Drainage Report Comments in Los Angeles County DPW Reviews

Drainage review at LA County Public Works follows a fixed sequence, and the comments reviewers send back are rarely random. They trace back to specific checklists, specific missing documents, and specific methodology choices that engineers can anticipate before a project is ever submitted.

How LA County DPW drainage report reviews work

The Drainage and Grading Plan Check process runs through five steps, and each one can decide whether the project moves forward or stalls. A completeness screen comes first, followed by a plan check engineer's review that produces a correction sheet. The applicant then corrects and resubmits, agencies weigh in with their own approvals, and DPW confirms those approvals and rechecks the plans. Final approval only follows once every prior step clears, and that approval is what lets a permit get issued.

Two separate review tracks run underneath that five-step structure, and confusing them produces delays that cost engineers time they do not get back. Building Drainage Review sits with the local Building and Safety District Office. Storm Drain Plan Review sits with the Land Development Division's Storm Drainage Unit. The two offices work from different checklists, issue different correction documents, and expect responses addressed to the right desk. An engineer who sends a storm drain response to the Building and Safety office, or the other way around, adds a delay that has nothing to do with the engineering itself.

The stakes of getting this right are concrete. Rough grade approval has to happen before a building permit gets issued, so a drainage comment that sits unresolved does not just slow one review, it holds up the entire permitting schedule behind it. A six-week hydrology dispute on a single project can push back grading, framing, and occupancy dates that were set assuming drainage would clear on schedule.

What engineers must submit before the review even begins

Many of the corrections that appear in the first round happen because something required at intake was missing when the project was submitted. That is a discipline problem, not a technical one, and it is the easiest category of comment to eliminate before a reviewer ever opens the file.

The plan check page lays out what Step 1 requires: two sets of plans, one set of a current soils report (no older than one year), and two sets of supplemental documents. Those supplemental documents include the hydrology and hydraulic report, output from the HydroCalc Calculator, LID documentation, any applicable easements, and deed restrictions. Plan check fees get paid at this same step. If you miss one piece, the completeness screen in Step 1 of the five-step process stops the project before a plan check engineer ever reviews the actual drainage design.

Storm drain submittals carry their own version of this requirement. The Storm Drain System page lists the minimum package as the storm drain plan itself, the plan check fee, approved planning documents, and an approved hydrology study. The page states that incomplete packages get delayed or rejected outright, with no partial credit for a submittal that is mostly there. Planning approval from the Department of Regional Planning has to exist before storm drain construction starts, and an engineer who shows up without it loses a place in the review queue.

Licensure matters here too. Storm drain plans can only be prepared by a California Registered Civil Engineer, and submittals that are unlicensed or carry an improper stamp are a recurring rejection trigger. None of this is a judgment call for the reviewer to make. It is a binary check: the document is either there and correctly executed, or the submittal does not move forward.

Hydrology study requirements

The hydrology study carries more weight than any other single document in a drainage submittal, because every downstream calculation, every BMP sizing decision, and every storm drain capacity figure depends on the runoff numbers it produces. An error here does not stay contained to one comment. It propagates into the LID review, the grading coordination check, and the storm drain geometry review, multiplying the correction count across sheets that look unrelated on their face.

The Land Development Hydrology Study page sets the specific guidance that governs these submissions, and it covers acceptable methods, formats, and supporting documentation. Engineers preparing a hydrology study for an LA County project need to work from that page's requirements directly, rather than carrying over methodology from a different jurisdiction's standards. The storm drain review will not proceed on geometry until an approved hydrology study exists behind it, because reviewers have nothing to validate pipe sizing or capacity against without it.

The HydroCalc Calculator gets referenced directly on the plan check page as a tool for hydrology submissions, and that reference signals something specific: DPW expects applicants to use it, and reports built on incompatible or unverified methods draw scrutiny precisely because they cannot be cross-checked the same way. Rational method calculations that do not document soil type, land use, and time-of-concentration assumptions in a form the reviewer can trace back to the source data generate comments almost automatically. Hydrology that does not match the tributary areas shown on the storm drain plan creates an internal inconsistency that a reviewer will catch on comparison. Reports that fail to address multiple storm frequencies where the project requires it leave a gap reviewers are trained to look for. And a soils report older than one year violates the currency requirement the plan check page states outright, which makes it one of the easiest corrections to avoid and one of the most common to see anyway.

LID compliance comments under the Standards Manual

Low Impact Development requirements sit on top of the conventional drainage calculation, not inside it, and that separation has a practical consequence: LID deficiencies get flagged on their own sheet, apart from the main drainage correction list. An engineer who treats LID as a minor addendum to the hydrology work ends up managing two independent correction queues instead of one, each running on its own schedule.

The plan check page specifies that LID may apply under Title 12, the county's Environmental Protection title, for both drainage plans and combined drainage and grading plans. When it applies, the plans need to show the required Best Management Practices along with the supporting documentation behind them, not just a symbol on a site plan indicating a bioretention area exists somewhere. The LID Review Sheet, dated 4-4-17, is the document reviewers actually work from when checking this. An engineer who has not gone through every item on that sheet before submitting is very likely to see comments drawn directly from it, because that sheet is the reviewer's checklist, not a general guideline.

Reviewers expect BMP design to align with the LA County LID Standards Manual, which covers sizing and siting criteria for the facilities shown on the plans. A few comment patterns recur often enough to flag specifically. The most basic is a failure to determine LID applicability before submitting at all: the plan check page directs applicants to the Standards Manual to make that determination up front, and a submittal that skips the step draws a comment regardless of how well the rest of the BMP design holds up. A second pattern is a disconnect between the LID documentation and the grading plan, where an infiltration facility appears in one set of drawings without being coordinated against the grade or soil conditions shown in the other. A third is missing deed restrictions or easements that the BMP requires in order to run with the land over time, rather than existing only as a feature on paper for the current ownership.

