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Sweetwater Authority - 9-033 COASTAL PLAIN OF SAN DIEGO
A. Applicant Information
Requesting Agency Information
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| Agency Name: | Sweetwater Authority | ||
| Address: | 505 Garrett Avenue | ||
| City: | Chula Vista | Zip: | 91910 |
| Work Phone: | Erick Del Bosque (619)-409-6752 | Cell Phone: | |
| Email: | edelbosque@sweetwater.org | Fax: | |
| Revision Request Manager Information
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| Person Name: | David Schug | ||
| Address: | AECOM, 401 West A Street, Suite 1200 | ||
| City: | San Diego | Zip: | 92101 |
| Work Phone: | (619) 610-7667 | Cell Phone: | (619) 888-0512 |
| Email: | david.schug@aecom.com | Fax: | |
B. Description of Proposed Boundary Modification
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The modification removes the south San Diego Bay salt ponds, aligns with the south part of the bay.
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- Scientific External
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In 2016, Sweetwater Authority and City of San Diego Public Utilities Department (collectively, the parties) submitted an application to DWR to recognize the San Diego Formation (SDF) aquifer system as an official groundwater basin of the state, and to consolidate into that basin the boundaries of three DWR-recognized alluvial groundwater basins: Lower Sweetwater River Valley, Otay River Valley, and Tijuana River Valley). DWR approved the application, and designated the new consolidated basin as the Coastal Plain of San Diego Basin, Basin 9-033. This is the basin which the parties now propose to make minor refinements to the boundaries with the current application. The proposed modification removes the south San Diego Bay salt ponds that were inadvertently included in the original boundary. The revised south bay boundary corresponds with the municipal boundary of the City of Imperial Beach. The proposed modification also moves the cutoff line of the Silver Strand peninsula southward, aligning this with the southern end of the bay and extending westerly to the Pacific Ocean along the municipal boundary of the City of Imperial Beach. The exclusion of the salt ponds forms a Scientific External modification of a small portion of the basin by moving the basin boundary to exclude mostly reclaimed land and salt marsh forming the south margin of San Diego Bay. As shown in Figure 1, the promontory of land proposed for exclusion is bordered by the Pacific Ocean and reclaimed land along the Bay. The small area to be excluded has limited connection to the main SDF aquifer and there is no groundwater use. There is a high potential for groundwater-seawater interconnection in this shoreline setting, such that the potential for economic utilization of this part of the basin is compromised. There is no clear geohydrologic basis for drawing the Silver Strand cutoff line in a particular precise location, and the delineation proposed is as scientifically reasonable as the previous delineation. According to online searches and other data, there is no available water well data for the area between the 2016 basin boundary and the City of Imperial Beach boundary. Similarly, there is no groundwater quality data available. The nearest wells (long abandoned) are about 1.5 miles southeast/inland from the coast (see Figure 4 of HCM). This suggests water wells have either never been drilled, or may have been drilled but were not completed in the small area of coastal land, likely due to the lack of potable groundwater. As described in the HCM, there is a high potential for wells in this portion of the basin to be low yield wells likely to produce brackish groundwater or even seawater from the SDF. Thus the proposed revision will have a small, but positive management affect by avoiding needless management of an area where there is no useable groundwater, and aligning the boundary with existing jurisdictional boundaries for management efficiency. GSA resources can be more appropriately focused towards sustainable management of the remaining, large area of the Coastal Plain of San Diego basin.
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- 9-033 COASTAL PLAIN OF SAN DIEGO
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No proposed name change.
C. Initial Notification and Combination of Requests
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No
Local Agency Potential Basin(s)/Subbasin(s) Sweetwater Authority 9-033 COASTAL PLAIN OF SAN DIEGO -
No
E. General Information
The modification removes the south San Diego Bay salt ponds and also moves the cutoff line of the Silver Strand peninsula southward, aligning with the southern end of the bay and extending westerly to the Pacific Ocean along the municipal boundary of the City of Imperial Beach. see Figure 1, attached to this section.
