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EIR: 03 Executive Summary 40 EXECUTIVE SUMMARY This Draft Environmental Impact Statement/Draft Environmental Impact Report (DEIS,/DEIR) describes existing environmental conditions of the marine environment in the nearshore areas off the City of Rancho Palos Verdes, and examines the potential environmental effects associated with a proposal to restore natural reef habitat in the nearshore. This DEIS'DEIR is intended to be the environmental support of the Rancho Palos Verdes Draft Feasibility Report (Main Report) This environmental restoration project is proposed by the U.S. Army Corps of Engineers (Corps), Los Angeles District, in conjunction with the City of Rancho Palos Verdes. The City pf Rancho Palos Verdes is the non-Federal sponsor of this Feasibility Study. This document was prepared by the Corps pursuant to the requirements of the National Environmental Policy Act (NEPA) and intended to satisfy the City's need to comply with the California Environmental Quality Act (CEQA). The purpose of this DEIS,DEIR is to identify the potentially significant environmental impacts which would result from the construction, operation. and maintenance of the proposed project. As necessary, feasible mitigation measures are identified to avoid or reduce the severity of potentially significant impacts. This DEISiDEIR discusses the analysis of alternative considered, and analyzes alternatives to the proposed action and the "no action" alternative. This Executive Summary provides a summary of the proposed action. briefly describes the alternatives considered, summarizes the environmental impacts, and identifies areas of concern identified in the DEIS/DEIR. SUMMARY OF THE PROPOSED ACTION The purpose of the feasibility study is to determine the Federal interest in measures to restore the marine environment in Portuguese Bend Cove and adjacent areas. The study focus is on controlling the sedimentation and turbidity in the nearshore and offshore zones that result from erosion at the shoreline and has impacted the marine biological community of the area. The proposed action(Alternative 2) involves the construction of dike located 400 feet seaward from the existing bluff toe and "surrounds" the Portuguese Bend slide area. The dike is located at about the -16 ft. MLLW contour line and the highest crest elevation is about +24 ft. \ILLW. The dike would have a core of quarry run material to +6 ft. MLLW to retain sediment to the Mean Higher High Water(M HW)tide level, thereby preventing or significantly reducing the landslide-generated sedimentation and turbidity downcoast. Rock for the construction of the dike would come from either a mainland quarry or a quarry on Catalina Island. Construction would take approximately 1.5 years to complete. To maintain the proposed structure, it is estimated that approximately 7 million cubic yards (cy) of • material will need to be removed from behind the nearshore dike every 50 years. Part of the material behind the dike is expected to be submerged in the water behind the dike, and part of the material is expected to be dry material adjacent to the landslide bluff. Material will be moved/removed by dozers and truck mounted or crawler cranes. Maintenance activities are estimated to take approximately 600 days. DESCRIPTION OF THE ALTERNATIVES CONSIDERED Ten concept plans were considered during the feasibilitystudy They included structures along the shoreline (e.g., revetment, flexible berm, gabions), offshore structures (e.g., containment dikes and breakwaters), and partial or complete removal of landslide material. Alternatives considered but withdrawn from further consideration Structural stability of a shoreline structure could not be assured due to the uncertainty associated with the actual location of the landslide toe. The Corps' geotechnical engineers conclude that a structure within 400 feet of shore could be subject to displacement by the landslide. A structure between 200- 400' is believed to have an acceptable degree of risk of maintaining its integrity provided encroaching sediment is removed from behind the dike. Any structures within 200' of the shore is believed to require frenitent repair and re.planerlent ---- were, therefore riot cnnsidereri e_,n-------_ngly feasible alternatives. i�VT LeA0 ,;die odi; io„+ ^ntain �n�,r r^;/4 and Ll , o, :. pv.