1. DEPARTMENT OF ENVIRONMENTAL PROTECTION
      2. Bureau of Watershed Management
      3. COMMENT AND RESPONSE DOCUMENT
      4. COMMENTATORS:
      5. COMMENTS AND RESPONSES:

DEPARTMENT OF ENVIRONMENTAL PROTECTION
Bureau of Watershed Management
COMMENT AND RESPONSE DOCUMENT
Technical Guidance #363-0300-002: Pennsylvania Stormwater Best Management Practices Manual
COMMENTATORS:
1. The Alliance for Aquatic Resources Monitoring (ALLARM)
Lauren Imgrund, Director
Dickinson College – Environmental Studies Dept.
Carlisle, PA 17013
2. Bob Bauer
(Commented via email, address unknown)
3. Borton-Lawson
Paul A. DeBarry P.E.
Hydrology / Hydraulics / GIS, Section Head
Lehigh Valley
Bethlehem, PA 18017
4. Bucks County Planning Commission
Lynn T. Bush
Executive Director
Doylestown, PA 18901
5. Chesapeake Bay Foundation
Harry Campbell III, Scientist
Old Waterworks Building
Harrisburg, PA 17101
6. Citizens for Pennsylvania's Future
Matt Royer
Staff Attorney
Harrisburg, PA 17101-1113
7. Clean Water Action
Robert Wendelgass
PA State Director
Philadelphia PA 19103
8. Commonwealth of Pennsylvania
Department of Transportation
Bureau of Design
Director Scott Christie
1

9. Commonwealth of Pennsylvania
PA Department of Transportation
PennDOT Engineering District 9-0
Brad J. Brumbaugh, P.E.
Senior Project Manager
10. Commonwealth of Pennsylvania
PA Department of Transportation
District 11-0
Mark J. Young
Environmental Project Manager
Bridgeville, PA 15017
11. Commonwealth of Pennsylvania
PA Department of Transportation
District 12-0
Michael Barrick
Uniontown PA 15401
12. CONTECH Stormwater Solutions Inc.
Joseph G. Battiata, P.E.
Regulatory Relations Manager
Mechanicsville, VA 23111
13. David J. Cooper, P.E., Civil Engineer
Pittsburgh, PA 15216
14. Delaware Riverkeeper Network
Maya K. van Rossem
Washington Crossing, PA 18977
15. DelVal Soil & Environmental Consultants, Inc.
William E Palkovics, PhD.
President
Doylestown, PA 18901
16. Digman Township
Chris Wood
Code Enforcement Officer
Milford, PA 18337
17. Dominion
Pamela F. Faggert
Vice President and Chief Environmental Officer
Glen Allen, VA 23060
18. EPA Region III
Paula Estornell
2

19. EP Henry
Kevin Earley
Manager, Permeable Pavement Solutions
Woodbury, NJ 08096
20. Fox Ridge Marketing, Inc.
Carl DuPoldt, MS, PE, PLS, SEO, PBH
Edgemont, PA 19341
21. William Lee Glover and T Glover
Rural Valley, Pa 16249
22. Green Valley Association
John Hoekstra
Director of Watershed Advocacy
23. Herbert, Rowland & Grubic, Inc.
Al Brulo, Vice President
Harrisburg, PA 17111
24. Independent Oil and Gas Association Environmental Committee
Bruce Snyder
Chairman
25. Interlocking Concrete Pavement Institute
David R. Smith
Technical Director
Washington, DC 20005
26. Keystone Consulting Engineers, Inc.
Dean L. Hass PLS
Elisa A Highley
Wescosville, PA 18106
27. Larson Design Group, Inc’s.
Quay Schappell
Samuel E. Young, P.E., P.L.S.
28. Lehigh Valley Planning Commission
Laura M. Eberly, P.E.
Senior Engineer
Allentown, PA 18109
29. Maiden Creek Watershed Association
Mark Fiorini, President
Kempton PA 19529
3

30. Mid-Atlantic Environmental Law Center
Jennifer Murphy, Staff Attorney
c/o Widener University School of Law
Wilmington, Delaware 19803
31. Richard G. Myers
Furlong, PA 18925
32. NRCS – Harrisburg
William J. Bowers, P.E.
Geoff Cerrelli, P.E.
State Conservation Engineer
33. PennEnvironment Director
David Masur
Philadelphia, PA 19102
34. Pennoni Associates Inc.
Andrew Bennett, P.E.
Associate Vice President
Regional Manager NE PA
Bethlehem, PA 18017
35. PA Chamber of Business and Industry
Sharon Roth, Director
Government Affairs and Customer Advocate
36. Pennsylvania Environmental Council
Gwyn W. Rowland
Director, Watershed Programs
Philadelphia, PA 19106
37. The Pennsylvania Housing Research
Scott A. Brown, P.E.
University Park, PA 19872
38. PA Organization for Watersheds & Rivers
Judith H. Jordan
Executive Director
39. Pennsylvania Resources Council, Inc.
Larry D. Myers
Executive Director
Newtown Square, PA 19073
40. Pennsylvania State Association of Township Supervisors
Elam M. Herr
Assistant Executive Director
Enola, PA 17025
4

41. Professional Recyclers of Pennsylvania
John Frederick
Executive Director
Bellwood, PA 16617
42. Pulte Homes of Pennsylvania, L.P.
Ray Grochowski, Jr.
Director of Land Entitlements
Delaware Valley Division
Trevose, PA 19053
43. Sierra Club
Lehigh Valley Group
Barbara Benson, Conservation Chair
44. Sierra Club – Pennsylvania Chapter
Tom Power, Chair
Harrisburg, PA 17108
45. Sierra Club
Southeastern Pennsylvania Group of the Sierra Club
Robin Mann
Water Issues Chair
Rosemont, PA 19010
46. Skelly and Loy, Inc.
Gary A. Miller
Environmental Specialist
Port Matilda, PA 16870
47. Sweetland Engineering & Associates, Inc.
Larry Fennessey, Ph.D., P.E.
State College, PA 16803
48. The Turtle Creek Watershed Association
Board of Directors
Diane D. Selvaggio
49. USCC STA
Al Rattie
Program Administrative Manager
50. Villanova Urban Stormwater Partnership
R. Traver, Ph.D., PE, D.WRE
Associate Professor, CEE Dept
Villanova University
Villanova, PA 19085
5

