Brentwood City Of - 5-022.15 SAN JOAQUIN VALLEY - TRACY

Brentwood City Of - 5-022.15 SAN JOAQUIN VALLEY - TRACY

A. Applicant Information

Requesting Agency Information
Agency Name: Brentwood City Of
Address: 150 City Park Way
City: Brentwood Zip: 94513-7344
Work Phone: (925) 516-6000 Cell Phone: (925) 382-9410
Email: Fax:
Revision Request Manager Information
Person Name: Chris Ehlers
Address: 2201 Elkins Way
City: Brentwood Zip: 945132
Work Phone: 925-516-6030 Cell Phone:
Email: Fax:

B. Description of Proposed Boundary Modification

  1. Subdivide Tracy Subbasin by counties on scientific and jurisdictional grounds.
    • Scientific Internal
    • Jurisdiction Subdivision
  2. The proposed modification would create a separate subbasin that comprises the portion of the Tracy Subbasin that lies within Contra Costa County. The current subbasin substantially consists of areas of San Joaquin County and east Contra Costa County, with a small portion of Alameda County. The Contra Costa County Line along Old River is proposed as the new eastern boundary of the new subbasin. The Contra Costa-Alameda County Line would be the new southern boundary. The new subbasin would be bounded by the Coast Ranges to the west (unchanged), Old River to the east (new), San Joaquin River to the north (unchanged), and Alameda County Line to the south (new). The proposed boundary modifications are consistent in nature with existing Bulletin 118 boundaries: Old River replaces the San Joaquin River (river) and Alameda County Line replaces the Stanislaus County line (political) to form the new subbasin within Contra Costa County. Eastern Contra Costa County has diverse sources of water supplies including surface water and groundwater, which are used for agricultural and municipal/domestic purposes. The proposed subdivision would affect no existing or historic water supply coordination with other local agencies in the subbasin. There are no published studies or agency reports that indicate a hydrogeologic connection between the east Contra Costa County portion of the subbasin and the San Joaquin/Alameda County portions. Recently published east Contra Costa Agency reports indicate no undesirable results affecting sustainable groundwater use in the area. These include a Groundwater Management Plan (Diablo Water District, 2007), a Water Master Plan (Town of Discovery Bay, 2012), a groundwater conditions report (Diablo Water District, 2011), and an IRWMP (2014). These documents are uploaded to support the proposed basin modification request.
  3. East Contra Costa Subbasin

C. Initial Notification and Combination of Requests

  1. Yes
    Local Agency Potential Basin(s)/Subbasin(s)
    San Luis & Delta-Mendota Water Authority 5-022.07 SAN JOAQUIN VALLEY - DELTA-MENDOTA , 5-022.15 SAN JOAQUIN VALLEY - TRACY
    Brentwood City Of 5-022.15 SAN JOAQUIN VALLEY - TRACY
    Brentwood City Of 5-022.15 SAN JOAQUIN VALLEY - TRACY
  2. No

D. Required Documents for All Modifications

Water supply for the City of Brentwood is addressed in the Infrastructure Element of the General Plan. Preliminarily, the City has determined that CEQA compliance for the proposed modification is by way of the General Plan EIR that was certified in 2014.

E. General Information

From Bulletin 118, Update 2003, the current boundaries for the Tracy Subbasin are described as follows: The Tracy Subbasin is defined by the areal extent of unconsolidated to semiconsolidated sedimentary deposits that are bounded by the Diablo Range on the west; the Mokelumne and San Joaquin Rivers on the north; the San Joaquin River to the east; and the San Joaquin-Stanislaus County line on the south.? The new subbasin would be bounded by the Coast Range to the west (unchanged), Old River to the east corresponding to the San Joaquin and Contra Costa county lines (new), San Joaquin River to the north (unchanged), and Alameda County Line to the south (new). The proposed boundary modifications are consistent in nature with the existing Bulletin 118 boundaries: Old River replaces the San Joaquin River (river) and Alameda County Line replaces the Stanislaus County Line (geopolitical) to form the new subbasin within Contra Costa County; East Contra Costa Subbasin.

F. Notice and Consultation

Counties: Alameda County Flood Control & Water Conservation District - Zone 7 (agency created by statute to manage groundwater in Alameda County portion of Tracy Subbasin) Contra Costa County San Joaquin County Cities: Antioch Brentwood Oakley Tracy Special Districts: Bethel Island Municipal Improvement District Byron Bethany Irrigation District Central Delta Water District Contra Costa Water District Diablo Water District Discovery Bay Community Services District East Contra Costa Water Irrigation District Ironhouse Sanitary District Mountain House Community Services District South Delta Water Agency Westside Irrigation District
Since December 2014, there have been numerous meetings between local agencies in the San Joaquin and Contra Costa portions of the Tracy Subbasin. The meetings have been concerned with GSA and GSP alternatives, as well as basin boundary modifications (a list of meetings and agendas is uploaded for documentation). Participants in the meetings were identified as being concerned with SGMA issues.
The east Contra Costa County agencies indicated interest in pursuing a basin modification to other attendees at a basin-wide meeting on 12/9/2015. The Contra Costa agencies met on 2/10/2016 and agreed to pursue a basin modification and solicit input/comments on forming a GSA from other agencies.
A summary of meetings is presented in tabular form and uploaded to this part.
Two uploaded correspondences represent feedback received. Informally, local agencies in the southern Tracy Subbasins indicated support to Town of Discovery Bay's General Manager with respect to coordination ("would make life easier"). RD 2065 indicated that it was neutral because of lack of defined benefit or harm. Letters of support are included in Section H.

