depth, with a groundwater level measurement record dating back to Groundwater levels in this well represent the confined portion of the aquifer. The groundwater levels in this well were monitored on a semi-annual basis until 1991, on a monthly basis from 1991 to about Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly April through October due to drought conditions. The figure shows that the average seasonal fluctuation (spring to fall) in groundwater levels is about 5 to 15 feet during years of normal precipitation and years of drought. Long-term comparison of spring-to-spring groundwater levels shows a decline of about 10 to 15 feet in groundwater levels associated with the drought, followed by a decline of about 15 to 20 feet associated with the and 1994 drought periods. Since the late 1990s after levels generally recovered, water levels have fallen about 30 feet. Overall, comparison of spring to spring groundwater levels associated with this confined portion of the aquifer system indicates that there was little change in spring groundwater levels until Although spring levels fell during the late 1990s and early 2000s, a wet 2006 returned the spring level to levels seen in the mid-1990s. Since then, severely dry years have caused water levels to fall below previously recorded lows. Water elevations have been monitored since 1947 at this location and the historical average of depth to water, including 2015 data, is about 20.6 feet in the spring and about 29.5 feet in the fall. M&T 2016 BMO 6

113 22N01E29R001 M&T 2016 BMO 7

114 22N01E32E004 M&T 2016 BMO 8

115 Groundwater Level Data without BMOs 21N01E13J001-3 *Note: multi-completion well added to network in 2012 M&T 2016 BMO 9

116 M&T 2016 BMO 10

117 21N01W11A001-3 *Note: multi-completion well added to network in 2010 M&T 2016 BMO 11

118 M&T 2016 BMO 12

119 BASIN MANAGEMENT OBJECTIVES NORTH YUBA SUBINVENTORY UNIT Butte County Water Advisory Committee Member Toni Ruggle Contact Information Phone Number: (530) Address: Description of the North Yuba Inventory Unit The North Yuba Inventory Unit (IU) covers about 47,500 acres in the southeastern portion of Butte County. It is bordered by the Feather River to the north and west, Yuba County to the south, and foothills to the east. In the northern portion of the IU, in areas surrounding Oroville, the land use is primarily urban. In the central and southern portions of the IU, the land uses are a mix of rural residential and agricultural. Agricultural land use is fairly diverse and consists of a combination of rice, orchards, grain, pasture, and field crops. The primary source of agricultural water in the North Yuba IU is groundwater. In a normal water year, about 25% of the North Yuba IU is in summer agricultural production supported by groundwater. Groundwater is also used as a municipal water source for portions of Oroville. The North Yuba IU is not divided into sub-inventory units. Current Conditions Cal Water s source of supply for Oroville residents is a combination of surface and well water. Cal Water has increased its use of surface water to serve its customers. Overall well levels continue to be healthy. In an effort to meet the Water Boards restrictions and reduction requirements, Cal Water put together its plan that was approved by the PUC. As a result customers have conserved (reduced) 28% through September 2015 as compared to They continue to reach out to customers with conservation programs that include rebates on high-efficiency toilets, clothes washers and smart irrigation controllers as well as free water saving devices for both indoor and outdoor use. A turf rebate program was rolled out this past summer for its customers. All of these rebates and programs are on their website; Cal Water made conservation/drought presentations to local schools, business groups and participated in conservation events in the area. Management Objective To maintain sufficient volumes of groundwater in storage within all aquifer systems to provide an adequate and affordable domestic water supply of adequate quality for consumption, including periods of extended drought and to assure that groundwater in storage is not depleted over time. It is the intent of this management objective to assure a sustainable domestic water supply now and into the future and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. The management objective is also to assure an adequate supply for groundwater from the Laguna Formation for all domestic users in the Inventory Unit. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the North Yuba Inventory Unit, from youngest (shallowest) to oldest (deepest), include: Quaternary Alluvium Modesto Formation North Yuba 2016 BMO 1

120 Riverbank Formation Laguna Formation Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the North Yuba Inventory Unit are: Modesto Formation Riverbank Formation Laguna Formation BMO Key Wells Selected for Groundwater Level Monitoring Cal Water wells used for groundwater level measurements within the California Water Service Company Oroville service area have been assigned arbitrary well numbers in the interest of security. The Alert Stages for wells CWS01, CWS02, CWS03 were calculated using the static water levels for the years 1980 through 2006, in the months of April and October. This information mirrors and reflects the historical data prior to SPRING Well ID First Aquifer Stage 1 Alerts Stage 2 Alerts Well Type Record System Elev. (ft) Depth (ft) Elev.(ft) Depth(ft) CWS Laguna Formation Domestic CWS Laguna Formation Domestic CWS Laguna Formation Domestic N03E03D Modesto Formation Irrigation N04E09N Laguna Formation Irrigation N04E22B Riverbank Formation Domestic N04E31F Laguna/Lower Tuscan Domestic FALL Aquifer System Stage 1 Alerts Elev. (ft) Depth (ft) Stage 2 Alerts Elev. (ft) Depth(ft) Well ID First Record Well Type CWS Laguna Formation Domestic CWS Laguna Formation Domestic CWS Laguna Formation Domestic N03E03D Modesto Formation Irrigation N04E09N Laguna Formation Irrigation N04E22B Riverbank Formation Domestic N04E31F Laguna/Lower Tuscan Domestic BMO Key Wells Selected for Groundwater Quality Monitoring In 2015 water quality samples were taken as per Environmental Protection Agency (EPA) and the State Water Resourced Control Board Division of Drinking Water guidelines and requirements for wells within the Cal Water service area. No water quality issues or violations were found. No wells solely measured for temperature, ph, and electrical conductivity by Butte County per Chapter 33A are located in the North Yuba IU. North Yuba 2016 BMO 2

