The Olivenhain Municipal Water District was in need of two environmentally sensitive roadway undercrossings for the McCrink Ranch development in Encinitas. The culverts would span two streams, one that outlets into a lake. A culvert was needed under both the Old Course Road and Lakeway Road.
Because the site was an environmentally sensitive area, natural, open bottom structures were essential for the project; however, due to poor soil conditions, strip footings were not feasible.
Contech worked with Laret Engineering on alternative solutions so that the integrity of the sensitive waters were kept. The solution decided upon included a slab foundation which was set four feet below the flowline to ensure that there were no scour issues. Cutoff walls were constructed at the inlet and outlet of the structure with weep holes allowing water to pass through the walls. The four feet were then filled with sediment to the flowline to mimic a natural channel.
The two CON/SPAN bridge systems were chosen for the project because they could handle the extreme fill height needed while also filling the “soft bottom” requirements. A 367.5 foot long structure with a 12 ft span and 8 ft rise was used on Old Course Road and a 74.5 ft long structure with a 12 ft span and 8 ft rise was used on Lakeway Road. The CON/SPAN structures provided a natural choice because they offered clear spans with small footprints that minimize intrusion into natural areas.
Olivenhain Water District was pleased with the solution at the time of construction. A recent visit to the site 6 years later (as shown in pictures) finds the culverts working well and the Water District pleased.