2019-09-11 - Stockstill, Ray - two questionsFrom:
scnbeach@earthlink.net
Sent:
Wednesday, September 11, 2019 3:05 PM
To:
AJ Ortega
Cc:
Ayu@laquintaca; gov
Subject:
RE: two questions
** EXTERNAL: This message originated outside of the City of La Quinta. Please use proper judgement and caution when
opening attachments, clicking links or responding to requests for information. **
Very helpful. Thanks. Just left a message for Amy. Ray 760-619-2868
Original email:
From: AJ Ortega Aortega@laquintaca.gov
Date: Wed, 11 Sep 2019 19:22:03 +0000
To: scnbeach@earthlink.net, Ayu@laquintaca.gov
Subject: RE: two questions
Ray,
I would rely on your engineers recommendation for adequate drainage of the area in question as the Building Code
doesnAEUR(tm)t specifically address your concerns.
Code references do exist but they donAEUR(tm)t contain specifics, for example within the CALGreen Code the
requirement of Section 4.1 (Site Development) is for AEURoeConstruction plans shall indicate how the site grading or
drainage system will manage all surface water flows to keep water from entering buildingsAEUR , but does not
elaborate further. Although it might seem odd I reference the CALGreen Code, but it comes up because the Residential
Code directs you there.
Specifically in the Residential Code, the requirement of Section R403.1 (Foundation AEUR" Drainage) is that a
EURoeSurface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does
not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall a
minimum of 6 inches (152 mm) within the first 10 feetAEUR , but again does not get specific to your concerns. So what
is the minimum slope of a rainwater pipeAEUR; I would say 5EURoesloped to drain5EUR as even in the Chapter 11
(Storm Drainage) of the Plumbing Code it references drainage slopes as low as 1/8AEUR per foot in Table 1101.6, which
is very low sloped.
Now I do feel your first question was a little more specific to Public Works, so in this response I have included Amy Yu
(760-777-7047) who is on the Engineering side of their division and can possibly weigh in. If you have any follow up
questions for me please let me know.
[cid:image001.png@01D4CA08.179DBE70]
AJ Ortega I Plans Examiner / Inspection Supervisor Design and Development Department City of La Quinta
78495 Calle Tampico I La Quinta, CA 92253 Phone 760.777.7018 www.laquintaca.gov<http://www.laquintaca.gov/>
www.playinlaquinta.com<http://www.playinlaquinta.com/>
From: Ray Stockstill <scnbeach@earthlink.net>
Sent: Thursday, September 05, 2019 9:06 AM
To: AJ Ortega <Aortega@laquintaca.gov>
Subject: two questions
** EXTERNAL: This message originated outside of the City of La Quinta.
Please use proper judgement and
caution when opening attachments, clicking links or responding to requests for information. **
AJ,
Thank you for your assistance.
I am working with an engineer and a contractor on redesigning the drainage of my interior courtyard and two questions
have come -up that IaEUR(tm)m hoping you can answer for us.
My interior courtyard is literally an interior courtyard. See below.
There are roofs that drain to the courtyard.
The surface of the roofs draining to the courtyard is more than 5 times the surface of the interior courtyard. Without a
manmade drainage system, the courtyard will flood whenever there is a 100-year storm. The distance between the top
of the interior courtyard and the top of the slab is around 5-inched.
There are 5 sets of French doors. The smallest distance by a door is 41/4-inch. The engineer said the drainage design
criteria for courtyard is as follows;
Design Criteria because of the greater than 1% risk of flooding annually The surface of the courtyard has to slope down
to the middle of the courtyard to create a sump condition and that is where the primary drainage system goes. The
slope has to be away from the foundation and away from the 5 sets of French doors.
There has to be a second back-up OVERFLOW drainage system at an elevation higher than the sump drain, because
there is no safe overland route of travel for the rainwater if the sump drain were to become blocked in a storm.
The top of the foundation has to be a minimum of one foot above the flood elevation in the courtyard. The gravity
system requires rainwater to pool in the courtyard. The engineer says the one foot above the flood elevation is measure
from the top of the pooled rainwater (WSE) that is needed for the drainage system to perform at the designed rate. He
feels that the one foot of clear space above the pooled rainwater is needed for a variety of reason and he said it is
consistent with the CityaEUR(tm)s precise grading plan checklist. IaEUR(tm)ve pasted the applicable section below.
My contractor doesnaEUR(tm)t think the 1 foot of clear space is needed just because the courtyard would flood every
time we had 1.43-inches of rain in an hour if there wasnaEUR(tm)t a manmade drainage system.
My first question - Is the 1 foot of clear space mentioned in the CityaEUR(tm)s precise grading plan checklist required as
part of the drainage design for my interior courtyard that is like a mini-100 year floodplain?
City of La Quinta Public Works Department - Commercial Precise Grading Plan Review Checklist (Includes Multi -Unit
Family PUD Precise Grading) PAD & FINISHED FLOOR ELEVATIONS/BUILDING/FLOOD CONTROL MEASURES Y -Pad
elevation shall be a minimum of 1 ft above 100 year flood elevation. 100 year flood elevation is generally considered to
be at the R/W AEUR" FOR should confirm same. FEMA minimum is that the finished floor elevation shall be a minimum
of 1 ft above 100 year flood elevation.
FEMA
aEURC Base Flood: The flood having a 1 percent chance of being equaled or exceeded in any given year.
aEURC Base Flood Elevation (BFE): The water surface elevation, expressed as an elevation above sea level, of the base
flood. This is the minimum elevation a community must adopt for building standards.
My second question has to do with the required minimum drainage pipe slope for my courtyard drainage system. Are
there any minimum slope requirements for the drainage pipes involving a rainwater siphoning type drainage system? He
has a significant section with zero slope and it was my understanding that the minimum requirement for a drainage
pipe/drainage line is A% -inch per foot.
Can you let us know the
correct minimum slope requirements for a siphoning type rainwater drainage system?
Thank you for your assistance.
Ray Stockstill
949-622-0232
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