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HomeMy WebLinkAboutWest End Flood Control Alt.do di SUPPLEMENTAL FLOOD CONT14,0L FAC .1-LITY ALTERNATIVES WEST END SPECIFIC PLAN CITY 02 FCNT November, 1984 Prepared By Bill Mann & Associates 1814 Commercenter West Suite A San Bernardino, CA 92408 a a 3 3 7 7 3 7 7 7 7 7 TABLE OF CONTENTS Page SECTION I. PURPOSE OF SUP_LEMENTAL REPORT 1 SECTION II. ALTERNATE SOLUTIONS FOR ELIMINATING 3 THE NEED FOR THE EXISTING SAN SEVAINE CHANNEL IN THE PROJECT AREA A. GENERAL 3 B. ALTERNATE PLANS FOR THE ELIMINATION 4 OF EXISTING SAN SEVAINE CHANNEL C. ANALYSIS OF ALTERNATE PLANS AND 13 RECOMMENDATIONS SECTION III. REIMBURSEMENT OF COSTS FOR REGIONAL 17 FLOOD CONTROL FACILITIES A. GENERAL DISCUSSION 17 B. DISTRIBUTION OF CONSTRUCTION COSTS 18 FOR THE SAN SEVAINE CREEK SYSTEM C. DISTRIBUTICN OF COSTS OF THE SAN 21 SEVAINE CREEK SYSTEM TO THE WEST END SPECIFIC PLAN D. REIMBURSEMENT OF REGIONAL FLOOD 22 CONTROL SYSTEM COSTS TO WEST END SPECIFIC PLAN DEVELOPMENT SECTION IV. DEVELOPMENT PHASING PLAN 25 A. GENERAL DISCUSSION 25 B. RECOMMENDED PHASING 26 APPENDIX i D SECTION I. PURPOSE OF SUPPLEMENTAL REPORT A Specific Plan and Environmental Impact Report are being prepared for the approximate 1,200 acres located north of Foothill Boulevard and east of East Avenue in the City of Fontana. The planning docu- ments are being prepared by the SWA Group. The firm of Bill Mann & Associates was retained to analyze drainage and flood problems associated with the project area and recommend solutions. A report entitled "West End Specific Plan, Flood Control Facilities Study ", dated September, 1984, was prepared by Bill Mann & Associates. This report is a supplement to the above referenced report and is devoted primarily to review several alternatives for eliminating the existing San Sevaine Channel that traverses the.easterly por- tion of the site. The "Flood Control Facilities Study" discusses the existing conditions, flood hazards, proposed flood control improvements in the Day, and San Sevaine Creeks System go Drainage Plan for the regional area, and drainage aspects. Except q. as necessary to describe alternate solutions for eliminating the do existing San Sevaine Channel traversing the site, the contents of the prior report are not repeated herein. on rri Figure Nos. 1 and 2 show the project area and its relation to the existing flood control facilities and proposed regional facilities di for the area in general. The prior report, "Flood Control Facili- ties Study" is referred to for other maps and a detailed discussion on existing conditions and proposed master planned flood control _ facilities. Section'II describes.two alternate solutions for providing the necessary flood control facilities for the project area. Estimated 1 costs, as known at this time, are provided for each alternate. Also included in Section II is an analysis of each alternate and recommendations. Due to the regional nature of the proposed flood control facilities for the general area, the total cost of the necessary flood control facilities traversing the project area and any necessary "offsite" flood control facilities constructed by the development should be spread over the entire tributary drainage area. Section III dis- cusses the reimbursement or cost - sharing of the regional flood control facilities. The distribution of cost for the regional facilities on a "gross acre" basis was provided for in the approved Day, Etiwanda and San Sevaine Creeks System Drainage Plan. The alternatives discussed in this supplemental report have been submitted to the San Bernardino County Flood Control District and the City of Fontana for review. 10 W 2 Vt t SECTION II. ALTERNATE SOLUTIONS FOR ELIMINATING THE NEED FOR THE EXISTING 'SAN SEVAINE CHANNEL INTHE PROJECT AREA A. GENERAL The drainage master plan for the Day, Etiwanda and San Sevaine Creeks System was completed in March, 1983. The drainage plan calls for the ultimate combining of the Etiwanda and San Sevaine Channels immedi- ately below the Devore Freeway and the construction of a concrete lined channel for the combined design flow southerly, from the Devore Freeway to the Santa Ana River. In accordance with the master plan, the combined channel below the Devore Freeway will be known as the San Sevaine Creek Channel. The aforementioned Day, Etiwanda and San Sevaine Creeks System master plan calls for the excavation of major flood storage and debris reten- tion facilities above the Devore Freeway and a concrete lined channel .