What is a drainage clearance and the Maricopa County grading matrix?

Before Maricopa County issues your construction permit, it wants proof that your lot is graded to move stormwater safely off the home and across the parcel. That confirmation is the drainage clearance. The county's Grading Matrix is a screening tool. It estimates how much engineered plan detail that clearance will require, based on your lot size, its slope, and how much earth you plan to cut or fill. In plain terms: the drainage clearance is the approval. The Grading Matrix is the tool that tells you how much engineering you need to earn it. Maricopa County says a builder must "obtain a Drainage Clearance in connection with a construction permit," and that "the Drainage Plan Reviewer will use the tool for all new residential permits requiring a drainage clearance." For a custom home on unincorporated county land like Rio Verde Foothills, this is one of the first gates your build has to clear.

This page explains what the drainage clearance is, how the Grading Matrix decides your plan level, and where both fit in the order of getting to the dozer. It is a companion to the broader earthwork-sequencing page, which covers grading permits and the state stormwater SWPPP together.

What a drainage clearance actually is

A drainage clearance is a separate county approval that your finished grade handles water correctly, and it is tied to your construction permit rather than replacing it. Maricopa County's policy, DD-4002-01, is the rule that governs residential engineered grading and drainage. It requires you to "obtain a Drainage Clearance in connection with a construction permit." So the clearance is not the building permit. It is a drainage-specific sign-off that the building permit depends on.

Why does the county run a separate drainage review at all? Desert lots shed water hard and fast during the monsoon. A pad set too low, or a graded yard that tilts the wrong way, can push runoff onto a neighbor's land. It can scour a natural wash. It can flood the home it was meant to protect. The drainage clearance confirms your plan moves water off the structure and across the parcel without harming the land next to you. The reviewer wants to see where your dirt comes from, where it goes, and how stormwater leaves the lot once the house and driveway are in.

This matters most on unincorporated Maricopa County land, where the county itself is the permitting authority. Rio Verde Foothills, much of Cave Creek's fringe, and other rural parcels Jematell builds on fall here. Inside a city like Scottsdale or Phoenix, the city runs its own grading and drainage review instead, but the idea is the same: significant earthwork gets its own clearance, separate from the building permit, and it has to clear before you grade.

How the Grading Matrix sets your plan level

The Grading Matrix is a tool that estimates how much engineered plan detail your drainage clearance needs, so you know up front whether you face a simple plan or a full engineered submittal. Maricopa County describes it directly: "The Grading Matrix tool is intended to give the property owner an estimate of the level of plan detail required." The county reviewer applies it to every qualifying permit, stating that "the Drainage Plan Reviewer will use the tool for all new residential permits requiring a drainage clearance."

The matrix scales the requirement to the lot and the work. The more earth you move, the steeper the parcel, and the closer it sits to a wash or floodplain, the more engineering the matrix calls for. A flat infill lot with minor grading lands at a lower plan level. A large hillside lot with heavy cut and fill near a wash lands at a higher one. That often means engineered grading and drainage plans stamped by a registered civil engineer. The county's companion grading rule is blunt about the trigger. Grading on a site is generally limited to the building pad. Move dirt beyond that pad and you usually need engineered plans.

Two cautions the county itself flags. First, the matrix is an estimate, not a final ruling. The county states the tool "is provided as a general guide only and the general public should not rely on the results produced." It adds that "the requirements for any particular application for any particular property will be determined by Maricopa County Drainage staff after full evaluation." Second, staff can deviate from the matrix when a lot is unusual. The reviewer obtains "approval from the Director, Engineering Manager, or Engineering Supervisor when a deviation from the matrix tool results is needed." So treat the matrix as your planning estimate. Then let the drainage reviewer confirm the real requirement.

Where the drainage clearance fits in the build order

The drainage clearance sits early in your build sequence, before the construction permit is issued and well before your first inspection. Breaking ground is not a single event. It is a stack of approvals, and the drainage clearance is one of the first because the construction permit depends on it. On a typical unincorporated-county custom build, the early order runs like this.

• Site and grading plans prepared. Your civil engineer or designer prepares the grading and drainage plan at the level the Grading Matrix indicated.
• Drainage clearance obtained. Maricopa County Drainage staff review the plan and issue the drainage clearance in connection with the construction permit.
• Construction permit issued. With the drainage clearance and the rest of your plan review complete, the county issues the building permit.
• Environmental permits and locates done. If your work trips the thresholds, the dust permit and the state stormwater SWPPP go in, along with the 811 locate, before any digging.
• Grading, then foundation. Only now can you grade the pad and start the foundation, where the first building inspection happens.

The drainage clearance lands near the front of that line, which is why it can hold up a start if it is left late. See whether you need a grading or earthwork permit and a SWPPP before you break ground for how grading and the state stormwater permit sequence together, and the difference between a dust control permit and a stormwater SWPPP permit for the two environmental permits that often run alongside.

How to plan around the grading matrix and clearance

Treat the Grading Matrix and the drainage clearance as early-design items, because the plan level the matrix sets drives your engineering cost and your schedule. The smartest move is to run your lot through the matrix during design, not after you have a permit application ready. If the matrix points to a higher plan level, you know early that you need a civil engineer and an engineered grading and drainage plan, and you can budget the time and cost for it instead of getting surprised at intake.

A practical approach on a Maricopa County custom build:

• Screen the lot with the matrix during design. Get an early read on whether you face a simple plan or a full engineered submittal.
• Engage a civil engineer when the matrix or the lot calls for it. Steep grade, heavy cut and fill, or a wash nearby usually means engineered plans.
• Map drainage before you set the pad elevation. Where water leaves the lot should shape the home's placement, not be solved after the fact.
• Build the clearance into the schedule. Plan the drainage review as a front-end item so it does not delay your construction permit or your grading window.

The matrix is only an estimate, and the county makes the final call. So confirm the actual plan level and any deviation with Maricopa County Drainage staff before you finalize the grading plan. The county also notes that fees and review steps can change. Verify the current drainage-clearance and grading specs at the time you apply. On a managed build, this is work your general contractor and civil engineer handle together. At Jematell Homes, we screen the lot with the Grading Matrix in design. We bring in the civil engineer when the lot needs one. And we carry the drainage clearance through review, so your construction permit and your dozer day are not waiting on it.

Building with Jematell Homes

We handle jurisdiction, submittals, and inspections as part of every build. If you are planning a custom home in Scottsdale, Rio Verde, or the greater Phoenix metro, we are happy to walk through your project.

Sources

• Maricopa County: Residential Engineered Grading and Drainage (DD-4002-01); Drainage Clearance and Grading Matrix tool
• Maricopa County: Construction Permit Information
• Maricopa County: Adopted Codes and Regulations (Drainage Regulation)