B. Description of Proposed Boundary Modification

1. Short Description

   External boundary modification of the Santa Clara River Valley East sub basin (Basin 4-4.07).
2. Type of basin boundary revision

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

   In conducting its planning activities and reviewing available geologic and hydrogeologic studies and the AB 3030 Groundwater Management Plan for the basin, Castaic Lake Water Agency (CLWA) has identified that the basin boundary of the East Subbasin does not align in all areas with the lateral extent of the Saugus Formation aquifer system, which is the deeper of the two principal aquifers that are present in the basin. Specifically, the modification is along the eastern outer boundary of the East Subbasin. The modification is requested because the current boundary does not include an area where geologic mapping shows the Saugus Formation (QTs) to be outcropping at the ground surface. The proposed modification facilitates sustainable management of the basin by including this area so as to provide a full accounting of all areas where the Saugus Formation is receiving recharge in exposed outcrops. This modification also is consistent with how the Saugus Formation is delineated in local hydrogeologic technical studies and water supply planning documents.

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

   • 4-004.07 SANTA CLARA RIVER VALLEY - SANTA CLARA RIVER VALLEY EAST
5. Provide the proposed name for the new basin(s) or subbasin(s)

   No name changes will occur to the existing basin and subbasin. The proposed modification to the location of the boundary is along the eastern portion of the Santa Clara River Valley East Subbasin (basin number 4-4.07).

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)
   Castaic Lake Water Agency	4-004.07 SANTA CLARA RIVER VALLEY - SANTA CLARA RIVER VALLEY EAST

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):

• CLWA Act.pdf (237.7kB) Uploaded on 03/29/2016 at 05:37PM

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

Attachment(s):

• Resolution No. 3095.pdf (78kB) Uploaded on 03/29/2016 at 02:52PM

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):

• FigureA_Affected_Agencies.pdf (698.2kB) Uploaded on 03/29/2016 at 07:11PM

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

Attachment(s):

• EastSubbasin_Proposed_GW_Basin.zip (31.8kB) Uploaded on 03/29/2016 at 07:11PM

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

Attachment(s):

• EastSubbasin_Affected_Agencies.zip (446.4kB) Uploaded on 03/29/2016 at 07:42PM

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

The Castaic Lake Water Agency has filed a Notice of Exemption (NOE) with Los Angeles County for this proposed basin boundary adjustment. The NOE is uploaded.

Attachment(s):

• March 25, 2016 NOE.pdf (132.4kB) Uploaded on 03/30/2016 at 08:44AM

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.

See the three attached files. File names: "Item E for DWR Template for SCV Basin Boundary Mod (2016-03-29)," "FigureB_Dibblee_Geology," and "Figure 2-6 from ModelDevelopmentReport2004"

Attachment(s):

• Item E for DWR Template for SCV Basin Boundary Mod (2016-03-29).pdf (137.8kB) Uploaded on 05/02/2016 at 05:46PM
• FigureB_Dibblee_Geology.pdf (873.9kB) Uploaded on 03/29/2016 at 07:14PM
• Figure 2-6 from ModelDevelopmentReport2004.pdf (2.8MB) Uploaded on 03/29/2016 at 07:14PM

F. Notice and Consultation

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

The City of Santa Clarita, the Valencia Water Company, Newhall County Water District, Los Angeles County Waterworks District Number 36, and Santa Clarita Water Division. See uploaded map "Figure A Affected Agencies"

Attachment(s):

• FigureA_Affected_Agencies.pdf (697.8kB) Uploaded on 03/29/2016 at 10:20AM

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

Identifying the interested local agencies and public water systems was straightforward. The identified local agencies and public water systems are those that were already included in the existing East Subbasin, and which each participate in other state-required water supply planning activities (such as the Urban Water Management Plan). These agencies and CLWA work together to manage groundwater resources in the subbasin. Staff reached out to these agencies informally, and more formally, such as through emailing the notice of the CLWA Board meeting where it would consider a resolution formally initiating the basin boundary request and seeking their input. The basin boundary modification issue was also publicized through the public notice of the March 10, 2016 CLWA Water Resources and Outreach Committee (WRO) meeting, and the March 23, 2016 CLWA Board of Directors meeting, and a description of it was placed on the CLWA website.

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.

CLWA works closely with each of the retailers and the City. In February an informal meeting was held with retailers where the basin boundary issue that is the subject of this request was discussed in general. Retailers were provided information that the initial notification was provided, that the CLWA Board would formally consider adopting a resolution initiating the basin boundary modification, and emails with information, and seeking input and support were sent. A brief table and supporting email communication is attached.