Drainage Review Sheet comments: what the formal correction checklist covers

The Drainage Review Sheet, revised 11-04-21, is the actual instrument a plan check engineer uses to mark up a submittal, its structure tells an engineer what DPW treats as non-negotiable, and it is a formal checklist that produces the comments an applicant receives back, so studying the sheet before submitting puts an engineer in the position of reviewing the same document the reviewer will use.

The sheet's scope runs across four code titles named directly on the plan check page: Title 26, the County Building Code; Title 30, the Residential Code; Title 31, the Green Building Standards Code; and Title 12, Environmental Protection. Comments on the sheet often cite the specific title that governs a given requirement, so an engineer responding to a correction needs to know which title the comment falls under in order to address it correctly.

The categories the sheet addresses follow logically from that code structure. Drainage plan content gets checked for whether existing and proposed drainage is shown clearly, whether the scale and legibility meet the standard a reviewer can actually read, and whether the scope of work is delineated clearly enough to evaluate. The hydrology and hydraulic report gets checked for completeness and for whether its methodology stays consistent with what the plan itself shows. LID BMP requirements get checked against the LID Review Sheet directly, tying the two documents together. Grading plan coordination gets checked to confirm that drainage patterns shown on one sheet match the proposed grades shown on another. And easements and deed restrictions get checked wherever the project requires them to exist. An engineer who obtains the Drainage Review Sheet and works through each of these categories before the first submittal is running the same audit the reviewer will run later, just earlier and on the engineer's own schedule.

Storm drain plan comments: the separate review track for public infrastructure

Storm drain plan review is not a variation on the building drainage process described above. It runs as its own track, with its own submittal requirements, its own correction document, its own agency referral chain, and its own fee structure, and conflating the two leads engineers to send responses to the wrong office or misjudge which checklist applies to their comments.

The Storm Drain System page describes the correction document for this track directly: for each plan submittal, DPW generates a check print carrying plan check comments and a corrections list, and sends it to the applicant. That check print functions as the storm drain equivalent of the Drainage Review Sheet, and the Storm Drain Review Sheet List is the formal reference engineers should work through before submitting, the same way the Drainage Review Sheet serves the building track.

A set of first-sheet requirements gets checked mechanically on every storm drain submittal, and most corrections in this category trace back to one of a short list of items. The plan needs a border sheet, general notes, and a benchmark. Drawings need to use an engineering scale of 1 inch equals 40 feet or larger, shown with a graphical scale on the sheet itself. Sheet size needs to be 24 by 36 inches or 36 by 48 inches. A vicinity map needs to show the nearest major cross streets along with the Thomas Guide page and grid numbers. Title blocks need to identify the civil engineer, the geotechnical consultant, the surveyor, and the owner or developer. And the plan should include only the statements that actually apply to the project, since reviewers flag boilerplate language left in from a template that does not match the site conditions.

Beyond DPW's own check, storm drain approval depends on sign-off from a list of outside agencies, and each one runs its own comment cycle independent of DPW's timeline. The list includes the Army Corps of Engineers, the California Department of Fish and Wildlife, the Regional Water Quality Control Board for both the Los Angeles region and the Lahontan region as separate sub-agencies, the Department of Regional Planning, the Fire Department's Forestry Division, and the Geotechnical and Materials Engineering Division. A delay at any one of these agencies holds up final storm drain approval regardless of how clean the DPW-facing portion of the submittal is.

Why the same comment categories recur across projects

Every comment category described in the sections above traces back to a fixed checklist: the Drainage Review Sheet, the LID Review Sheet, or the Storm Drain Review Sheet List. Because those checklists exist and do not change project to project, the gap between a clean first submission and a four-round correction cycle comes down almost entirely to whether the engineer worked through the applicable checklist before submitting, rather than finding out its contents one correction at a time.

The cost of skipping that step is concrete: the Storm Drain System page sets a five-review limit on what the plan check fee covers, and every round beyond the fifth carries an additional fee. A project that burns through four rounds of avoidable comments on first-sheet formatting or missing agency referrals has already spent most of its covered reviews before addressing anything substantive about the drainage design itself.

A handful of pre-submittal steps follow directly from how the review structure works. Obtaining the Drainage Review Sheet (11-04-21) and using it as a self-audit before the first submission catches the categories a plan check engineer will look for anyway. Running the LID applicability determination against the LID Standards Manual before preparing BMP plans, and then marking off every item on the LID Review Sheet (4-4-17), keeps LID deficiencies from splitting into a correction queue separate from the main drainage list, as described earlier. For storm drain projects, matching plan content item by item against the Storm Drain Review Sheet List, and confirming that every required agency referral is already in motion before submitting, closes off the most common source of delay on that track. DPW's Drainage Unit also offers appointment-based pre-submittal consultations, available Monday through Thursday from 7 a.m. to 5 p.m. through its online appointment portal, so an engineer can surface problems before the formal review clock starts running. Confirming that the soils report is less than a year old and that the hydrology study carries current approval status rounds out the package check before submission.

One more point applies regardless of what tools or methods produce the underlying calculations. Where hydrology reports, drainage plans, or LID documentation get produced with the help of software or automated drafting tools, the professional engineer who reviews and stamps that work carries the same compliance responsibility as on any other submission. DPW's review process runs on fixed checklists, and that means the final output has to map to each line item on the Drainage Review Sheet, the LID Review Sheet, and the Storm Drain Review Sheet List no matter how the document was produced. The checklist does not care about the drafting process. It cares about whether the submittal in front of the reviewer satisfies every item on the sheet.