Test learners' ability to assess and apply principles for designing a residential rain garden to reduce stormwater runoff and improve water quality. Scope includes site assessment (slope, soils, setbacks, drainage), runoff volume and sizing calculations from impervious areas, soil/media and underdrain/overflow design, selection of appropriate native plants for pollutant uptake and infiltration, basic maintenance considerations, and explanation of expected water-quality benefits; learners will produce a scaled layout and justify design choices with simple calculations and ecological rationale.