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Building Code Reference

Got a CALGreen 4.106.2 correction?

Stormwater runoff control

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CALGreen 4.106.2 requires that any construction project disturbing soil implement controls to manage stormwater runoff and prevent polluted discharge from leaving the site. You need a grading and drainage plan showing how runoff will be contained on site or directed to an approved disposal point, along with temporary best management practices (BMPs) during the construction phase. The section applies to residential and nonresidential projects covered by the California Green Building Standards Code, and plan-checkers will flag it on any permit where grading or earthwork is in scope.

How to fix it

  1. Confirm whether your project falls under the NPDES CGP or local drainage plan only

    Projects disturbing one or more acres of soil typically require a Stormwater Pollution Prevention Plan (SWPPP) under the NPDES Construction General Permit issued by the State Water Resources Control Board. If you are under one acre of disturbed area, you skip the state CGP but still owe the city a site-level drainage plan that satisfies CALGreen 4.106.2 as a local building code requirement. Calculate your total disturbed area (include all graded, cleared, or stockpile areas) before deciding what document to prepare.

  2. Prepare a grading and drainage plan showing proposed grades and flow paths

    The drainage plan must show existing and proposed grades, drainage flow arrows, and spot elevations at key grade-change points such as property corners, pad elevation, and swale bottom. Identify where runoff exits the site and confirm it flows to an approved discharge point: a street gutter, a permitted inlet, or an on-site detention basin. Contour intervals of one foot are standard on residential lots. Showing runoff draining onto a neighboring parcel is not acceptable and will trigger another correction.

  3. Specify temporary BMPs for the construction phase

    Plan-checkers want documentation of how you will control runoff while soil is disturbed before permanent drainage is installed. Call out at least two temporary best management practices on the plan: silt fence along the downslope perimeter, fiber rolls or wattles at adjacent gutter inlets, straw wattles at grade breaks, a stabilized construction entrance, or a check dam at any on-site swale. Reference the BMP detail number or a city-standard BMP sheet if your jurisdiction provides one.

  4. Show that runoff will not discharge onto adjacent property

    Include a note or callout on the drainage plan explicitly stating that construction stormwater will be contained on site or directed to an approved outlet. If the lot is tight against neighboring properties, show the grade relationship with spot elevations at the property line. On sloped lots, a cross-section detail is very useful. The plan-checker needs to see that runoff and sediment cannot wash across a shared fence line during rain events.

  5. Cross-reference the drainage plan from your architectural cover sheet

    Many corrections are returned because a drainage plan exists on civil sheets but the architectural plans have no cross-reference to it. Building departments often review architectural sheets first. Add a note on A0 or T-1 stating that construction stormwater runoff is controlled per CALGreen 4.106.2 and referencing the civil sheet number. This single note is often the item the plan-checker is scanning for before signing off on the green building checklist.

  6. Complete the CALGreen checklist and include it in your submittal

    Most California jurisdictions require a completed CALGreen Mandatory Measures Checklist as part of the building permit submittal package. Section 4.106.2 has a line item on that checklist. Make sure the box is checked and the corresponding plan sheet is referenced in the checklist column. Submitting without a completed checklist is a separate correction trigger, and it is one of the easier things to fix before your initial submittal rather than after a first correction.

  7. Resubmit with a response letter addressing the 4.106.2 correction by item

    When you resubmit, include a response letter that addresses the 4.106.2 correction specifically: name the sheet where the drainage plan appears, list the BMPs you specified, and note where the cross-reference appears on the architectural sheets. Reviewers process many resubmittals each day. A response letter that maps each correction to a specific sheet and plan note is the fastest path to approval. Do not assume the reviewer will hunt through the plan set to verify your fix on their own.

Take the CALGreen 4.106.2 fix steps with you

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Why you got flagged

The most common reason contractors get flagged on CALGreen 4.106.2 is a missing or incomplete grading and drainage plan. If your plan set shows site grading but the sheets don't include drainage arrows, spot elevations, or a note calling out how runoff will be managed during construction, the plan-checker will cite this section. Even a modest addition with minor earthwork can trigger the correction if grading is part of the scope. The reviewer is looking for evidence that you've mapped the path of water off your disturbed soil before the permit gets approved.