�. below the Devore Freeway. The master plan provides for the elimina- tion of the existing San Sevaine Channel through the project area as a major flood control facility, at such time as the ultimate channel below Foothill Boulevard is constructed and /or the flood storage facility (Lower San Sevaine Basin) is constructed. Refer to the "Flood Control Facilities Study, West End Specific Plan" for a dis- cussion on the overall proposed regional flood control improvements. 3 10 As discussed in the "Flood Control Facilities Study, West End Speci- fic Plan ", dated September, 1984 once the ultimate San Sevaine Creek Channel (combined ; San Sevaine - Etiwanda Creek flows) is con - structed, there will no longer be a need for the existing San Sevaine Creek Channel traversing the easterly part of the site in its present form. The aforementioned Day, Etiwanda and San Sevaine Creeks System master plan calls for the excavation of major flood storage and debris reten- tion facilities above the Devore Freeway and a concrete lined channel .�. below the Devore Freeway. The master plan provides for the elimina- tion of the existing San Sevaine Channel through the project area as a major flood control facility, at such time as the ultimate channel below Foothill Boulevard is constructed and /or the flood storage facility (Lower San Sevaine Basin) is constructed. Refer to the "Flood Control Facilities Study, West End Specific Plan" for a dis- cussion on the overall proposed regional flood control improvements. 3 10 s V Due to the extensive cost involved and the degree of necessary coordination and planning for the regional system, the construction of the ultimate regional plan is not possible at this time. There- fore, an effort is being made to develop a plan, short of the total regional master plan, to allow the development of the project area. Alternate plans to resolve the existing San Sevaine Creek flooding problem and facilitate the elimination of the channel through the project area are discussed below. 3 The proposed alternates discussed herein are presently being re- viewed by the San Bernardino County Flood Control District and the City of Fontana. Therefore, the alternatives reviewed herein, al- though considered viable alternatives, have not been approved. B. ALTERNATE PLANS FOR THE ELIMINATION OF EXISTING SAN*SEVAINE CHANNEL There are two primary alternates, except for complete construction of the master plan facilities, for solving the flood problems and eliminating the existing San Sevaine Channel from the project area. .�, These are discussed below as Alternate "A" and Alternate "B ". Any other alternatives would necessarily be combinations of Alternates "A" and "B ". Alternate "A" is shown on Figure No. 1 and Alternate "B" is shown on Figure No. 2. 1. Alternate "A" Alternate ".A" generally inclydes the construction of the ultimate San Sevaine Channel between the Devore Freeway and Foothill Boulevard, and the excavation of the Lower San Sevaine Basin above the Devore Freeway. Refer to Figure No. 1 for a schematic location and description of the components of this alternative. 4 10 F Specifically, the features and estimated cost of Alternate "A" are as follows: 1.1 Construction of the ultimate San Sevaine Channel (combined Etiwanda and San Sevaine Creeks flow) from the Devore Freeway to Foothill Boulevard, with a transition to the di existing RCB under Foothill Boulevard. 4M .r Estimated Cost = $ 3,965,000 OM 1.2 Excavation and construction of the Lower San Sevaine Basin r to provide for debris and flood storage for a 100 -year frequency, 24 -hour duration flood. Estimated Cost = $ 6,250,000 00 1.3 Develop "offsite." drainage retention capability in Vic - „ toria Basin to partially compensate for the necessary "onsite" retention of development drainage flows. Estimated Cost = $ 95,000 d Subtotal = $10,310,000 1.4 Because of the area below the Devore Freeway tributary to the existing San Sevaine Channel, it will be necessary to San construct a channel or storm drain from the existing Sevaine Channel to the proposed concrete lined channel for purposes of conveying local drainage flows to the proposed channel. The excavation of the Lower San Sevaine Basin does not provide for local drainage flows north and north- east of the site, originating southeasterly of the Devore E G t V II!, Freeway. The storm drain or channel would be located along Baseline Avenue and is shown schematically on Figure