B. Description of Proposed Boundary Modification

1. Short Description

   MSWD would like to have the Garnet Hill Subbasin be added as a Bulletin 118 Subbasin.
2. Type of basin boundary revision

   • Scientific Internal
3. Provide a narrative overview of the boundary modification request and how the resulting modification would affect likelihood of sustainable management.

   Currently, the Garnet Hill Subbasin is included within Whitewater (Indio) Subbasin (Basin No. 7-21.01). However, the Garnet Hill Subbasin area is located between the Garnet Hill Fault and the Banning Fault and is a distinct separate groundwater subbasin. Separation of the Garnet Hill Subbasin will prevent its management from being lumped into the much larger Indio Subbasin of significantly different character. Management of the Garnet Hill Subbasin is managed locally in collaboration with the management of the Mission Creek Subbasin.

   Attachment(s):
4. List the existing basin(s)/subbasin(s) to be modified by this request

   • 7-021.01 COACHELLA VALLEY - INDIO
5. Provide the proposed name for the new basin(s) or subbasin(s)

   Garnet Hill Subbasin

C. Initial Notification and Combination of Requests

1. Was an initial notification submitted to the Department?

   Yes
   List of submitted initial notification for the selected basin(s)/subbasin(s).

   Local Agency	Potential Basin(s)/Subbasin(s)
   Mission Springs Water District	7-021.01 COACHELLA VALLEY - INDIO

2. Does this application include a combination of requests?

   No

D. Required Documents for All Modifications

1. A copy of the statutory or other legal authority under which the requesting agency was created with specific citations to the provisions setting forth the duties and responsibilities of the agency.

Attachment(s):

• D.1. Agency Legal Authority.pdf (1.5MB) Uploaded on 03/31/2016 at 03:10PM

2. A copy of the signed resolution adopted by the requesting agency formally initiating the boundary modification request process.

Attachment(s):

• D.2. Resolution.pdf (28.8kB) Uploaded on 03/31/2016 at 05:17PM
• D.2. Reso 2016-06 Basin Boundary Modification.pdf (788kB) Uploaded on 04/21/2016 at 02:51PM

3. A map of adequate scale (no greater than 1:24,000; e.g., 1:10,000 is not acceptable) showing the proposed modified basin boundary in relation to the existing Bulletin-118 basin boundary and the local agencies that are within or bordering the existing and proposed basin.

Attachment(s):

• D.3. Modified Basin Boundary w. local agencies_opt..pdf (912.5kB) Uploaded on 03/31/2016 at 05:03PM

4. A GIS shapefile of the proposed modified groundwater basin boundaries. Download Existing B118 basin shape file | DWR Spatial Data Standards

Attachment(s):

• D.4. Proposed Boundary Shapefile.zip (1.6kB) Uploaded on 03/31/2016 at 05:09PM

5. A GIS shapefile of the political boundaries of any affected or adjacent local agency. Download water agency shape file

Attachment(s):

• D.5. Political Boundaries Shapefile.zip (27.3kB) Uploaded on 03/31/2016 at 05:12PM

6. Any information, if necessary, to enable DWR to satisfy the requirements of a responsible agency pursuant to the California Environmental Quality Act.

Mission Springs Water District, a County Water District and public agency formed pursuant to Water Code §§ 30000 et seq. has legal authority to file as the responsible agency for all CEQA District related efforts.

E. General Information

1. Describe the lateral boundaries of the alluvial aquifer or aquifers that form the groundwater basin and the definable bottom of the basin. The description must be in terms that are clear, definite, and sufficiently detailed to allow an authoritative map of the proposed basin boundaries to be plotted using the given description.