A second scenario involves sloped lots. Any time the site has significant grade change, the reviewer wants to see where water goes when it rains mid-construction. If water could sheet across bare soil and reach a neighboring property or the street gutter, that's a direct 4.106.2 flag. On hillside lots, drainage calculations or a graded swale detail showing containment are typically required. Sheet flow onto an adjacent parcel is specifically what the section is designed to prevent.

You can also receive this correction when your drainage plan exists but reads as too vague. A note that says "drainage per civil" without referencing actual sheet numbers or specifying temporary BMPs won't satisfy the reviewer. Silt fencing, fiber rolls, and inlet protection need to be called out on the plan, not left implied. Reviewers aren't there to interpret your intent: they need to see it documented.

Larger projects subject to the NPDES Construction General Permit from the State Water Resources Control Board address this through a SWPPP (Stormwater Pollution Prevention Plan). Smaller projects under the CGP acreage threshold still owe the city a site-level drainage plan showing 4.106.2 compliance. Many contractors assume the CGP exemption covers local code requirements too. It does not.

The official code

California Green Building Standards Code (CALGreen) — Official Adopted Code, DGS Building Standards Commission

Read the source →

Common questions

Does CALGreen 4.106.2 apply to ADU projects?
Yes, if the ADU involves any grading or soil disturbance. A detached ADU with a new foundation, grading for site access, or drainage changes to accommodate the structure falls under 4.106.2. If the ADU is a garage conversion with no grading and no drainage changes, the section may not apply, but confirm with your local building department before assuming you are exempt. Many jurisdictions apply it broadly to any new dwelling unit construction. If you are submitting an ADU with a civil sheet, include the drainage plan and BMP callouts from the start.
What has to be on the grading and drainage plan to satisfy 4.106.2?
At minimum: a plan view with existing and proposed grades (spot elevations or contours), drainage flow direction arrows, the proposed discharge point for stormwater, and at least two temporary BMP callouts showing how you will control runoff during construction. For residential infill, a single annotated site plan or C-sheet usually covers it. A note saying "drainage per civil" without civil sheets in the package will not pass plan check. The reviewer needs to trace the path of water from the disturbed area to an approved outlet directly on the plan.
My project is under one acre. Do I still need to address 4.106.2?
Yes. The one-acre threshold applies to the state NPDES Construction General Permit (CGP) from the State Water Resources Control Board, which requires a full SWPPP. CALGreen 4.106.2 is a separate local building code requirement that applies regardless of project size. A room addition with grading can be flagged on 4.106.2 even if it involves a few hundred square feet of disturbed area. The CGP and 4.106.2 are different requirements from different agencies. You may owe both, but CGP compliance does not automatically satisfy your local plan-check.
What BMPs does the plan-checker typically want to see called out?
Common BMPs that clear plan check: silt fence or fiber rolls along the downslope property boundary, inlet protection (filter bags or wattles) at curb inlets adjacent to the site, a stabilized construction entrance to limit soil tracking, and sediment basins or check dams if the site has significant slope. You typically need to specify at least two. Most cities publish standard BMP plan sheets you can reference by detail number. Check your city's plan-check portal or ask the building department which BMP details they accept before you draw your own.
Can I combine the drainage and grading plan on one sheet?
Yes, and for residential projects that is the preferred approach. A single sheet showing existing contours, proposed finish grade, drainage flow arrows, spot elevations, and BMP locations covers 4.106.2 in one place. Label it Grading and Drainage Plan and add a title block note citing CALGreen 4.106.2. Splitting drainage across multiple sheets without clear cross-references is one of the reasons this correction comes back a second time. Keep it on one sheet and reference it from your architectural cover.
Does 4.106.2 apply to commercial and nonresidential projects?
Yes. CALGreen Part 5 (nonresidential) carries equivalent stormwater runoff control requirements for commercial, office, and mixed-use projects. The scope and documentation expectations are similar in concept, though commercial projects often require a separate grading permit from the local public works or engineering department in addition to the building permit. Confirm with your city whether one plan set satisfies both the grading permit and the CALGreen checklist, or whether two separate submittals are required.

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