�isj' rvuuwiig wi ne �.. wnu�.v:. :.villi nv�vv u ) u.v.. ) ' y a fraction of the sedimentation, associated. with eroded material Since they would not meet the environmental objective, they were eliminated. Landslide material removal was rejected because of the high risk and uncertainty associated with material removal. Alternatives under consideration The containment dikes (with an option of dredging sediment off selected areas) were the only concepts that fell within the objectives and constraints of the feasibility study (i.e., contain sediment and turbidity but not alter the existing landslide). Alternative 1 (Nearshore Dike) involves the construction of a 2520 foot-long dike located 200 feet seaward from the existing bluff toe and "surrounds" the Portuguese Bend slide area. The dike is located at about the -10 ft. MI LLW countour line and the highest crest elevation is about +21 ft_ MI LW. Like the proposed action, the dike would have a core of quarry run material to +6 ft. vi • MLLWW'to retain sediment to the Mean Higher High Water (M HW) tide level. thereby preventing or significantly reducing the landslide-generated sedimentation and turbidity downcoast. Rock for the construction of the dike would come from either a mainland quarry or a quarry on Catalina Island. Construction would take approximately 1 year to complete. Alternative la(Nearshore dredging) is identical to Alternative 1. except that the dredging of sediment off 62 nearshore acres to expedite reef recovery is not proposed. Alternative 2a is identical to the Proposed Action (Alternative 2), except that it proposes to dredge sediment off some 52 nearshore acres of rock reefs in Portuguese Bend and Bunker Point to expedite the recovery of marine plants and animals on the reefs. Maintenance under Alternative 2a is identical to the Proposed Acton (Alternative 2). SUMMARY OF ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES Impacts: beneficial and adverse Significant net beneficial impacts to the nearshore marine environment of Portuguese Bend and 1111) immediately downcoast are expected. The proposed action is expected to result in the restoration of almost 90 acres of hardrock reef that is currently covered with landslide-generated sediment. This area is expected to be re-colonized by marine plants and animals. A robust, healthy kelp forest once known to the area is expected to be restored. Also, the quality of some 400 acres of existing kelp bed would be improved to optimal conditions as the near-constant, nearshore turbidity plum is eliminated. An adverse impact is expected from the loss of about 9 acres of existing, poor quality marine habitat which would be lost under and/or behind the proposed dike. This impact is expected to be more than offset by the large beneficial impact to marine biological community. Water quality behind the dike is expected to be poor but not significantly affected. Adverse air quality impacts are expected if rock must be trucked from a mainland source. This could be mitigated by extending the construction window to reduce the number of daily truck trips. Barging rock from an island source is not expected to result in significant air quality impacts. No underwater archeological or cultural resources are known for the project area. A detailed underwater survey, however, will be conducted of the project area during the Preconstruction Engineering and Design (PED) phase to determine if any significant cultural/archeological resources exist. • vii Mitigation measures • The only mitigation measures proposed relate to minimizing impacts to air quality from construction activities. They include watering the construction site twice daily to reduce fugitive dust emissions and extending the construction window from 1.5 year to 2 years to reduce the number of daily truck trips necessary to haul rock from a mainland source. ISSUES TO BE RESOLVED The quality of the water behind the proposed dike is of some concern. It is estimated that 25 percent of the water volume would be exchanged during each tidal cycle and, therefore, should not create any significant deterioration of the water quality_ .A more quantitative evaluation of the movement and exchange of water behind the dike is proposed during the PED phase to verify the assessment. The Corps and the US Fish & Wildlife Service have fundamental disagreements on the potential positive and adverse effects of the proposed action on the environment. The Service's Draft CAR identifies information gaps they feel are necessary to complete