No. 1. Storm Drain Estimated Cost = $ 1,000,000 Estimated Alternate "A" Cost = $11,310,000 The firm of Hall and Foreman is preparing an analysis and cost estimate for the necessary onsite storm drain and drainage retention facilities. Those costs are not included in the above costs. Alternate "A" is the flood control facilities plan called for in the Day, Etiwanda and San Sevaine Creeks Drainage Plan. How- ever, the facilities are regional in nature and possibly more expensive than the subject development can sustain, even on a d reimbursement basis. The Lower San Sevaine Basin excavation provides regional benefits due to flood flow storage all the way to the Santa Ana River. Also, the right -of -way for the basin is still in the process of being transferred from Caltrans to the Flood Control District, and there is some concern re- garding the possible need of the basin material for the future Foothill Freeway. Refer to Figure No. 1 for a schematic description of proposed facilities. 2. Alternate "B" Alternate "B" generally includes the construction of the ulti- mate San Sevaine Channel between the Devore Freeway and Foothill IV 7 t Boulevard, construction of an "interim" channel between Foot- hill Boulevard and the Santa Fe Railroad to the south, and the excavation for some debris and storm flow capacity in the proposed Lower San Sevaine Basin. Refer to Figure No. 2 for a schematic location and description of the components of Alternative "B ". Specifically, the features and estimated cost of Alternate "B" are as follows: fl I Estimated Cost - $ 5,175,000 2.2 Construction of an "interim" earth channel along the ulti- mate channel alignment from Foothill Boulevard southerly 7 M 9 2.1 Construction of the ultimate San Sevaine Channel (combined Etiwanda and San Sevaine Creeks flow) from the Devore Free- way to Foothill Boulevard. Until the ultimate San Sevaine Channel is constructed below Foothill Boulevard in accor- dance with the "Drainage Plan" and /or the Lower San Sevaine Basin is constructed, existing Etiwanda and San Sevaine Creek flows cannot be comingled. Therefore, a trapezoidal 4, concrete channel is proposed with a separator wall separa- di Ling the flows. Existing Etiwanda Creek flows would be directed to the existing RCB under Foothill Boulevard,and existing San Sevaine Creek flows would be directed to the proposed "interim" channel south of Foothill Boulevard. Due to the need to separate Etiwanda and San Sevaine Creek flows, the channel cost for this reach is higher than the channel in Alternate "A ". fl I Estimated Cost - $ 5,175,000 2.2 Construction of an "interim" earth channel along the ulti- mate channel alignment from Foothill Boulevard southerly 7 M 9 Fl d to connect to the existing San Sevaine Channel immediately south of the Santa Fe Railroad. The construction would include the ultimate road crossing structures. A set of schematic plans for the interim channel construction is included in the Appendix for general information only. Estimated Cost = $ 1,800,000 h; E F 2.3 Develop "offsite" drainage retention capability in Victoria Basin and the Lower San Sevaine Basin to partially compen- sate for necessary "onsite" retention of drainage flows. Excavation in the Lower San Sevaine Basin would approximate 200,000 yd Estimated Cost = $ 445,000 2.4 Develop 200,0 • 00yd of debris storage in Lower San Sevaine Basin to provide for major flood debris production on San Sevaine Creek. Estimated Cost = $ 350,000 on k e Subtotal = $ 7,770,000 2.5 Because of the area below the Devore Freeway tributary to the existing San Sevaine Channel, it will be necessary to construct a channel or storm drain from the existing San Sevaine Channel to the proposed concrete lined channel for purposes of conveying local drainage flows to the channel. The excavation of the Lower San Sevaine Basin does not pro- vide for local drainage flows north and northeast of the site originating southeasterly of the Devore Freeway. The 10 0 storm drain or channel would be located along Baseline Avenue and is shown schematically on Figure No. 1. Storm Drain Estimated Cost = $ 1,000,000 Estimated Alternate "B" Cost = $ 8,770,000 RR As indicated in the discussion of Alternate "A ", the cost of the onsite storm drain and drainage retention system is not included herein. Alternate "B ", as proposed herein, is approximately $2,500,000 less expensive than Alternate "A ". However, the facilities pro - posed under Alternate "A" are regional in nature and will provide