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Home My WebLink About; Aviara Local Coastal Program- Permit Grading; Aviara Local Coastal Program- Permit Grading; 1991-11-01COASTAL COMMISSION PERMIT No. 6-61-46 (A) PHASE II 45 Day Winter Grading Extension Request NOVEMBER 1991 AVIARA Prepared for: AVIARA LAND ASSOCIATES LIMITED PARTNERSHIP 2011 Palomar Airport Road, Suite 206 Carlsbad, California 92009 TABLE OF CONTENTS I. INTRODUCTION II. NEED FOR WINTER GRADING EXTENSION III. REQUEST FOR WINTER GRADING PERMIT. IV. WINTER GRADING PROGRAM . ARE A OF WINTER GRADING . EROSION CONTROL PROVISIONS • DESILTATION BASIN DESIGN . • PHASE II WINTER GRADING EXHIBIT V. CONCLUSION ATTACHMENTS ICG INCORPORATED • P&D TECHNOLOGIES . page 2 pageS page 4 page 4 pageS page 6 AVIARA Phase II Winter Grading Extension Booklet Prepared By: PLANNING SYSTEMS 2111 Palomar Airport Road, Suite 100 Carlsbad, California 92009 (619) 931-0780 7 November 1991 #911046 /. INTRODUCTION The Aviara Local Coastal Program (East Batiquitos Lagoon/Hunt Properties LCP) and coastal permit (6-87-680) were approved by the Coastal Commission in April of 1988. The LCP uses the City of Carlsbad's Master Plan as implementing ordinances. Since project approval, the Commission has reviewed and approved a number of amendments to the LCP and permit documents. Additionally, Aviara has occasionally provided the Com- mission with updates on progress of master plan implementation relative to erosion control and other matters. A coastal permit for Phase II was issued on May 7,1991 (No. 6-911-46.) Grading was allowed only during the period of April 1 through November 15. Phase II is located along the western side of the Aviara Master Plan, and consists of single family residential area and undisturbed, deed restricted, coastal resource areas. The site is 247 total acres and bounded by Alga Road on the north, residential and agricultural uses to the east (outside of the Master Plan,) Batiquitos lagoon on the south and the Aviara/Four Seasons Golf Course to the east. Much of Phase II's mass grading has been completed. Some areas, including most of the areas south of Batiquitos Drive, will not be graded until the spring of 1992. The coastal resource areas will, of course, remain undisturbed permanently. AVIARA LOCATION MAP PHASE II PACIFIC OCEAN AVIARA Page 2 J /. NEED FOR WINTER GRADING As a result of a delay in achieving the city grading permit for Phase II, and a problem with the quantity of reclaimed water utilized in the grading operation, grading of Phase II is behind schedule. Although the Phase n coastal permit was issued on May 7,1991, final engineering plans were not signed by the City Engineer until some weeks later. Once grading did commence, the op- eration immediately began to experience low reclaimed water volumes from the City's plant. This resulted in a slower than anticipated grading operation. The water volume problem has since been resolved. Unfortunately, these problems have resulted in a circumstance where mitigation of the Phase II ancient landslide problem cannot be fully corrected (the grading cannot be completed in the landslide buttress area) during the existing (Nov. 15) grading season limit. The soils engineers have concluded that the necessary stability factor must be achieved by full grading per the approved plans (letter attached at end of this booklet.) PHASE II LOCATION MAP ANCENTT LANDSUDE AREA ^-PLANNING AREA CTYPJ WINTER GRADING AREAS (TYPICAL SYMBOL) FOUR SEASONS HOTEL PHASE II Page 3 III. REQUEST FOR WINTER GRADING PERMIT Aviara is requesting a 45 day exemption (from November 15 until December 31,1991) to the winter grading prohibition contained in the Coastal Permit The purpose of the exemption is to provide time to complete land stabilization work in the ancient landslide area. Grading will be limited to a limited portion of Phase n and the grading program described herein. No sedi- mentation of Batiquitos Lagoon or other coastal areas will result from this operation. IV. WINTER GRADING PROGRAM • AREA OF WINTER GRADING Four specific areas of grading are proposed. Three areas will be cut to provide fill for a single fill site. The fill site is the location of the landslide stabilization effort. These areas are all located over 1/3 of a mile from Batiquitos Lagoon, the prominent envi- ronmental feature of the area and the ultimate designation of the site's runoff. Sedimentatio n and erosion control systems will be provided as outlined below. • EROSION CONTROL PROVISIONS A tiered drainage and erosion control system has been permanently installed. Extensive temporary erosion control devices are also used. Drainage and erosion control devices are cur- rently in place and will be maintained through- out grading operations. The comprehensive program is demonstrated graphically on the following page. The tiered system employs the following de- vices and techniques: * Localized systems - Surface grading and bladed swales provide runoff control - Check dams reduce runoff velocity - Localized desiltation basins collect sedi- mentation from runoff * Off site systems - Closed storm drains prevent erosion - Open storm channels collect runoff and prevent erosion - Existing fully landscaped golf course and mature tree groves prevent erosion and filter runoff - Batiquitos Drive (grading of which is completed) is configured as a large dike, separating