their analysis; the Corps contends that the there is sufficient existing information for the Service to make a determination on the effect of the proposed action on fish and wildlife resources as required by the Fish and Wildlife Coordination Act. The Corps has formally commented on the Draft CAR and will request the Service to finalize the Report. Areas of Controversy An area of controversy known to the Corps and City of Rancho Palos Verdes at this time involves the project itself There is some debate as to whether it is prudent to proceed with a project that focuses solely on restoration of rock-bottom marine habitat through containment of landslide sedimentation, but does not attempt to stabilize the Portuguese Bend landslide. This was a common concern expressed at the public scoping meeting at the initiation of the EIS/EIR process. viii • i i SUMMARY OF ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES FOR ACTION ALTERNATIVES Environmental Impacts of Alternatives Recommended Impact Issue Under Consideration Mitigation Measures Significance GEOLOGY Alt. 1: Removal of approx. 264,50(1 tons of stone material from None for any alternative. Alt. 1: Class III inland or island quarry. No impact to onshore topography. Dike Alt. 1 a: Class III may be within toe of landslide,but is not expected to have any Alt. 2: Class III accelerating elect on the landslide. Dike would likely be subject Alt. 2a: Class III to displacement by additional landslide movement,requiring periodic dredging to maintain dike's integrity. Approx. 3 million cubic yards of dredging required every 20 years for normal maintenance. Alt. la: Same as Alt. 1,phis dredging during initial dike construction to remove sediment from hard rock reef. Alt. 2: Removal of approx. 144,(1011 tons of stone material from inland or island quarry. No impact to onshorc topography. I)ike would be beyond toe of landslide. Approx. 7 million cubic yards of dredging required once during life of dike,for normal maintenance. Alt. 2a: Same as Alt. 2,plus dredging during initial dike construction to remove sediment from hard rock reef. MARINE CURRENTS Alt. 1: Short-terns elects on local currents may result during dike None,for any alternative. Alt. I: Class III AND TIDES construction. No effect on tidal movements or shoreline accretion. Alt. la: Class Ill Alt. 2: Class III Alt. I a: Same as Alt. 1 Alt. 2a: Class III Alt. 2: Same as Alt 1, although larger dike may result in more short-term construction impact on local currents. Alt. 2a: Sante as Alt 2 rag(' I .1-7 SUMMARY OF ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES FOR ACTION ALTERNATIVES (cont.) Environmental Impacts of Alternatives Recommended Impact Issue _ Under Consideration Mitigation Measures Significance AIR QUALITY AND Alt. 1: Trucking of mainland quarry stone would generate NOx 1. Apply dust control Alt. 1: Class 11 CLIMATE levels above SCAQMI) significance thresholds. Ilargiag from an measures. Alt. la: Class II island quarry would not exceed SCAQMD thresholds. I)ike 2. Increase total work days Alt. 2: Class II construction would generate fugitive dust levels above SCAQMI) (e.g. by extending Alt. 2a: Class II thresholds. Periodic maintenance may generate dust levels above workweek to six days) SCAQMD thresholds and/or extend construction period by another quarter to Alt. I a: Same as Alt. I,plus additional emissions associated with reduce total NOx emissions tnick or barge transport of construction phase dredged materials. associated with truck traffic. Alt. 2: Same effects as Alt. 1,with higher notal emissions Same measures for all associated with quarrying and transporting larger amount of alternatives. quarry materials and larger amount of dredging during one-time maintenance event. Alt. 2a: Same Alt. 2,plus additional emissions associated with _ truck or barge transport of construction yhase dredged materials. WATER RESOURCES Alt. 1: No impact on surface water quality or quantity or the None for any alternative. Alt. 1: Class III within the dike, AND WATER amount,rate or direction of surface runoff. Water quality would Class V ocean side of dike. QUALITY deteriorate within the dike, as landslide materials and other sedimentation settle into those waters and reduce total dissolved - Alt. la: Class IIII within the oxygen. I)issolved oxygen levels ire not expected to fall below 2 dike,Class V ocean side of dike. Ppm. Alt. 2: Class III within the dike, Significant improvement in