am benefits to the area in general, both to the north and south of IN the site. Components of Alternate "B" are also regional in nature. Alternate "B" will provide direct benefits to the area along Banana Street south of Foothill Boulevard at less expense to the region. This alternate will not require the complete ex- cavation of the Lower San Sevaine Basin initially, and will re- serve the bulk of the material to be excavated for.the construc- tion of the Foothill Freeway, if needed. Because of the liabilities involved with comingling Etiwanda and San Sevaine Creeks flows prior to an adequate concrete lined channel being constructed downstream of the project area, these flows must be kept separated. Therefore, a trapezoidal channel with a wall separating the flows is recommended. A schematic depiction of the channel is included herein as Figure No. 3. The final size and configuration of the channel cross - section will depend on final design of the channel system. � 11 CHANNEL R/W 100 - 105' SEPARATOR WALL ETIWANDA CREEK FLOWS 15' r 1.51 FIGURE NO. 3 SAN SEVAINE CREEK FLOWS M r VARIES -� 9 VARIES 13'- 14! VARIES 24'- 2.6 COMBINED - CHANNEL ETIWANDA AND SAN SEVAINE CREEKS FLOWS NOTE - CHANNEL DIMENSIONS ARE PRELIMINARY. FINAL DIMENSIONS WILL DEPEND ON FIN AL HYDRAULICS AND DESIGN. t. . E IV C. ANALYSIS OF ALTERNATE PLANS AND RECOMMENDATIONS 1. Analysis of Alternates "A" and "B" Both alternate plans ( "A" and "B ") discussed in Section II,B above, will resolve the flood control issues. Either plan provides the necessary flood control protection facilities and provides for the elimination of the existing San Sevaine Channel traversing the easterly portion of the project area. M, „ Both plans provide for the construction of the ultimate San Sevaine Channel (combined Etiwanda and San Sevaine flow) from di the Devore Freeway to Foothill Boulevard in accordance with the approved Day, Etiwanda and San Sevaine Creeks System Drainage Plan. The channel is larger and more expensive in Alternate "B" than Alternate "A" because of the necessity of separating Etiwanda and San Sevaine flows. The separation of flows will di be necessary until adequate downstream channel facilities, or upstream flood storage facilities, are constructed to remove the potential legal liabilities involved with combining the flows. The Drainage Plan assumes the flows will be combined, but the construction of the combined channel requires the construction of the downstream channel and /or other mitigating measures. .r Both plans provide for a drainage ditch or storm drain along Baseline Avenue from the existing San Sevaine Channel north of Baseline to the proposed concrete lined channel. The storm drain facility will be necessary to intercept local drainage flows from the north, and therefore, facilitate the removal of the existing San Sevaine Channel traversing the site. IV 13 E The major difference in the two plans is the "interim channel" below Foothill Boulevard proposed in Alternate "B" in lieu of the 2,000,000 to 3,000,000 yd basin excavation proposed above the Devore Freeway in Alternate "A ". Alternate "A" is approx- imately $2,500,000 more expensive than "B ". Aside from the expense involved, the excavation of the Lower San Sevaine Basin above the Devore Freeway may necessarily be delayed due to the 4M transfer of rights -of -way for the basin and a decision on the need for the basin excavation material for the proposed Foothill 4M Freeway. W The construction of the "interim channel" south of Foothill Boulevard will provide direct benefit to the area south of Foothill Boulevard by removing flood flows from Banana Street. The interim channel will be located along the ultimate channel ar alignment; therefore, the excavation and street and railroad crossings can be designed to meet the ultimate plan. di Schematic plans of the interim channel are included in the Appendix of this report. Refer to Figure Nos. 1 and 2 for the location of Banana Street. 