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Grading & Drainage Permit in Unincorporated Ada County, Idaho

Required for grading and drainage work in unincorporated Ada County. Three tiers apply based on the area of disturbance and project type: Tier 1 for residential grading under one acre, Tier 2 for disturbance of one acre or more, and Tier 3 for commercial projects and new subdivisions. Governed by the 2018 International Building Code and Ada County Code (ACC 8-6). Applications submitted digitally by email.

Verified 2026-06-29 · Source

When you need this permit

  • Tier 1 (residential, area of disturbance less than 1 acre): site plan/drainage plan with property lines, easements, structures, well/septic locations, area of disturbance, stormwater flow arrows, and narrative
  • Tier 2 (disturbance 1 acre or greater): all Tier 1 items plus plan prepared by a design professional; soils report may be required
  • Tier 3 (commercial/drainage projects, new subdivisions): detailed drainage plan drawn to scale with all grading, drainage system essentials, stormwater routing, discharge flows, and evidence of consent from affected irrigation/drainage entities
  • Submit Grading & Drainage Application with all required documents to mechanical@adacounty.id.gov

Required documents

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Fee schedule

Tier 1 — Residential grading, area of disturbance less than 1 acreAda County Grading & Drainage Application (2025)
$100.00
Tier 2 — Area of disturbance 1 acre or greaterAda County Grading & Drainage Application (2025)
$500.00
Tier 3 — Commercial grading/drainage projects, new subdivisionsAda County Grading & Drainage Application (2025)
$1,500.00

Review timeline

Plan reviewTypical estimate — confirm current times with the Unincorporated Ada County building department
~5–21 business days

How long did your Grading & Drainage Permit permit actually take in Unincorporated Ada County?

Anonymous — one question, no email. Answers are combined and only shown once at least 5 people have reported.

Inspection process

  1. 1

    Erosion Control (pre-grading)

    Erosion control measures must be in place before work begins

  2. 2

    Final Grade

    Drainage verified, slopes stabilized, and grading matches approved plan

See the full Unincorporated Ada County inspection guide — scheduling & re-inspection fees →

Tips

  • Ada County's contact for grading/drainage questions is 208-287-7947 (Benjamin Pavelka, Permitting Manager).
  • Tier 2 drainage plans must be prepared by a licensed design professional; soils reports may be required at the reviewer's discretion.
  • For Tier 3 projects, provide documentary evidence of consent from all affected irrigation and drainage entities with rights to facilities on the site (ACC 8-6).
  • Call 811 before any excavation to locate underground utilities.

Frequently asked questions

If you are disturbing less than one acre on a residential property, you need a Tier 1 Grading/Drainage Permit ($100). Projects disturbing one acre or more require a Tier 2 permit ($500) with a design-professional-prepared drainage plan. Submit the Grading & Drainage Application to mechanical@adacounty.id.gov. Source: Ada County Grading & Drainage Application (2025).

In Unincorporated Ada County, the published Tier 1 — Residential grading, area of disturbance less than 1 acre is: $100.00. Additional published fees: Tier 2 — Area of disturbance 1 acre or greater — $500.00; Tier 3 — Commercial grading/drainage projects, new subdivisions — $1,500.00. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Plan review for a grading & drainage permit in Unincorporated Ada County typically runs 5–21 business days. This is an estimate, not a published figure — confirm current review times with Ada County Development Services — Building Division at 208-287-7900.

You'll need: Grading & Drainage Application (2025); Site Plan / Drainage Plan. Depending on your project, Unincorporated Ada County may also ask for: Design Professional Drainage Plan (Tier 2 and Tier 3). See the required-documents checklist on this page for details on each.

Unincorporated Ada County requires 2 inspection(s) for a grading & drainage permit, in order: Erosion Control (pre-grading), Final Grade. Schedule each through Ada County Development Services — Building Division (208-287-7900).

Apply through Ada County Development Services — Building Division at 200 W. Front Street (Ada County Courthouse, 2nd Floor), Boise, ID 83702-7300. Phone: 208-287-7900, email: mechanical@adacounty.id.gov. Office hours: Mon–Fri 8:00 AM – 5:00 PM. Official information: https://adacounty.id.gov/developmentservices/building-division/.

Unincorporated Ada County, Idaho has adopted: 2018 International Building Code (IBC) — adopted via Ordinance #919, Ada County Code; 2018 International Residential Code (IRC) — adopted via Ordinance #919; 2018 International Existing Building Code (IEBC) — adopted via Ordinance #919; 2018 International Energy Conservation Code (IECC) — Commercial Provisions; Residential as modified by Idaho Statute Title 39 Chapter 41; adopted via Ordinance #919; 2018 International Mechanical Code (IMC) — adopted via Ordinance #919; 2018 International Fuel Gas Code (IFGC) — adopted via Ordinance #919; 2018 International Urban-Wildland Interface Code (IUWIC) — adopted via Ordinance #919; 2018 International Swimming Pool and Spa Code (ISPSC) — adopted via Ordinance #919. Local amendments apply — see the Unincorporated Ada County overview page for the full list.

Sources & verification

Verified against official sources. Last reviewed 2026-06-29.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Unincorporated Ada County building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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