Attachment(s):

• Communication notes with retailers and City of Santa Clarita.pdf (50.3kB) Uploaded on 03/30/2016 at 09:26AM
• Communication email with retailers and City of Santa Clarita.pdf (467.1kB) Uploaded on 03/29/2016 at 06:32PM

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 proposed basin boundary modification was discussed at a publicly noticed Castaic Lake Water Agency, Water Resources and Outreach Committee Meeting. The proposed basin boundary modification was discussed at a publicly noticed Castaic Lake Water Agency Board meeting. At that meeting, the CLWA adopted a resolution in support of initiating the basin boundary modification. The CLWA Board item and proposed resolution is attached.

Attachment(s):

• March 10 2016 WRO Meeting Notice and Item.pdf (763.8kB) Uploaded on 03/30/2016 at 09:43AM
• March 23 2016 Meeting Notice and Item.pdf (328.1kB) Uploaded on 03/30/2016 at 09:43AM
• March 23 2016 Adopted Resolution No. 3095.pdf (78kB) Uploaded on 03/30/2016 at 09:43AM

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.

No written comments regarding the proposed boundary modification were received by CLWA. Three letters of support, and one email letter of support was received and are uploaded in a following section.

H. Local Support

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

Section F of this document describes the communication of information and outreach. Sufficient information was provided to affected agencies and systems, such as through publicly noticed meetings, email correspondence (and follow up), and a website posting (attached). Email communication provided information, requested feedback, and sought to determine if the affected agencies supported or didn't support the proposed basin boundary modification.

Attachment(s):

• Communication email with retailers and City of Santa Clarita.pdf (467.1kB) Uploaded on 03/29/2016 at 06:32PM
• Communication notes with retailers and City of Santa Clarita.pdf (50.3kB) Uploaded on 03/30/2016 at 09:26AM
• March 10 2016 WRO Meeting Notice and Item.pdf (763.8kB) Uploaded on 03/30/2016 at 09:43AM
• March 23 2016 Meeting Notice and Item.pdf (328.1kB) Uploaded on 03/30/2016 at 09:43AM
• Website Posting.pdf (76.1kB) Uploaded on 03/30/2016 at 01:17PM

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.

The Los Angeles County Waterworks District No. 36, the Santa Clarita Water Division, the Valencia Water Company, and the Newhall County Water District provided letters of support. The City of Santa Clarita has provided verbal support and may send a letter of support. Given the short time frame , the agencies were not able to create formal resolutions of support.

Attachment(s):

• Letters of Support.pdf (1MB) Uploaded on 03/29/2016 at 07:04PM

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

No opposition to the proposed basin 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.

Section 3 of the attached uploaded document "Item I FINAL TechMemo-SCRV Basin Mod 2016-03-29" contains discussions of each of the four items in this category.

Attachment(s):

• FINAL TechMemo-SCRV Basin Mod 2016-03-29.pdf (4.1MB) Uploaded on 05/02/2016 at 05:52PM

J. Technical Studies for External Scientific Modifications

1. A qualified map that depicts the lateral boundaries of the aquifers that define the basin or subbasin.

See the attached Figure B prepared by GSI Water Solutions, which is a map showing the Dibblee Geologic Map in the Mint Canyon Quadrangle (Dibblee, 1996) and the boundary adjustment in the localized area where the External Scientific Boundary Modification is requested by CLWA.

Attachment(s):

• FigureB_Dibblee_Geology.pdf (873.9kB) Uploaded on 03/29/2016 at 07:23PM

2. A technical study that provides subsurface data that demonstrates the vertical thickness and relevant physical properties of the alluvial aquifer or stacked series of alluvial aquifers.

This information is presented in detail in the CH2M HILL report titled Final Report: Regional Groundwater Flow Model for the Santa Clarita Valley, Santa Clarita, California: Model Development and Calibration. Section 2 is titled Hydrogeology of the Santa Clarita Valley, including Section 2.5 which discusses physical properties of the Alluvial Aquifer and the Saugus Formation. See file name "Basin 4-4.07 (Section2 from ModelDevelopmentReport2004)" Figures 3-3 through 3-9 are thickness maps from that same report, showing the multiple layers in the groundwater flow model that simulate the Alluvial Aquifer and the Saugus Formation together. For layer 1, Figure 3-3 shows the thickness of the Saugus Formation outside of the red-outlined areas. See file name "Basin 4-4.07 (Modeled Aquifer Thickness Maps from ModelDevelopmentReport2004"

Attachment(s):

• Basin 4-4.07 (Modeled Aquifer Thickness Maps from ModelDevelopmentReport2004).pdf (19MB) Uploaded on 03/29/2016 at 07:28PM
• Basin 4-4.07 (Section2 from ModelDevelopmentReport2004).pdf (57.3MB) Uploaded on 03/29/2016 at 07:27PM