Rain Guardian Bunker

Compact, lightweight pretreatment designed for residential and small-scale bioretention systems

Product Overview

The Rain Guardian Bunker is a recycled high-density polyethylene (HDPE) pretreatment chamber engineered for durability, ease of maintenance, and reliable hydraulic performance in residential and light-duty bioretention applications. Its lightweight construction and compact form make it well suited for small practices and retrofit installations.

Constructed from 95 percent or greater recycled HDPE plastic lumber, the Bunker provides structural strength while offering resistance to rot, pests, and weathering. The unit is installed on a concrete pad, not included, and features a removable steel grate rated for a 316-pound concentrated load. The grate weighs approximately 35 pounds, allowing straightforward inspection and maintenance access.

Performance and Design Considerations

Hydraulic Performance
Integrated overflow points ensure inflows are not restricted as water enters the bioretention practice.

• Inlet capacity: up to 3.07 cubic feet per second

• Outlet capacity: up to 6.11 cubic feet per second

• Internal storage volume: 2.85 cubic feet

Ponding Depth Flexibility
The standard Rain Guardian Bunker is designed for a 12-inch ponding depth. An alternate Bunker configuration is available for applications requiring a 9-inch ponding depth.

With minor field modifications, either unit can be installed in bioretention practices with both shallower and deeper ponding depths. For deeper practices, a gradual slope can be used to transition from the base of the Bunker to the base of the rain garden. For shallower practices, a short course of retaining wall block can be used adjacent to the chamber to achieve the correct installation elevation.