HomeMy WebLinkAbout3338; Agua Hedionda & Calavera Creek Dredging; Calavera Creek Riprap Installation Project US Army Corps; 2005-06-03CALAVERA CREEK RIPRAP INSTALLATION PROJECT CARLSBAD, CALIFORNIA CORPS FILE NO. 200500957 RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION U.S. ARMY CORPS OF ENGINEERS REQUEST RELAYED VIA LETTER FROM MARK DURHAM, DATED 3 / 15 / 05 Responses prepared by: PLANNING SYSTEMS 1530 Faraday Ave. Suite 100 Carlsbad, CA 92008 Design Engineer: O'DAY CONSULTANTS 2710 Loker Ave. West Suite 100 Carlsbad, CA 92008 Hydrologist: CHANG CONSULTANTS P.O. Box 9496 Rancho Santa Fe, CA 92067
RESPONSES TO THE USACE REQUEST FOR ADDITIONAL INFORMATION REGARDING THE CALAVERA CREEK RIPRAP INSTALLATION PROJECT DATED 3/15/05 The following are responses to the above-referenced request, in the order of the items requested in the March 15,2005 letter to David Hauser. DESCRIPTION OF ACTWrn 1. Detailed written description (incl. area, volume, dimensions) of activity to be permitted. Response: The project involves the removal of emergency riprap placed during flooding conditions on January 10,2005 over approximately 0.02 acres (900 sf) of the south bank of Calavera Creek, and its replacement with larger riprap over an increased area of the creek, all for erosion control purposes. The activities associated with the January 10 emergency placement were authorized pursuant to RGP Permit #200500957. The area is situated in a bend in Calavera Creek, at the confluence of Little Encinas Creek and Calavera Creek. The riprap placement was also the subject of a request for amendment to the Calavera Hills /Bridge and Thoroughfare District/Detention Basins permit (#200100215-RLK) on November 18,2003, but processing by USACE was rejected at that time due to USACE uncertainty over the larger-picture flood control program for the area. Undermining of the Calavera Creek stream bank occurred during the January 2005 rains, which resulted in the temporary riprap placement, and the subsequent USACE emergency permit. Since the January 2005 emergency placement of riprap, the applicant has been informed by the hydrologist that the riprap placed was too small in size and area to address erosion during possible future extreme flood conditions. Therefore the present proposal involves removal of the laid emergency riprap and its replacement and expansion with additional (and larger - 1 ton) rip rap (approximately 100 cu. yds. total) for a length of up to 111 feet of creek length. The total area impacted by the rip rap protection is approximately 111 ft. long x 45 ft. wide. This equals 0.11 ac. of area. Proposed specifications are as shown on the following table: 2. Complete descriytion of overall project, please describe the long-term solution for the current flooding problem in Calavera Creek and Agua Hedionda Creek. Area Dimensions Materials Volume Responses to USACE Request Additional Infirmation 1 6/3/05 Spec@cations 0.11 total acres affected 111 ft. long X 45 ft. wide 1 ton riprap 100 cubic yards
Response: Ultimate flood control for the Ranch Carlsbad Mobile Home Park (RCMHP) area along Calavera Creek and Agua Hedionda Creek is anticipated to involve permit processing for the dredging and improvement to portions of both of these creeks within and adjacent to RCMHP. In total, this full project is related to a series of regional projects anticipated to restore 100-year flood protection to as many of the units in RCMHP as possible. As indicated by the FEMA maps, in excess of 300 exiting homesites are currently subject to inundation in the 100-year storm event. Although a number of regional improvements are planned (including construction of upstream detention basins) in order to achieve the desired flood control results, the ultimate Calavera Creek and Agua Hedionda Creek improvements are expected to involve dredging of the Agua Hedionda Creek channel, elimination of the existing weir wall structure at the Calavera Creek outlet from Detention Basin BJB, modifications to the Basin BJB outlet, construction of an 84-inch flood control pipe within Cannon Road parallel to Calavera Creek, and also downstream modifications to the Agua Hedionda Creek Cannon Road and El Camino Real bridges. Hydrologic analysis has concluded that the presently-proposed riprap installation project will complement, and is not expected to in any way adversely affect or otherwise negatively impact these anticipated future improvements. The presently-proposed riprap project is located at the confluence of Little Encinas Creek and Calavera Creek, at a bend in the creek course within RCMHP. Hydrological analysis concludes that installation of the approximately 100 cu. yds. of riprap is necessary at this bend in order to minimize the potential for scour and creekbank erosion at this bend. It is the applicant's position that the riprap is urgently needed in order to minimize existing damage that is occurring from undercutting by the flow of the creeks, and could increasingly take place to property and the downstream environment if high floodwater volumes were to occur. The risk of such damage increases if the riprap is delayed for inclusion with the larger, regional dredging and improvements program, which are anticipated to take years for environmental review and permit processing. As a result, the project applicant requests that the proposed riprap be authorized for installation prior to the 2005-06 winter rainy season, in order to minimize the risk of property and environmental damage that could result from high rainfall amounts and flood conditions. 3. Precise coordinates of the project location (either as latitude/longitude or UTM). Response: The riprap installation project is located within Calavera Creek at latitude and longitude as indicated below: Responses to USACE Request Additional Infirmation 2 6/3/05 Latitude: Longitude: 33009'14" 117017'13''