51. L James Watters III
Norristown Pa 19403
52. Westmoreland County Conservation District
Jim Pillsbury
Greensburg, PA 15601
53. Harlow Flory
Assistant Executive Director
COMMENTS AND RESPONSES:
Comment:
Support: This Manual presents a catalyst towards bringing stormwater management in
Pennsylvania inline with the current state of the science. The guidelines are clear, yet sufficient
flexibility in choosing BMPs and developing plans which incorporate nonstructural and structural BMPs
is built into the process to account for variability in site conditions. To this end, the Manual represents a
significant step forward in providing a blueprint for achieving watershed protection in a more cost-
effective manner. The manual is an improved and detailed document, presenting a thorough range of
structural and nonstructural best management practices (BMPs) for reducing the environmental impacts
associated with stormwater management, minimize stormwater runoff therefore reducing damage to our
roads and bridges, recharge the natural groundwater regime, and to reduce pollution impacts on streams.
(1) (3) (5) (7) (14) (17) (19) (20) (21) (25) (35) (36) (38) (39) (40) (41) (44) (45) (47) (51) (53)
Response:
DEP acknowledges the comment and support for the manual.
Comment:
Non-support: The manual is not applicable in all areas of the Commonwealth or to existing
small lots (1/4 to 1/2 acre parcels). I would strongly suggest that the manual not be implemented until
such time as viable solutions are found for the existing properties in the Northeast portion of the State.
(2) (16)
Response:
The goal of the BMP Manual is to provide guidance on meeting the regulatory standard to
protect ground and surface water resources when performing land development activities by replicating,
to the maximum extent practicable, the infiltration and runoff characteristics of the site prior to the
development activity. To achieve this goal, the BMP Manual establishes an approach to stormwater
management that emphasizes procedures that avoid, minimize, and then mitigate effects through BMPs
that focus on infiltration, water quality treatment, and volume and rate discharge controls.
DEP recognizes the commentator’s concerns related to the use of infiltration in some areas. Where on-site
assessments indicate infiltration is not practical because of potential harm to the environment or public
safety, infiltration is not appropriate. In these circumstances, the project designer still must ensure the
post-construction stormwater management plan is designed to protect existing stream uses in all streams
and to maintain water quality in High Quality and Exceptional Value streams. Project plans and narrative
will be required to support the alternative methods of post-construction stormwater controls. An
assortment of BMPs described in the Stormwater BMP Manual can be used to achieve this goal. Prior to
proposing a land development activity, land developers, consultants, contractors, etc. will need to make
careful choices regarding the type of stormwater BMPs to be implemented in order to compensate for the
hydrologic changes caused by the development activity. The BMPs will need to reduce nuisance flooding,
reduce stormwater pollutant loads, maintain ground water recharge, and protect stream channels and
streambanks from scour and erosion. Selecting either non-structural or structural BMPs for a specific site
6

will require consideration of soil type, topography, geologic features, landscape position, hydrology,
climatic conditions, and other pertinent information. The BMP Manual provides BMP efficiencies,
specifications, standard drawings, and other essential information to guide the user in the selection and
development of stormwater BMPs for these types of activities.
Comment:
General - Training: We urge the Department to launch a comprehensive program to educate
developers and municipal officials, engineers and solicitors about the new Manual. Because the Manual
represents a significant paradigm shift and because so much of the Manual will be actually implemented
at the municipal level, it is critical that municipal officials and staff understand its concepts and operation.
A series of workshops, new informational materials including booklets and a possible DVD, and seminars
at meetings of groups like the Pennsylvania State Association of Township Supervisors will be critical to
ensure that the Manual is uniformly and successfully implemented across the state. (7) (18) (36)
Response:
DEP agrees. An aggressive training and education program is essential for the successful
implementation of the BMP Manual. DEP, with assistance from public and private partners, will ensure
that a series of comprehensive training opportunities is provided to all potential users.
Comment:
General - Model Ordinance/Manual: The Department must directly incorporate the Manual
into the new Model Ordinance that it recommends for municipalities in the state. The new Model
Ordinance must be completely consistent with the Manual and incorporate it by reference. Differences
between the Manual and Model Ordinance will be confusing for developers and municipalities. Because
developers will follow the legally binding ordinances instead of the Manual, failure to incorporate the
Manual into the new Model Ordinance will ensure that the Manual will have a limited impact, wasting the
thousands of dollars and hours that went into its development. (7)
Response:
DEP has revised the Model Ordinance to specifically reference the design considerations
identified in the BMP Manual.
Comment:
The Department should require all municipalities that have already adopted stormwater
management ordinances to ensure that their ordinances are at least as strong and protective as the new
Manual and Model Ordinance. Many municipalities have already adopted stormwater management
ordinances, some of which are not consistent with the new approaches in the Manual. Allowing
municipalities to retain these weaker ordinances in the long-term will weaken the effectiveness of the
Manual, and allow flooding, groundwater and baseflow depletion and stream impacts to continue.
We urge the Department to require all municipalities to review their ordinances within six months from
the final adoption of the Manual and to revise their ordinances as soon as possible thereafter to ensure that
they are at least as protective as the new Manual and Model Ordinance. This will ensure that all
communities across the commonwealth will benefit from the new approaches and strategies in the
Manual. (7) (14) (22) (28) (36) (40)
Response:
Municipal involvement is an essential factor in successfully addressing stormwater runoff
problems around the Commonwealth. The Model Ordinance has uniform requirements that have
statewide applicability to address such impacts. The Model Ordinance establishes the minimum baseline
requirements for counties and municipalities involved with Act 167 planning and implementation, and
MS4 municipalities. All other municipalities will be encouraged to update their existing stormwater
ordinances to be consistent with the model ordinance. Within resource constraints, DEP will assist
municipal officials in this effort when requested.
7

Comment:
Stormwater BMP retrofitting is not adequately addressed. Many of Pennsylvania’s older
developments have little or no stormwater management practices. And, unfortunately, many of today’s
developments employ outdated and ineffective methodologies. The result has had a significant, and
growing, impact on our water resources. As such, a significant effort to retrofit existing developments
with today’s state-of-the-art stormwater BMPs is needed. To facilitate such, the Manual should include a
chapter on such opportunities, including those in ultra-urban settings where no stormwater BMPs may
exist.
Focus on Prevention: Throughout the Manual, it is important that DEP make the point that use of best
management practices will reduce the pollution, flooding, erosion, habitat loss, drought and community
harm created by inappropriate development and peak rate focused stormwater management strategies.
Discussion about the benefits of a best management practices approach (as opposed to a peak rate focused
approach) is limited in the current draft.
The proposed manual is inadequate because it fails to focus on best management practices such as design
that would actually prevent stormwater runoff. Instead the manual presupposes that stormwater runoff is
inevitable and focuses upon a peak rate approach. Such an approach will not solve or assist with
stormwater runoff because it will create the same cycle of sediment and erosion problems and inadequate
measures that we presently see, thereby harming water quality.
The manual discusses many scientific data and approaches that I do not believe are scientifically accurate
or valuable. For example, to discuss base pollutant loading with a chart derived from the NJ coastal plain
is irrelevant. I am utterly confused by Chapter 8 and hope that we will be able to comment again, once
this chapter has been simplified and revised.
As a more editorial comment, the Council recommends that the Department review many of the images
that were copied from other documents and placed into the Manual and make sure that the resolution is
high and the images are sharp and clear. While the Council is aware that this is a “living document”, the
Manual will also be used as an everyday guide; therefore, to the extent the images are highly legible and
readable it will facilitate better understanding and comprehension by users, particularly those individuals
less familiar with these practices.
There is a lot of good information in this manual. However, chapters 2, 3, and 8 need significant
additional attention. The manual presents far too many general “rules of thumb” without stating they are
just “rules of thumb”. This will result in reviewers potentially making designers modify good designs into
poor designs.
We are very concerned that the above important elements are not sufficiently emphasized and supported
in the present draft. The Manual, for example, should emphasize, throughout, the use of strategies to
prevent the generation of stormwater runoff. And it should discourage both unnecessary destruction of
natural resources that provide natural capture of precipitation and also the use of outmoded and harmful
peak rate focused stormwater management strategies.
Large runoff events will always occur, continue to get worse, and become more frequent despite this
manual. Therefore, the State should include outright restrictions against any development within
floodplains or drainageways, or other critical stormwater areas, some of which are addressed in Chapter 5.
8

