Planning commission examines RM, MU and Innovation Center test cases; staff proposes density and dimensional tweaks

Planning staff walked the Leesburg Planning Commission through three zoning “test cases” on Oct. 2 — Residential Medium (RM), Mixed Use (MU) and Innovation Center (IC) — using example parcels to show how the draft rewrite’s dimensional standards, open-space and stormwater requirements would affect redevelopment yields.

Why it matters: The commission is rewriting the town zoning to implement Legacy Leesburg policy goals (infill, housing choice and context-sensitive development). Test cases showed that stormwater, open-space and tree-canopy rules materially reduce theoretical yield if dimensional standards stay as drafted; staff proposed targeted reductions in lot widths, small adjustments to setbacks and changes to mixed-use ratios to better match policy aims.

RM (Residential Medium) test case Michael Watkins, Department of Community Development planner, presented a 4-acre block in the Lowenbach (Loanbach/Lowenbach) area to illustrate how dimensional standards plus required stormwater (assumed ~10% of site), required open space (10%) and 20-year tree-canopy requirements constrain achievable housing yields. He said a simple application of 6 dwelling units per acre would yield 24 units on a 4-acre block, but after applying stormwater, open space and tree canopy allotments and lot/dimensional standards the practical yield dropped; example scenarios showed roughly 20 units for detached and 26 units for attached forms.

Staff recommended several revisions: reduce minimum lot width for single-family detached from 65 feet to 55 feet (staff later discussed 50 feet for some contexts), increase single-family attached density from 8 to 10 dwelling units per acre to meet town-plan objectives, add a garage setback provision so a front-loaded garage wouldn’t consume the entire required front yard, and reduce side-yard setbacks (for detached) from 10 feet to 5 feet and rear from 20 feet to 15 feet to better match existing neighborhood patterns.

Commissioner concerns: Several commissioners said the illustrated block is an established neighborhood and that piecemeal infill (single-parcel redevelopment) is more likely than assembly of an entire block, which raises questions about how open-space and stormwater requirements would be met on smaller projects. Commissioners also expressed worries about increased pressure on local streets and older water infrastructure if density rises. The commission asked staff to test an infill (single-parcel) scenario and to model impacts on roads and utilities.

MU (Mixed Use) test case Staff analyzed the Village At Leesburg northern land bay (about 57.2 acres) to test the draft MU district, which initially used a high residential-density approach and a strict ratio linking residential units to nonresidential floor area (a stated example required 2,500 sq. ft. of nonresidential space per dwelling unit). The test produced a nonresidential demand far above what exists.

Staff recommended simplifying the MU mix requirement to a gross-floor-area ratio: residential minimum 30%/maximum 60% and nonresidential minimum 40%/maximum 70%. Staff said the Village At Leesburg existing mix (about 35% residential / 64% nonresidential on the portions tested) falls within the proposed new range and that the simplified approach produces a more realistic balance for retrofit and infill projects.

IC (Innovation Center) test case For the Leagate property and other designated IC areas, staff tested an IC district that would allow higher-intensity employment and technology uses. The consultant’s draft applied a residential-capable density of 24 dwelling units per acre in test scenarios; staff recommended treating residential as an accessory rather than primary use in ICs, setting a residential gross-floor-area cap of 30% (staff suggested 0–30% residential, 70–100% nonresidential) and requiring nonresidential uses to be developed in the first phase (a “shall” phasing requirement) to avoid projects that build housing first and delay intended employment or commercial uses.

Other technical notes Staff said open-space requirements (10%), assumed stormwater footprint (~10% for the sample), and a 20% 20-year tree-canopy requirement were applied in the test math. Staff noted established examples (White Oak cluster subdivision) where smaller lots and 5-foot side yards have been used successfully and suggested some of the proposed RM dimensional changes mirror those precedents.

Quotations "When you apply the subdivision regulations, stormwater management, open space requirements and the tree canopy, you can't achieve the permitted underlying density," Michael Watkins said during the RM explanation. Commissioner McAfee said: "If we're taking another example where you've got a lot that may be a half acre or 3/4 of an acre, what would that look like within the context of an existing neighborhood?"

Ending Staff will run follow-up test cases (infill single-parcel scenarios and additional GIS searches for realistically assemblable parcels), refine dimensional numbers (including potential 50-foot lot widths in specific contexts), and return to the commission with updated materials. Commissioners signaled interest in matching policy objectives while preserving neighborhood context and asked staff to model transportation and utilities impacts as part of future analyses.