Grading Plan Review Comments in Maricopa County

Not every residential project in unincorporated Maricopa County needs engineered grading and drainage plans, and figuring out whether a given project does is the first decision point in the whole process. The governing document is DD-4002-01, Residential Engineered Grading and Drainage, which has gone through revisions since it was first adopted and replaces an older directive, DD-2011-08. Any engineer still working from that earlier directive is building a project on guidance the county no longer follows.

The county's Grading Matrix tool, found on the Planning Permit (PlanningApp) page, is where this question gets answered first. It estimates how much plan detail a given residential project needs in order to get a Drainage Clearance, based on project specifics. The Drainage Plan Reviewer makes the final call after looking at what's actually submitted, and the tool exists to guide that judgment, not replace it. When a project's circumstances call for a deviation from what the matrix suggests, the reviewer has to get sign-off from the Director, the Engineering Manager, or the Engineering Supervisor before granting it. Drainage Review itself runs under the Planning and Development Department as a standing regulatory function across all of unincorporated Maricopa County, and the trigger for its authority is broad. Any man-made change to land that affects how water moves across it falls under this review. Confirming the threshold early, rather than assuming a project is too small to matter, saves time later.

What the submittal checklist requires before review begins

Once a project clears the question of whether engineered plans are required, the next hurdle is making sure the plan set itself contains everything the county expects to see. Most first-round review comments in Maricopa County come down to submittal gaps that the county has already published, in detail, before anyone submits anything. That makes them avoidable in a way that design comments often aren't.

The county's Engineered Plan Submittal Requirements tool builds a printable checklist specific to a given project, based on which elements the plan includes. Plan scale has to be a standard engineering scale, capped at 1 inch equals 40 feet, with only four scales accepted: 1 inch equals 10, 20, 30, or 40 feet. The plan needs a site address and a location map referenced to the nearest cross streets, and it needs contact information, name, address, phone, and email, for both the owner or applicant and the engineer of record. Driveway and site access locations and materials, easement locations and their purpose, and the location of any septic system and leach field round out the baseline.

Seal and signature details are where a disproportionate number of comments start. The Arizona Registered Professional Civil Engineer's signature, seal, and date have to be current and revised to match the latest version of the plan, not carried over from an earlier draft. Seals, whether hand-drawn or electronic, have to meet AAC R4-30-304 (E) and (G), and the outside diameter of the seal has to fall within a tolerance set by AAC R4-30-303 (A). Two certification statements also have to appear on the plans exactly as written, with no paraphrasing, and the standard Maricopa County Planning and Development general notes and conditions block has to be present. Leaving that notes block off the plan is treated as its own comment, independent of everything else on the sheet.

Grading-specific plan requirements that draw the most review comments

Within the grading discipline specifically, four requirements generate most of the comments: topographic currency, benchmark placement, slope limits, and how contours are drawn. Each one is specified precisely enough in the checklist that getting it wrong is usually a matter of what made it onto the sheet, not a flaw in the underlying design.

Topographic survey currency is the first. The survey has to show the date of the field survey, and if that survey is more than a year old, the plan needs a certification of accuracy using this exact language: "I HEREBY CERTIFY THAT THE TOPOGRAPHIC INFORMATION SHOWN ON THESE PLANS IS ACCURATE BASED ON A SITE VISIT CONDUCTED ON [date]." An undated topo, or one that's aged past a year without that certification attached, draws a comment almost automatically, regardless of how accurate the data actually is.

Benchmark requirements come next. A certified temporary benchmark has to be referenced to the site datum, located onsite within 400 feet horizontally and no more than 6 feet vertically from the structures it serves, and described on the plan along with its height relative to grade (the checklist gives "TBM IP FND 1" AG" as an example format). Slope limits are a hard numeric threshold rather than a design preference: fill slopes can't exceed 3:1, cut slopes can't exceed 2:1, and anything steeper than those ratios requires a geotechnical stability analysis as a separate deliverable, not an optional add-on. Existing and proposed drainage patterns, flow arrows, and grade breaks all need to be shown on the same sheet.

Drainage design requirements and the calculations reviewers check first

Drainage comments follow a similar logic to grading comments, but they tend to repeat across review cycles more often, because they usually trace back to missing calculations. Maricopa County's Drainage Policies and Standards (DPS) manual already answers most of the design questions that generate these comments. When a comment comes back on a culvert or channel design, it's typically a sign that the DPS section governing that element wasn't applied in full, not that the underlying design approach is wrong.

Culvert design has to conform to DPS Section 6.7, and the plan has to show upstream and downstream invert elevations along with a cross-section view of the installation that includes invert elevation, headwater elevation, and cover over the pipe. Open channel design follows DPS Section 6.8, with side slopes governed by DPS Tables 6.12, 6.13, and 6.14. A typical channel cross section is required, flow line elevation has to be shown every 50 feet and at every grade break, freeboard has to be addressed, and the design needs its own supporting calculations.

Erosion protection applies to washes carrying flow above a set threshold, and on-lot retention basins, required for lots in subdivisions with on-lot retention, carry the most exacting language requirements in the entire submittal. Basin plans need to show bottom-of-basin and high-water elevations, with grading tied into the surrounding terrain, and berms need a minimum top width of 8 feet. Any basin deeper than one foot needs a soil percolation test and a drain-down time calculation, and every basin needs calculations showing it can hold the required 100-year, 2-hour storm volume. Rip-rap, gabions, and gabion mattress installations need their own construction details, including excavation and embankment work and filter fabric specs, plus staking requirements for mattresses and the manufacturer's installation specifications.