Some commentators had detailed comments directly related to a specific BMP. These comments have not
been added to this summary, however are generally represented in the comments above. (1) (5) (8) (29)
(30) (33) (34) (36) (37) (45) (46) (49) (47) (50) (52)
Response:
DEP recognizes the problems associated with the lack of, or inadequate past stormwater
management practices. The BMP Manual primarily focuses on new land development rather than
restoration and remediation, retrofitting stormwater management BMPs for past practices. Remedial
actions could be a component of a local Act 167 Stormwater Plan, MS4 municipality, or other locally
approved ordinance. Depending on site conditions, most of the BMPs highlighted in the manual can be
used to manage stormwater from redevelopment.
DEP agrees that problem prevention should be the primary means of addressing stormwater and it is
emphasized throughout the Manual. Prevention is the first and most effective means of controlling
stormwater runoff. The manual identifies prevention, minimization and mitigation as the hierarchy of
stormwater management strategies. The manual addresses all aspects of stormwater management
including peak rate, volume and water quality.
Chapters 2, 3, and 8 have been substantially edited to improve readability and enhance understanding of
the document. The manual will be published with the clearest and highest quality pictures and graphics
feasible.
While DEP generally agrees that floodplain development should be restricted, the Manual is not a
regulation and is not the proper vehicle to address the issue. Avoiding sensitive areas and preserving
“green infrastructure”, is a major theme of Chapter 5 and it is highlighted throughout the document.
Comment:
General - Application of standards, consistency: A clear methodology and process for
reconciling the differences of stormwater management approaches needs to be established. It is unclear
how differences between requirements, standards, criteria and approvals at the local, county, and the state
or DEP regional level will be reconciled in advance of projects being run through the process. Current
approaches at various levels of government are not consistent and sometimes are directly contradictory in
their requirements. (For example, where the Manual calls for BMPs that foster infiltration of stormwater,
some communities with karst conditions or other concerns have ordinances that preclude such infiltration
designs.)
While recognizing that Pennsylvania is a state of many socio-economic and physiographic regions, and
that solutions from one region may not be desirable for another region, DEP must, as part of its
implementation of the Manual, ensure that inconsistencies in interpretation and application between
regions and programs are reduced. In that regard, one of our more serious concerns is that some regional
DEP staff will treat this Manual as if it were a “regulation,” providing a cookbook recipe for what BMPs
can or should be undertaken at each development. Our experience has been that such an approach is
impractical and unworkable. Department staff, as well as county and municipal officials, needs clear
direction that this Manual is a reference point and resource for BMP ideas, not a prescription for every
case. Site-by-site considerations and a balancing of factors is required to select the right BMPs for any
property or development, and creativity, common sense and good engineer practices must be applied in
the BMP selection and implementation process.
A good BMP manual contains specific guidance on how to select, size, design, construct, and maintain
practices at each development site. Both the construction and long-term operation and maintenance of
stormwater management practices need to be consistently evaluated.
9

Who will review these new design guidelines/criteria? Neither the State, Counties, nor municipalities
have adequately educated staff to review these new criteria. The State must consider the consequences of
providing unlicensed regulatory officials with methods to evaluate designs or computations performed by
a licensed professional (engineer, land surveyor, landscape architect). (30) (35) (42) (47) (48)
Response:
DEP, in conjunction with the Stormwater Manual Oversight Committee, has
endeavored to identify the best and most innovative BMPs in the Pennsylvania Stormwater BMP Manual.
This Manual will promote and improve consistency among all levels of government by providing rational,
scientifically supportable strategies and methods of properly controlling stormwater. The model
ordinance is designed to support this objective. Education will by key to maximizing consistency among
potential user groups.
The Manual has been revised to further emphasize that it is a guidance document and not a regulation.
This key point will be clearly conveyed at all training and outreach sessions, and at all other presentations
and meetings. The Manual has also been revised to more clearly state that its intent is that of a technical
reference of planning concepts and design standards that must be tailored to local site conditions. It is not
a “cookbook” and not a substitute for good judgment or good engineering practice.
It is anticipated that individual BMP operation and maintenance will be performed and evaluated by the
BMP owners, as well as local and state government. The model ordinance highlights the need for
effective operation and maintenance and identification of responsible parties. New BMPs will
undoubtedly continue to emerge through research, innovative designs and business ventures. BMPs not
currently listed in the manual may be used if their efficiency can be documented and verified.
Comment:
General - Regulatory status of Manual: In summary, we request that Pennsylvania retain and
perhaps embellish on language in the Manual that makes it clear that the manual is guidance, not
regulation, and should be used in the field in a flexible manner.
When the process began to develop the Stormwater BMP Manual, it was emphasized that this was a Best
Management Practices Manual only and there would be no regulation. However, now there is the
accompanying Model Ordinance that local municipalities can adopt. This is a major concern to our
industry here in Pennsylvania. (17) (24)
Response:
This guidance has been developed in accordance with longstanding DEP practice and with
public participation. It is not a regulation or statute. It describes the framework for stormwater
management in Pennsylvania, utilizing existing statutory and regulatory authority. These statutes and
regulations were duly promulgated in accordance with law. Solutions other than those presented in the
Manual of protecting water quality will be evaluated on a site-by-site basis.
Comment:
General - Liability for problems from failed BMPs especially infiltration. Can this policy be
implemented statewide and across all soils types and topography? Karst areas, in particular, are difficult
to infiltrate into and the recharge may result in unforeseen problems and potential liability.
If a designer states that mandated “volume control” is not physically possible or recommended, but DEP
staff insists it upon, will DEP staff be considered culpable to future litigation that results? Additionally, if
DEP requires a professional to seal “engineered infiltration” designs, then the DEP reviewer should
likewise be required to professionally seal their review. How else will reviewers be held accountable?
(26) (34) (40) (47) (48)
10

