Technical Note

For Sizing Infiltration Basins and Bioretention Devices to meet State of Wisconsin Stormwater Infiltration Performance Standards

Introduction

This technical note includes several tools approved by the Wisconsin Department of Natural Resources to design infiltration basins and bioretention devices capable of meeting the state of Wisconsin stormwater infiltration performance standards contained in ss. NR 151.12(5)(c) and NR 151.24(5), Wis. Adm. Code. The purpose of this technical note is to describe where these tools can be found and how they are used. The Department of Natural Resources recognizes the existence of other models that estimate stormwater infiltration. These other models and tools may also be used to meet the state of Wisconsin infiltration performance standards if approved by the Department of Natural Resources.

The tools included in this technical note are:

• a chart for determining target stay-on depth;
• RECARGA, an infiltration model that can be used to determine the required effective infiltration area for infiltration basins and bioretention devices;
• a set of design charts, developed using RECARGA, which can be used to determine the required effective infiltration area for infiltration basins.

The University of Wisconsin-Madison Department of Civil Engineering developed the RECARGA model. The University of Wisconsin and Department of Natural Resources staff developed the other design charts included in this technical note.

To design an infiltration basin or bioretention device, one or more conservation practice standards must be used in conjunction with this technical note. These conservation practice standards include other important requirements relating to siting, dimensions, construction, operation and maintenance of infiltration practices. The applicable conservation practice standards include:

• DNR Conservation Practice Standard 1002, Site Evaluation for Stormwater Infiltration [PDF 183KB]
• DNR Conservation Practice Standard 1003, Infiltration Basin [ZIP 901KB]
• DNR Conservation Practice Standard 1004, Bioretention for Infiltration [ZIP 773KB]
• Wisconsin Department of Natural Resources Specification S100, Compost [PDF 90KB]

The designer will use Parts 2 and 3 of this technical note and the DNR Conservation Practice Standard 1003 to determine the required effective infiltration area for an infiltration basin. Part 5 of this technical note may also be used. To determine the effective infiltration area for a bioretention device, the designer will use Parts 2, 4 and 5 of this technical note in conjunction with DNR Conservation Practice Standard 1004. In addition, DNR Conservation Practice Standards 1002 and S100 apply to both devices.

This technical note also cross-references several digital files that can be used to size infiltration basins and bioretention devices. A list of these digital files is shown in Table 1. Note that some of the digital files will be used in designing both infiltration basins and bioretention devices while others are specific to only one of these practices.