water clarity and quality expected Class V ocean side of dike. outside of dike,due to containment of landslide material and other sedimentation. Alt. 2a: Class IIII within the Alt. I a: Same as Alt. I Page 2of7 i S • SUMMARY OF ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES FOR ACTION ALTERNATIVES (cont.) Environmental Impacts of Alternatives Recommended Impact Issue Under Consideration Miti.ation Measures Si:nificance WATER RESOURCES Alt. 2: Same effects as Alt. 1,except reduction in dissolved dike,Class V ocean side of dike. AND WATER oxygen levels may not occur as quickly,due to larger amount of QUALITY water within the dike. (cont.) Alt, 2a: TERRESTRIAL Alt. 1: Removal of less than 0.5 acre of disturbed,ruderal None for any alternative. Alt. 1: Class IV BIOLOGICAL vegetation for easternand western dike land connections. Alt. I a: Class IV RESOURCES Disturbance of 0.7 of grasslands on bluff for haul road extension. Alt. 2: Class IV No sensitive terrestrial resources impacted. Alt. 2a: Class IV Alt. la: same as Alt. I Alt. 2: Same as Alt. I Alt, 2a: Same as Alt. 1 MARINE Alt. I: Marine vegetation within the dike would be smothered and None for any alternative. Alt. 1: Class III within the dike, BIOLOGICAL destroyed by landslide material and other sediment. All Class V ocean side of dike. RESOURCES vertebrates or fish within the dike would also he destroyed, however,no rare,endangered or threatened fish have been Alt. I a: Class III within the identified in the Portuguese lien('area. dike,Class V ocean side of dike. )utside of the dike,it is estimated that approximately 504)0 acres Alt. 2: Class Il I within the dike,- of hard rock reef will he re-exposed and re-colonized by marine Class V ocean side of dike. vegetation and animals,especially giant kelp and its associated biological community of plants and animals. In addition, Alt. 2a: Class Ill within the approximately 173 acres of existing kelp lurests at Bunker Point dike,Class V ocean side of dike. and 230 acres at Bunker Point to Whites point are expected to benefit from reduced turbidity. The ocean side of the(like is also expected to create intertidal and subtidal hard rock habitat that would be colonized by invertebrate animals, immediately atler coustriietion. I':m� 1.1 7 SUMMARY OF' ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES FOR ACTION ALTERNATIVES (cont.) Environmental Impacts of Alternatives Recommended Impact Issue Under Consideration Miti_!ation Measures _ Significance MARINE Alt. la: Same as Alt. 1,except recolonization of hard rock reef BIOLOGICAL habitat would occur sooner,due to dredging during dike RESOURCES construction (cont.) Alt. 2: Same as Alt. I -with slightly less total testored hard rock reef habitat • Alt. 2a: Same as Alt. Ia, with slightly less iotalll restored hard rock reef habitat. LAND USE AND Alt. 1: No effect on existing or planned land uses. Minor None for any alternative. Alt. 1: Class III within the dike, RECREATION reduction in water-based recreational opportunities,within the Class V outside of dike. dike. Possible improvement in recreational opportunities (snorkeling,scuba diving)outside of dike due to improved water Alt. I a: Class Ill within the dike, quality trod because of improvement in health efvegetation and Class V outside of,1 t-,• animal life. Alt. 2: Class III within the dike, Alt. la: Same as Alt. 1 Class V outside of dike. Alt. 2: Same as Alt. 1 Class 2a: Class Ill within the dike,Class V outside of dike. Alt. 2a: Same as Alt. I _ AESTHETICS Alt I: Large,stone dike structure would alter scenic views from No measures available to avoid Alt. I: Class I- local; Class III - Portuguese fiend residential areas that presently do not include or reduce the visual impacts to regional any man-made structures within the ocean `scale.' local residents of the dike without also obstructing scenic Alt. I a: Same as Alt. 1 Alt. la: Same as Alt. I ocean views. Alt 2: Same as Alt. 1 Alt 2a: Same as Alt. l • Page-I of 7 • El' •; • S i SUMMARY OF ENVIRONMEN'T'AL IMPACTS AND MITIGATION MEASURES FOR ACTION ALTERNATIVES (cont.) Environmental Impacts of Alternatives Recommended Impact Issue Under Consideration Mitigation Measures Si.ignificance AESTHETICS Alt. 2: Sante type of effect as Alt. 1,with larger dike structure and (cont.) thus larger visual impact Alt. 2a: Sallie as Alt. 2 SEDIMENT Alt. 1 I;PA estimates no effect upon bioavailability 01' None for any alter native Alt. I Class IV ('l1EM