Response:
The BMP Manual outlines an approach that identifies avoidance, minimization, and
mitigation of stormwater to recharge groundwater, provide base flows to watercourses over the year,
reduce pollutant loadings to streams, and reduce the threat of flash flooding and stream bank erosion
during storm events. Groundwater recharge through infiltration BMPs, where appropriate, can be a key
objective of an effective stormwater management plan to support and sustain groundwater resources, and
to maintain baseflow of streams. The goal is to minimize potential problems resulting from land
development activities to ground and surface water resources by replicating to the maximum extent
practicable, the infiltration and runoff characteristics of the site prior to the development activity. To
achieve this goal an approach to stormwater management that emphasizes infiltration, water quality
treatment, and volume and rate discharge controls is recommended. Selecting infiltration and other BMPs
for a specific site will require consideration of soil type, topography, geologic features, landscape
position, hydrology, climatic conditions, and other pertinent information.
DEP recognizes the commentator’s concerns related to the use of infiltration in some areas. Where on-site
assessments, field measurements, and the collection of other data conducted by professional hydro-
geologists indicate infiltration is not practical because of potential harm to the environment or public
safety, infiltration may not be appropriate. In these circumstances, the project designer must utilize other
BMPs that address volume to ensure that the post-construction stormwater management plan is designed
to protect existing stream uses in all streams and to maintain water quality in High Quality and
Exceptional Value streams. Project plans and narrative will be required to support the demonstration of
non-discharge alternatives and Antidegradation Best Available Combination Of Technologies (ABACT)
methods for post-construction stormwater controls. An assortment of BMPs can be utilized to achieve
these water quality protection goals. The BMPs contained within the stormwater BMP manual are
considered environmentally sound and cost effective when used according to the standards, specifications,
and other information provided within the Manual.
Prior to proposing a land development activity, land developers, consultants, contractors, etc. will need to
make careful choices regarding the type of stormwater BMPs to be implemented in order to compensate
for the hydrologic changes caused by the development activity. The BMPs will need to prevent flooding,
reduce stormwater pollutant loads, maintain ground water recharge, and protect stream channels and
streambanks from scour and erosion.
This Manual will provide BMP standards, specifications, standard drawings, and other essential
information to guide the user in the selection and development of stormwater BMPs, however it is not
intended to replace the decision making of professionals in private practice. DEP is aware and concerned
of potential environmental and safety issues. Project developers and planners will be responsible for site
assessment to determine the site limitations.
Comment:
General – Variability of socio-economic conditions: The Manual as written does not
evaluate or address the economic costs associated with implementation of the recommended BMPs. Early
in the Commonwealth’s development of this proposal, it was determined that DEP did not need any
further laws or regulations to meet the EPA requirements for stormwater management. Given the breadth
of the program and its increased scope to address water quality and quantity issues, this decision needs to
be reopened. The Manual creates an iterative process for managing stormwater. This approach provides
little regard for the costs involved in this process. Those costs will be passed on to homebuyers and
consumers, and/or can have significant impacts on the economic competitiveness of the Commonwealth
in attracting new plants and investments. The full range of costs associated with how these BMP’s will be
implemented (including costs on governmental agencies at all levels, and capital and O&M costs imposed
on property owners) need to be clearly articulated and understood. In order to understand the true impact
11

of the regulatory program being promoted, this Manual should go through the same type of socio-
economic impact evaluation as would be applied to a regulation. (35)
Response:
The Stormwater BMP Manual is a DEP guidance document and not a regulation. Stormwater
management is already being incorporated into most land development plans to meet existing local
ordinances, and state and federal regulatory requirements. This guidance document refocuses those plans
to more effectively manage and protect our ground and surface water resources. Costs associated with
these BMPs should not significantly affect the overall project costs, and in many cases could prove to be
less costly. From a cost effective perspective, improved stormwater management will translate to less
frequent downstream flooding, reducing property damage and associated costs.
Comment:
PENNDOT, The Turnpike, and DEP develop a Stormwater manual (this would be a chapter
in the DEP Manual) as a guideline for future highway reconstruction and development. (11)
Response:
Chapter 7 specifically references roads and highways. The purpose of this chapter is to
consider the most suitable BMPs for managing runoff from roadways. It is imperative that careful
consideration of roadway design, construction, and maintenance should be included in the selection of
BMPs that minimize the rate and volume, and enhance the quality of road and highway runoff.
Mitigating the impacts of runoff from highways and roads is a concern not only for state highway
managers (such as PennDOT and the PA Turnpike Commission) but also for municipalities, particularly
those with and NPDES stormwater management responsibilities.
Comment:
Please extend the comment period for an additional 30 days for the PA Stormwater Manual.
The draft ordinance was released half way through the comment period for the manual and it is
appropriate that both be considered together as they should complement each other. (5) (6) (7) (31)
Response:
The comment period was extended until July 14, 2006.
Comment:
Chapter 2 - More soils information:
Section 2.2 – General:
This chapter needs to be a well
organized and technically correct discussion of hydrologic and hydropedologic processes in Pennsylvania
as they relate to stormwater management. A good chapter 2 is critical as a foundation for the rest of the
manual. This document promotes engineered infiltration into and through soils, but nowhere does it
provide a discussion of soils and the importance of water movement through soils as it relates to the
design of engineered infiltration facilities. You have some “process” information mixed in the chapter, but
it is not complete or well organized. And there is still misleading information included (see comments
above).
Critical missing information includes:
a general discussion of soil characteristics and their relationship to the movement of water in soils;
a discussion of soil and geologic structure in PA and how that might impact water movement; (37)
Response:
Chapter 2 provides more on the natural structure (not texture) of undisturbed soils (or
amended soils) and the enhanced infiltration that this provides especially in the surface horizons.
Structure can sometimes play a larger role in infiltration than the soil texture. The surface horizons are
important because they provide a convenient opportunity to addresses wide array of water quality
treatment needs, especially if rain gardens and organically amended soils are considered here. The
purpose of this chapter is to provide a concise background about the important role soil plays in managing
and renovating stormwater, and to underscore that it is critical to understand soil characteristics of a given
12

