Project Description

Location

The project is located on I-25 at the intersection of Meadows & Founders Parkways at the north edge of Castle Rock, approximately milepost 184.

Total Interchange Reconstruction

The I-25 Meadows/Founders Parkway Interchange project consisted of the reconstruction of the Meadows Parkway Bridge over I-25, and reconstruction of the adjoining on/off-ramps. The project included the associated standard amenities and fixture replacements such as sidewalk, lighting, signalization, signing and striping, curb and gutter, guard rail, impact attenuators, retaining walls, grading, topsoil, and seeding. Mitigation efforts on the project included sound barriers along the residential area in the northeast quadrant of the interchange.

Detailed Description of Total Interchange Reconstruction

I-25, Meadows/Founders Interchange

Former Conditions - the old interchange was a typical diamond interchange, with two on-ramps and two off-ramps. The on-ramps and off-ramps joined the cross streets of Meadows/Founders Parkway at signalized intersections close to the bridge over I-25, which limited storage capacity between the intersections causing delays in clearing ramp traffic from I-25 at peak hours. Left turn traffic from Meadows/Founders to the I-25 ramps was required to stop and wait to cross oncoming traffic. This condition restricted the interchanges overall capacity. Traffic turning from Meadows/Founders to I-25 on-ramps had to slow to exit directly from through lanes.

New Construction - the new interchange, a large partial cloverleaf/diamond has four diamond ramps and two additional loop ramps. The new diamond ramps join the cross streets much farther from the bridge, allowing double left turns from the ramps in order to clear them more quickly, as well as increase the storage capacity. The two new loop ramps eliminate the left turns from Meadows/Founders to I-25, preventing traffic storage buildup on Meadows/Founders. The new Meadows/Founders includes two through lanes in each direction and an additional dedicated lane for each of the two diamond on-ramps. These two ramp lanes do not need to stop at the signalized intersections with the off-ramps which will increase the interchange capacity and improve traffic flow.

Meadows Parkway Bridge

Former Conditions - the old bridge structure was two lanes wide with left turns onto the on-ramps immediately off the structure. The width of the old bridge restricted through traffic on Meadows/Founders Parkway and, therefore, contributed to delays in clearing off-ramp traffic from I-25 at peak hours. The length of the old bridge also restricted many possible improvement options for I-25 below the overpass. Limited accommodations for pedestrians.

New Construction - the new Meadows/Founders Bridge (STU 0252-294 I-25) has four continuous through lanes and two additional dedicated lanes to the new loop ramps (see diagram). The newly completed Meadows/Founders Bridge over I-25 is 114 feet wide. There are two through lanes in each direction, plus a dedicated turn lane to the loop ramps, which match the new Meadows/Founders roadway section. The new bridge is long enough to accommodate any options for improving I-25, which may be determined necessary by the South I-25 Corridor and US 85 Corridor EIS. To safely accommodate an increase in pedestrian traffic, due to the developing commercial and residential nature of the area, 8-foot sidewalks have been added to each side, along with a 17-foot wide raised median.

Noise Walls

Former Conditions - there were previously no noise walls.

New Construction - Noise Walls, MSE (Mechanically Stabilized Earth) Sound Barrier has been constructed in the NE quadrant, along the northeast diamond loop ramp which carries traffic from Founders Parkway onto I-25. The noise walls provide noise protection to the residences in the Silver Heights Subdivision. The walls were designed and constructed with a vertical face on one side and reinforced earth berm on the other. The reinforced earth that holds the wall in place is more cost effective to construct than the traditional vertical wall set with a below ground foundation, and eliminated the long "canyon" effect, which was a concern of local residents. A noise analysis was conducted to quantify the impact of traffic noise on both current and future development in the vicinity of the interchange. The purpose of the analysis was to assess noise impact in the Silver Heights residential neighborhood, and to determine what traffic noise abatement measures were appropriate there. Land use in the remaining area around the interchange is either commercial or undeveloped. The decision to place the masonry barrier supported on one side by earth fill is a result of a joint effort with the homeowners affected, CDOT and the FHWA. This alternative was more cost effective than a vertical wall and better blends with natural surroundings.

Lighting and Signalization

Existing Conditions - a Span Wire traffic signal system.

New Construction - Mast Arm traffic signal system. All of the lighting at the interchange has been upgraded to current standards. Fiber optic inter-connect wire has been installed for coordination/timing of light cycles with four other intersections along the Meadows/Founders corridor.