Princeton University
OP-22: Rainwater Management

The 2026 Campus Plan established the University’s approach to stormwater management by focusing on restoring natural resources, incorporating an ecological systems approach, and promoting the implementation of green infrastructure (GI) for all new developments on campus. Through the 2016 and 2026 Campus Plans, the University has built an extensive network of green infrastructure best management practices (GI BMPs) to reduce rainwater runoff and improve water quality. These GI BMPs include green roofs, bioretention systems, porous pavement on paths and parking, infiltrating turf fields, subsurface storage, rainwater harvesting systems, and manufactured treatment devices. Today, there are over 150 GI BMP installations on campus. Before the 2026 Campus Plan, the University conducted campus-wide monitoring and metering to measure water quality and discharge flow at Lake Carnegie. Currently, the University is reactivating this program to measure water quality and quantity improvements resulting from the 2026 Campus Plan projects, creating a comparative baseline to track progress. The University also integrated stormwater management as a primary goal in the 2019 Sustainability Action Plan by establishing a comprehensive system to track the area on campus that meets the Campus Plan stormwater goals over time. Areas of land that align with New Jersey Department of Environmental Protection regulations and the Campus Plan stormwater goals are considered areas under enhanced stormwater management. As of 2023, 191 acres (including 65 acres of paved impervious area) were under enhanced stormwater management on the main campus and Meadows Neighborhood combined. Updates to the stormwater strategy outlined in the 2026 Campus Plan are underway, and a comprehensive stormwater study is anticipated to be finalized in August 2024. These updates will ensure that the University is going beyond mere regulatory compliance and guide the University's continued commitment to enhancing existing natural resources and bolstering resilience on campus. 

The 2026 Campus Plan established two tiers of project-based stormwater performance standards for capital projects. The Campus Plan Stormwater Goals were adopted into the University's Design Standards Manual (DSM) and serve as a project requirement for capital projects on campus. The Campus Plan Stormwater Goals established two tiers of performance standards. Tier 1 standard is considered the minimum for all campus projects, while the Tier 2 standard was developed to strengthen the stormwater performance recommendations from the 2016 Campus Plan. Tier 1 developments must retain on-site, evaporate, infiltrate, and/or reuse the 90th percentile rainfall depth (i.e., the first 1.25-inches of rainfall), and Tier 2 developments must retain on-site, evaporate, infiltrate, and/or reuse the 95th percentile rainfall depth (i.e., the first 1.60-inches of rainfall). The University also established additional performance standards for district-scale opportunities. The district-scale approach allocates land outside, adjacent to, and within development parcels for a centralized stormwater management solution to address clusters of adjacent projects, taking the form of ecological stormwater treatment landscapes and green infrastructure corridors. Green infrastructure corridors should be leveraged to meet Tier 2 performance standards using a combination of site-based and district-scale approaches, while ecological stormwater treatment landscapes should be designed to manage up to the 98th percentile rainfall depth (i.e. the first 2.25 inches of rainfall) in a manner that mimics the natural water balance of lands prior to development. 

Not all major renovation projects upgrade their stormwater management practices