HomeMy WebLinkAboutCT 93-04; Rancho Carrillo Village Q; Tentative Map (CT)5620 Friars Road Rj^ ENGINEERING COMPANY
San Diego
California 92110-2596
(619) 291-0707
FAX: (619) 291-4165
June 30, 1993
Ms. Terri Woods
City of Carlsbad
Planning Department
2075 Las Palmas Drive
Carlsbad, California 92009
SUBJECT: RANCHO CARRILLO, VJJLLAGE "Q," CT 93-04
(RICK ENGINEERING JOB NUMBER 12004-F)
Dear Terri:
This letter is in response to your concerns over the aesthetic quality of the trail system. We
share your concern and are also interested in keeping the rural feel of the trails. Some of the
trails on the property double as access roads for maintenance of the sewer or storm drainage
systems. In addition, many portion of the trail have grades in excess of seven percent which
require special treatment to prevent erosion.
By separate cover, we are submitting a map showing areas which may require AC paving
because they exceed seven percent or are maintenance roads. There are alternatives to paving
these areas which are outlined below:
Alternative 1: Increase the cross slope on the trail to shorten the travel path of drainage. San
Diego Gas and Electric has a standard, TA-2458 (copy attached) for their roads in natural
ground. The standard increases the cross slope from two percent to a maximum of eight percent
for roads on a grade of up to 20 percent. Since our trails are intended for use by bicyclists and
pedestrians, we do not recommend excluding five percent cross slope. In the case of a 14-inch
wide DG trail at 20 percent, drainage would travel only 56 feet before reaching the drainage
ditch. This would minimize erosion problems on the trails without requiring AC paving and
could be combined with alternatives discussed below.
Ms. Terri Woods
June 30, 1993
Page 2
Alternative 2: Add redwood headers (4" x 8" perhaps) to chevron across the road at 50-foot
intervals. These headers would be installed level with the trail and serve to prevent formation
of rivlets on the trail. They would also stop drainage from undercutting along the edge of the
drainage ditch. However, these headers would not decrease travel path of the drainage. A 20-
percent trail grade with the normal two percent crossfall (14-foot wide) would allow 140 feet
of travel for drainage.
Alternative 3: Provide alternating low and high points in the trails, 6-inches to 12-inches apart
in elevation, creating a berm and swale effect, at 45 degrees to the drainage ditch. The berm
will rise over a distance of four feet to six feet to void creating a tripping hazard. Installed at
a close enough interval, these facilities will percent severe erosion. This method is commonly
used by the Forest Service on their roads. As a side benefit, they can also slow cyclists
descending the trail and help percent accidents with other trail users.
I have attached a sketch showing these alternatives. Please review these with your engineering
and utilities/maintenance departments and let me know which standards the City desires. If you
would like to discuss this issue further, please give me a call.
Sincerely,
RICK ENGINEERING COMPANY
Ptr
Raymond L. Martin, P.E.
RLM:cea.002
Attachments
Copy with attachments:
Mr. Chris Chambers, Continental Homes
Mr. Ken Quon, City of Carlsbad
Mr. Norman C. Arndt, Rick Engineering Company
Mr. Craig J. Kahlen, Rick Engineering Company
ROAD <£ GRADE
(PERCENT)
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13- 15
16- 17
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(PERCENT)
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