HomeMy WebLinkAboutCT 98-14; Thompson/Tabata; Tentative Map (CT) (83)Investigative Science and Engineering
3511 Cam/no Del Rio South, Suite 302 Phone/Fax: €19-640-9379/619-640-0763
San Diego, CA 92108-4003 www.ise-advantage.com
July 13, 1999
Ms. Melissa Allen
Jack Henthom & Associates
5375 Avenida Encinas, Suite D
Carlsbad, CA 92008
Re: Standard Pacific Poinsettia Property Addendum Analysis
(ISE Report #98-017a)
Dear Ms. Allen:
At the request of Standard Pacific Properties and Jack Henthom and
Associates, Investigative Science and Engineering (ISE) has performed a brief
comparative analysis of our acoustical report for the proposed Poinsettia Properties
residential development located in Carlsbad, California (ISE Report #98-017) and an
earlier study prepared for the Mariners Point Tentative Tract 91-12 (Source: Robert
Kahn, John Kain & Associates, 1/24/92).
The purpose of the analysis was to reconcile differences in proposed mitigation
measures for the two projects along Aviara Parkway for City staff. The results of the
analysis are presented in this letter report.
Introduction and Definitions
The Standard Pacific Poinsettia Properties project site consists of 74.9 acres
located in the central portion of the City of Carlsbad in San Diego County, California.
The site resides on both sides of Poinsettia Lane, approximately 1 mile east of
Interstate 5. The lots are bound by Aviara Parkway to the east, single-family residential
housing to the north, and high-density single-family housing to the west and south
(including the Mariners Point project site). The site is currently zoned L-C and R-1-
10000 with a proposed zoning of R-1-7500 and RD-M-Q.
The eastern portion of the project site contains moderate westward facing
slopes while the western half of the site contains gentle slopes with minor relief.
Elevations on the site range from approximately 308 feet above mean sea level (MSL)
at the northeastern portion of the property to approximately 195 feet MSL at the
southwestern comer of the property.
Ms. Melissa Allen
Standard Pacific Poinsettia Property Addendum Analysis
ISE Report #98-017a
July 13, 1999
PageS
3. The Mariners Point project was analyzed using a proprietary computer
program developed by the consultant based upon the FHWA's RD-77/108
Noise Abatement Methodology. The Poinsettia Property project was
analyzed using the Caltrans Sound 32 Traffic Noise Prediction Model which
was developed by Caltrans and is used statewide.
4. The Mariners Point project set the receptor height at 6.0 feet AGL. The
accepted standardized receptor height for acoustical modeling is 5.0 feet
AGL. This value is used in the Poinsettia Property report.
5. Finally, the Mariners Point report set the receptor point at 5.0 feet from the
slope edge. The Poinsettia Property report sets the rear yard receptor point
approximately midway within the back yard area or approximately 10 feet
back from the slope edge. This methodology is consistent with the City's
Noise Guidelines Manual.
Conclusion
Based upon our findings, the future sound levels expected within Lots #235
through #240 (inclusive) reflect the conditions present at the proposed project site and
are consistent with the expected levels present at a 10 foot setback from the top of the
proposed slope edge. No additional modifications are necessary.
Should you have any questions regarding the above findings, please do not
hesitate to contact me at (619) 640-9379.
Sincerely,
RickTavares, REA, INCE
Project Principal
Investigative Science and Engineering
Cc: Gregg Linhoff, Standard Pacific Homes
Glen Laube, ISE
Ms. Melissa Allen
Standard Pacific Poinsettia Property Addendum Analysis
ISE Report #98-017a
July 13, 1999
Page 2
Comparison Findings
A review of the two reports found several differences consistent with individual
modeling strategies and analytical techniques. Both reports were fashioned using the
FHWA's RD-77/108 Noise Abatement Methodology which is consistent with the
guidelines outlined in the City of Carlsbad Noise Guidelines Manual. Both reports
utilized correct noise impact thresholds per noise element guidelines.
Specific concern expressed by the City centers around six lots within the
Poinsettia Property (Lots #235 through #240 inclusive) and the lack of recommended
mitigation measures. Past mitigation measures (in the form of a six-foot high AGL
masonry wall) were recommend for the Mariners Point project site Lot #56 which is
directly adjacent to Poinsettia Property Lot #235. The following observations were
made which clarifies the differences:
1. The principal reason for the differing opinion of mitigation design on the
affected lots is that the Mariners Point project report assessed impacts to the
project site based upon an acoustical model, which did not include the
attenuating effects of local existing topography. The Poinsettia Property
project report includes the effects of topography per City and ISE's standard
modeling guidelines.
Comment: This fact was verified through examination of the Poinsettia
Property acoustical model at Lot #235. With the attenuating effects of
topography (and a receptor point 10 feet from the edge of slope) the
calculated peak hourly sound level is 57.2 dBA, which is below the City's
impact threshold. Upon removal of the local topography (a non-realistic
configuration), the peak hourly level increases to 63.7 dBA.
The future sound level identified in the Mariners Point project report for Lot
#56 (directly adjacent to Poinsettia Property Lot #235) is 65.7 dBA. The
difference of 2.0 dBA is directly attributable to differences in future traffic
volumes (below), the conversion between peak hour Leq and CNEL, and
modeling differences.
2. The traffic volumes used in the Mariners Point project report for Aviara
Parkway (formerly College Boulevard) was 23,000 ADT with a mix of 97.42
percent automobiles, 1.84 percent medium trucks, and 0.74 heavy trucks (or
97.42/1.84/0.74). The peak hour percentage was taken at 10 percent and
the speed was set at 45 MPH. These levels are based upon a June 1991
traffic study performed by Wilden and Associates.
The traffic volumes utilized in the Poinsettia Property report for the same
roadway segment was 19,000 ADT with a mix of 98/1/1. The peak hour
percentage was taken at 8 percent and the speed was set at 40 MPH.
These levels are based upon a 1998 traffic report prepared for the project
site by Urban Systems Associates.