2. Review 'of Other A lternatives 'or Comb'inati'on of Al't'ernatives Other alternatives to solving the flood hazard problem and pro - viding for the phasing out of the existing San Sevaine Channel were reviewed and found to be infeasible. These alternatives are listed below in general, but are not discussed in detail. a. Maintain the Existing San Sevaine Channel' in Perpetuity The perpetuation of the existing San Sevaine Channel tra- versing the easterly part of the project area would not be 14 W in accordance with the Day, Etiwanda and San Sevaine Creeks System Drainage Plan. The channel has limited capacity, is subject to overflow, and the area adjacent to the channel has been determined to be a flood plain by the Federal Insurance Administration (see "Flood Con - trol Facilities Study" dated September, 1984). The channel would have to be improved to handle the design flows and removed at a later date unless the Master Drainage Plan is +rri revised. The Specific Plan does not show the channel, and therefore, an additional alternate to the plan would be necessary. Due to the problems listed above and the additional cost involved, this alternate does not appear to be feasible. b. Maintain the Rkistin Sari 'Sedaihe 'Channel' Tetra op raril �un� ani Vitiate ownstream Uh annel o� o'the' fro osed Upstream Floc 'Stotage Facility 'is' 'Constructe This alternate would not provide for the full development ++� of the project area due to the flood hazards unless the channel is improved. If the channel is improved, then this alternate is no different than 2a above. c. Development of Flood Storage Basins for San Sevaine. Creek, eith Onsite or North ot Baseline Avenue A This alternate would require the construction of flood storage basin of sufficient size to store a 100 - year, 24- hour storm in order to eliminate or reduce San Sevaine Creek flows to an acceptable level. 15 0 If the basin, or basins, were to be excavated, it would be about as expensive to later reclaim the land as it would be 15 0 to excavate the basins. If this type of flood storage is to be provided, it should be accomplished as part of the ultimate flood control facility, namely, above the Devore Freeway as the Lower San Sevaine Basin. 3. Recommendations Other than Alternates "A" and "B ", there does not appear to be any other viable or feasible alternatives. Alternate "g" is less expensive, provides a benefit to the area below Foothill Boulevard, and the right -of -way necessary for the "interim channel" below Foothill Boulevard is existing. The "interim channel" follows the alignment of the ultimate Master Planned facility, and the interim facility can be utilized when the ultimate channel below the site is constructed. Alternate "B" does not require the total resolving of the right - of -way and excavation of the Lower San Sevaine Basin at this time. Because of these advantages, Alternate Plan "B" is recommended. Because the proposed flood control facilities are regional in nature, and will benefit the City of Fontana, the unincorporated �+ area, and other developments, a reimbursement arrangement to reimburse the project area development for those costs exceeding its pro -rata share is recommended. IF 16 SECTION III. REIMBURSEMENT OF COSTS FOR REGIONAL FLOOD CONTROL FACILITIES +� A. GENERAL DISCUSSION The Day, Etiwanda and San Sevaine Creeks System Drainage Plan was completed and accepted by the various involved jurisdictions in 1983. The report on "Funding Mechanisms for the Day, Etiwanda and San Sevaine Creek System Drainage Plan ", dated March, 1983, was a part of the Drainage Plan. Because the proposed combined Etiwanda -San Sevaine Channel System is a regional system, the cost of any part of the system constructed as a part of a development should be analyzed to determine the pro- rata share to be financed by the development. The construction of the Etiwanda -San Sevaine Channel, the connection from Etiwanda Channel to the Victoria Basin, and any work in the Lower San Sevaine Basin will benefit the overall regional area. Therefore, the costs of the system should be distributed over the entire benefitted area. The report on "Funding Mechanisms for the Day, Etiwanda and San Sevaine Creeks System Drainage Plan" is included in the Appendix rrr for ready reference. The important points of the report are sum- marized herein. W The referenced "funding mechanisms" report was accepted by the Day Creek Technical and Steering Committees, the Cities of Fontana, Rancho Cucamonga and Ontario, and San Bernardino and Riverside Counties. The Technical Committee recommended the distribution of costs by jurisdiction based on gross areas within the drainage system watershed boundaries. The gross areas within the San Sevaine Creek System and the cost per gross acre and cost per jurisdiction 17 1K_ are provided below in Section III,B. The cost per gross acre provides a negotiating base by which a cost distribution for the West End Specific Plan development can be determined. B. DISTRIBUTION OF