AB Pipeline Replacement Project

The project consists of the replacement of an existing 1,700-linear foot (LF) Vista Irrigation District (VID) gravity powered water pipeline in the City of San Marcos and unincorporated San Diego County. The existing 14-inch-diameter pipeline is located primarily underground with portions located aboveground. The existing pipeline would be removed or abandoned and replaced with an 18-inch-diameter gravity powered pipeline. Although the project would replace an existing 14-inch pipe with an upsized 18-inch pipe, it would have the same water supply capacity and would maintain flows for existing and planned development in the area. The project would not substantially increase water flows in the area and would not require the expansion of associated VID infrastructure. Future development proposing connections to VID infrastructure would be required to undergo separate review by VID to ensure capacity to accommodate proposed water flows. Three potential project alignment options are being considered for replacing VID’s existing AB pipeline. The three project alignment options being considered are the Existing Alignment, SE10 Alternative Alignment, and Road Alternative Alignment options. For the purposes of this Initial Study, all three alignments are analyzed individually for each issue area to assess the potential environmental impacts of each option; however, the Road Alternative Alignment Option is the preferred option. Existing Alignment Option If the Existing Alignment Option is chosen, the project would replace the existing 1,700-LF AB pipeline at its current location or abandon the pipeline and construct a new 1,700-LF pipeline adjacent to the existing alignment, within the 20-foot-wide existing VID utility easement for the AB pipeline. The existing aboveground portions of the pipeline would be removed and replaced with an entirely underground alignment. SE10 Alternative Alignment Option The SE10 Alternative Alignment Option would abandon the existing 1,700-LF AB pipeline and construct a new 1,800-LF pipeline north of the Existing Alignment along the northern boundary of the parcel. The SE10 Alternative Alignment Option would occur partially within a previously recorded, but not utilized, VID 20-foot-wide utility easement. The eastern portions of the alignment would also be located partially within the existing San Diego County Water Authority aqueduct easement. Road Alternative Alignment Option (Preferred) The Road Alternative Alignment Option would abandon the existing 1,700-LF AB pipeline and construct a new 1,720-LF pipeline as follows: the western 1,300-LF portion of the alignment would be within an existing dirt road immediately north and outside of any VID existing utility easements, requiring the recording of a new 20-foot-wide utility easement for this reach; the eastern portion of the alignment would be located within the 20-foot-wide existing VID utility easement for the AB pipeline that crosses the San Diego County Water Authority aqueduct easement.