winter grading areas from Batiquitos Lagoon * Project wide desilting structures - Permanent desiltation basins at lagoo- wetlands collect sedimentation - Enclosed desiltation basin outflows dis- charge water only - Silt fences and energy dissipaters slow discharge velocity • DESILTATION BASIN DESIGN The project wide desilta tion basin located within Phase II is noteworthy as to its current size and configuration. The basin has been constructed temporarily in a size which greatly exceeds its final design. The temporary configuration of the basin provides a capacity of 11,120 cubic yards (CY) where 860 CY is required, and an area of 80,800 square feet (SF) where 13,160 SF is required. Moreover, the required sizes are based upon a 96.4 acre grading area, where only 78.6 acres will be disturbed pursuant to the revised Phase n mass grading plans. The basin is oversized by a factor exceeding 5, while the area of disturbance has been de- creased by 23%. The project engineer has docu- mented the basin's size in a letter attached at the end of this booklet. A AVIARA Page 4 PHASE II WINTER GRADING EXHIBIT PHASE II WINTER GRADING PROGRAM NOV. 15 • DEC. 31, 1991 • COMMENCEMENT AFTE BATIOUITOS LAGOON \ LOCALIZED TEMPORARY DESILT BASIN PERMANENT PROJECT DESILT BASIN SECTION A Page 5 V. CONCLUSION • Certain unexpected delays in the anticipated grading program have been experienced. • Aviara is requesting a 45 day exemption from the winter grading prohibition, from November 15th through December 31st, 1991. • The purpose of the winter grading exemption is to complete landslide stabilization improve- ments. • Existing erosion control structures and devices will mitigate runoff and sedimentation. These structures have effectively serviced the site for three years. AVIARA Page 6 ATTACHMENTS The following letters, submitted by the geotechnical and civil engineer respectively, document to the need for landslide stabilization and the size of the temporary desiltation basin. S>n DiegoCounty OHIe*: 9740 Trad* Place. Suit* 100 San Dirg'i 619536-110? la« 619/S36-1306 Inland Empire OMce 1906 Orange Tree Lane. Suite 240 Rrrtands. C» 92374 714/792-4222 lax 714/798-1644 Orange County Oirices Construction Inspection and Testing 2992 La Raima. Suite A Anaheim CA 92606 714<632?«80 la< 714/632-9209 Geolechnicat 15 Mason Irvine. CA 92718 714/9518668 lai 714/951-7969 Coachella Valley Ollice: 77-775 Jackal Drive. Suite C Bermuda Dunes. CA 92201 619772-3162 la» 619.772 3184 Corporate Olfice 15 Mason Irvine. CA 92718 7I4»95I 8G66 lai 714/951-7969 ICGincofyotiated October 21, 1991 Aviara Land Associates Limited Partnership 2011 Palomar Airport Road, Suite 206 Carlsbad, California 92130 Job No. 04-3179-012-00-00 Log No. 1-2151 Attention: SUBJECT: Gentlemen: Mr. Curt Noland EXTENDED GRADING OPERATIONS PA 25 and 26N Aviara, Phase 2 Carlsbad, California It is our understanding that due to Costal Commission regulations grading operations for Phase II in the vicinity of Planning Areas 25 and 26N at Aviara will be terminated on November 15, 1991 for the winter season. As we all know these two planning areas are in a very sensitive landslide area. If grading ends on November 15 is originally planned these areas will not be near completion and the slope stabilization measures planned will not be in place. In their present state these areas exhibit a factor of safety of between 1.2 and 1.5 which is considered stable for temporary conditions but not for long term. It is our opinion that grading operations should continue in these areas after November 15 in order to enhance the stability of these two planning areas. Leaving these two areas in a partially completed condition could, in the event of a long wet winter, result in damage to the homes and property located at the top of the slide area. Should any questions arise please contact our office. Very truly yours, ICG Incorporated Anthony F. Belfast, P.E. 40333 Expiration Dale: 3-31-95 Chief Engineer EJN/AFB/ (Votwrhnirnl Spfvi . Construction Inspection PHASE II Page? 401 W A" Situ*&HW2500San Diego. C* 92101FAX 619/234 3022 619/2324466 Planning Engineering Transportation Environmental fconomics Landscape Architecture October 14, 1991 An Employee-Owned Company OCT i 5 Mr. Curt Noland Aviara Land Associates 2011 Palomar Airport Road Suite 206 Carlsbad, California 92009 Dear Curt: RE: AVIARA, DESILTING BASIN #5 Per your request I have reviewed the capacity of temporary desilting basin #5 within Phase II of Aviara. Due to the configuration of the basin, the resulting capacity of 11,120 CY for sediment and water far exceeds the required amount of 860.2 CY as calculated in the desilling basin study prepared by VTN Southwest. Inc., dated July 21, 1988 (pages 31-42). The same holds true for the basin area capacity of 80,800 SF vs. only 13,160 SF required per the calculations. The study was prepared using a worst case scenario where grading occurs simultaneously over 96.4 AC. The approved grading plans for Phase It mass excavation show a disturbed area of 78.6 AC, a 23% decrease from the original assumption. It. therefore, seems that the basin was sized larger than required for the temporary condition and should accommodate the grading effort now underway on Phase II. If you have any questions concerning the above, please call. Sincerely, P&D TECHNOLOGIES JohK W. Norman ^Director of Engineering JWN:pc AVIARA Page 8