CONSTRUCTION COSTS FOR THE SAN SEVAINE CREEK SYSTEM The proposed San Sevaine Creek Channel below the Devore Freeway, the Upper Etiwanda Creek Channel above the Devore Freeway, and the debris and water conservation facilities appurtenant to both chan- nels are known as the San Sevaine Creek Channel System. The "existing" San Sevaine Channel between the Devore and Foot- "" hill Boulevard is proposed to be phased out. Therefore, the existing channel is not considered a part of the future flood con- trol system. The gross area within the San Sevaine Creek System drainage area is provided below in Table I. The construction costs of the San Sevaine Creek System is summarized in Table II. It should be noted the construction and distribution costs are based on March, 1983 dollars and an adjustment is necessary to reflect November, 1984 dollars. IN IF 18 TABLE I Gross Areas Within San Sevaine Creek System * Jurisdiction Acres Percentage Unincorporated Area 12,470 39.8 Fontana 15,850 50.5 Rancho Cucamonga 3,040 9.7 Ontario 0 0 TOTAL 31,360 100.0 * From the "Funding Mechanisms for the Day, Etiwanda and San Sevaine Creeks System Drainage Plan" report, dated March, 1983. M ' TABLE II Cost of San Sevaine Creek System ** San Sevaine Creek Svstem Etiwanda Creek Debris Dam $ 1,950,000 San Sevaine Basin and Lower 9,950,000 San Sevaine Basin Jurupa Basin 5,950,000 Channel System 23,025,000 Subtotal $40,875,000 ** Construction cost estimated as of March, 1983, and taken from "Funding Mechanisms for the Day, Etiwanda and San Sevaine Creeks System Drainage Plan" report. 19 As indicated above, it was decided at the Technical Committee meeting on December 14, 1982, that the cost distribution per juris- diction and /or per acre within the system drainage area would be di computed on a gross acre rather than a net developable basis. no The cost per gross acre and per jurisdiction within the San Sevaine Creek Channel System drainage area are provided below. wri 1. Cost of San Sevaine Creek System per Gross Acre �r $40,875,000/31,360 acres = $1,304 /acre USE $1,310 /acre wr 2. Cost of San Sevaine Creek System per Jurisdiction City of Fontana �•. $40,875,000 x 0.505 = $20,641,875 rr Unincorporated Area �. $40,875,000 x 0.398 = $16,268,250 City_of Rancho Cucamonga $40,875,000 x 0.097 = $ 3,964,875 Total = $40,875,000 * Construction cost estimates as of March, 1983, from "Funding Mechanisms for the Day, Etiwanda and San Sevaine Creeks System Drainage Plan ". 3. Net Developable Areas The net developable area (percentage) is provided below for reference purposes only. It should be noted the net 20 err P1 1 developable area percentages are based on the "Funding Mechanisms" report dated March, 1983, and may not reflect actual percentages today. That is the reason the Technical Committee recommended the cost distribution should be based on gross areas. di 0" The developable area in the City of Fontana was estimated at 75%. The developable area in the City of Rancho Cuca- monga was estimated at 60% in the San Sevaine Creek water- shed. The developable area in the unincorporated area was estimated at 45% in the San Sevaine Creek watershed. The approximate net developable areas can be obtained by applying the above percentages by areas (acres) provided in Table I. It is again noted the percentages indicated above may not exactly reflect the net developable area today. C. DISTRIBUTION OF COSTS OF THE SAN S'EVAINE CREEK SYSTEM TO THE ST END SPECIFIC PLAN Based on the recommendations of the Day Creek Committee, the recom- mended distribution of costs to the West End Specific Plan project area is based on gross acreage within the overall San Sevaine Creek Channel System drainage area. The area within the subject planning area is approximately 1,250 acres. During the approximate two years since the Day, Etiwanda and San Sevaine Creeks System Drainage Plan was completed, there have been some preliminary changes and additional planning in the proposed flood control facilities above the Devore Freeway. These recom- mended changes, if adopted, will probably reduce the system costs. 