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nature finance·7 min read

MS4 compliance through green infrastructure: a municipal guide

how to access federal funding for nature-based stormwater solutions and meet permit requirements

The EPA letter arrives. Your MS4 permit is up for renewal. The new requirements include green infrastructure targets you don't know how to fund. The consent decree from the last enforcement action is still hanging over your budget.

Meanwhile, there's federal money sitting on the table — IIJA, IRA, BRIC — but your staff doesn't have capacity to navigate the applications.

This is the municipal stormwater trap: increasing requirements, constrained budgets, and available funding that's hard to access.

the MS4 compliance challenge

Municipal Separate Storm Sewer System (MS4) permits are getting stricter. EPA and state agencies are requiring:

RequirementWhat It Means
Post-construction controlsNew development must manage runoff on-site
Retrofit requirementsExisting impervious areas need treatment
Green infrastructure targetsSpecific acreage or volume requirements
Monitoring and reportingProve your BMPs are working
TMDL complianceMeet watershed-level pollutant limits

For municipalities already struggling with basic infrastructure maintenance, these requirements feel impossible.

Many cities are operating under consent decrees from past Clean Water Act violations. The numbers are staggering:

CityConsent Decree Cost
Atlanta$4 billion+
Kansas City$2.5 billion
Cleveland$3 billion
Louisville$850 million
St. Louis$4.7 billion

Smaller municipalities face proportionally similar burdens. The choice appears to be: massive gray infrastructure investment or ongoing violation.

But there's a third option.

green vs gray: the cost comparison

Nature-based stormwater solutions often cost less than conventional infrastructure:

ApproachCapital CostLifecycle CostCo-Benefits
Conventional pipe/tank$$$$High maintenanceNone
Bioswales$$Low maintenanceHabitat, aesthetics
Constructed wetlands$$-$$$Self-maintainingWater quality, habitat
Urban forest canopy$Long-term assetHeat reduction, air quality
Permeable pavement$$-$$$ModerateGroundwater recharge
Green roofs$$$ModerateEnergy savings, habitat

Philadelphia's Green City, Clean Waters program projects $2.5 billion in green infrastructure investment will deliver the same stormwater management as $8 billion in conventional tunnels — with added community benefits.

federal funding is available now

Multiple federal programs are specifically funding nature-based infrastructure:

IIJA (Bipartisan Infrastructure Law)

  • Clean Water State Revolving Fund — $11.7 billion for water infrastructure including green stormwater
  • EPA Environmental and Climate Justice Grants — Green infrastructure in underserved communities
  • USDA Urban and Community Forestry — $1.5 billion for urban tree planting

IRA (Inflation Reduction Act)

  • EPA Climate Pollution Reduction Grants — Nature-based solutions qualify
  • USDA Conservation Programs — Urban agriculture and green space

FEMA BRIC

  • Building Resilient Infrastructure and Communities — Explicit support for nature-based solutions
  • Hazard mitigation — Green infrastructure for flood reduction
  • 5% set-aside — Guaranteed funding for nature-based approaches

EPA Water Finance Center

  • WIFIA loans — Low-interest financing for green infrastructure
  • Environmental Finance Center support — Technical assistance for applications

The money exists. The challenge is capacity to access it.

what municipalities need

GapWhat's Missing
PlanningGreen infrastructure portfolio design, site selection
EngineeringNature-based BMP specifications, performance standards
Grant writingFederal application expertise, matching fund strategies
ImplementationContractor coordination, phased deployment
MonitoringLong-term performance verification, permit documentation

Most municipal public works departments don't have staff with all these capabilities. That's not a criticism — it's a capacity reality.

how to structure green stormwater investment

municipal approach

  1. Assess your permit requirements — What does your MS4 permit actually require? What's the timeline?
  2. Inventory opportunities — Where can green infrastructure be deployed? Public land, rights-of-way, partnerships with private property?
  3. Design the portfolio — Mix of bioswales, wetlands, urban forest, permeable surfaces based on site conditions
  4. Stack the funding — Federal grants + state programs + local match + ensurance instruments
  5. Deploy agents — Accounts for each project or watershed zone for ongoing stewardship
  6. Monitor and report — MRV documentation for permit compliance and future grant applications

regional approach

Multiple municipalities in the same watershed can coordinate:

  • Ensurance syndicates pooling resources for watershed-level solutions
  • Shared agents managing cross-jurisdictional projects
  • Collective grant applications with stronger competitive position
  • Unified monitoring reducing per-municipality MRV costs

public-private partnerships

Private property owners can participate through:

  • Green infrastructure incentives funded by stormwater fees
  • Ensurance certificates tied to private green infrastructure projects
  • Performance payments for verified runoff reduction

what BASIN provides

ServiceWhat You Get
Watershed & Hydrology ServicesStormwater modeling, BMP sizing, site selection
Regional Resilience PlanningGreen infrastructure portfolio design
Grant Application SupportFederal funding navigation, application development
Ensurance IssuanceCertificates and instruments for project funding
MRV & MonitoringContinuous performance verification

See our full services overview.

existing instruments are available now

frequently asked questions

can green infrastructure actually meet our permit requirements?

Yes. EPA explicitly recognizes green infrastructure for MS4 compliance. Many permits now include green infrastructure as a preferred or required approach. The key is proper design, installation, and documentation.

what's the timeline for federal funding?

IIJA and IRA funds are being distributed now through 2026 and beyond. BRIC has annual application cycles. State Revolving Funds operate on rolling basis. The window is open — capacity to apply is the constraint.

how do we maintain green infrastructure long-term?

This is where ensurance instruments add value. Certificates and agents create perpetual funding streams for ongoing maintenance — not just capital deployment but lifecycle stewardship.

what if we don't have matching funds?

Some federal programs require 25% local match. Ensurance instruments can provide matching capital. Private participation through certificates can also satisfy match requirements in some programs.

Yes. Many consent decrees now allow or encourage green infrastructure approaches. EPA has issued guidance supporting green infrastructure for CSO and SSO compliance. Document your approach early and engage with regulators.

the bottom line

MS4 permits are getting stricter. Consent decrees are expensive. Federal funding is available but hard to access.

Green infrastructure costs less than gray infrastructure, delivers better outcomes, and creates community benefits. The barrier isn't the solution — it's capacity to plan, fund, and implement.

That capacity exists. The funding exists. The regulatory framework supports it. The only question is whether you'll access it before the permit deadline.


related reading:

Explore watershed & hydrology services →

See natural assets in the binder →

Talk to someone about municipal stormwater →

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