Mission Springs Water District GSA - Indio - 7-021.01 COACHELLA VALLEY - INDIO

Mission Springs Water District GSA - Indio - 7-021.01 COACHELLA VALLEY - INDIO

A. Applicant Information

Requesting Agency Information
Agency Name: Mission Springs Water District GSA - Indio
Address: 66575 Second Street
City: Desert Hot Springs Zip: 92240
Work Phone: (760) 329-5169 Cell Phone: (760) 404-8023
Email: dfriend@mswd.org Fax: (760) 329-2482
Revision Request Manager Information
Person Name: Danny Friend
Address: 66575 Second Street
City: Desert Hot Springs Zip: 92240
Work Phone: (760) 329-5169 Cell Phone: (760) 404-8023
Email: dfriend@mswd.org Fax:
 

B. Description of Proposed Boundary Modification

  1. MSWD would like to have the Garnet Hill Subbasin be added as a Bulletin 118 Subbasin.
    • Scientific Internal
  2. 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.
    • 7-021.01 COACHELLA VALLEY - INDIO
  3. Garnet Hill Subbasin

C. Initial Notification and Combination of Requests

  1. Yes
    Local Agency Potential Basin(s)/Subbasin(s)
    Mission Springs Water District 7-021.01 COACHELLA VALLEY - INDIO
  2. No

D. Required Documents for All Modifications

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

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

Mission Springs Water District (MSWD), Desert Water Authority (DWA), and Coachella Valley Water District (CVWD).
MSWD, DWA, and CVWD are the only public water system agencies which have service boundaries within the Garnet Hill Subbasin Area.
The affected agencies were contacted via email and given notice that MSWD was requesting a Basin Boundary Modification.
The attached agenda was publically posted at least 72 hours in advance of the meeting and in compliance with Government Code Section 54945.2.
The attached meeting minutes from MSWD's board meeting show that there was no public comment regarding the proposed boundary modification.

H. Local Support

All requests for boundary modification must include the following:
The affected agencies were contacted via email and given notice that MSWD was requesting a Basin Boundary Modification.
No opposition or support was provided by neighboring agencies.
No opposition to the proposed boundary modification was received.

I. Hydrogeologic Conceptual Model

Requests for boundary modification, must include a document or text to a clearly defined hydrogeologic conceptual model demonstrating each of the following:
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.

K. Technical Studies for Internal Scientific Modifications

Requests for an internal scientific modification involving a hydrogeologic barrier must include a document or text that demonstrates the presence or absence of subsurface restrictions on lateral groundwater flow. Provide the following:
Created on 03/31/2016 at 3:08PM, last modified on 01/02/2018 at 11:23AM and page generated on 12/12/2024 at 12:35AM