Arapahoe County advances $40 million I‑70/Monahan interchange plan; proposes tiered impact fee

Arapahoe County public-works staff briefed commissioners on a proposed redesign of the I‑70/Airpark–Monahan interchange and presented a financing proposal that would rely principally on a developer-funded construction bond reimbursed through a new county impact fee.

The project and the problem: County planners described an alignment to move the current interchange east along Monahan so the interchange can be widened, improve capacity and provide a safer crossing of the railroad tracks as development north of I‑70 proceeds. The preliminary construction estimate is $40 million for the phase south of I‑70; staff added an estimated $28 million in financing costs to produce a $68 million total planning figure.

How the county proposes to pay: Staff proposed an impact-fee district that would cover 6 square miles around the interchange and create two fee tiers. Tier 1 (zones closest to the interchange) would pay the largest share of the improvement. Using the county’s traffic forecasts and current cost estimates, consultants produced example per‑unit fees: a Tier‑1 single-family dwelling impact fee of roughly $7,900 per unit and a Tier‑2 fee of roughly $1,000 per unit. Example nonresidential fees were also shown (retail, office, industrial) using dollars-per-trip calculations.

Who is paying now: Mark Harding of Sky Ranch told commissioners that Sky Ranch Metro District plans to finance construction up front (bond the work) so the interchange can be built when construction triggers an identified need; the Metro District would be reimbursed by impact-fee receipts over time. Harding said the district would structure repayment through a trustee and backstop the bonds with reserved mill levies as required to make bonds credible.

Permitting and approvals: Public-works staff said the county must complete a CDOT “1601” interstate-access process and secure federal concurrence; planned next steps include environmental-clearance/traffic-demand-management work and a minor-interchange modification request to FHWA plus any required Section‑241 permit filings.

Budget math and risk: Consultants estimated total fee revenue of about $65 million based on the proposed fee geometry and future growth forecast — a shortfall of roughly $3 million against the $68 million project total. Staff warned commissioners that if neighboring jurisdictions (notably Aurora) do not adopt comparable fees on developments in their portion of the study area, the shortfall could grow to roughly $15–18 million; county staff said Aurora’s participation was not guaranteed. Commissioners asked staff to: (a) do deeper financial analysis of repayment timing, interest and scenarios that assume Aurora does and does not adopt fees; (b) examine alternative funding mechanisms if a gap remains; and (c) widen outreach to surrounding jurisdictions and affected developers.

Commissioner questions and reaction

Commissioners applauded the attempt to “get ahead” of the capacity limits and to attach developer impact fees to new growth. Several commissioners and staff asked for more detailed financial modeling showing: a range of interest-rate scenarios, faster-or-slower buildout forecasts, payoff schedules that would allow early repayment and the consequences if Aurora or Adams County declines to adopt the fee. Commissioners also asked staff to make the case politically to Aurora and Adams County and to present a contingency plan if the county must absorb part of a shortfall.

Next steps

County staff will: finalize the system-level study and traffic analysis; submit documents to CDOT as the 1601 process proceeds; develop a more detailed financial plan in coordination with finance staff; pursue conversations with Aurora and Adams County about adoption of aligned fees; and return with refined revenue scenarios and an outreach/IG A approach. If commissioners agree, staff will bring a draft impact-fee ordinance for formal consideration only after that additional financial and intergovernmental work is complete.