The Garnet Hill Subbasin is located area between the Garnet Hill Fault and the Banning Fault. The Garnet Hill Fault is a branch of the San Andreas Fault system consisting of a series of left stepping northwest-trending right-lateral faults with active folds at each step over. These folds are exhibited a series of small hills (West Whitewater Hill, East Whitewater Hill, Garnet Hill, Edom Hill and several small unnamed hills) between each fault segment. The subbasin was considered a subarea of the Whitewater River (Indio) subbasin by DWR (1964) and it was considered a distinct subbasin by the USGS for the effectiveness of the Banning and Garnet Hill Faults as barriers to groundwater movement. This was illustrated by a difference of 170 feet in groundwater elevation in a horizontal distance of 3,200 feet across the Garnet Hill Fault, as measured in the Spring of 1961. The fault does not reach the surface and is probably effective as a barrier to groundwater movement only below a depth of about 100 feet

F. Notice and Consultation

1. List all local agencies and public water systems affected by the basin(s) modification request.

Mission Springs Water District (MSWD), Desert Water Authority (DWA), and Coachella Valley Water District (CVWD).

2. Explain the methods used to identify interested local agencies and public water systems in the affected basin(s):

MSWD, DWA, and CVWD are the only public water system agencies which have service boundaries within the Garnet Hill Subbasin Area.

3. Provide information regarding the nature of consultations with affected or interested agencies. Attach and cite any copies of correspondences with local agencies and public water systems and/or any other persons or entities consulted.

The affected agencies were contacted via email and given notice that MSWD was requesting a Basin Boundary Modification.

Attachment(s):

• F.3. Consultation w. Affected Agencies.pdf (74.3kB) Uploaded on 04/22/2016 at 04:39PM

4. Provide a summary of all public meetings at which the proposed boundary modification was discussed or considered by the requesting agency. Attach and cite any copies of agendas and notices published.

The attached agenda was publically posted at least 72 hours in advance of the meeting and in compliance with Government Code Section 54945.2.

Attachment(s):

• F.4. 04 2016 Reg Mtg Agenda.pdf (121.9kB) Uploaded on 04/21/2016 at 03:04PM

5. Attach a copy of all comments regarding the proposed boundary modification received by the requesting agency and a summary of any responses made by the requesting agency.

The attached meeting minutes from MSWD's board meeting show that there was no public comment regarding the proposed boundary modification.

Attachment(s):

• F.5. 04 18 2016 Regular meeting minutes.docx (54.7kB) Uploaded on 04/22/2016 at 02:10PM

H. Local Support

1. Provide any evidence that sufficient information was provided to affected agencies and systems regarding the proposed boundary modification.

The affected agencies were contacted via email and given notice that MSWD was requesting a Basin Boundary Modification.

Attachment(s):

• H.1. Consultation w. Affected Agencies - Copy.pdf (74.3kB) Uploaded on 04/22/2016 at 04:41PM

2. Provide a list of all affected agencies and affected systems that submitted comments and/or documents in support or opposition to the proposed boundary. The agency submitting their support or opposition for a boundary modification must provide a copy of a resolution formally adopted by the decision-making body of the affected agency or system or a letter signed by an executive officer or other official with appropriate delegated authority who represents the agency or system. Attach copies of the resolution and/or signed letter detailing the support or opposition submitted.

No opposition or support was provided by neighboring agencies.

3. Provide any evidence that rebuts any opposition to the proposed boundary modification.

No opposition to the proposed boundary modification was received.

I. Hydrogeologic Conceptual Model

1. Principal aquifer units within requested basin.
2. Lateral boundaries of the proposed basin, including:
   1. Geologic features that significantly impede or impact groundwater flow.
   2. Aquifer characteristics that significantly impede or impact groundwater flow.
   3. Significant geologic and hydrologic features and conditions of the principle aquifer units, as appropriate, including information regarding the confined or unconfined nature of the aquifer, facies changes, truncation of units, the presence of faults or folds that impede groundwater flow, or other groundwater flow restricting features.
   4. Key surface water bodies, groundwater divides and significant recharge sources.
3. Recharge and discharge areas within the basin.
4. Definable bottom of the basin or subbasin.

The department may waive this requirement for an internal boundary modification if the requesting agency is able to demonstrate that the proposed boundary modification is unlikely to affect sustainable groundwater management.

