Initial Study #25-0037 - Brandt Road Bridge Replacement

Initial Study #25-0037 - Brandt Road Bridge Replacement

The project would replace an existing wood bridge constructed in 1950 that spans the Alamo River. Brandt Road is a two-lane, paved road that extends north and south of the existing bridge. The existing wooden structure consists of an approximately 150-foot-long, ten-span bridge, with pile bents located within the Alamo River. The project would demolish and dispose of the existing bridge and supporting features, followed by the construction of a new single-span bridge within the same alignment. The proposed single-span bridge would not impede the flow of the Alamo River. Figure 4 presents the proposed bridge plan and section .6.d.dge and Approach Road The proposed two-lane bridge would be located within the same alignment as the existing two lane bridge. The proposed approaches would consist of two 12-foot-wide lanes and two 8-footwide unpaved shoulders with a design speed of 55 miles per hour (mph). The approaches would be tapered to provide a transition between the existing segments of Brandt Road north and south of the project site that have unpaved shoulders and there placement bridge that would include paved shoulders. ~Staging areas would be used to store project materials and equipment throughout construction. Staging areas would include existing segments of Brandt Road north and south of the project site, as well as segments of the banks of the Alamo River that front the project site. The affected portion of Brandt Road would be closed during the entire duration of construction. Traffic control, barricades, and construction and detour sign plans would be prepared to ensure no public traffic enters this area. Demolition/Removal The existing bridge abutments and associated piles would be demolished and removed prior to vegetation removal and the construction of the new bridge. Demolition activities would be designed to minimize impacts to the Alamo River. Removal of the existing wooden bridge pile supports would consist of breaking them off at, or just under, the channel bottom surface level. The lateral load imposed by a large excavator would fracture the piles near or below the drain bottom. Once the piles are broken off, they would be lifted out of the drain by an excavator with a chain and transported to an appropriate disposal facility. The use of a temporary sheet pile containment system and removal of the temporary sheet piles would result in a larger amount of "dirty water" than breaking them off without containment. The abutment piles, most of which are exposed due to drain bank erosion, would be removed in a similar manner. All work would need to occur while the river is flowing, with no proposed bypass or containment. All equipment required for removal of the existing bridge abutments and piles would be staged and operated from the banks of the river and/or Brandt Road. Vegetation would be removed during site preparation to clear the channel for the placement of any slope protection at the proposed bridge abutments. This may be performed after bridge demolition and removal, including the removal of existing wood piles from the Alamo River channel. Road Replacement, After bridge construction is complete, the Brandt Road approaches, extending approximately 200 feet in each direction, would be placed. The structural section of the roadway would consist of aggregate base and asphalt concrete with striping and any signage needed to match existing roadway on each side of the bridge. The approaches would also include drainage features that would prevent erosion of the riverbanks. Water Consumption, Project construction would use water for dust control during ground-disturbing and earth compaction activities. Water would likely be obtained from a nearby Imperial Irrigation District canal, through the Imperial Irrigation District encroachment permit process. Traffic Control and Detour, The affected portion of Brandt Road would be closed during the entire duration of construction to ensure safety. Nearby roads primarily serving existing agricultural and geothermal uses would be used for detours. These would include Eddins Road north of the existing bridge and Rutherford Road south of the existing bridge. Kalin Road, approximately one mile west of Brandt Road, would serve as the north-south alternate. Bight-of-Way The project would not require acquisition of any new right-of-way, as the replacement bridge would be constructed entirely within the existing right-of-way of Brandt Road. Similarly, all construction staging areas would also be located entirely within the right-of-way of existing County roads. The proposed approaches to the replacement bridge would consist of two 12-foot-wide lanes and two 8-foot-wide unpaved shoulders. The approaches would be tapered to provide a transition between the existing segments of Brandt Road north and south of the project site that have unpaved shoulders and the replacement bridge that would include paved shoulders.

Calipatria

Imperial

Countywide

Imperial