121 BMO Key Well(s) Selected for Land Subsidence Monitoring Land Subsidence is continuously monitored by the Department of Water Resources and Butte County Water and Resource Conservation at the closest extensometers in the Western Canal Water District sub-inventory unit. Stakeholder Interaction Each year, California Water Service Company (Cal Water) conducts significant outreach to its customers and other stakeholders regarding water conservation. In light of the ongoing drought, Cal Water has rolled out a robust customer outreach plan, which builds on the customer communications we conduct every year, even when there is not a drought. Cal Water s outreach has included: Bill inserts Press releases Social media updates Print advertising Radio advertising Public service announcements A dedicated page on calwater.com about the drought Instructional videos Cal Water also has informational table tents for local restaurants to support requirements that they only serve water to customers upon request. Cal Water will be reaching out to targeted customers who use relatively large amounts of water, and has launched a new school education program designed to further encourage water conservation. Finally, Cal Water offers its customers a number of tools to help them manage their water use. These include everything from conservation kits that contain water-efficient plumbing fixtures to rebates on water-efficient appliances and devices. Future Monitoring Recommendations Work with staff to explore options for installing multi-completion monitoring wells to more accurately measure aquifer-specific water quality and levels as funding becomes available. Supporting Data Hydrographs depicting yearly spring and fall level measurements with established alert levels. QM Questionable Measurement North Yuba 2016 BMO 3

122 CWS-01 North Yuba 2016 BMO 4

123 CWS-02 North Yuba 2016 BMO 5

124 CWS-03 North Yuba 2016 BMO 6

125 17N03E03D001M This has long been a Key Well highlighted in the Butte Basin Water Users Annual report and is a BMO well. The figure on the following page is a hydrograph for well 17N03E03D001M, located in the western portion of the North Yuba sub-area. The area surrounding the well is characterized by rural, agricultural land use supported by the application of both surface and groundwater. The well is an active irrigation well drawing water from the upper and middle portions of the aquifer system, with a groundwater level measurement record dating back to late The groundwater level in this well was monitored on a semi-annual basis until 1991, on a monthly basis from 1991 to approximately Levels are typically monitored four times a year during March, July, August and October but in 2014 and 2015, levels were monitored monthly April through October due to drought conditions. The figure shows that the seasonal fluctuation (spring to fall) in groundwater levels is about 5 to 10 feet during years of average precipitation and less than 5 feet during years of drought. Long-term comparison of spring-to-spring groundwater levels shows about a 10-foot decline in spring groundwater levels associated with , and 1994 drought periods. Fall groundwater levels remain particularly consistent even during years of below average precipitation. This is likely due to the well s close proximity to the Feather River. Although spring groundwater levels have remained within feet of historical high levels, the majority of measurements in the past several years have been closer to historical lows. Water elevations have been monitored since 1947 at this location. The historical averages for depth to water, including 2015 data, are 21.7 feet in the spring and 25 feet in the fall below ground surface. North Yuba 2016 BMO 7

126 North Yuba 2016 BMO 8

127 17N04E09N002 North Yuba 2016 BMO 9

128 17N04E22B001 North Yuba 2016 BMO 10

129 19N04E31F001 North Yuba 2016 BMO 11

130 BASIN MANAGEMENT OBJECTIVES PENTZ SUBINVENTORY UNIT Butte County Water Advisory Committee Member Vacant Contact Information Phone Number: Address: Description of the Pentz Sub-Inventory Unit The Pentz Sub-Inventory Unit (SIU) covers an area of about 1,900 acres in the northern portion of the East Butte Inventory Unit. It is bordered by Butte Creek to the north, the North Fork of Dry Creek to the south, foothills to the east, and Highway 99 to the west. The land uses within this SIU are non-irrigated native vegetation, pasture, and low density residential. Current groundwater use in the Pentz SIU is minimal. Management Objective It is the intent of this objective to maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply, and to assure a sustainable agricultural supply of good quality water now and into the future. The management objective is also to assure an adequate groundwater supply of adequate quality from the alluvial aquifer system for all domestic users in the sub-inventory unit and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Pentz SIU, from youngest (shallowest) to oldest (deepest), include: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Pentz SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring The DWR completed installation of a multi-completion monitoring well, SWN 21N02E26E003-6 in September This well was constructed as a quadruple completion well, which means the borehole contains four casings isolated in separate geologic strata, allowing for monitoring of the groundwater levels contained in the respective aquifer systems. Dedicated monitoring wells are constructed specifically for measuring groundwater levels and groundwater will not be extracted from the newly installed monitoring well. The data set is not yet sufficient for establishing BMOs for these wells. Pentz 2016 BMO 1

