Shoalwater methodology framework for distributed green stormwater infrastructure
THE PRINCIPLE

Physical infrastructure and water claims are not the same thing.

A rain garden can be installed and verified as a physical asset. A cistern can have known dimensions and a documented contributing roof. A project can be functioning without automatically supporting every type of replenishment, volumetric-benefit, or disclosure claim.

Shoalwater separates what is observed, what is modeled, and what can responsibly be claimed.

THE FRAMEWORK

Five layers from field evidence to watershed context.

01 IDENTIFY

Project Identity

Record the property, project location, installation type, ownership context, project status, and relevant basin.

02 QUANTIFY

Physical Inputs

Record contributing impervious area, storage, treatment area, system dimensions, and other measurable project characteristics.

03 EVIDENCE

Project Record

Preserve installation evidence, post-inspection records, photographs, contractor documentation, and other supporting files.

04 MODEL

Water Performance

Translate physical project inputs and rainfall assumptions into clearly defined modeled water-performance metrics.

05 CONTEXTUALIZE

Basin Context

Connect individual projects to watershed, drainage, and portfolio context without obscuring property-level evidence.

WHAT WE TRACK

A persistent record for each project.

PROPERTY
  • Property location
  • Ownership or host context
  • Watershed / basin attribution
  • Project access and consent status
INFRASTRUCTURE
  • GSI project type
  • Installation date
  • System dimensions
  • Storage or treatment characteristics
HYDROLOGY
  • Contributing impervious area
  • Roof or drainage area
  • Rainfall assumptions
  • Modeled annual water performance
EVIDENCE
  • Post-inspection records
  • Installation photographs
  • Contractor / project documents
  • Maintenance and condition records
WATER PERFORMANCE

Not all managed water is the same.

01

Captured

Water physically intercepted by the system before discharge.

02

Detained

Water temporarily stored and released more slowly to reduce peak flow.

03

Infiltrated

Water routed into soil where site and system conditions support infiltration.

04

Reused

Captured water used for an appropriate non-potable application such as irrigation.

05

Treated

Runoff passed through a system designed to improve water quality.

06

Peak Reduced

A modeled reduction in discharge intensity or timing during storm events.

MODELING APPROACH

Transparent assumptions over black-box numbers.

Shoalwater uses project-specific physical inputs and clearly stated rainfall assumptions to estimate water performance. Where calculations depend on infiltration, drawdown, storage behavior, or other site-specific conditions, those assumptions are identified explicitly.

01 Known Inputs

Roof area, system dimensions, contributing area, storage, and project type.

02 Declared Assumptions

Rainfall, drawdown behavior, infiltration, reuse, or other modeled conditions.

03 Defined Output

Each metric is labeled by what it actually represents.

04 Traceable Method

Project calculations remain linked to the underlying physical record.

METHODS & CONTROLS

Consistency matters as the project network grows.

01

Source Records

Preserve original project documentation and distinguish source evidence from derived values.

02

Standard Units

Normalize contributing area, storage, rainfall, and water volumes into consistent units.

03

QA Status

Track whether records are complete, incomplete, pending review, or suitable for aggregation.

04

Consent & Attribution

Preserve property-owner permissions and clarify how project data may be used in aggregated reporting.

05

Project Status

Distinguish candidate, planned, installed, active, restored, and inactive infrastructure.

06

Version Control

Maintain clear methodology versions as assumptions, standards, and project requirements evolve.

CLAIMS BOUNDARY

A project record does not automatically equal a replenishment claim.

Corporate water stewardship, volumetric water benefits, replenishment accounting, and public disclosure can require additional methodology, baseline, additionality, duration, stakeholder, and assurance considerations.

Shoalwater does not treat every GSI project as interchangeable or automatically eligible for every water claim.

Physical project → documented evidence → modeled outcome → portfolio context → claim only where appropriate.
TECHNICAL BOUNDARY

Shoalwater documents and develops projects. It does not replace licensed technical practice.

Where a project requires civil engineering, geotechnical review, hydraulic modeling, permitting, structural analysis, plumbing design, regulatory certification, or specialist technical judgment, Shoalwater works with appropriately qualified professionals.

The methodology is designed to strengthen project traceability, not blur professional responsibility.

REFERENCE FRAMEWORKS

Built to remain compatible with established water-stewardship practice.

AWS Water stewardship principles and site / catchment context
VWBA 2.0 Volumetric water-benefit accounting concepts where applicable
TNFD Location-specific nature and water-risk context
CDP / GRI Corporate water disclosure and reporting context

Reference to a framework does not imply certification, endorsement, or automatic conformity. Applicability depends on project type, program requirements, and the specific claim being made.

BUILD THE RECORD

Better infrastructure starts with better project evidence.

Shoalwater is building a consistent documentation layer for distributed green infrastructure across Puget Sound.

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