10 21 10 However, the major channel costs below the Foothill Boulevard have increased in cost due to inflation. Avery rudimentary analysis indicates these costs are probably offsetting and the overall system costs have not changed significantly. Therefore, the overall San Sevaine Creek Channel System cost of $40,875,000 is used in the pre- ""' liminary estimate of cost distribution provided below. An analysis "' and update of costs for the entire channel system would have to be done to arrive at a more reliable construction cost estimate. The $1,310 /acre figure, based on "gross acreage" within the overall watershed, is used to compute the equitable cost of developments within the San Sevaine Creek System drainage area: If "net developable area" is used, based on the percentages used in the di Day, Etiwanda and San Sevaine Creeks System Drainage Plan, the dis- tribution cost per acre increases to $2,116 /acre. I" The "gross acreage" distribution cost factor of $1,310 /acre is di more equitable for new development projects because the proposed „ regional flood control system will benefit existing development within the drainage area, the Cities of Fontana, Ontario and Rancho Cucamonga, the Counties of San Bernardino and Riverside, and the .i many utility and transportation systems that cross the channels. In addition, the proposed facilities will benefit the water industry due to the extensive water conservation facilities proposed. D. REIMBURSEMENT OF REGIONAL FLOOD CONTROL SYSTEM COSTS TO WEST END . SP ECIFI'C PLAN DEVELOPMENT Based on the $1,310 /acre cost distribution factor, the estimated reimbursement of-the regional flood control facilities construction costs to the West End Specific Plan development is estimated below. The estimated reimbursement for both Alternates "A” and "B" plans discussed in Section II are provided. 22 rr J IV Because the proposed storm drain along Baseline Avenue (from the existing San Sevaine Channel to the future San Sevaine Channel) is not part of the regional flood control facilities system, it is not included in the cost for Alternates "A" and "B" below. This ,wr does not mean the cost of the drain should not be shared with other proposed developments to the east and northeast. Oft 2. Alternate "B" , Yr See Section II,B -2, page 10. Estimated cost is $7,770,000; „ $1,310 /acre distribution cost for 1,250 acres is $1,637,500. $7,770,000 -$1,637,500= $6,132,500. As explained in Section II,B -2 above, Alternate Plan "B" is preferred. 44 It is recognized a reimbursement of approximately $6,000,000 can be challenged on the basis the channel for the ultimate system traverses the subject project, and direct flood protection benefits are provided for the property. However, the proposed channel and debris facilities will benefit other properties, both existing and proposed, below the project area and above the project area. Many areas proposed for development cannot be adequately drained until 23 10 1. Alternate "A" See Section II,B -1, page 6. Estimated cost is $10,310,000; $1,310 /acre distribution cost for 1,250 acres is $1,637,500. $10,310,000- $1,637,500 =$8,672,500. a Therefore, the estimated reimbursement for regional flood con- trol facilities under Alternate "A" is $8,672,500. Oft 2. Alternate "B" , Yr See Section II,B -2, page 10. Estimated cost is $7,770,000; „ $1,310 /acre distribution cost for 1,250 acres is $1,637,500. $7,770,000 -$1,637,500= $6,132,500. As explained in Section II,B -2 above, Alternate Plan "B" is preferred. 44 It is recognized a reimbursement of approximately $6,000,000 can be challenged on the basis the channel for the ultimate system traverses the subject project, and direct flood protection benefits are provided for the property. However, the proposed channel and debris facilities will benefit other properties, both existing and proposed, below the project area and above the project area. Many areas proposed for development cannot be adequately drained until 23 10 the backbone facilities are constructed. The San Sevaine Creek Channel System is the backbone system for approximately 60 square miles of tributary drainage area. ?4 V SECTION IV. DEVELOPMENT PHASING PLAN A. GENERAL DISCUSSION Due to the potential overflow and debris deposition from the existing San Sevaine Creek Channel and the potential channel erosion along the existing Etiwanda Creek Channel, an initial development between the two flood hazard areas is recommended. The remaining areas can be developed as the flood control facili- ties recommended in Section II are provided. Refer to Figure No. 4 for a schematic depiction of the recommended development phasing. Except as necessary to describe the recommended development phasing herein, the flood hazards are not discussed in detail in this supplemental report. Reference is made to the prior report refer- enced above for detailed discussion on flood