Mountain View Municipal Code Div. 10 Nonresidential Stormwater Pollution Prevention Requirements

Subsections 5.106.1 through 5.106.1.2 of the 2025 California Building Standards Codes are amended and a new subsection 5.106.1.3 is added to read as follows:

5.106.1 Stormwater pollution prevention for projects that disturb less than one acre of land. Newly constructed projects and additions which disturb less than one acre of land and are not part of a larger common plan of development or sale shall implement a stormwater sediment and erosion control plan that has been designed specific to the project site through the following measures:

5.106.1.1 Stormwater sediment and erosion control plan. The stormwater sediment and erosion control plan shall be developed to provide equivalent protection to projects regulated by California's National Pollutant Discharge Elimination System (NPDES) construction permit (for greater than 1 acre of disturbed land) and Chapter 35 Sec. 35.32.10.1(T) of the City Code. The stormwater pollutant control measures that shall be included in the plan are erosion control, run-on and run-off control, sediment control, advanced treatment (as appropriate), good site management and nonstormwater management through all phases of construction until it is fully stabilized by landscaping or the installation of permanent erosion control measures.

No state permit is required, but construction best management practices, as approved by the city, shall be followed per Sec. 5.106.1.2.

5.106.1.2 Best management practices (BMP's). Prevent the loss of soil through wind or water erosion by implementing an effective combination of erosion and sediment control and good housekeeping BMP's. BMP's include, but are not limited to the following:

1. Erosion and sediment control BMP's include, but are not limited to, the following:

a. Scheduling construction activity.

b. Preservation of natural features, vegetation, soil.

c. Drainage swales or lined ditches to control stormwater flow.

d. Mulching or hydroseeding to stabilize disturbed soils.

e. Erosion control to protect slopes.

f. Protection of storm drain inlets (gravel bags or catch basin inserts).

g. Perimeter sediment control (perimeter silt fence, fiber rolls).

h. Sediment trap or sediment basin to retain sediment on site.

i. Stabilized construction exits.

j. Wind erosion control.

k. Other soil loss BMP's acceptable to the enforcing agency.

2. Good housekeeping BMP's to manage construction equipment, materials, non-stormwater discharges and wastes include, but are not limited to, the following:

a. Material handling and waste management.

b. Building materials stockpile management.

c. Management of washout areas (concrete, paints, stucco, etc.).

d. Control of vehicle/equipment fueling to contractor's staging area.

e. Vehicle and equipment cleaning performed off site.

f. Spill prevention and control.

5.106.1.3 Postconstruction stormwater control requirements. Postconstruction stormwater controls are required for certain projects as defined and described in Provision C.3 of the Municipal Regional Stormwater NPDES Permit, and Chapter 35 Sec. 35.32.3 of the City Code.

(Ord. No. 9.2025, § 6(Exh. B), 9/9/25.)

Subsection 5.106.2 of the 2025 California Building Standards Codes is amended and a new subsection 5.106.2.1 is added to read as follows:

5.106.2 Stormwater pollution prevention for projects that disturb one or more acres of land. Projects that disturb one acre or more of land, or disturb less than one acre of land but are part of a larger common plan of development or sale are required to obtain coverage under the State of California Construction General Permit prior to issuance of a demolition permit or a grading permit from the city. A "Notice of Intent" (NOI) and "Stormwater Pollution Prevention Plan" (SWPPP) shall be prepared and submitted to the state, and proof of coverage under the Construction General Permit shall be submitted to the city.

The NPDES permits require post construction runoff (post-project hydrology) to match the preconstruction runoff (pre-project hydrology) with the installation of postconstruction stormwater management measures. The NPDES permits emphasize runoff reduction through on-site stormwater use, interception, evapotranspiration and infiltration through nonstructural controls, such as Low Impact Development (LID) practices and conservation design measures. Stormwater volume that cannot be addressed using nonstructural practices is required to be captured in structural practices and be approved by the enforcing agency.

Refer to the current applicable permits on the State Water Resources Control Board website at: www.waterboards.ca.gov/constructionstormwater. Consideration to the stormwater runoff management measures should be given during the initial design process for appropriate integration into site development.

5.106.2.1 Postconstruction stormwater control requirements. Postconstruction stormwater controls are required for certain projects as defined and described in Provision C.3 of the Municipal Regional Stormwater NPDES Permit, and Sec. 35.32.3 of the City Code.

(Ord. No. 9.2025, § 6(Exh. B), 9/9/25.)