The area between the Garnet Hill Fault and the Banning Fault is named the Garnet Hill subbasin. The Garnet Hill Fault is a branch of the San Andreas Fault system consisting of a series of left stepping northwest-trending right-lateral faults with active folds at each step over. These folds are exhibited in a series of small hills (West Whitewater Hill, East Whitewater Hill, Garnet Hill, Edom Hill and several small unnamed hills) between each fault segment. The subbasin was considered a subarea of the Whitewater River (Indio) subbasin by DWR (1964) and it was considered a distinct subbasin by the USGS for the effectiveness of the Banning and Garnet Hill Faults as barriers to groundwater movement. This was illustrated by a difference of 170 feet in groundwater elevation in a horizontal distance of 3,200 feet across the Garnet Hill Fault, as measured in the Spring of 1961 (DWR, 1964). The fault does not reach the surface and is probably effective as a barrier to groundwater movement only below a depth of about 100 feet. DWR observed that limited data existed to characterize the hydrogeology of this subbasin. The Garnet Hill Subbasin is considered an unconfined aquifer with a saturated thickness of 1,000 feet or more and an estimated total storage capacity on the order of 1.0 million acre-ft. The subbasin is naturally recharged by subsurface flow from the Mission Creek Subbasin and percolation of runoff and subsurface flow from the Whitewater River watershed on the west. Irrigation return flow and discharges from municipal and individual subsurface wastewater disposal systems also contribute to recharge but are considered very small. Although some recharge to this subbasin may come from Mission Creek and other streams that pass through during periods of high flood flows, the main sources of recharge to the subbasin are channel infiltration and subsurface flow in the Whitewater River, subsurface flow through the semi-permeable deposits which underlie Whitewater Hill and from subsurface flow across the Banning Fault from the Mission Creek subbasin. In general, there is subsurface flow from the Garnet Hill subbasin across the Garnet Hill Fault to the Whitewater River subbasin westerly of the Garnet Hill outcrop. The Garnet Hill and Banning faults form partially effective barriers to groundwater flow based on water level differences across the faults. DWR indicated the Garnet Hill fault does not reach the ground surface and is probably effective as a barrier to groundwater movement only below a depth of 100 ft. The effectiveness of the Garnet Hill Fault as a barrier is believed to diminish east of Garnet Hill. DWR noted a constriction in the alluvial cross section near Garnet Hill has caused a small groundwater cascade. This is inferred from current water level data.

Attachment(s):

• I. Hydrogeologic Conceptual Model.pdf (4.6MB) Uploaded on 04/21/2016 at 03:33PM

K. Technical Studies for Internal Scientific Modifications

1. A qualified map depicting structural geologic features that could significant impact or impede lateral groundwater flow.

Attachment(s):

• K.1. Structural Geologic Features.pdf (5.5MB) Uploaded on 04/21/2016 at 04:24PM

2. Geologic and hydrologic evidence of groundwater conditions by attaching or providing a URL to any of the following:
   1. Historical and current potentiometric surface maps, groundwater levels, groundwater recharge and discharge areas of the aquifer system within the vicinity of the proposed boundary modification.
   2. Aquifer performance testing results demonstrating basin boundary condition response.
   3. Water quality information of the aquifer system including but not limited to general water quality parameters and isotopic analysis.
   4. Supporting certified geophysical studies.
   5. Any other pertinent information.

Attachment(s):

• K.2. Mission Creek_Garnet Hill WMP-Final Jan. 2013.pdf (19.2MB) Uploaded on 04/21/2016 at 04:29PM
• K.2. Mission Creek Garnet Hill WMP-Final Report-Appendices.pdf (5.5MB) Uploaded on 04/21/2016 at 04:29PM
• K.2. Tyley, 1974 (Analog Model Study of the Ground-Water Basin of the Upper Coachella Valley, CA).pdf (2.5MB) Uploaded on 04/21/2016 at 05:18PM
• K.2. Reichard and Meadows, 1992 (Eval. of a Groundwater Model of the Upper Coachella Valley).pdf (24.8MB) Uploaded on 04/21/2016 at 05:25PM