G. General Existing Groundwater Management

All requests for jurisdictional modification pursuant to Section 342.4 MUST include responses to the following questions.
The proposed basin modification would align historical and current planning and management efforts with SGMA. The new subbasin boundaries would be effectively integrated to existing AB3030, IRWMP, CASGEM plan areas. The local agencies that have historically coordinated these and other activities, also intend to enter into an MOU for the creation of a GSA that covers the proposed new subbasin. Cooperation among east Contra Costa County agencies has been a factor in development of a hydrogeologic conceptualization and a monitoring program to detect undesirable results if they should arise. Consistent with the Medium Priority ranking of the greater Tracy Subbasin, sustainable groundwater management presently exists within the proposed new subbasin. Hydrographs for representative wells show stable conditions in key areas of the east Conrta Costa County area. A table showing existing and future projected groundwater use is a planning component for GSP development, which is tied to current water level monitoring.
Due to hydrogeologic variations across the Tracy Subbasin (see K.2.), there are no expected constraints on sustainability posed by the modification in the balance of the subbasin. The following explains why the modification does not affect sustainable management in other adjoining subbasins: North: This boundary is unchanged. West: This boundary is uncharged and there is no subbasin in the Coast Ranges adjoining the proposed new subbasin. East: The boundary shift from San Joaquin River to Old River (i.e., to the Contra Costa-San Joaquin county border) is across the Delta islands where groundwater occurrence and availability is restricted (see K.2.). South: This boundary is shifted north from the Stanislaus County line to Alameda County line. Within this shift is the Tracy area, which is hydrogeologically distinct from east Contra Costa County with little to no groundwater use between (e.g., Clifton Forebay area). The southern portion of the Tracy Subbasin adjoins the Delta-Mendota Subbasin, which is known to be hydraulically connected. There is no history of joint water resource planning or integration that would be affected by the proposed southern boundary shift. The San Luis & Delta-Mendota Water Authority has members in both subbasins, including the City of Tracy, and has indicated support for the proposed basin modification.
In 1999, members of the East Contra Costa Water Management Association commissioned a study of local groundwater conditions that led to increased awareness of the need to monitor groundwater levels in the region due to lack of systematic programs. The same local agencies cooperated in Diablo Water District?s 2007 AB3030 Groundwater Management Plan preparation that identified the need for groundwater level monitoring and reporting. In 2011, Diablo Water District produced a groundwater monitoring report to update information compiled in the 2007 GWMP. Wells of major groundwater users are part of the 2014 CASGEM plan that covers the entire proposed basin modification area. As part of the region?s IRWMP Update 2013, the cooperating agencies identified data gaps to address a determination of safe yield for the east Contra Costa area.
The proposed boundary modification has no impact on existing state programs as the east Contra Costa area has complied and developed plans that have been independent of the rest of the Tracy Subbasin. The attached exhibits indicate that CASGEM coverage is complete within the proposed new subbasin, the East Contra Costa County IRWMP Update 2013 does not extent into any other portion of the subbasin, and previous AB3030 plan areas are aligned within areas that would not be affected by the proposed modification.

H. Local Support

All requests for boundary modification must include the following:
The uploaded solicitation was submitted to identified interested local agencies.
The City of Brentwood adopted the uploaded resolution to make an Initial Notification for basin modification. Brentwood acted on behalf of other east Contra Costa County agenices including Byron Bethany Irrigation District, City of Antioch, Contra Costa County and Contra Costa Water Agency, Contra Costa Water District, Diablo Water District, East Contra Costa Irrigation District, Town of Discovery Bay
Not applicable.
A summary table and compiled responses are uploaded.

