Pasadena Low Impact Development and Stormwater Rules

Pasadena Stormwater and Low Impact Development Rules

Pasadena regulates runoff under Chapter 8.70 of its Municipal Code, Stormwater Management and Discharge Control, and every new driveway, patio or pool deck adds hard surface that sends more rain toward the street. Whether a particular project triggers formal Low Impact Development requirements depends on its size; that threshold wasn't confirmed for this guide, so check with the City.

PMC Chapter 8.70

LID threshold: ask the City

Slope to landscaping

Keep washout out of drains

Last reviewed October 2026.

Pasadena's stormwater ordinance and new concrete

Rain that lands on concrete doesn't soak in. It runs off, picks up whatever is on the surface, and heads for the nearest catch basin. Pasadena's storm drain system is large: Pasadena Now, covering the launch of the City's stormwater compliance website in 2026, described more than 140 miles of pipe, 1,351 catch basins and 1,700 manholes. Chapter 8.70 of the Municipal Code, Stormwater Management and Discharge Control, governs what may go into it.

For a homeowner, that touches concrete work in two ways: during construction, when concrete washout, slurry and dust must stay out of the gutter, and afterward, when a bigger driveway or patio changes how much water leaves the lot.

New concrete driveway cut into panels by control joints, running up to a detached two-car garage — A new driveway on a Pasadena job, cut into panels by control joints so any cracking follows the lines.

Low Impact Development: what is and isn't confirmed

Low Impact Development, or LID, asks larger projects to retain, infiltrate or treat rain on site. Whether a residential driveway, patio or ADU project in Pasadena crosses the line into formal LID requirements depends on how much new or replaced impervious surface it adds. That square-footage trigger wasn't confirmed for this guide.

Stormwater questions by type of project

Project	Adds impervious surface?	What to ask the City
Replace a driveway at the same size	No net change	Construction practices only
Widen a driveway or add a parking pad	Yes	Does the added area trigger LID review?
Patio replacing lawn	Yes	Size threshold; drainage plan
Pool deck or new pool	Yes	Size threshold; pool discharge rules
ADU with new slab, roof and walks	Yes, often the most	Whether the project as a whole needs LID measures

Swipe the table sideways to see every column →

A planning summary, not a City determination.

Practical ways to keep rain on a Pasadena lot

Even where no formal requirement applies, the same ideas make a slab drain better and keep water away from the house:

Slope patios and walks toward lawn or planting beds rather than toward the driveway or street
Add a gravel or river rock strip along a slab edge where water can soak in
Send downspouts to planted areas instead of onto the driveway
Break up a large paved area with planters or a permeable section
Consider permeable pavers or pervious concrete for parking pads on a deep gravel base
Keep concrete washout, saw-cut slurry and dust out of the gutter during the job

White Spanish-style house with arched openings behind cactus and agave — A Spanish-style house with arched openings and a dry garden.

Pervious concrete and permeable pavers

Pervious concrete leaves out most of the sand so water drains straight through, and permeable pavers do the same with open joints. Both need a deep, open-graded gravel base to hold the water while it soaks in, and both need occasional vacuuming so the pores don't clog. On most Pasadena homes, sending runoff from an ordinary slab into landscaping gets most of the benefit for less.

Pools

The City's stormwater site also covers pool discharge rules, which apply when a pool is drained, separate from the deck. See the concrete pool deck page for deck drainage.

Backyard pool with a wide flat gray deck running to a covered outdoor kitchen — A wide, flat deck between a pool and a covered outdoor kitchen.

Related: concrete driveways, concrete patios and ADU foundations in Pasadena.

Pasadena Stormwater and LID Questions

A Spanish-style house with arched openings and a dry garden.

What is Pasadena's stormwater ordinance?

Chapter 8.70 of the Pasadena Municipal Code, Stormwater Management and Discharge Control. It governs what may run into the City's storm drain system, which Pasadena Now describes as more than 140 miles of pipe, 1,351 catch basins and 1,700 manholes.

Does a new driveway or patio trigger Low Impact Development requirements in Pasadena?

It depends on the size and type of project, and the exact square-footage trigger wasn't confirmed for this guide. Many Los Angeles County cities follow a regional template with thresholds for new and replaced impervious surface, but don't assume that number applies; check with the City of Pasadena's stormwater program.

What is Low Impact Development?

A way of designing a site so rain soaks in, is held or is treated close to where it falls, instead of running straight off hard surfaces into the street. For concrete work it usually means sloping slabs toward planted areas, adding gravel or permeable sections, and keeping downspouts out of the driveway.

Can concrete be permeable?

Pervious concrete, made with little or no sand so water passes through, exists, and permeable pavers do the same job with open joints. Both need a deep gravel base. Most residential projects get most of the benefit more simply, by sending runoff from ordinary concrete into landscaping.

Who do I ask about stormwater rules in Pasadena?

The City's stormwater program. Pasadena Now's coverage of the City's 2026 stormwater compliance website lists SWAdministrator@cityofpasadena.net as the contact, and the site covers permit requirements, pool discharge rules and construction best practices.