site when selecting and designing stormwater BMPs. The BMP Manual includes a general discussion of
soil characteristics, water movement and Pennsylvania soil conditions.
Comment:
Chapter 2 - Need to refine/set the stage for SWM: Section 2.2.1 neglects the temporal
seasonal effect of rainfall. Additionally, in most of Pennsylvania the distribution of precipitation event
magnitudes is only approximately uniform over the year for minor or negligible precipitation events. For
example, Figure 1 shows the average monthly rainfall for the State College area by event magnitude for a
100-year period. From the graph it can be observed that rainfall events less than or equal to 0.25” account
for approximately 20% of the average annual rainfall and are uniformly distributed throughout the year.
However, these events often never generate surface runoff or “recharge”. The most important trend to
notice in Figure 1 is that the majority of the rainfall events (especially high intensity events) greater than
1” occur when Evapotranspiration (ET) is greatest, or when soil moisture is the most depleted, which
provides a buffering effect against flooding. Make it clear that flooding increases with rain events of all
sizes including the smaller storms, whereas the current version of the manual suggests that flooding
increases only with the smaller storms. (14) (47)
Response:
There is no “Figure 1” in Chapter 2, however the concerns expressed in the comment have
been addressed. The discussion of annual precipitation distribution is based on records that have been
kept for decades or, in some cases, over a century. Section 2.2.2 clearly discusses seasonal variations in
evapotranspiration, and its affect on infiltration and groundwater recharge. The Chapter has been revised
to place added emphasis on the importance of controlling all sizes of storm events.
Comment:
Chapter 2- Better organization on the “process”: You have some “process” information
mixed in the chapter, but it is not complete or well organized. And there is still misleading information
included. Failures are due more to a misunderstanding of hydrologic processes. Unfortunately, the entire
document then uses these same weak standard hydrologic modeling tools to make all of the new
arguments of what should be done. This indicates the authors do not understand the difference between
simplified hydrologic tools used for engineering and actual hydrologic processes. This is the main reason
this manual will result in new types of problems the authors do not yet understand. (47) (37)
Response:
The intent of Chapter 2 is to generally describe the hydrologic process, how it is altered by
activity on the land, and how stormwater can best be managed to compensate for the resultant hydrologic
imbalance. The chapter also acknowledges that the presentation of the hydrologic process is an
oversimplification of complex interactions that define surface and subsurface flow processes in
Pennsylvania. DEP disagrees that that the information in Chapter 2 is misleading, or that it affects the
validity of the entire document.
Comment:
Chapter 3 - Concern of CG-1 vs. CG-2 being equivalent standards: Control Guideline 1
(CG-1) and 2 inappropriately apply static statewide design criteria to sites across the entire state and
should be eliminated in favor of statewide design criteria algorithms.
By relying on CG-1 and CG-2 to be applied across-the-board statewide, the Manual ignores site-specific
conditions that may limit the ability of the site to achieve the prescribed level of control. To remedy this
condition, CG-1 and 2 should be eliminated in favor of design criteria algorithms, which dictate site-
specific design specifications.
Numerous other state manuals, including Maryland, New York, Vermont, Iowa, Georgia, and other states
and counties employ a site-specific approach for sizing stormwater best management practices (BMPs) to
meet pollutant removal goals, maintenance and enhancement of groundwater resources, reduction in
13

channel erosion, prevention of overbank flooding and extreme floods. The algorithms employed in these
manuals require site-specific inputs to determine how pre-development site conditions, particularly
hydrology, can be maintained post-development.
Such an approach provides a set of discrete and scientifically justifiable algorithms in which existing site
conditions (e.g., soil type) and other parameters dictate the appropriate level of stormwater management
so as to maintain hydrological balance, including infiltration. It is CBFs position that this methodology is
vastly superior to the CG-1 and 2 concept presented in the Manual. (5)
Response:
DEP chose to use a series of site control guidelines as a basis for managing the rate, volume
and quality of stormwater that are comprehensive and consistent with Pennsylvania’s Comprehensive
Stormwater Management Policy. It is recognized that other options are available, but the guidelines were
selected as the most effective and equitable means managing stormwater runoff in Pennsylvania. DEP
made its decision after considerable discussion with the members of the Stormwater Management
Oversight Committee. While the volume control guidelines in particular may be specific concerning the
volume of runoff to be controlled from a development site, it does not limit or prescribe the methods to be
use to accomplish the goal. The selection of BMPs is left to the design professionals based on site
conditions.
Comment:
Chapter 3 - Establish a hierarchy of situations or identify limited application(s) for CG-2:
The Manual should either eliminate Control Guidance 2 (CG-2) or at the very least set CG-1 as the
preferred control guidance. Using two guidance strategies is both confusing and also will not guarantee
that the most effective measures are being used when dealing with stormwater management in the
Commonwealth. Since the Manual identifies the CG-1 as the most effective strategy for addressing
stormwater management, this should be the put front and center for use in Pennsylvania. Proposing a
second, weaker standard only hinders the state from using the strongest possible stormwater management
practices and will confuse officials who must implement these practices. (1) (5) (7) (12) (14) (27) (28)
(29) (30) (33) (38) (43) (44) (45) (47)
Response:
The Manual will continue to present two volume control guidelines. However, because of
concerns raised about the effectiveness of CG-2 on larger projects, this control guidance is limited to
projects that disturb 1 acre or less. DEP has outlined circumstances in which either CG-1 or CG-2 can be
utilized. CG-1 is recommended to be used for the design of stormwater management strategies and
controls for most land development projects. CG-2 will be more useful for small projects such as
building expansions or additions on single lots or some redevelopment projects. Chapter 3 has been
expanded to highlight the most likely and preferred application of the two guidelines and the application
or limitation on CG-2.
Comment:
There is a consistent lack of objective criteria that can be used for design and evaluation of
BMPs. Review and enforcement of the principles in this manual will be uneven and arbitrary depending
on the emphasis of individual reviewers. (23)
Response:
Chapter 6 presents twenty-one structural BMPs for consideration. The presentations list “Key
Design Elements”, make reference to Protocol 1 (Site Evaluation and Soil Infiltration Testing) and
Protocol 2 (Infiltration Systems Guidelines) where relevant and Chapter 8 (Stormwater Calculations and
Methodology) where appropriate; provides design considerations, discusses construction sequence,
describes maintenance and cost issues, lists specifications, and shows typical drawings. In addition,
Appendix D presents a Case Study that includes stormwater calculations and methodologies. This level
of guidance should be sufficient for professionals to design BMPs customized to the project site, and be a
14

sound technical reference for plan reviewers. The Manual will ensure consistency in project design and
review.
Comment:
Chapter 3 - Evaluate use of BMP efficiencies as a water quality indicator or pollutant loading
criteria: The recommended Water Quality Control Guidelines of striving to achieve specific reductions in
pollutant loads, i.e. 85% reduction in TSS, by assuming a percent removal efficiency of stormwater BMPs
from Table 8.4, I feel will lead to many cases of litigation throughout the State. As we all know, and as
was discussed in the SMOC meetings, there are two many variables to assign a pollutant removal
efficiency to BMPs including design configuration, percent imperviousness and size of drainage area, etc.
This concept promotes concentrating “dirty” runoff to the BMP, since a BMP will more easily achieve a
percent reduction in pollutants from “dirty” runoff, than from “clean” runoff. This defeats the whole
impetus of promoting nonstructural BMPs and promoting clean runoff on-site before it reaches the BMP.
DEP may also want to consider the legal justification to assuming BMP treatment efficiency (Table 8.4)
with no reference and no quantitative backing of the numbers. This was discussed in the SMOC and I
though it was decided that legally, scientifically and engineering wise, these numbers could not be
generalized. (3)
Response:
The overarching strategy of avoiding, minimizing and mitigating stormwater problems
should first be applied. Managing stormwater to minimize pollutant loading includes reducing the sources
of these pollutants as well as restoring and protecting the natural systems that are able to remove
pollutants. To reduce the impact from land development, the recommended approach is to avoid any
increase in rate and volume of surface runoff, including the pollutants transported with this runoff that
comprises an equally significant impact. Management strategies that address quantity will in most cases
address quality.
The intent of the Water Quality Control Guideline is to assist the designer in the selection of both non-
structural and structural BMPs that will achieve water quality protection goals. The numerical reduction
goals in Chapter 3 are not effluent limitations or performance standards, but are composite efficiency
goals that can be used to select appropriate BMPs for a specific site. When the volume and peak rate
control guidelines are followed, the identified pollution reduction efficiencies for typical stormwater
pollutants at typical concentrations should be met.
Comment:
Chapter 3 - Consider individual BMP efficiencies and the contribution to the plans
effectiveness in meeting WQS: The water quality control guidelines, which require removal of 85% of
sediment loads, 85% of phosphorus loads and 50% of solute loads (as represented by NO3-N) are
important standards, and CBF commends the Department for establishing them in this Manual. However,
unlike other states such as New Jersey, the Department has chosen to consider the WQCs as guidelines
and not requirements. Simply stated, the WQC guidelines should be incorporated into the Department’s
Comprehensive Stormwater Policy, Technical Guidance Document No. 392-0300-002 (September 28,
2002) as requirements and municipalities should be required to adopt the WQC guidelines as standards in
local stormwater management ordinances in order to minimize pollutant loads to the maximum extent
practicable. (5) (23) (35)
Response:
The commentator has correctly stated that the Water Quality Control Guideline is not a
requirement, nor does the guideline establish a set of numerical effluent limitations. The intent of the
Water Quality Control Guideline is to assist the designer in the selection of both non-structural and
structural BMPs that will achieve water quality protection goals. The numerical reduction goals in
Chapter 3 are composite efficiency goals that can be used to select appropriate BMPs for a specific site.
Because stormwater BMPs are subject to highly variable field conditions, precise numerical efficiencies
15