4. Estimated area in acres of waters of the United States that will be impacted byfilling, draining, orjlooding for the entire proposed activity, please include tempora y impacts, if any. Response: Please refer to the Wetland Delineation Study for the Calavera Creek Rip Rap Placement Project, prepared by Planning Systems, dated June 2,2005, which is attached as Appendix A to this response report. This delineation study concludes that 0.076 acres are calculated to consist of "Waters of the U.S." which will be impacted by the riprap removal and replacement. No temporary impacts beyond the permanent area of riprap placement are anticipated. Permanent Impacts to Waters of the U.S. Suvface Type I I 5. Quantity in cubic yards of material to be dredged or used asfill. Vegetated Creek Banks Creek Bottom Response: Approximately 100 cubic yards of riprap material will be used to line the banks and bottom of Calavera Creek. Impacted Width (Feet) PROrECT PURPOSE 30 10 6. Need for project, please describe the need for riprap placement within the context of a long-tern flooding solution for the area. Impacted Area (feet21 Total Response: The purpose of the project is to eliminate the potential for sigruficant loss of property and downstream environmental damage resulting from soil erosion at the bend in the stream course at the confluence of Little Encina Creek and Calavera Creek. This is documented in conclusion of an analysis by Chang Consultants in his letter to Total Acres Impacted 2222 0.076 - 1089 McMillin land Development of Feb. 10,2005, titled ~obesson's Ranch - East Village, - Calavera Creek Protection at Weir Wall. This hydrologic analysis is provided as Appendix B to this response report. 0.051 0.025 The physical geometry of the bend in the stream course at the subject location will not be affected by the improvements anticipated in the long-term flooding solution for the area. It is concluded that the proposed riprap armoring of the subject area will be necessary whether or not the balance of the flood improvements are implemented. Responses to USACE Request Additional Infomzation 3 6/3/05
mTFORh4ATION REQUIRED FOR NATIONWIDE PERMIT NOTIFICATIONS 7. Compensate y mitigation proposal to ofiet permanent losses of waters of the U.S., including a statement describing how tempora y losses of waters of the U.S. will be minimized to the maximum extent practicable; or, justification explaining why compensato y mitigation should not be required. Response: The proposed riprap replacement and expansion project involves the *u.m placement necessary in order to properly maintain the integrity of the stream channel banks, as documented in the Chang report, attached as Appendix B to this response report. Since the riprap can be placed by crane from a perch located on an adjacent urbanized residential street, no temporary impacts are anticipated. As indicated in the Wetland Delineation Studv for the Calavera Creek Rip - Rap Placement Project, prepared by Planning Systems, dated June 2,2005, all vegetation existing in the proposed work area is of exotic ornamental species, including Oleander (Nerium oleander), Pink Hawthorne (Rhaphiolepis indica), Lemon Bottlebrush (Callistemon citrinus), Mexican Fan Palm (Washintonia robusta) and Canary Island Pine (Pinus canariensis). No obligate or facultative wetland plants have been identified in the work area. The "Waters of the U.S." impacted consist of domestic vegetated creek banks and the open channel creek bottom. As a result of the fact that no sensitive or native vegetation will be impacted by the proposed project, and that impacts to domestic vegetation does not require compensatory mitigation, and that the open channel creek bottom will continue to function as an open channel creek bottom (albeit with a riprap surface), it is not proposed that mitigation be required. This factor notwithstanding, area does exist which could accommodate the expansion of southern willow scrub (SWS) adjacent to the previously-approved wetland mitigation site for the Calavera Hills/Bridge and Thoroughfare District/Detention Basin project, located approximately 400 feet northerly of the site, if compensatory mitigation is determined to be necessary for implementation of the riprap project. Details of this mitigation area are on file with the USACE, however we can provide additional information as requested. 8. Written statement explaining how avoidance and nzinimimtion of losses of waters of the U.S. were achieved. Response: As indicated in the analysis by the hydrologist (Appendix B attached), the proposed riprap area, amount and volume is the minimum necessary in order to adequately protect the subject stream course bed and bank from undercutting and erosion damage. No other less-impacting design program exists to our knowledge. 9. Delineation of waters of the U.S., including wetlands. Responses to USACE Request Additional lnfomzation 4 6/3/05
