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Home My WebLink AboutCT 03-01-01; LA COSTA RESORT & SPA MSTR PLAN; DRAINAGE REPORT; 2010-11-05HUNSAKER ^ASSOCIATES DIECO, PLANNING ENGINEERINC SURVEYING IRVINE LOSANGELES RIVERSIDE SAN DIEGO ARIZONA DRAINAGE STUDY for LA COSTA RESORT & SPA GOLF COURSE RENOVATION City of Carlsbad, California Prepared for: KSL Developnnent Corporation 2100 Costa Del Mar Road Carlsbad, CA 92009 w.o. 2833-1 Novembers, 2010 Hunsaker & Associates San Dlego, Inc. DAVE HAMMAR LEX WILLIMAN ALISA VIALPANDO DAN SMITH RAY MARTIN CHUCK CATER 9707 Waples Street San Diego, CA 92121 (858) 558-4500 PH (858) 558-1414 FX www.HunsakerSD.com lnfo@HunsakerSD.com R^rriond L. Martin, R.C.E. Vice President JD:kc K\2833\2010\AO?g wo 2833-1 11/8/2010 8^ AM f 2 LJal Drainage Study for La Costa Resort and Spa Golf Course Renovation Introduction The La Costa Resort and Spa is proposing to renovate the golf course, which includes minor site grading for 22 of the 36 existing holes. The goal is to reduce maintenance costs while increasing play on the course, including attracting professional level tournaments. Primarily, this will be achieved by an aggressive turf replacement program that places new, healthy turf over a sand cap within the fainways to establish a healthier root zone. Turf area reduction is included both outside existing fainways and reducing the size of some fainways. These areas will be replaced with native plant materials in order to reduce mowing and maintenance costs. Golf course irrigation will also be upgraded to a more efficient system which combined with the reduction in turf, will decrease water usage and frequency of watering. While performing the turf replacement, bunkers, tee boxes and other golf features will be adjusted to improve aesthetics and overall playability of the course. This drainage report accompanies grading plans forthe proposed golf course renovation. Existing Conditions The La Costa Resort and Spa is located in the City of Carlsbad, east of El Camino Real and north of La Costa Avenue. The resort consists of approximately 392 acres, and includes golf course, driving range, clubhouse, ballroom, tennis courts, hotel, spa, and commercial dwelling units. The resort is bordered by existing residential development on the north and east. The resort operates in conformance with Master Plan 03-02. There are seven planning areas, the golf course being #7 and the largest, making up 360 acres of the resort. Generally the site topography slopes southerly and westerly. An un-named tributary collects water from Poinsettia Lane at the north, conveys southerly under Alga Road and continues southerly toward the southwest corner of the project. There, this un-named tributary discharges into San l\/larcos Creek, which drains the eastern portion of the resort, as well as a large area of southeastern Carlsbad. San Marcos Creek then flows under El Camino Real to the Batiquitos Lagoon and eventually drains to the Pacific Ocean. The current golf course includes 11 lakes, 4 of which are jurisdictional and will not be touched during construction of this plan. There is a network of subsurface area drains that collect runoff within the golf course and outlet into the existing creeks. Runoff from the surrounding residential areas are collected in a series of ditches and placed in storm drain systems that also drain to the creeks. All drain outlets within the creek limits will remain in place and not be disturbed by the proposed renovation, due to the sensitive nature of the creeks. The current golf course includes 11 lakes, 4 of which have been identified as valuable environmental resources and are in-line with the un-named tributary. Since alteration of jurisdictional waters would require resource agency permitting, this plan avoids any impacts by not touching any sensitive habitat during construction ofthis plan. Much of the golf course at the La Costa Resort is currently within the 100 year floodplain established by FEMA. There has been a history of flooding within portions of the golf course. The project site soil consists primarily of a surface layer of silty clays and clayey sands overlaying native silty sands. These current soil conditions make it difficult to maintain healthy turf; so existing conditions cause much of the course to require regular use of fertilizer and herbicides. jDid R:Mo,2«H,dHydrology\Drainage Report.doc w.o. 2S33-1 11/8/2010 9:03 AM Drainage Study for La Costa Resort and Spa Golf Course Renovation Proposed Project The proposed La Costa Golf Course renovation will include minor grading to reconfigure greens, tees, and sand traps in orderto improve golf experience and attract PGA/LPGA tournaments. Of the 360 acres that make up the golf course, proposed grading operations will disturb approximately 57 acres and be confined to 22 of the 36 existing holes. Fainways in low lying areas will be raised in order to reduce the frequency of inundation when creeks crest. Two lakes and other low lying areas outside of play will be created to compensate for fill placement in order to provide no net fill within the regulated flood plain. Redundant and unnecessary cart paths will be removed thus reducing impervious surfaces. Also, turf areas will be replaced with native plant species which may improve infiltration over heavily trafficked turf surfaces currently existing on the course. These site improvements will have a significant positive impact on the ability of the course to drain during small storm events, due to a healthier turf and root structure, as well as reduce many storm water quality issues that currently exist. Run-off generated on-site or passing through the project will have a better ability to infiltrate into the soil, due to the 7" sand cap that will be placed on top of the clayey soils that currently exists as part of the turf replacement. By eliminating surface area of cart paths, the proposed design will also decrease the total percentage of impervious area. The proposed grading associated with this project does not have an overall impact on the limits of floodplain, as cuts and fills are balanced within the floodplain area. The goal is to raise playable areas outside of the floodplain, and lower other areas to collect storm runoff in a major storm event. Conclusions and Recommendations Renovation of the golf course will have an overall positive impact on site drainage during small storm events. Turf areas will have better infiltration rates and overall imperviousness of the golf course will be reduced. Drainage patterns will remain the same as the site will continue to drain into San Marcos Creek and its tributary through current drainage outlets and surface "sheet" flow patterns. The site area remains the same as existing, and the small reduction in impervious area will reduce the runoff coefficient, no increase in runoff is expected. This project will not cause an increase in runoff during the 100-year storm, and therefore we recommend approval of this report and issuance of permits allowing the proposed renovations to proceed. jDjd R:Moi2«Hyd\Hydrology\Drainage Report.doc w.o. 2833-1 11/8/2010 9:03 AU i