or limitations will not be required. DEP will continue to use a performance-based, presumptive approach
to water quality protection. When the guidelines are not followed or BMPs other than those identified in
the manual are used, the burden of proof is on the applicant to demonstrate required levels of water
resource protection.
Comment:
Chapter 3 - Regulatory/scientific justification for the 2-year/24 hour standard: The 2-year
rainfall event is selected as the basis for Control Guidance 1. The justification is that 95% of the total
rainfall volume falling during an average year occurs in events less than or equal to the 2 year rainfall
event. What is the justification for using the 95% value? Why not 90%, or 85%, or 99%? The 2-year
rainfall event is still an extreme event. What scientific basis is there for selection of the 2-year or 95%
event? Provide scientific justification for using this value….or simply state that it was an arbitrarily
selected value. (34) (37)
Response:
As stated in Chapter 3, the basis for Volume Control Guideline 1 is as follows:
The 2-year event represents over 95% of the annual runoff volume across the state. Most stream
channel erosion results from storms under a 2-year storm event (95-98% of rainfall events).
Volume reduction BMPs based on this standard will provide a storage capacity to help reduce to
help reduce the increase in peak flow rates for larger runoff events.
In a natural stream system in Mid-Atlantic States, the bank full stream flow occurs with a period
of approximately 1.5 years. If the runoff volume from storms less than the 2-year event is not
increased, the fluvial impacts on the stream will be reduced.
The 2-year storm is well defined and data is readily accessible for use in the stormwater
management calculations.
Comment
: Chapter 4 - Need to include more narrative on cost benefits/cost effectiveness of LID:
Integral to initiating the necessary paradigm shift to comprehensive stormwater management that
integrates site design techniques that minimize the generation of stormwater and treat it in decentralized
micro-scale techniques is addressing the concerns of developers on the issue of cost.
Construction costs can be either higher or lower for a LID project than they would be for a conventional
development, depending on the site. However, overall research continues to indicate that LID is more
cost-effective than conventional development in the medium and long-term.
In fact, recent research in Maryland and Illinois show that new residential developments using LID saved
$3,500 to $4,500 per lot (quarter-to-half-acre lots) when compared to new developments with
conventional stormwater controls.
Because of its emphasis on preserving natural processes and micro-scale management practices, LID is
often less costly than conventional stormwater controls. LID practices have a longer life cycle cost than
centralized stormwater strategies and developers benefit by spending less on pavement, curbs, gutters,
piping, and inlet structures. And LID creates a desirable product that often sells faster and at a higher
price than equivalent conventional developments.
Given the importance of economic considerations by those in the development community, CBF contends
that it is imperative that information detailing the cost-effectiveness of such techniques be clearly
presented in detail in the Manual. (5)
16

Response:
DEP agrees with the comment. Although Chapters 5 and 6 (Non-Structural
BMPs, and Structural BMPs) both have sections of each BMP description devoted to cost, DEP
agrees that a discussion of economic considerations and cost-effectiveness would enhance
Chapter 4 (Integrating Site Design and Stormwater Management).
Comment:
Chapter 4 - Need to recognize the cost of BMP implementation and maintenance:
Although the procedure contained in this chapter is the ideal method to look at land development, the
state needs to consider the cost to implement these regulations, both to the municipalities required to
enforce it, the developers who will need to construct to the required standards, and the consultants
who will be designing using it. Developers especially will not appreciate the cost for the multiple
cycles of testing and fitting preventative Non-structural BMPs to the site. The increases in cost will
have to be passed on to the purchasers of the lots, including future maintenance and replacement costs
for the BMPs. Even Non-Structural BMPs have a cost related to them and require management that is
not understood by the general public or municipalities who become responsible for them. Dollars are
also a resource that needs to be considered. When the cost of construction, operation and maintenance
become unreasonable, they may be constructed but it is unlikely they will receive proper operation
and maintenance unless the owners are threatened with litigation and/or fines. (27)
Response:
Some form of stormwater management is already being incorporated into most land
development plans to meet existing local ordinances, and state and federal regulatory requirements.
This policy refocuses those plans to more effectively manage and protect our ground and surface
water resources. Costs associated with these BMPs should not significantly affect the overall project
costs, and in many cases could prove to be less costly than the previous methods of stormwater
management. From a cost effective perspective, improved stormwater management will translate to
less frequent downstream flooding and a possible reduction in property damage.
Comment:
Chapter 4 - Provide more emphasis on the hierarchy of preferred BMPs, especially
Structural BMPs: The only addition we highly recommend is to separate out the volume and quality
focused BMPs from the peak rate focused BMPs and to make clear that structures focused on
infiltration, volume reduction and that provide water quality benefits are encouraged third, with
structures focused on peak rate (e.g. detention basins) being the least desirable, and therefore the
fourth place, strategy that is recommended. (14)
Response:
Comprehensive stormwater management must address the peak rate and quantity of the
discharge, and protect water quality. DEP has proposed a BMP approach that recommends technical
methods, structural or non-structural, that will meet these objectives.
Prior to proposing a land development activity, careful choices regarding the type of stormwater
BMPs to be implemented in order to compensate for the hydrologic changes caused by the
development activity will need to be made. The BMPs will need to prevent flooding, reduce
stormwater pollutant loads, maintain ground water recharge, and protect stream channels and
streambanks from scour and erosion. In selecting BMPs, the responsible party should first evaluate
specific site considerations such as soil type, topography, geologic features, landscape position,
hydrology, climatic conditions, natural drainage features, riparian buffers, and other pertinent
information. These natural features need to be incorporated into the design to avoid and minimize the
generation of increased volume and rate of stormwater. The BMP Manual presents structural
stormwater management BMPs that can be utilized to address infiltration, water quality treatment, and
volume and rate discharge.
17

