HomeMy WebLinkAboutCT 93-07; Carrillo Ranch Villages F, G, & P; Tentative Map (CT) (5)cMO Fmn, RU,,J foCK ENGINEERING COMPANY
San Diego
California 92110-2596
(619) 291-0707
FAX: (619) 291-4165
July 26, 1993
Mr. Bob Wojcik
City of Carlsbad
2075 Las Palmas Drive
Carlsbad, California 92009
SUBJECT: MAINTENANCE ACCESS ROADS
(RICK ENGINEERING JOB NUMBER 12004-F)
Dear Bob:
In recent years, the City of Carlsbad has implemented a policy of requiring all weather
maintenance access roads to all storm drain inlets and outlets. City Engineering staff has
provided standards for these roads as summarized below:
Minimum Width 14 feet
Surface Treatment 0% - 7% D.G.
7% - 14% A.C.
14% - 20% Brushed Concrete
Work Area at Bottom 30' x 30' pad at grade
less than 5%. Locate
within 15 feet of inlet
or outlet.
The implementation of this policy has resulted in designs for access roads which impact areas
which would have otherwise remained natural. It is my opinion that many of these roads are
unnecessary. I request your assistance in creating a more balanced policy. Following are my
thoughts on this issue.
There are two main benefits for construction of access roads with projects. Firstly, the roads
make it easy for maintenance personnel to do their job. Secondly, they are constructed at no
cost to the City. However, there are some disadvantages which argue for not building these
roads. These include disturbances to open space/natural areas, encroachment onto riparian/flood
plane areas, long term maintenance cost for the road and liability for creating what might be
called an alternative nuisance, if used by skateboarders.
Mr. Bob Wojcik
July 26, 1993
Page 2
Storm Drain Inlets
Access to an inlet is typically more critical than an outlet. Inlets tend to silt up during storms
due to deposition of silt that occurs as the flows encounter water ponded at the inlet. If the inlet
became clogged with debris, the rising waters might overflow into other areas and damage
property. The determination as to whether to require an access road should consider the risk
of failure and the need to gain quick access to correct a problem. If the level of risk is low
based on the volume of drainage being handled, the characteristics of the drainage basin (risk
of clogging), ease of access without a road and the factor of safety in the design, then
consideration to not require a road should be made. This is especially important where
construction of the road presents a significant disturbance to areas which would otherwise remain
natural.
Storm Drain Outlets
Access to the typical outlet should, in my opinion, be rarely constructed. The exception would
be where the outlet is within a detention or desiltation facility which requires removal of siltation
to maintain their effectiveness. In these cases, the access should always be provided. For
smaller basins, the access may be only to the top of the basin. When the outlet is not within a
basin, it must typically be carried down steep slopes (natural or manufactured) to an area where
release of the drainage would be non-erosive. The typical installation includes construction of
an energy dissipator to decrease velocity to an acceptable level. During times of low flows, such
as Southern California has experienced in the late 1980's, these dissipators collect sediment as
the bed load capacity of drainage is reduced during energy dissipation. These pads become
somewhat self clearing during large storms with their faster flows and the high energy levels and
bed load capacity of the drainage. Keep in mind that the drainage will find its way out of such
a system, with or without a clean rock pad to land on. My opinion is that a road to an outlet
is seldom needed. Further supporting this is the fact that the level of disturbance to natural
areas is normally much larger for constructing a road to an outlet. The roads are normally
longer because of the larger elevation differential and terminate in areas containing sensitive
plants. To illustrate this point, I have attached a copy of a plan and tentative map for a project
showing an area where requirements for an access road to storm drain outlets greatly harmed
the project.
Please call me to discuss this letter. I am available to participate in discussions with City staff
if you choose. I would appreciate it if a policy allowing for flexibility on these could be issued.
c o
Mr. Bob Wojcik
July 26, 1993
Page 3
In addition, where roads are required, we request consideration of alternatives in my letter
dated, June 30, 1993 (attached) to reduce initial construction and long term maintenance costs.
I would also like to meet with you to review access road requirements for proposed inlet and
outlet locations on the Rancho Carrillo property in light of the above.
Sincerely,
RICK ENGINEERING COMPANY
Raymond L. Martin, PE
RLM:cea.006
Copy with attachments:
Mr. Mike Shirey, City of Carlsbad Engineering Department
Copy without attachments:
Mr. Chris Chamber, Continental Homes
Mr. Mike Howes, Hofman Planning Associates
Mr. Ken Quon, City of Carlsbad Engineering Department
Ms. Terri Wood, City of Carlsbad Planning Department
Mr. Norman C. Arndt, Rick Engineering Company Engineering Department
Mr. Craig J. Kahlen, Rick Engineering Company Engineering Department
Ms. Lesley Terry, Rick Engineering Company Engineering Department
Mr. Robert E. Wilkinson, Rick Engineering Company Planning Department