Centennial P&Z reviews ‘WaterNow’ landscaping and irrigation changes for new and redeveloped sites

Stephanie Rowan, planner for the City of Centennial, told the Planning and Zoning Commission on Feb. 26 that staff is proposing a package of Land Development Code amendments based on research funded by the WaterNow Alliance and Western Resource Advocates that would apply to new and redeveloped sites.

Rowan said the package—called WaterNow in staff materials—would introduce hydrozones (grouping plants by water need), require low‑water irrigation methods such as drip or bubbler systems for low‑water zones, and require EPA WaterSense labeled, weather‑based “smart” irrigation controllers on new projects. “All of these amendments tonight that are being proposed are only for new or redeveloped projects,” Rowan said.

The proposal would also replace Centennial’s static approved plant list with a dynamic list managed through PlantSelect (a site maintained by Colorado State University and Denver Botanic Gardens), expand and encourage xeriscaping (a mix of mulch, rock and drought‑tolerant plants rather than bare rock), and explore a soil amendment requirement for new plantings with an exception for native plantings. Rowan said staff is also considering limits on nonnative turfgrass (for example, Kentucky bluegrass) and requiring contiguous turf areas when nonnative turf is used.

Why this matters: the changes aim to reduce outdoor water use and increase landscaping resilience on properties developed or redeveloped after the ordinance takes effect. Rowan told commissioners that many recommendations came from the consultant study produced with WaterNow Alliance funding and that the goal is to bring Centennial’s standards in line with industry practice while preserving design flexibility.

Staff emphasized that the amendments would not require retrofitting private, existing landscapes. “This is only for new and redeveloped development projects,” Rowan said. She also noted that the WaterNow LDC amendments are tentatively scheduled for a second reading at City Council on April 5, 2025.

Commission discussion focused on sources and on how prescriptive the code should be. Commissioner French urged staff to broaden references beyond PlantSelect to include Colorado State University Extension, the Colorado Native Plant Society and other Colorado‑focused resources, noting those resources may list a larger set of native plants and regional recommendations. Michael Grama, a city staff member who answered several code and building‑code questions, told commissioners that the city currently operates under the 2021 plumbing code and that adoption timing of new plumbing code editions is driven by internal policy and market stability.

Commissioners asked for clarity on several items discussed by staff. Commissioner Unger asked staff to avoid conflating trees used solely for landscaping with green stormwater infrastructure intended to treat runoff; Rowan and staff said stormwater facilities are treated separately and that state law (Senate Bill 24‑005) includes specific language for water quality facilities. Rowan told the commission that Senate Bill 24‑005, passed in 2024, will take effect Jan. 1, 2026, and regulates functional turf, nonfunctional turf and artificial turf; staff said the city is reviewing how to implement the state law’s exemptions and flexibility.

Commissioners also discussed buffer yard alternatives for infill and redevelopment sites, the heat‑island effects of large ground‑cover rock areas, and whether the city should set maximum percentages for rock versus plants in xeriscapes. Several commissioners urged staff to keep requirements flexible and to include recommendations rather than strict mandates for items such as soil amendment type and mulch.

Ending: Staff said they will return with refined language after incorporating commissioner feedback; Rowan reiterated the April 5, 2025 tentative City Council second‑reading date and asked the commission for direction rather than a vote at the study session.