Comment:
Chapter 4 - Need to clarify (flow chart) the relationship of BMP manual to Act 167: The
recommended site design procedure is certainly interesting, but if Figure 4-1 is supposed to be a flow
chart, it is extremely difficult to follow. At the same time, the chart and the text fail to mention the
requirements of Act 167 stormwater management plans, and just how they fit in this process. Indeed,
the Manual seems to dismiss the Stormwater Management Act entirely, and assumes that stormwater
management is simply a matter of municipal input coupled with the suggested guidance and design
recommendations in this Manual. (This is again mirrored in the draft Model Stormwater Ordinance,
which as we read it attempts to establish municipal stormwater control measures that exceed the
requirements of the Stormwater Management Act as well as the PaDEP Comprehensive Stormwater
Management Policy.) (35)
Response:
DEP has made the revision to the final policy as recommended by the commentator.
Comment:
Chapter 5 - Too much emphasis on creation and preservation of open space: There is too
much text devoted within Chapter 5 to the creation and preservation of open space. While this is a key
element in promoting healthy, livable communities and reducing the volume of runoff created, it is not
necessarily the topic of this manual. The manual overall may be better suited, and much less bulky, by
eliminating some of this superfluous text. There are many good open space documents already
written. We are fearful that by emphasizing this approach and by putting it first in the manual, DEP
expects that it will happen and that it will help solve stormwater problems. We have outlined some of
the specific problems in our comments below. (4)
Response:
Chapter 5 (Non-Structural BMPs) presents a number of BMPs that encourage the
protection of sensitive areas, clustering and concentrating building, minimizing disturbance and
required maintenance, reducing impervious cover, and disconnecting and decentralizing stormwater
sources of runoff. These practices are very important considerations that must be employed where
feasible to avoid and minimize stormwater runoff problems. When placed in the proper context, the
presentation of these BMPs does not infer that the creation and preservation of open space is the topic
of the Manual. By their nature, these practices in many cases result in the creation and preservation
of open space as a side benefit to comprehensive stormwater management. In recognition of the
commentators concern related to the size of Chapter 5, it has been reviewed and edited to condense or
remove unnecessary text where possible.
Comment:
Chapter 5 - Subjective rather than objective criteria: Chapter 5 contains very few
objective criteria. Most of the BMPs in the chapter are subjective. How will the regulators evaluate
the use of the BMP when no objective standard is contained in the manual? What happens when local
ordinances dictate design that is contrary to the BMP manual? (23)
Response:
Chapter 5 (Non-Structural BMPs) includes key design elements, applications, and design
considerations for each BMP in the chapter. Inherently, concise and objective design criteria for non-
structural BMPs usually cannot be provided. The application of non-structural BMPs relies on a
considerable amount of judgment and the will to carry them out. Evaluators will use the Manual as a
starting point for reviewing proposals, and need to work closely with the owner/developer and
engineer to resolve any concerns. Local ordinances will always prevail in the face of a conflict with
the Manual. It is incumbent upon the municipality to amend ordinances, if necessary, to remove
obstacles that may be preventing the application of effective stormwater management techniques.
Comment:
Chapter 6 - Recommend establishment of a technical review team to evaluate/verify
structural BMP performance: The disclaimer states that the DEP has not verified or confirmed
accuracy of any product performance. If so, then why are any listed. Recommend that a Technical
18

Review Committee (TRC) or similar group be established to manage the Commonwealth’s TARP
membership. The TRC can consist of state and local regulators, consultants, academia, etc. Referring
to other programs such as EvTEC, ETV, NJCAT, etc. without proper state oversight forces localities
to evaluate the products, leading to inconsistency. (12)
Response:
DEP will give consideration to establishing a Technical Review Committee.
Comment
: Questions exist regarding the ability of the practices listed in Chapter 6 to be able to store
the runoff required when using CG-1 or CG-2 criteria. The manual could be improved by showing
some case studies that include acceptable hydrologic and hydraulic calculations related to stormwater
management. (32)
Response:
The case studies that have been included in Chapter 9 are designed to not only focus on
successful BMP application, but also to identify the unique hydrology and hydraulic conditions that
may be encountered. This case study discussion will be expanded to include lists of what to avoid and
what does not work as well. DEP invites all interested stormwater stakeholders to submit case study
information in the future for additional projects. Chapter 9,Section 9.2 is a list of information and
data items that case study descriptions should address, although it is recognized that some data gaps
may exist.
Comment:
Chapter 7 - Consider off-site mitigation/compensation for special management areas, esp.
highways. For road improvement and new road projects the applicant should be allowed to develop a
trading system or otherwise get credit and bank credits for:
a) Improvements to existing stormwater discharges that are more easily made in the same or
adjacent watershed where site limitations exclude or make implementing BMPs difficult
and costly or where there is an environmental advantage to going off site. For example a
section of road maybe placed in a cut through a hillside where there is no room for a basin
or other BMP. The applicant should be able to compensate for that section at another
nearby section. A road section maybe being placed adjacent to a cold water stream where
temperature impacts from discharges from equalization or infiltration (infiltration adjacent
to a stream in most cases will go right into the stream) would be adverse to stream biology.
b) Removal of stormwater contributions from combined sewer systems. PennDOT has many
sections of road connected to municipal combined sewer systems. These contributions
where they can be, should be required to be removed from the sewer system. Separate
stormwater lines and outfalls should be provided without the requirement for equalization
or infiltration. Road stormwater contributions to combined sewer systems consume
conveyance and treatment capacity that would be better dedicated to assuring greater
volumes of municipal sewage from homes, schools, hospitals... gets conveyed for
treatment.
c) Removal of streams from combined sewer systems. While the manual dismisses stream
removal, there are several streams connected to the Pittsburgh area sewer system that pass
under PennDOT roads that could be removed with PennDOT cooperation. The combined
sewers in the Pittsburgh area bypass at minimal precipitation events. Rt 28 improvements
reportedly include removal of two streams from the sewer system. Rt 28 overtly cuts-off
these streams from the nearby Allegheny River and they now enter the combined sewer
system. (Portions or all of the road drainage system are probably connected to the
combined sewer system also.). Both the stream flows and road runoff could be easily
conveyed to the Allegheny River as part of the proposed roadwork. The increased surface
19

