A newly developed multifamily project in Anaheim was just finishing up construction when the contractor discovered the permeable paver system used to create the interior driveways was not functioning as intended. During even small rainfall events, stormwater was running off and ponding for long periods of time instead of disappearing into the engineered paver system. After some investigation, it was discovered that the paver bedding had gotten compacted beyond what the manufacturer recommended, preventing stormwater from draining away. Because the permeable pavers were part of the infiltration BMP and overall drainage design, this had to be remedied before the project could be closed out and homes could be sold.
This is when the development team asked Torrent Resources for help. After reviewing the boring logs from several drywell installations close to the project, we knew there was highly permeable material beneath the subject site. Knowing the drywell was a viable option, Torrent staff worked with the civil engineer to come up with a design that was simple and as unobtrusive as possible because the paver work was complete.
The proposed design included a perforated pipe connected to a MaxWell IV strategically located to intercept stormwater for infiltration. The small footprint of the proposed remedy allowed for minimal disturbance of the newly installed pavers, which helped keep costs down. With an overall depth of 40’, including a 20’ penetration into sand, the constant head percolation test on the completed MaxWell yielded a stabilized perc rate of 0.57 CFS (256 gpm). Even with a safety factor of 2, each drywell can handle a peak flow of 0.285 CFS and dispose of 49,248 ft3 in 48 hours.
These installations represent our 57th and 58th drywell installations in the City of Anaheim. Please let us know if you have a project in Anaheim and we will review the boring log and performance data for these systems to give you an idea if deep infiltration is feasible or not.