Standards Oversight Council (SOC)
Developing effective technical standards that protect Wisconsin’s natural resources
131 W. Wilson St., Suite #601, Madison, Wisconsin 53703
(608) 441-2677 || Fax (608) 441-2676 || socwisconsin.org
Rain Garden Standard Team
MEETING NOTES
Tuesday, Dec. 6, 2016 ▲ 9:00am – 12:00pm ▲ Dane Co. LWCD, 5201 Fen Oak Drive, Madison
Present: Perry Lindquist – Team Leader – Waukesha Co., Roger Bannerman – USGS, Judy Horwatich – USGS, Jim Baumann – former DNR, Eric Jacobson – private landscape, Ken Potter – former UW, Leif Hauge – Waukesha Co. Jennifer Thieme – Team Facilitator – WI Land+Water
Standards Oversight Council & Rain Garden Team
The Standards Oversight Council is an interagency collaboration to create and revise state technical standards. SOC strives for quality standards, uniformity in their application, and accountability throughout the process. Teams are assembled to contain broad representation. This team will gain further input through a review process, during which a complete draft is circulated among peers, colleagues, and the public for input.
Team website:
Team listserv:
Background
As a result of recent legislative updates, county shoreland zoning ordinances had to be updated to meet state standards under NR 115. Individual home/lot owners in shoreland zones are now subject to impervious surface limits, and must “treat” runoff coming from new impervious surfaces that exceed those limits (e.g., new home, addition on existing home). “Treating” the runoff would entail the application of stormwater BMP’s, such as a rain gardens, pervious pavement, green roofs, etc. In Waukesha Co.’s experience, rain gardens are viewed as the most common means by which to “treat” said runoff.
Leif had previously run calculations showing that one could meet TSS, infiltration and peak discharge performance standards (in NR 151) by infiltrating 100% of the first ½ inch of runoff. Waukesha Co. has used this standard in their stormwater ordinance for over 15 years and recently incorporated it into their shoreland zoning ordinance. Treatment can be allowed to occur anywhere on the property, not limited to adjacent to the impervious surface.
The DNR will be adopting this technical standard. Anyone using rain gardens to obtain credit for meeting nonpoint performance standards will be able to use the criteria in this document to meet the performance standards. Following this technical standard may also be used to demonstrate compliance with performance standards in local ordinances.
NOTE that the purpose of this team is to write the minimum criteria to design and construct a properly functioning rain garden; it is NOT writing a regulation.
There was considerable discussion regarding minimum sizing of rain gardens. It seems a technical standard should not mandate the stay-on (i.e., volume of water that rain gardens are designed to capture and infiltrate); yet, some sizing criteria is needed in the standard to avoid failure from too high of runoff to storage ratio; If there is no local ordinance, then this can provide the minimum.
Sizing
The team listed several local volume control ordinances:
- X% average annual non-winter rainfall
- Peak discharge (10, 25, 50, or 100 yr) design storm
- X% infiltration of precondition infiltration
- X inches rainfall depth from the impervious surface being treated
Jim recommended running models/testing for each of the three items listed above. If they converge, that will help the team’s decision-making process and streamline standard creation. If they do not converge, the team will know to move forward with separate criteria for each situation, or can seek an alternative approach.
Ken raised concern over writing the standard for the way one county currently handles this situation. He currently serves on a local committee that will seek 100% runoff control. Additionally, there is concern about disconnect between what is enforced in urban areas vs. shoreland; will the team adopt something much more restrictive than what could be passed in urban landscapes?
Primary question: What guidance (e.g., in a chart) does the team provide to the user for sizing? Roger and Judy have seen 50:1 ratios on some bioretentions, which is much smaller than they would recommend for sizing.
Sizing is a major topic and will drive much of the criteria. This will be addressed at the next meeting.
DECISIONS
- During next meeting:
- Review Leif’s model and assess ½” recommendation
- Discuss different scales (e.g., single home, subdivision)
- Get DNR’s input via Roger prior to meeting
- CONSIDER the option to make this standard the minimum size if there is no local mandate requiring otherwise
Audience
Perry initially recommended this be developed for the average homeowner. The team agreed that the current draft could not be implemented by this audience. A landscape professional would be much better equipped to use this technical document, although it may exceed some landscapers’ level of expertise. The team noted that the cost of hiring a professional landscaper is very small compared to the cost of building a new or expanding an existing lake house; therefore, hiring a professional to assist in meeting shoreland ordinance will rarely be prohibitively expensive.
It was noted that a technical standard could be used for private/contractual purpose, or several public purposes:
- Meeting a regulatory standard/ordinance requirement
- Applying for a stormwater utility fee credit
- Qualifying for public cost-sharing
Several members acknowledged that undersized rain gardens are being installed, and this standard can help address that issue.
Frank often uses/references the 2003 rain garden manual and finds this type of guidance helpful. There will still be a need for this level of guidance aside from the technical standard. Perry noted that an example will play an important role, as most users will migrate toward the examples.
Jim: While the current O&M seems intimidating, it does not preclude the use of an off-the-shelf O&M plan. Consider simplifying/clarifying this and other sections that seem unnecessarily complex.
An individual homeowner not in a shoreland zone is not required to meet performance standards – then are they even an audience?
Many team members raised concern that people who are required to meet stormwater standards will use rain gardens IF rain gardens are less restrictive. Take care not to design criteria that way, or to otherwise avoid that.
DECISIONS
- Confirm audience at next meeting
Draft Standard Text
The team reviewed Definition through Criteria V.A.1.
Criteria section currently states that 1002 Site Evaluation for Infiltration must be followed. The team discussed how to make this more appropriate and user-friendly. At its most basic level, 1002 seeks the soil type, soil texture, and depth to groundwater or bedrock. It was suggested to list these items specifically for individual homeowners, and consider retaining 1002 requirements for larger projects such as subdivisions.
SUMMARY OF PRIMARY DECISIONS
- Remove the word “device”
- Remove reference to “mulch” in Definition
- Add Purposes (to be wordsmithed)
- Increase groundwater recharge
- Avoid soil erosion & mitigate adverse drainage
- Maximize distribution of stormwater
- Consider where to place a note/reference to the benefits for wildlife
- Rain gardens are best suited to “…residential and commercial rooftops.” This excludes industrial roofs.
- Ensure consistency with regard to salt-based deicers; update Conditions Where Practice Applies if Criteria changes
- Add note that local laws may contain more strict/specific information on rain gardens
ACTION ITEMS
ROGER
- Talk with DNR regarding this standard’s link to performance standard and the team’s authority to make certain decisions
- Update drafted text as needed
KEN
- Send Jennifer the name of specific developers to invite to a future meeting and/or include in the draft’s initial review
TEAM
- BY DEC. 23, fill out Doodle poll for next meetings
- Review 1002 and contact Roger with questions
- Review the draft: The 1st paragraph under Site Criteria section (lines 42-44) & Infiltration Rates (lines 72-79)
- Bring a recommendation on audience to the next meeting:
- To whom does this standard apply?
- Which audiences should follow 1002?
- If an audience should not follow 1002, what siting survey do you recommend?
- Consider these audiences & scales:
- Land subject to stormwater ordinances (commercial, subdivision)
- Homeowners subject to shoreland ordinance
- Homeowners not subject to shoreland ordinances
- If you have minor comments on the draft, share them with Roger
JENNIFER
- Distribute meeting notes & 1002 standard; Reformat and share the drafted standard; Send Doodle poll for next meetings; Create team webpage
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