131 Sub-Inventory Unit Additionally, five of the monitoring wells installed by Butte County Public Works at the Neal Road Recycling and Waste Facility have been selected for inclusion in this report. These are identified as MW-4, 4A, 6, 8B, 10 and 10A. Monitoring of groundwater is a regulatory requirement for operation of the waste facility. Groundwater is monitored quarterly at each of the waste facility s monitoring wells, and both level and quality measurements are taken. The monitoring wells are located within the waste facility property. A function of the monitoring wells is to calculate groundwater flow direction and velocity. The operation and monitoring of the wells located at the waste facility are under the direction of the Department of Public Works. Public Works staff will continue to provide groundwater elevation data, however, at this time BMOs have not been officially established for these wells. BMO Key Wells Selected for Groundwater Quality Monitoring When the Butte County Groundwater Trend Monitoring Program began, a well was sampled close to the border of the Pentz and Cherokee sub-inventory units. Groundwater was measured from this well from 2002 through In 2007, a new well was located and sampled approximately 2.4 miles from the Pentz-Butte Valley well. Data is presented for both of these wells. State Well Number Annual Groundwater Temperature Measurement ( o C) Pentz 21N03E29J03M Pentz-Butte Valley 21N03E26E01M Sub-Inventory Unit State Well Number Annual Groundwater ph Measurement Pentz 21N03E29J03M Pentz-Butte Valley 21N03E26E01M Sub-Inventory Unit Annual Groundwater Electrical Conductivity Measurement (microsiemens/cm) State Well Number Pentz 21N03E29J03M Pentz-Butte Valley 21N03E26E01M Pentz 2016 BMO 2

132 Electrical Conductivity (µs) ph Pentz EC=700 ph= Butte Valley Well- 26E01 Pentz Well- 29J ph= Year EC ph BMO Key Well(s) Selected for Land Subsidence Monitoring State Well Number 20N01E18L03M located in the Western Canal Water District. Maximum annual inelastic land subsidence shall not exceed 0.01 feet per year. BMO Alert Stage Definitions and Compliance Methodologies When enough years of data have been collected from the multi-completion monitoring well, the Pentz Sub-Inventory Unit will establish BMOs for those wells pursuant to the Basin Management Objective Ordinance. Future Monitoring Recommendations Efforts will be made to identify additional domestic wells that could be added to the existing monitoring well network in the sub-inventory unit to allow for development of additional management objectives for the alluvial aquifer system. Locate additional wells, either irrigation or domestic, with sufficient historical construction information to include in the water quality monitoring network, and initiate data collection in the future. Supporting Data Hydrographs depicting groundwater level measurements. Data from the Neal Road Landfill wells comes from the Third Quarter 2013 Monitoring Summary Report prepared for Butte County Department of Public Works by SCS Engineers. QM Questionable Measurement Pentz 2016 BMO 3

133 Multi-completion Monitoring Well: 26E Pentz 2016 BMO 4

134 Pentz 2016 BMO 5

135 21N02E26F001 This has long been a key well highlighted in the Butte Basin Water Users annual report. 21N02E26F001M is an irrigation well located just west of Highway 99E, near the intersection of Durham-Pentz Road and Oro-Chico Highway. Within a two-mile radius of the well, groundwater is used to support agricultural production of orchard and row crops, and smallscale industrial uses associated with a beverage distribution plant. The well is a deep irrigation well with shallow casing, and a groundwater level measurement record dating back to the late-1960s. Groundwater levels in this well represent a mixture of the unconfined and confined portions of the aquifer system. The groundwater levels in this well were monitored on a semi-annual basis (spring and fall) until 1991, on a monthly basis from 1991 to about 1994, and are then four times a year during March, July, August and October.. Measurements were discontinued at this location in spring The figure shows that the average seasonal fluctuation (spring to fall) in groundwater levels averages about 3 to 10 feet during years of normal precipitation and approximately 3 to 5 feet during years of drought. Long-term comparison of spring-to-spring groundwater levels shows a decline in groundwater levels during the period of , related, at least in part, to the drought. Since a groundwater elevation high of approximately 145 feet in 1985 the measured groundwater levels in this well have continued to decline. Recent groundwater level measurements indicate that the groundwater elevation in this well is approximately feet lower than the historical high in Water elevations have been monitored since 1967 at this location and the historical averages are; Spring=133 feet and Fall=126 feet. Since 1985 spring groundwater levels in this well have been declining and the spring 2008 measurement remained ten feet below historical high levels and more recent measurements continue the downward trend on the hydrograph. The long-term trend of decline observed in this well was such a point of concern it prompted the drilling of a new monitoring well to evaluate the potential causes for the decline. DWR installed a new dedicated monitoring well (21N02E26E03-6) near this existing key well in August Pentz 2016 BMO 6