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 proposed boundary modification realigns the Tracy Subbasin according to hydrogeologic variations previously published by DWR in Bulletin 74-5, Water Well Standards San Joaquin County Final Supplement, 1969 (see upload). This DWR publication supports a boundary shift from the San Joaquin River to the Contra Costa County Line along Old River, across the Delta islands, on the basis of the following description: ?In the zone of contact, the Delta deposits and the coarser alluvial deposits interfinger. Ground water in the Delta Area occurs in a series of poorly connected sand and gravel lenses, locally confined by silts and clays which cause artesian effects in some localities. The large percentage of fine-grained materials and the lenticular nature of the deposits result in low permeability. Wells in this material usually yield only moderate quantities of water, with large draw-downs. The base of the fresh water is quite shallow and generally coincides with the base of the organic deposits. It is difficult to obtain a sufficient amount of ground water of suitable quality for domestic and irrigation purposes in a large portion of the Delta Area.? ?Saline waters are found throughout all depths in the Delta deposits except for the thin lenses of fresh water extending usually to a depth of less than 150 feet. The deltaic sediments apparently were deposited in marine or brackish water. The fine-grained composition of the sediments has prevented the better quality water of the fresh water sloughs within the Delta and the good quality water surrounding the Delta Area from replacing the saline water.? ?Fresh water recharge to the Delta Area is obtained from infiltration of rainfall and excess irrigation water.? Bulletin 74-5 also distinguishes the Tracy area in the southern portion of the Tracy Subbasin based on the following description: ?Near the top of the Tulare Formation, a regionally extensive clay bed, the Corcoran Clay, separates the continental sediments into upper and lower portions. The aquifers in the lower portion are confined by this clay. Most water well drillers log the Corcoran Clay as ?blue clay?. The clay is considered to be of Pleistocene age. An important distinguishing feature of the Corcoran Clay is the large amount of diatoms it contains. The clay is well-sorted, and no sand is noticeable. Marginal zones, however, have lenses of sand, silt, and gravel interfingering with the clay bed. Most of the clay was formed in fresh water as a lacustrine deposit. Its thickness in the Tracy Area ranges from 10 to 160 feet.? The 2016 geologic study by Kenneth Utley, Luhdorff & Scalmanini (see upload) interprets the geologic history of the greater Tracy Subbasin and provides explanations for the lack of Corcoran Clay deposits in the east Contra Costa County area that are of concern in the southern portion of the subbasin in San Joaquin County. It is the lack of the Corcoran member in east Contra Costa County that reflects different occurrence and availability of groundwater compared to the south. East Contra Costa County is also notable for occurrence of freshwater aquifers a greater depths and are a significant source of irrigation and municipal supply in contrast to very limited occurrence and availability in the Delta islands. These factors gave rise to separate groundwater use patterns in each area; for example, variable water quality in the Tracy area with notable improved quality below the Corcoran clay; little availability in the Delta islands; and few restrictions on availability in east Contra Costa County. In addition, no available studies indicate hydrogeologic connections of any consequence to sustainable groundwater resources in the Tracy Subbasin regions between northwest (east Contra Costa area), southern (Tracy area), and eastern (Delta islands).

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:
Plate 1 of the 2016 geologic report depicts the primary structural features that impede groundwater flow in the Tracy Subbasin: the Coast Ranges on the western edge of the subbasin.

L. Technical Studies for All Jurisdictional Modifications

Requests for a jurisdictional boundary must attach or provide a URL or upload a file for the following:
The following east Contra Costa County agencies have agreed to work cooperatively to comply with the requirements of SGMA:City of Antioch, Byron Bethany Irrigation District, City of Brentwood, Contra Costa County, Contra Costa Water District, Diablo Water District, East Contra Costa Irrigation District, Town of Discovery by Community Services District. Tthese agencies are currently developing an MOU framework through which they will seek to form a GSA that covers the east Contra Costa County portion of the Tracy Subbasin. Contra Costa County will serve to address White Areas and is updating service area boundaries to identify overlaps and ensure complete coverage of the region for sustainability purposes (see uploaded maps).

M. Technical Studies for Jurisdictional Subdivision Modifications

Requests for jurisdictional subdivisions must include a document that describes the historical and current groundwater conditions and coordination within the existing basin or subbasin related to the following, where applicable:
East Contra Costa County water agencies have worked cooperatively to address water supply issues through the East County Water Management Association, established in the mid-1990s. This group of water agency managers first commissioned a study of groundwater conditions in the east County area in 1999. Conjunctive use of groundwater and surface water are currently practiced by Diablo Water District and City of Brentwood. Contra Costa Water District and East Contra Costa Irrigation District entered into a dry year water transfer program in 2004. The agenicies also cooperated in an IRWMP update (2013), and conduct monitoring to fulfil CASGEM requirements. The CASGEM plan area covers the entire Contra Costa portion of the Tracy Subbasin. Although no agency has reported undesirable results with respect to local groundwater conditions, the agencies have entered into discussions to develop an agreement to proactively protect and conserve groundwater resources in the future as part of a local Groundwater Sustainability Plan. Possible measures include groundwater conservation in normal to wet years through in-lieu recharge and increased surface water utilization, and possible conservation of local runoff in areas recognized for their recharge potential. The recharge area map is are based on the deposition facies model from the 1999 study in relation to the three primary watersheds in the east Contra Costa County area (see uploaded map).
Created on 03/18/2016 at 4:23PM, last modified on 01/02/2018 at 11:23AM and page generated on 01/17/2020 at 2:36PM