2024 Ad-Hoc Structural Stormwater Controls (SSC) subcommittee
whitepaper
Please send questions/comments to:
Blair Scott, King County [email protected]
Angela Gallardo, City of Tacoma [email protected]
Introduction:
The best outcome for the SSC Policy Advisory Committee (PAC) discussions would be one that leads to
permit actions that improve WQ (WQ here taken to mean water quality and flow control, inclusive) and
creates flexibility for how structural stormwater controls occur. Local jurisdictions have the best
understandings of local stormwater problems and priorities, but don’t have enough resources to solve
all these issues. Such an outcome would:
a. Facilitate and reward the solutions that align with jurisdictions / permittees goals to
solve these issues.
b. Leverages work being done outside of C.5. Development and Redevelopment
c. Be clearly communicated in the Permit and facilitate clear and accountable compliance.
The current Phase I Permit S5.C.7 framework, while not perfect, allows for flexibility and an achievable
level of effort. Based upon the outcome of the Structural Stormwater Control Science Review and
Synthesis, it appears there is no scientifically based definitive answer for an appropriate metric to
measure activities for Section S5.C.7 of the Phase I Permit. Further, it seems that there is a lack of
scientific basis for making major changes in the current S5.C.7 framework. In consideration of this, the
following would be appropriate and recommended:
Ecology should consider additional scientific basis for changes to the S5.C.7 framework, beyond the
‘water quality benefits’ of individual SSCs.
It’s understandable that until there is additional information, the current multiple metrics provided in
the Phase I Permit’s S5.C7 framework will remain an imprecise, broad brush accounting of SSC
environmental benefits due to the scientific limits of quantifying these benefits (as described in TAC
white paper). The concern is that the point system has become a driver of priorities for SSC projects,
and this may not result in the most beneficial projects for each unique basin and receiving water. That
being said, the current use of multiple metrics acknowledges the inherent differences in the way each
SSC project type needs to be considered for WQ benefit measurement. The range and diversity of SSC
project types and metrics facilitates flexibility for local programs.
Incremental refinements to the current Phase I Permit S5.C.7 framework should only be made as
necessary, based on science and/or clear water quality goals and justification.
The following is intended to capture information from the SSC 2024 Ad-Hoc subgroup discussions for
consideration during the PAC discussions. This information came from group discussion in addition to
individual participant contributions.
Concerns/Questions:
Concerned with how arbitrary the point system is.
How do we account for a property with multiple SSC efforts occurring over time? For example: if
we purchase a property (SSC #5 Property Acquisition), then remove impervious (SSC #10 Removal
of impervious surfaces), followed by restoration of forest cover (SCC #8 Restoration of forest
cover).
Add clarity in this section to specify if projects implemented through other regulatory
requirements (i.e., Industrial SW permits, etc.) are eligible for credit
Consider a better way to value enhanced treatment projects
Does the current point application push projects to less developed/rural areas or more
developed/urban areas?
If added to the Phase II Permit, there needs to be more scalability in point requirements given the
large variability in size (geographic scope and ratepayer base), staffing, and budgets between
these permittees. Considerations for the unique nature of Phase II county permits which only
govern a portion of their jurisdiction should be addressed.
Preservation and Conservation (Rural/Habitat/Acquisitions) seems historically better resourced
than Restoration (Urban, MS4 runoff). When SSC credits are conflated across Preservation,
Conservation, and Restoration, urban runoff appears to take on a lower priority. This is likely due
to perceived costs, but has Salmon survival implications (triage of urban runoff) and Equity and
Social Justice implications (environmental justice/historically underfunded communities). How
can we reflect this reality through how various projects are rewarded in the SSC point system?
Land management appears to be more cost effective/politically supported than investing in built
assets to directly mitigate MS4 Runoff from existing development.
Will jurisdictions get credit for doing SSC projects prior to reissuance of the Permit? Maybe within
established agreement with Ecology or recent projects.
Could permittees get credit for incentives and support of private redevelopment of existing
developed parcels/TODs?