Right-of-way and floodplain permit requirements that layer on top of grading review

Grading review doesn't happen in isolation on every project. Projects that touch the public right-of-way or sit within a regulated floodplain carry additional permit requirements that run alongside, not instead of, grading review, and treating these as a separate problem to solve later is a common source of repeat comments.

A right-of-way permit, where it applies, has its own general requirements: documentation for any new driveway connection, offsite improvements, surety bonds and contractor liability insurance, and a traffic control plan. A Floodplain Use Permit, where a project falls within a Regulated Special Flood Hazard Area, requires clearance for any disturbance within that area, clearance for structures located within it, and additional documentation where a LOMA, LOMR, or CLOMR applies, along with post-development requirements once construction wraps up. The Drainage Review page is direct about the practical consequence: floodplain projects bring additional fees and additional review steps that Planning & Development staff initiate separately, and anyone with floodplain exposure is pointed to call the office at (602) 506-3301 or reach the On Call reviewers for an overview before getting too far into design.

None of this changes the grading design itself. The fix is coordinating these requirements before submittal, not redesigning anything afterward.

Drainage Plan Review Division submittal processing and delay points

The review process has a defined structure behind it, and understanding that structure changes how productively an engineer can respond when comments come back. The Drainage Plan Reviewer's authority has real limits. Deviating from the Grading Matrix result isn't something a reviewer can simply decide to allow. It requires sign-off from the Director, the Engineering Manager, or the Engineering Supervisor, so an engineer asking for that kind of deviation needs to build the case for it explicitly rather than assuming the reviewer has the discretion to grant it on the spot.

The Drainage Review page points to the on-call reviewer channel as a resource meant to be used before submittal, not after. Calling that line before plans go in is the most reliable way to surface a jurisdiction-specific question, whether it's about a borderline matrix result or an unusual site condition, before it turns into a first-round comment that costs a full review cycle to resolve. The scope of what counts as regulated "development" is also wider than it might first appear: the county's drainage regulations cover any man-made change to a property that affects how water moves across it, not just large-scale grading. Engineers who treat a minor site change as too small to fall under this authority, without confirming that assumption, are taking on risk the county's own definition doesn't support.

The comment patterns that repeat most often

Across projects, the comments that come back from the county's drainage plan review staff aren't scattered randomly. They cluster around a short, consistent list of requirements, each specific enough to check mechanically, but each one also easy to lose track of in a plan production schedule moving at normal speed.

Seal deficiencies are one of the most frequent: an outside diameter outside the required tolerance, an electronic seal format that doesn't meet AAC R4-30-304 (E) and (G), or a seal that wasn't revised after a late-stage plan change. The Finished Floor Certification, the Declaration of Responsible Charge, and the Retention Basin Certification all need to appear word-for-word, and a paraphrased or shortened version draws a comment even when it communicates the same thing the county is asking for. And retention basin notes, especially the 36-hour drain-down certification and the percolation test results required for basins deeper than one foot, get missed often enough that they count among the highest-frequency findings in the whole checklist.

None of these patterns reflect a single engineer's mistake so much as the structure of plan production itself: detailed, checklist-driven requirements are the first things to slip when a deadline compresses.

A pre-submittal review approach that reduces comment cycles

Maricopa County has already published the tools that catch most of these comments before a reviewer ever opens the file. The gap is whether a firm applies that information the same way on every project, rather than relying on memory or an outdated template.

Generating the Engineered Plan Submittal Requirements checklist at the beginning of production is the starting point. Because the checklist changes based on what elements the plan includes, pulling it late in the process means discovering requirements after the sheets are already built, which is a far more expensive place to find them. The verbatim certification language, the Finished Floor Certification, the Declaration of Responsible Charge, and the Retention Basin Certification, belongs in the firm's standard title block and general notes templates, so it can't be dropped by oversight. These are the cheapest comments to prevent and the most expensive to fix after submittal, since a missed certification often means a full re-seal cycle. A firm-level seal compliance check, confirming the outside diameter and AAC R4-30-304 (E) and (G) compliance before anything leaves production, is a one-time setup that removes a recurring comment permanently once it's in place. Checking the field survey date against the one-year threshold at scope intake, rather than during plan production, gives enough lead time to order a new survey or an accuracy certification before it becomes a deadline problem.

For drainage elements, the fix is matching each design piece, culvert, channel, retention basin, erosion protection, with its DPS reference and its required calculation in the project task list from the start, so the calculations get built alongside the design. Any project with floodplain exposure or a borderline Grading Matrix result benefits from a call to the on-call reviewer line at (602) 506-3301 before engineered plans are produced, since that conversation is faster than waiting for a comment to surface the same question. And where a deviation from the matrix result is likely, the justification for Director, Engineering Manager, or Engineering Supervisor review should be prepared ahead of the submittal meeting, not written in response to a first-round comment asking for it.

Firms producing a high volume of plan sets have also started using software built specifically for design and construction workflows to run this kind of checklist review automatically across projects, flagging missing certifications, out-of-tolerance seals, or incomplete calculation sets before a set goes out the door. Used well, that kind of tool applies the same structured checks described above at scale, rather than relying on each reviewer to remember every line item on every project. It doesn't replace the engineer's judgment on design, and it doesn't substitute for the pre-submittal call to county staff on a genuinely ambiguous project. It makes the mechanical, checklist-level parts of review consistent, which is exactly where most of these comments originate.