area runoff quantity and quality for the new road should be more than offset by taking the
stream section contributions (which end up being bypassed after mixing with sewage at the
nearby Allegheny river diversion structures) out of the sewer system. Credit should be
given for taking out the ongoing contribution of debris from steam transport, which
consumes sewer capacity. This work would result in less sewage bypassing during dry and
wet weather.
d) In urban or otherwise built up areas give credit for participation in the removal and
demolition of abandoned buildings with disconnects from combined sewer systems.
Reducing the amount discharging from nearby combined sewer diversion structures could
offset road stormwater (quantity and quality) discharges. The community would also
benefit from the removal of problem structures that pose safety, crime, and blight
problems.
e) Construction or installation of riparian buffers in the same, adjacent, or nearby higher
quality watershed. (10) (13) (21)
Response:
Where on site BMPs cannot be effectively utilized to adequately address stormwater
discharges, then DEP may consider offsite compensation projects in the same watershed and
preferably upstream from the project site. These projects would be evaluated on their ability to
protect and maintain water quality. If DEP would consider offsite compensation projects, these
projects will be evaluated on a case-by-case, site-by-site basis.
Comment:
Chapter 7 - Infiltration should be precluded, esp. brownfields, mined areas: Infiltration in
brown field sites should be precluded unless there is an evaluation of the potential to contaminate or
increase the contamination of ground or surface waters. Many of these sites are "cleaned up" to a very
relaxed standard, which allows ground water pollution, surface water pollution, and contaminated
soils to remain in place. Infiltration ponds in these areas will increase the spread of whatever
contamination remains and pose a potential use limitation to surface and ground water and pose a
threat to public health, safety, and property. (5) (21) (35)
Response:
DEP agrees that infiltration in potentially contaminated areas should only be employed
where it will not cause or contribute to the contamination of local surface or ground water resources.
Comment:
Chapter 7 - Karst - scientific basis for hydrostatic pressure (buoyancy): Hydrostatic
pressure is known to support the weak geologic limestone structure in karst areas of Florida. However
Pennsylvania limestone is much harder and can form vast cavern ceilings without collapsing. I’ve
never heard of a fluctuating water surfaces causing structural instability of the subsurface in
Pennsylvania. Provide an example to demonstrate that this actually happens in Pennsylvania. If it
doesn’t, then remove this from the text. (37)
Response:
DEP has revised this Chapter to clarify the “buoyancy” factor as it relates to
Pennsylvania’s Karst geology.
Comment:
Chapter 8 - Tree Credit-scientific basis: I know of no tree that can remove 1” of rainfall
across the canopy area. Provide scientific data to support this amount or remove. (47)
Response:
DEP acknowledges the comment. The purpose of establishing a credit system is to
provide incentive to developers, consultants, and municipal officials to design and implement low
impact or better site design developments in a manner that causes less impact to the Commonwealth’s
water resources. Scientific data has been established that documents that trees decrease stormwater
20

volume, peak rate, and pollutant concentrations. Further trees also provide an economic incentive for
decreasing detention costs. The goal is to provide volume of runoff credits that can be estimated for
certain site design practices and site conditions that can result in the reduction of runoff volume, rate,
and pollutant concentration.
Comment:
Chapter 8 - Additional information/guidance is needed on choosing appropriate
stormwater methodologies: The spreadsheets presented for the computational methods appear to be
made so anyone can do, or review, stormwater designs. This removes the use of engineering
judgment, or skill, or any understanding of hydrologic processes from the design process. We do not
need canned spreadsheets or tables, but rather simply define how something should be done. The
manual fails at providing sound basic computational methods or guidance for designers to use. (47)
Response:
Chapter 6 presents 21 structural BMPs for consideration. The presentations list “Key
Design Elements”, make reference to Protocol 1 (Site Evaluation and Soil Infiltration Testing) and
Protocol 2 (Infiltration Systems Guidelines) where relevant and Chapter 8 (Stormwater Calculations
and Methodology) where appropriate; provides design considerations, discusses construction
sequence, describes maintenance and cost issues, lists specifications, and shows typical drawings. In
addition, Appendix D presents a Case Study that includes stormwater calculations and methodologies.
This level of guidance should be sufficient for design professionals to design BMPs customized to the
project site, and be a sound technical reference for plan reviewers. There is no expectation that this
Manual be regarded as a “cookbook”, or substitute for professional judgment and good engineering
practice.
Comment:
Appendix B - Recommend adding salt tolerant, identifying salt sensitive native species:
Plants sensitive to salt spray can be sued in highway landscaping but care must be exercised to locate
the plants in areas that are not too close to the edge of the roadway. (8)
Response:
The appendix will be revised as recommended.
Comment:
Appendix C - Infiltration failures should include hillside hydrology: Certain topographic
features need to be considered when locating BMPs (or infiltration test). We will elucidate the
potential for infiltration failures, vulnerable and “special areas”. (9) (18) (47)
Response:
DEP will consolidate and reiterate where necessary vulnerable or risk areas in the manual.
A maximum % slope will be recommended for subsurface infiltration. DEP is aware of the prospect
of side slope “bleeding”. Concave slopes and prominent swales should be avoided for subsurface
infiltration BMPs. This will be included in the appendix C and again in the Design Considerations
along with “special areas” treatment.
Comment:
Appendix C - Infiltration testing protocol should separate testing approach from testing
standards: Certain test (percolation) and test results are not appropriate to determine BMP efficiency.
Permeability Testing - Please note that the pictured Turf Tec Infiltrometer has double rings, which are
too small, and do not meet testing requirements as put forth in the new procedures. Should it be
indicated that the Turf Tec is to be used as possible support or for confirmatory testing?
The manual suggests a preferred calculation for percolation testing procedures, however, does not
give a specific calculation for the double ring infiltration testing, is there a preferred calculation? (8)
(15) (27) (37)
21

22
Response:
DEP will attempt to simplify and clarify this area to some extent, including references to
support any procedures or adjustment factors where necessary. Virtually all tests have limitations and
therefore appropriate references will be provided to address these limitations and appropriate
adjustments. The purpose of the testing procedure should be to provide an infiltration rate that most
nearly reflects saturated hydraulic conductivity, since this is the rate measure that most reliably
predicts the soils capacity to infiltrate external sources of water.
Comment:
Appendix C - Emphasis should be placed on natural soil health and quality to maintain
infiltration and water quality treatment. (41) (47)
Response:
Reference is made to soils in Chapter 2.
Comment:
Appendix C - Infiltration rate of 0.10 inches /hour is extremely low. Cost at many sites
would be exorbitant because of the required size of the BMP treatment area. (27)
Response:
A 0.10”/hour rate might corresponds to percolation rates of nearly 0.5”/hour or more in
some cases. Recall that the design rate would be half this and therefore, the system design will be
doubled to accommodate a 0.1’/hour rate.
Comment:
Appendix C - Loading rate of 5:1 is not practical for small sites. (16)
Response:
Because a 5:1 loading rate represents a higher proportion of runoff to treatment area, this
rate actually favors smaller lots that have a high proportion of impervious area. A 5:1 loading may
not be feasible if infiltration rates are low. A 2:1 loading could be problem for smaller lots because
the proportion of BMP area is larger. DEP is considering using a maximum design safety factor of 2
rather than 4; meaning the designer would no more than double the BMP design based on a given
infiltration rate. This would reduce cost. CG2 may be an option for some small lot development.
Comment:
Appendix C - Assessment, planning and construction quality assurance is crucial to
ensuring BMP performance, whether it be at the consultant level, contractor level, DEP regional level
or conservation district level. Some level of consistency is required. (27) (48)
Response:
DEP agrees and will work on programmatic processes and internal guidance to address
this issue properly.

Back to top