Trends Summer 2011 | Page 8

familiar with the process before moving forward . “ The City was looking for an alternative solution that would be both cost-effective and constructible ,” Jacobsen said , adding it was also important that scour protection remain buried to replicate a natural stream bed under the bridge .
Despite initial skepticism , the process went smoothly . The riprap installation required careful maneuvering of a concrete pump truck and extendable boom under the bridge to place the grout properly . Ayres Associates oversaw the installation to see that it was achieved according to plan .
Danny Tezak , president of Tezak Heavy Equipment , the project ’ s contractor , said the partially grouted riprap was easier to install than traditional large boulders . “ I think the ( partially grouted riprap ) will have its place ,” he said , such as in confined spaces with tight clearances . “ The concept is very good .”
Tezak is the first contractor in the United States to use this innovative grouting technique , and Pennington praised their willingness to tackle the job . “ Tezak showed a lot of patience and diligence throughout the construction process , resulting in a high-quality project ,” he said .
Ayres Associates adapted the partially grouted riprap method to United States engineering practices as part of ongoing research for the Federal Highway Administration . The process was published in September 2009 as an approved countermeasure for protecting bridge piers against scour .
Construction of the riprap , grade control structure , and bank stabilization measures were completed without affecting the public . The pedestrian trail along the river remained open during construction so the link to the neighboring high school and surrounding areas remained intact , and the bridge remained open to traffic . Construction was sequenced so Sand Creek flows were diverted to one side of the channel while riprap and grout were installed on the other side . This allowed construction to occur in dry conditions to avoid environmental and construction issues commonly associated with placing grout in flowing water .
The improvements will increase public safety by protecting the bridge and surrounding areas in case of flooding . “ This was a total team effort ,” Pennington said . “ The efforts between the City stormwater division , the City bridge department , the batch ( concrete ) plant , Tezak , and Ayres Associates went very well and resulted in an outstanding product enhancing the community ’ s safety .”
If conventional materials and design methods had been used for the riprap design , protection against the 50-year flood would have cost the City approximately $ 140,000 . The partially grouted riprap alternative cost $ 47,000 and provides protection against a 500-year flood .
Ayres Associates exceeded the City ’ s expectations , Jacobsen said , by presenting an innovative approach resulting in an aesthetically pleasing and sustainable solution that did not disrupt traffic during construction .
“ We hired Ayres Associates for its expertise in channel restoration and bridge scour countermeasures , and they did not disappoint ,” Jacobsen said . “ The project was completed on time , and Ayres Associates ’ design saved us considerable money while providing a better solution to a complex problem .”