As previously noted in our September posts, PA DEP has convened a BMP Manual Revision Committee. In their notification to attendees, they noted that

… recommended updates may include edits to existing portions, complete omissions, or additions of new material.  All changes much be justified through acceptable principles of engineering or science.  If unable, to do so, subgroups may bring new ideas before the bigger committee for consideration and feedback.

Following is PA DEPs statement on the focus of this  Sub-Group, as presented at the first Committee Meeting:

Much attention has been given to the “loading ratios” approach for sizing infiltration BMPs.  It has been found that this approach is better suited as a planning tool and default for practitioners who do not want to do a more thorough site assessment.  Therefore, this subgroup is tasked with developing clearer and more thorough criteria for sizing infiltration BMPs.  Questions:

Should hydraulic depth be utilized more as limiting factor (to avoid compaction at the air-soil interface)?

Should a risk-based approach to infiltration BMP design be incorporated into the manual?  For instance, should there be a maximum drainage area?  Should underground systems be designed more conservatively than above-ground systems?  What other factors should be considered in the design of infiltration BMPs.  See white paper for discussion on this matter.

Should mandatory pretreatment be incorporated into all infiltration systems (to what level  or particle size - 100 micron?)

Site evaluation and soil infiltration testing:

• Subgroup should reviewt and “beef up” the Soil Testing Protocol for infiltration BMPs
• Entire Appendix C, Protocols 1 and 2 should be evaluated for update.
• Infiltration Range from 0.1 to 10 in/hr;
• infiltration in fill (how long of a consolidation time before an area is no longer considered fill - 5 years?)
• Subgroup should review setbacks from dwellings, septic systems, drinking wells, property lines?  Should topography play a role - hillside hydrology.

Geological Issues (karst, other geologic formation, etc.)

• Should depth to limiting zones be kept at 2 feet.  Should it vary depending on soil permeability?
• When, if at all, should a mounding analysis be required?  Should PA follow NJ’s lead?

Water quality issues (nitrates)  (see Subgroup Topic E)

Infiltration on contaminated sites.  (See Subgroup Topic G)

Should infiltration of storms greater than the 2-year 24-hour event be “specifically” discouraged?   There are some municipalities who require infiltration of the 100-year storm.  Depending on the extent of the project, this can lead to issues in the future.  Many municipalities defer to the PA BMP Manual for technical guidance (MS4 etc.).   Discussion of this topic is important since infiltrating too much water has been identified as a concern.

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There is no doubt that the Manual needs to be edited and updated.  For example, new technical information relating to BMPs has emerged which can and should be integrated.  At the same time, the line between “technical” and “policy” is a slippery one.   Sub-groups have been formed assigned to control Guidelines (i.e., stormwater standards) as well as methodologies.  Though issues surrounding both of these vital topics are hugely technical, they ultimately also are very policy oriented.  One could even argue that design specifications relating to how to build infiltration BMPs are policy oriented as well.

Understanding this somewhat “murky” separation between technical and policy, state environmental groups such as the Pennsylvania Campaign for Clean Water have contacted PADEP and are requesting that  the Revision Committee be expanded (see their letter below) in order to guarantee that important issues of water quality, hydrology, habitat, landscape ecology, and other aspects of environmental planning be fully represented and balanced in this Manual revision process (similar to the Oversight Committee which oversaw development of the existing Manual).  We will try to keep you informed as this process unfolds…

September 14, 2009

John Hines
Deputy Secretary
PA DEP
Rachel Carson Office Building
Harrisburg PA 17105

Dear John:

We recently learned about a series of meetings being convened by Domenic Rocco of the Southeast Regional Office to consider possible changes to the Stormwater BMP Manual.  We are very concerned that the group invited to these meetings includes few if any environmental stakeholders, and is overly representative of the interests of the regulated community–developers and the engineers that work and advocate for them.

As you know, the development of the BMP Manual was a rigorous process that included an Oversight Committee with broad stakeholder involvement and several public hearings to solicit public input.  The product of that effort was a technically sound guidance manual for reducing the generation of and properly managing post-construction stormwater runoff in Pennsylvania.  While we agree that the Manual should not be a static document and should be revised over time to reflect advances in the state of the art, any changes should be made in a very transparent way, with full involvement by a broad range of stakeholders, including the environmental and conservation communities. We believe the current process falls far short of this standard.

We encourage the Department to clarify the purpose of the meetings convened by Mr. Rocco.  If this is indeed the start of a process to revise the Manual, particularly the control guidances, we strongly encourage the Department to broaden the participants in the group, in particular adding representatives of the environmental and conservation communities, along with other interested groups including Conservation Districts and municipal officials.  In addition, the Department should clarify its plans regarding public participation in the Manual review process and the goals for such a process.

We look forward to hearing from you regarding our concerns at your earliest convenience.

Sincerely,

Bob Wendelgass
PA Campaign for Clean Water
1315 Walnut Street, Suite 1650
Philadelphia PA 19107

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