The rule BPCA invokes — who BPCA has said requires it, what FEMA said when asked, where the rule came from, and the variances that have preserved mature trees.
In its May 2026 response to residents, BPCA referred to the “15-foot USACE ‘buffer’ zone” as part of the justification for removing 502 mature trees along the North/West Battery Park City waterfront. That zone comes from a single U.S. Army Corps of Engineers guidance document.
This page covers how BPCA’s explanation of the buffer has changed, what FEMA said in writing when asked whether it requires one, and then the USACE document itself — what it says, how it has been challenged, and the variances that have preserved mature trees, including along an urban floodwall.
BPCA has cited the buffer as a reason for removals since 2022. But the authority it says stands behind the buffer has shifted at every step — from a flat FEMA requirement, to USACE guidance FEMA accepts, to BPCA’s own “conservative interpretation,” to guidance the certifying engineer only has to “consider.”
The cutting never relented. While the wording softened, the number of trees marked for removal only rose: 420 in the Draft EIS, 435 in the Final EIS, an estimated 500 in BPCA’s December 2025 technical memorandum (“design refinements,” no Supplemental EIS), and 502 on BPCA’s tree map of May 14, 2026.
BPCA has already shown the distance can be judged tree by tree — but only for new trees. Between the Draft and Final EIS, it stopped treating 15 feet as absolute for replacement plantings, placing them “between 10 and 15 feet from the flood barrier system in specific locations,” each evaluated for wave impact, elevation, and proximity to gates. The trees already standing never got the same review.
Asked directly, through FEMA’s Mapping & Insurance eXchange, whether a vegetation-free buffer is required to certify a floodwall like this one, FEMA Region 2’s MT-2 map-revision coordinator replied in writing:
“FEMA does not impose a fixed vegetation-free zone requirement as part of 44 CFR §65.10.” FEMA Region 2, MT-2 Revision Coordinator — written reply, June 18, 2026
On the USACE vegetation document (EM 1110-2-583, the predecessor of today’s EP 1110-2-18): “Just as guidance.” And on what vegetation standard applies to a non-federal floodwall:
“There are no vegetation standards. Whatever they certify as appropriate.” FEMA Region 2, MT-2 Revision Coordinator — written reply, June 18, 2026
So the two authorities BPCA has pointed to don’t carry the blanket rule: FEMA says it doesn’t require one, and BPCA says USACE’s guidelines don’t directly apply to this project. What’s left is the USACE guidance itself — below.
The current document is USACE Engineer Pamphlet (EP) 1110-2-18, published May 2019. It is the latest version of guidance USACE has been re-issuing in different formats since the 1970s. Three things about the document itself are worth knowing before anything else.
The primary purpose is access — not structural protection. EP 1110-2-18 Section 2-2(b):
“The primary purpose of the vegetation-free zone is to provide a reliable corridor of access… to assure adequate access by personnel and equipment for surveillance, inspection, maintenance, monitoring, and flood-fighting.” USACE EP 1110-2-18, Section 2-2(b)
The document specifies the access is for “tractors, bulldozers, dump trucks, and helicopters.” Root protection is described as a secondary purpose, and the document itself concedes the 15-foot zone is “not adequate for all situations” for root protection.
The number “15” is not based on engineering. Section 2-2(c) says the dimensions are “based on lessons learned from flood-fighting experience” — no formula, no peer-reviewed study, no structural analysis. A field rule of thumb.
The document explicitly tells designers it is not a hard rule. Section 1-1 frames it as “a guide for safe design and not as a restriction to the initiative of designers” that should be “tailored to the specific requirements and conditions of each individual project.”
When the 15-foot zone was formalized as national policy in 2009, there was no variance procedure. The variance — the formal mechanism that lets a sponsor request an exception to preserve trees — was added in 2012, after sustained pressure from lawsuits, environmental groups, state agencies, and Congress. The variance is itself evidence that the original rule did not stand up to scrutiny.
The combined record of the rule and the opposition to it:
The agency that wrote the rule no longer treats “vegetation-free” as the framing. From the 2024 USACE document:
“There can be more flexibility for allowing trees and shrubs to grow up to the waterside toe of the levee… placing and managing carefully selected vegetation on a waterside slope may not increase uncertainty or risk. Plant root architecture is well enough understood that species can be selected for desired characteristics.” USACE, Best Practices for Vegetation Management on Levees (Draft, March 2024)
The peer-reviewed record points the same direction: Shields (1992) found woody vegetation roots increased shear strength on levees. California's full-scale field testing at Twitchell Island — the most rigorous study ever done on this question — found that “global seepage-induced stability does not appear to be largely impacted by the presence of a tree.” The blanket 15-foot rule has never had a peer-reviewed engineering basis, and USACE's own research describes the underlying effects as unquantifiable.
USACE has formally granted vegetation variances that allowed mature trees to remain where the blanket 15-foot rule would have required clearing. Two of those are directly relevant here.
The Sacramento Area Flood Control Agency and the Central Valley Flood Protection Board submitted a variance request to the USACE Sacramento District covering the levees ringing the Natomas Basin north of downtown Sacramento.
The request was the first vegetation variance ever approved nationally under the post-2009 policy. It permitted mature riparian trees to remain on roughly 42 of 42.4 miles of perimeter levee.
“This decision highlights the intent of the Corps' vegetation variance process: to allow the Corps and its partners to conserve trees on levees where they don't pose a risk to public safety.” Col. Thomas Chapman, USACE Sacramento District Commander
The City of Indianapolis Department of Public Works, working with the USACE Louisville District, prepared a vegetation variance for the White River North Local Flood Damage Reduction Project — specifically the floodwall reaches through the Warfleigh and Rocky Ripple neighborhoods.
The variance covered 2,730 linear feet of floodwall across six “Variance Reaches.” By varying from the ETL, the design reduced required clearing by 1.82 acres — preserving mature riparian woody vegetation that the blanket rule would have removed.
“[Varying] from the ETL in order to provide structural stability, functionality, access for flood fighting, and OMRR&R, while minimizing the clearing of mature riparian woody vegetation growing along the White River.” North Indy LFDRP Vegetation Variance, certified 2016
The 15-foot rule has been walked back, reframed, and varied. USACE itself treats it as flexible guidance, adjustable to site conditions. BPCA's removal of 502 mature trees in its name is a design choice, not a fixed requirement.