Response: A Wetland Delineation Studv for the Calavera Creek Rip Rap Placement - Project, prepared by Planning Systems, dated June 2,2005, is attached as Appendix A to this response report. This report addresses both 'Waters of the U.S'and "jurisdictional wetlands". STATUS OF ADDITIONAL PERMITS OR CERTIFICATIONS 10. California Coastal Conzmission -federal consistency determination, if project is within the coastal zone. Response: The project is not located within the Coastal Zone. The eastern limit of Coastal Commission jurisdiction El Carnino Real, which is located one mile westerly of the subject riprap improvements. Therefore a federal consistency determination is not required for the project. 11. Regional Water Quality Control Board - 401 Certification. Response: A Regional Water Quality Control Board application is being prepared for application and submittal. REOUIRED FIGURES AND DZAGRAMS 12. Scale plan view diagram of existing (pre-project) conditions indicating Corps jurisdiction. Response: Pre-project conditions (including authorized emergency riprap placed on Jan. 10,2005) are shown on the "Existinn - Pre-Proiect Conditions" exhibit by Planning Systems (1" = 10' scale), attached to this response report as Appendix C. 13. Scale plan view diagram of anticipated conditions following construction of project indicating Corps jurisdiction. Response: Post-project conditions are shown on the "Anticipated Conditions Followinn Rip-Rap Installation" exhibit by Planning Systems (1" = 10' scale), attached to this response report as Appendix D. 14. Cross section or lateral view of proposed activity indicating Corps jurisdiction. Response: A cross-section of the proposed riprap installation is shown as Section A- A on the "Anticipated Conditions Followinn Rip-Rap Installation" exhibit by Planning Systems (1" = 10' scale), attached to this response report as Appendix D. 15. Project site as sketched on a Xeroxed portion of USGS quad map identzjijing quadrangle name, township and section Responses to USACE Request Additional Infirmution 5 6/3/05
Response: The project site is shown on the USGS Quadrangle Map, attached to this response report as Appendix E. 16. Delineation of Corps jurisdiction including afected special aquatic sites such as wetlands, showing boundaries and areas af tempora y and permanent impacts. Response: A Wetland Delineation Studv for the Calavera Creek Rip Rap - Placement Proiect, prepared by Planning Systems, dated June 2,2005, is attached as Appendix A to this response report. This report addresses "Waters of the U.S, "jurisdictional wetlands" and all permanent impacts. No temporary impacts are anticipated through implementation of the project. LIST OF ADDrrIONAL IiVFOXMATION RECOMMENDED TO EXPEDITE EVALUATION OF INDIVIDUAL PERMIT APPLICATION 17. Results of focused surveys for endangered species and designated critical habitat. Response: No focused surveys for endangered species have been conducted inasmuch as the proposed project impacts a man-made channel, surrounded by existing urban development. No sensitive habitats are within or near the subject project location. Critical habitat for the California gnatcatcher (CAGN) is shown on attached Appendix F. 18. Report of archaeological/historical resources onlnear project site compiledfrom a record search by a qualified professional archaeologist/historian at the regional center in your locale. Response: The project does not propose any grading or excavation of soil, and thus will not have the potential to adversely impact archaeological or historical resources in the area. The subject project will be placing riprap improvements within an existing creek bed located within an urbanized mobile home park neighborhood. The project could not be expected to impact any cultural resources. 19. Other information: Please provide information regarding how the existing and proposed riprap may fit into the long-term solution to theflooding issues in Calavera Creek and Agua Hedionda Creek. Response: The existing and proposed riprap is necessary whether or not the ultimate flood control for the RCMHP area along Calavera Creek and Agua Hedionda Creek is implemented in the future. As mentioned, the ultimate Calavera Creek and Agua Hedionda Creek improvements are expected to involve channel dredging of the Agua Hedionda Creek channel, elimination of the existing weir wall structure at the outlet from Detention Basin BJB, modifications to the Basin BJB outlet, construction of an 84- inch flood control pipe in Cannon Road parallel to Calavera Creek, and modifications to Responses to USACE Request Additional Information 6/3/05
the downstream Cannon Road and El Camino Real bridges over Agua Hedionda Creek. The presently proposed project will complement, and is not expected to in any way adversely affect or otherwise negatively impact these anticipated future improvements. Hydrological analysis by Chang Consultants (Appendix B) concludes that installation of the riprap is necessary in order to minimize the potential for scour and creekbank erosion at this confluence and .bend in the creek. Further, the riprap is urgently necessary in order to minimize damage that is occurring from undercutting by the flow of the creeks, and could increasingly occur to property and the downstream environment if extreme flooding were to take place. The risk of such damage increases if the riprap is delayed for inclusion with the larger, regional dredging and improvements program, which are expected to take years to process CEQA review and agency pennits. Therefore the project applicant requests that the proposed riprap be authorized for installation prior to the 2005-06 winter rainy season, in order to minimize the risk of property and environmental damage that could result from flooding rainstorms. The existing and proposed riprap is necessary whether or not the ultimate flood control program for Calavera Creek and Agua Hedionda Creek is implemented in the future. Responses to USACE Request Additional Infirmation 7 6/3/05