The principal aquifer units in the area of the proposed modified basin are similar to the basin at large (described for the 2016 basin boundary modification, attached) including Pleistocene sediment overlying the San Diego Formation of Pliocene age. Basin lateral boundaries include the La Nacion fault on the east, the U.S.- Mexico International Border on the south, Mission Valley on the north and the Pacific Ocean and San Diego Bay on the west. The proposed modification removes a small point of land at the southwest end of the bay, and the reclaimed land forming the salt evaporation ponds along the southern margin of the bay. The Miocene Otay Formation forms the basin bottom over most of the Coastal Plain of San Diego. The Otay Formation appears to pinch out to the west, below San Diego Bay, and may not be present at depth below the proposed basin modification. In the absence of the Otay Formation, Tertiary or Cretaceous sedimentary formations form the basin bottom. See attached 2018 HCM for additional lateral boundary information and geologic cross section depicting basin bottom.
F. Notice and Consultation
Sweetwater Authority, Cities of San Diego, Imperial Beach and Coronado.
Coordination Outreach Meeting Re: Groundwater Sustainability Agency (GSA) Formation
Thursday December 1, 2016, Sweetwater Authority Offices, 505 Garrett Ave, Chula Vista
Outreach Meeting Re. SGMA Review and Participation Options for Imperial Beach / Coronado Area, Tuesday April 18, 2017
Imperial Beach City Hall, 825 Imperial Beach Blvd.
Letter correspondence between Sweetwater Authority, City of San Diego and City of Coronado (April 3 and April 10, 2018)
Sweetwater Authority Regular Board Meeting, May 23 2018
No comments have been received.
H. Local Support
All requests for boundary modification must include the following:
Outreach meeting of April 18, 2017, agenda and sign in sheet attached. Also see Section F.
Follow up notifications from Sweetwater Authority to local agencies were sent by email June 26, 2018 (copy attached).
Follow up notifications from Sweetwater Authority to potential stakeholders were sent by email June 26, 2018 (copy attached).
Sweetwater Authority Board Resolution May 23, 2018
Also see Section F.
There has been no opposition to the proposed boundary modification.
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 HCM for the proposed 2018 BBM was modified and abbreviated from the HCM prepared for the entire basin in 2016 (attached), see attached Hydrogeologic Concept Model 6-15-2018 rev.pdf.
1.The principal aquifer units in the area of the proposed modified basin are similar to the basin at large. The area is underlain by a thick sequence of Pleistocene age sediment overlying the San Diego Formation (SDF) of Pliocene age. The SDF aquifer is mostly confined within the entire basin.
2.Basin lateral boundaries include the La Nacion fault on the east, the U.S.- Mexico International Border on the south, Mission Valley on the north and the Pacific Ocean and San Diego Bay on the west. The proposed modification removes a small point of land at the southwest end of the bay, and the reclaimed land forming the salt evaporation ponds along the southern margin of the bay.
3. Natural discharge from the SDF and overlying Pleistocene sediments is believed to occur primarily as underflow along the coast at San Diego Bay and further offshore in the ocean. Recharge to the SDF mostly occurs as deep flow from the higher elevation mountain ranges east of the coastal plain. The small area proposed for modification likely does not contribute to basin recharge in a significant way.
4. The Otay Formation forms the basin bottom over most of the Coastal Plain of San Diego. The Otay Formation appears to pinch out to the west, below San Diego Bay, and may not be present at depth below the proposed basin modification. In the absence of the Otay Formation, Tertiary or Cretaceous sedimentary formations form the basin bottom.
The land is physically isolated from the basin at large, and likely has little hydrogeologic interconnection with the basin. Historically the area has not been utilized for groundwater, and is not likely to be an important groundwater resource in the future. Therefore the proposed modification will not affect sustainable groundwater management of the Coastal Plain of San Diego 9-033.
See attached HCM for additional information.
J. Technical Studies for External Scientific Modifications
Requests for a scientific modification must include a document containing information that demonstrates the extent of the aquifer. Provide the following:
See attached geologic map, Figure 2 Geology of Coastal Plain SD_07272018.pdf
Characterizations of the San Diego Formation aquifer are supported by many years of investigation by the USGS, see San Diego Hydrology Project website below.
Results of previous aquifer tests performed in the San Diego Formation in a similar coastal setting are provided in Woodward Clyde (1994), attached.
Also see 2016 and 2018 HCM, attached in Section I .