Credit for removal of impervious surface should not be contingent upon restrictions to future
development. Any future installation of impervious surface would be required to install
stormwater controls per development standards, yielding a net benefit vs. existing untreated
impervious. Restricting future development will greatly curtail the use of this SSC.
Why does the point system, plus past project cost information from the Phase 1 permittees (35
projects), yielded a range of $4000/point and $839,000/point?
General Comments for further discussion in the Policy Advisory Committee (PAC):
• The SSC Ad Hoc topic group recommends minimal change until the Permit(s) articulate a
clear goal for defining level of effort expectations for the SSC requirement.
• The SSC Ad Hoc topic group recommends that the PAC consider adjusting multipliers as a
way to ensure they reflect actions that result in WQ improvements. The examples below
illustrate adjustments to consider:
o When comparing other SSC project types, the basis for the Incentive Factor assignments
become even more uncertain. How to value flow control versus treatment? How to
value other project types relative to each other?
o The same number of points are awarded to a one-acre roadway project that provides
enhanced treatment whether the roadway is a rarely travelled rural roadway or a highly
travel arterial in an industrialized urban area. Although both projects receive the same
points, the industrial roadway project most likely has a greater environmental benefit
but is also likely to cost significantly more. A stormwater manager faced with limited
funding may be forced to prioritize the rarely travelled rural roadway project to get
points to meet the Phase I Permit’s S5.C.7 requirements.
o Rewarding projects that address 6PPDE-q through the SSC point multipliers based on
criteria to target areas where treatment is triggered.
The difference in cost (Dollars per point variance) between types of projects should be
considered by the PAC.
• Orient focus more on stormwater program-related priorities outcomes achieved rather
than credit for activity categories. For example, for Phase IIs this would allow
actions/investments to support priorities identified in SMAP efforts and comp planning,
providing a more context sensitive approach that reflects variation among permit’s land
use characteristics, water resource and non-riverine flooding challenges, etc.
• Some (many?) members of the The SSC Ad Hoc topic group are supportive of the
development of a Regional SW retrofit fund, possibly through a method such as that set
forth by the Regional Priorities and Incentives Ad Hoc subgroup, as long as there are
meaningful protections in place to opt in or out (i.e., doesn’t include punitive measures
and allows permittees to focus on local values and needs). We recommend this idea be
discussed further in the Policy Advisory Committee (PAC)
o Example questions to be discussed:
â–ª How do regional SW retrofit priorities get set?
â–ª How are the proportional funding contributions/credits calculated?
â–ª How are costs associated with ongoing operations and maintenance
allocated?
â–ª What legal constraints may exist for some jurisdictions in funding
projects sited outside their jurisdictional boundary, including projects
benefiting receiving waters beyond their jurisdictional boundary.
â–ª How would SSC point credits be allocated?
• Maintenance requirements for ensuring SSC projects continue to provide intended
benefit:
o Recommendations:
• Recommendations for annual reporting requirements for SSC:
Phase I comments:
• If the SSC program points needed for compliance are going up, we may want to consider
more enhanced maintenance options.
• Some jurisdictions purchased HE sweepers for SSC. Concerned introducing a sweeping
Permit requirement under O&M will reduce opportunities to achieve SSC points through
these actions; will the sweeping requirements only be a portion of the permit areas so
anything above and beyond would still be eligible to accumulate SSC points?
(Coordinate with O&M) More flexibility in handling obstructions and tracking would be
helpful (state objectives and not specify methods).
• Pipe flushing points questionable, will those change (coordinate with O&M)
• Are there specific BMPs that merit their point allocation to be dramatically increased?
While a review and overhaul of the whole point system may be too big of a task,
refinements to the some (e.g., land acquisition) might be an achievable exercise
• The PAC should discuss what a reasonable total number of points that will demonstrably
improve water quality could entail.
• SSC-type requirements coming from other directions.. (e.g., TMDL, etc.) retrofits should
get credit regardless of the underlying driver
• Will implementing SMAP actions in the next Phase II permit be eligible for points should
the SSC become a Phase II permit requirement. If so, will points have multiplier in SMAP
priority basins? For regional cooperation?
• Summarized categories of questions = point totals, multipliers, and what projects get
credit