IC'AL contaminants from chemically polluted near shore or off shore Alt. I a: ('lass IV CONTAMINA'T'ION areas when compared to without project. Alt. 2: Plass I V Alt. 2a. ('lass IV Alt. la: 1'l'A estimates no effect upon hioavailahility of contaminants from chemically polluted neat shore or off shore areas when compared without project_ Alt. 2: ITA estimates no effect upon bioavailability of contaminants from chemically polluted near shore or offshore areas when compared to without project Alt. 2a: I':I'A estimates no effect upon hioavailahility of contaminants from chemically polluted near shore or offshore areas vViten cotnrared to without project. ('f)I;1TURAT, All. I No impact to significant land based cultural resources is lino land-based excavation is Alt. I: ('la,s II RESOUR('ES expected Potentially submerged;uclaeological resources nray he required, a pre-construction Alt. I a. class II disturbed during dike construction further archaeological survey will he conducted by a Alt. 2. Class II investigations are needed to determine in of professional archaeologist Alt 11: Class II significant cultural/archaeological resources within the within the land arra directly coustnrction impact Titbits. allected by dike consti action to identify and recover any in face- Alt. la S ane:IS Alt I level resources that may exist If excavation is required, are Alt 2 ti;nie type of ctfecl as All I, vvtlh largo dike. footpr nit ,rid archaeological monitor will be associated increased potential fur dislnrlance to submerged retained to ensure identification archaeological r'sources and recovery of archaeological resources that may hr. encountered. I':re5 I , SUMMARY OF ENVIRONMENTAL. IMPACTS AND MI'1'ICA'FION MEASURES FOR ACTION ALTERNATIVES (cont.) Environmental I Impacts of Alternatives Recommended Impact Issue Under Consideration Mitigation Measures Significance _ CULTURAL Alt. 2a: Same as Alt. 2. RESOURCES A detailed underwater (cont.) archaeological sui vey will he conducted prior to completion of final plans and spccilicatiom for the dike structure Ary identified archacologial resources will he evaluated regarding eligibility for listing in the National Register of I historic Places and in accordance with the criteria defined in Section 21083 2(g)of the.Californil Public Resources Code.Public 1\lll �lll 1,l'1 L,l/U c'. Impacts to any significant resources that are ducInncntcd will he mitigated through data recovery,capping. and/or fcc payment, in accordance with the options and limitation-;provided for in `vection 2 111;1 i 1' of the ('alitoinia Public Resource!; ('ode. Same measures l),r:ill dike alternatives. page (ot7 S?: • • SUMMARY OF ENVIRONMENTAL IMPACTS AND MITIGATION MEASURES FOR ACTION ALTERNATIVES (cont.) Environmental — Impacts of Alternatives Recommended Impact Issue Under Consideration Mitigation Measures Significance CUMULATIVE Alt. I: ('onstruction dust and NOx emissions would exceed See measures previously Alt. 1: Class ti (Air Quality IMPACTS SCAQMI)thresholds and would therefore he cumulatively identified for construction- only) considerable. Construction traffic and noise could contribute to related air quality impacts. short-tern cumulative impacts resulting from other planned Alt. la: Class II (Air Quality projects in and near the Portuguese Bend area. only) Long-term effects are generally beneficial or benign. Significant Alt. 2 Plass II (Air Quality project-level aesthetic impact would not result in significant only) cumulative aesthetic impacts. Potential impacts to cultural resources would not be cumulatively considerable. Alt. 2a: Class II (Air Quality only) Alt. I a Same as Alt. 1. Alt. 2: Satre types of effects as Alt. 1, with sonic increase in construction traffic,noise and air pollution due to larger dike structure. Alt. 2a- Same as All 2. GROWTT1 Alt. I: No impact. None for any alternative. Alt. 1 Class IV INDUCEMENT All. I a: ('lass IV Alt. I a. No impact. Alt. 2 Class IV Alt. 2a Class IV Alt. 2 No impact. All. 2a: No impact. Definitions of Alternatives Definitions of Impact Significance Allcnuar,vc l Neatsliore 1)ikc ('lass I Significant,cannot be mitigated to ;i level that is not significant Alternative I:L Neaushorc I)ike With Dredging ('lass Il = Significant, but can he mitigated to an insignificant level Allcunat'ivc 2. t)11shoie Dike ('lass Ill Adverse, but not significant Alternative 2n_ I)ll hole Dike With Dredging ('lass IV No Impact ('lass V Iicnctici;il ling 7 of 7