Careers Contact Us
Contech Design Center mobile

Deer Ridge Memory Care

Puyallup, Washington


SCJ Alliance




June 2020

Technical Description:

1,750LF 960 of 78” PERF ALT2 CMP

A new elderly care facility in Puyallup, Washington, required a large amount of stormwater runoff capture due to the large amount of impervious surfaces.

Infiltration could not be done due to poor soils and high groundwater, so a detention system was required. The detention system was initially designed using a plastic crate system. However, Contech was able to show the engineer how corrugated metal pipe (CMP) could meet the detention requirements, fit within the site, and overall be installed at a a lower installed cost.

Contech also worked with the engineer for over a year fine-tuning the design to deal with emerging site constraints and conditions. One such condition being the discovery of high groundwater. This discovery led to the use of an impermeable liner as a leakage barrier, and to a redesign from solid CMP to perforated CMP to optimize the footprint even further. Contech Stormwater Engineers worked closely with the engineer to revise the system layout and provided stage storage calculations as needed.

After the design was finished, the developer, eager to find some savings, looked at some alternative detention solutions. Plastic chambers, CIP concrete, precast concrete, and plastics crates were all considered potential alternates, but none were more cost effective than CMP provided by Contech.

The biggest challenges we faced on this detentention design were the site constraints. The detention system required a highly customized layout to fit within the irregularly shaped footprint that was designed to avoid important landscaping areas. Due to high groundwater, the system also required a water leakage barrier. To address this, the engineer elected to use a 30mil impermeable liner wrapped around the perforated CMP/stone backfill.

CMP proved to be the best solution for several reasons.It was the most cost-effective option, Contech associates helped the engineer through numerous design changes, and CMP was flexible enough to fit within the tight, constricted site.

Installation was a success using only nylon straps and an excavator, with the system being installed in two phases. The Consulting Engineer at SCJ Alliance, Mallory Dobbs, said “Contech went above and beyond to support me through the ongoing design changes, no one comes close to their level of service!”

Technical Description:

1,750LF 960 of 78” PERF ALT2 CMP

800-338-1122 |

© 2022 Contech Engineered Solutions LLC, a QUIKRETE Company