The California Department of Transportation, using state and federal funding, proposes to reconfigure the existing intersection of SR 99 and South Avenue in Tehama County by replacing the existing minor leg stop-controlled only intersection with a roundabout; the limits of work on State Route 99 are from post mile 4.2 to 4.8. The purpose of the project is to reduce the frequency and severity of collisions. The project is needed because between January 1, 2012 and December 31, 2017, there were a total of 17 collisions: 11 involved injuries, and 6 were property damage only. The total collision rate is 4.7 times the statewide average for similar facility types, and the fatal plus injury rate is 7.0 times the statewide average.
Two project alternatives, a build alternative and a no-build/no-action alternative, were considered as viable options during preparation of this Initial Study/Environmental Assessment. Details of each alternative are provided below.
Alternative 1—Build Alternative (Roundabout)
The build alternative would include:
• Constructing a roundabout with three legs at the intersection of SR 99 and South Avenue and relocating the intersection of SR 99 and South Avenue to the northwest. The roundabout would consist of a center island with mountable curb, textured median paving, and interior curb. The roundabout would have an inscribed diameter that is 165 feet. This diameter, along with a circling single lane and truck apron width of up to 45 feet, would accommodate all vehicle sizes from bicycles to Surface Transportation Assistance Act (STAA) trucks. Traffic speed in the roundabout would be 25 miles per hour (MPH). The roundabout would receive architectural treatment appropriate to the project setting.
• Realigning the approaches to the roundabout, including installing splitter islands to separate traffic lanes and a bypass that is approximately 0.15 mile in length for traffic eastbound on South Avenue to merge onto southbound SR 99. The roundabout would be designed so that the speed of traffic slows to 25 MPH within the roundabout.
• Installing advance flashing beacons north and south of the roundabout along SR 99.
• Installing 13 electroliers (poles with lights that provide intersection lighting). Each pole would be approximately 30 to 35 feet tall.
• Installing a new steel truss tower that is approximately 45 feet tall and 4 feet wide to the southeast of the proposed roundabout, relocating the existing closed-circuit television from the existing pole to the new tower, and removing the existing pole. Maintenance access and parking will be provided at the base of the tower, along with new electrical control cabinets.
• Installing new road signs.
• Extending a 4-barrel (each barrel is approximately 5.5 feet tall and 4.5 feet wide) concrete box culvert that conveys Hoag Slough under SR 99 approximately 45 feet to the west of SR 99.
• Installing six culverts (~17 feet of 24-inch diameter culvert, ~140 feet of 24-inch diameter culvert, ~153 feet of 24-inch diameter culvert, ~124 feet of 24-inch diameter culvert, ~57 feet of 24-inch diameter culvert, and ~65 feet of 24-inch diameter culvert) under the roadway to convey stormwater runoff.
• Installing six new drainage inlets on the roadway to collect stormwater runoff and direct it into new culverts.
• Removing an existing culvert under SR 99 that is approximately 125 feet long and 18 inches in diameter.
• Installing approximately 15-foot-wide biofiltration strips along the edge of pavement throughout the project limits.
• Installing biofiltration swales at the outlets of new culverts and constructing a drainage ditch south of South Avenue that would collect runoff from the biofiltration swales and discharge flow to Hoag Slough. The ditch, which would be protected with a permanent drainage easement, would be approximately 300 feet in length, 6 feet wide, and lined with Class 1 rock slope protection (RSP).
• Rehabilitating abandoned sections of roadway and applying erosion controls as needed.
Construction of the project would disturb approximately 10.18 acres of ground surface and require the excavation of approximately 14,000 cubic yards of soil. Maximum excavation depths are estimated at approximately 2.5 feet deep for the structural section work and approximately 5 feet deep for the culvert work. Earthwork would be balanced onsite and would not require disposal or borrow sites. Construction of the project would generate approximately 4,000 cubic yards of asphalt grindings, which would become property of the contractor. Asphalt grindings may be reused onsite (excluding a minimal amount of grindings associated with yellow and white road striping).
This project will increase impervious area by 0.58 acres and replace (perpetuate) 2.41 acres of existing impervious area.
A staging area approximately 100 feet wide and 300 feet long would be located south of South Avenue and west of the intersection of South Avenue and SR 99.
Existing communication utilities within the project limits may need to be relocated.
Caltrans would permanently acquire approximately 2.75 acres of right-of-way from a private landowner to accommodate the new roundabout and reconfigured intersection. In addition, Caltrans would obtain a temporary construction easement to utilize approximately 0.73 acre of the same landowner’s property south of South Avenue for project staging and constructing a drainage ditch. Caltrans would also establish an approximately 0.086-acre permanent easement around the drainage ditch for future maintenance operations on the landowner’s property.
Construction of the project would be staged and would utilize one-way reversing traffic control as needed.
The work would be completed in one construction season and would require approximately 120 working days.
Alternative 2—No-Build/No-Action Alternative
The no-build/no-action alternative would make no improvements to the intersection of SR 99 and South Avenue and it would be expected that the vehicle collision rate and fatal plus injury rate at this intersection would continue at their present rates into the future.
Comparison of Alternatives
After comparing and weighing the benefits and impacts of all feasible alternatives, the Project Development Team has identified the build alternative as the preferred alternative, subject to public review. Final identification of a preferred alternative would occur after the public review and comment period. The no-build/no-action alternative is not preferred because it would not reduce the severity and frequency of collisions and would not meet the project purpose. The build alternative is preferred because it would meet the project purpose.
After the public circulation period, all comments would be considered, and the Department would select a preferred alternative and make the final determination of the project’s effect on the environment. Under the California Environmental Quality Act (CEQA), if no unmitigable significant adverse impacts are identified, the Department will prepare a Negative Declaration (ND) or Mitigated ND.
Similarly, if the Department, as assigned by the Federal Highway Administration (FHWA), determines the National Environmental Policy Act (NEPA) action does not significantly impact the environment, the Department will issue a Finding of No Significant Impact (FONSI).