hazards, the 1969 flood overflow map, and the FIA (HUD) overflow map. Recommended phasing of the development is discussed below. The necessary flood control improvements to eliminate flood hazards to various portions of the site and to eliminate the necessity of San Sevaine Channel traversing the site are those included in Section II of this report. The easterly part of the project area, generally that area east of the San Sevaine Creek overflow area, is unrestricted from a flood The report entitled "West End Specific Plan, Flood Control Facili- ties Study " , dated September, 1984, by Bill Mann & Associates, described the flood hazards to the project area in detail. The 1 potential overflow adjacent to the San Sevaine Creek Channel, based on the Federal Insurance Administration (HUD) map, is also shown in the prior report. Except as necessary to describe the recommended development phasing herein, the flood hazards are not discussed in detail in this supplemental report. Reference is made to the prior report refer- enced above for detailed discussion on flood hazards, the 1969 flood overflow map, and the FIA (HUD) overflow map. Recommended phasing of the development is discussed below. The necessary flood control improvements to eliminate flood hazards to various portions of the site and to eliminate the necessity of San Sevaine Channel traversing the site are those included in Section II of this report. The easterly part of the project area, generally that area east of the San Sevaine Creek overflow area, is unrestricted from a flood 25 Fl h hazard standpoint. Therefore, the area is not shown as a phase. However, some protection measures adjacent to the San Sevaine Creek overflow area may be necessary prior to the construction of the flood control facilities referred to in Section II. B. RECOMMENDED PHASING 1. Phase I Phase I is that area generally located between the existing Etiwanda Creek Channel and the overflow limits of San Sevaine Creek. In addition, Phase I includes the area within the northwest corner of the project area south of Baseline Avenue. di The Phase I limits are shown on Figure No. 4. an The existing Etiwanda Creek Channel did not overflow during •.� the floods of 1969. ,,However, the channel bank did suffer .r serious erosion. Therefore, a 200' structure setback from the channel is recommended until the concrete lined channel is constructed. The easterly limit of Phase I is the west line of the San Sevaine Creek overflow area. If a setback from the existing Etiwanda Creek is established, the northwesterly do Dortion of the site south of Baseline Avenue could be developed prior to the construction -of the concrete lined channel referred to in Section II. Phase I development would be subject to normal flood hazard protection measures adjacent to overflow areas, existing earth channels, and /or major water - carrying streets on swales. The area adjacent to the overflow area and existing channel can be reasonably protected by the following methods or combination of methods. The actual flood protection measures would be based 26 8 d M on conditions by the City of Fontana and possibly the Flood Control District. a. A perimeter street adjacent to the overflow area with lots raised a minimum of 2 feet above the top of curb,. OW " b. A 3 to 4 -foot high landscaped perimeter berm along �+ the overflow area with a graded ditch outside the berm. �. c. A levee at the northeast corner of the 1st phase development to divert any overflow crossing Baseline Avenue at the PERR back to the San Sevaine Creek Channel. d. Low block walls (3 to 4 feet) along the overflow area or 6 -foot high structural block walls at the northeast corner of the development. A wall or other protective ., measures may be.necessary along Baseline Avenue. e. A 200± foot setback or 1 -lot depth setback adjacent do to the existing Etiwanda Channel with elevated lots or a landscaped berm. dw 2. Phase II Phase•II is that area immediately adjacent to the existing ..�, Etiwanda Creek Channel, except for the area east of the channel Sri and north of Baseline Avenue. It is assumed that the San Sevaine Channel (combined Etiwanda- San Sevaine Channel) will be constructed prior to or concur- rently with the completion of Phase I of the development building program. P] 27 10 V At such time as the San Sevaine Channel is constructed, Phase II of the development (refer to Figure No. 4) could be initiated. The San Sevaine Channel construction could be under Alternate "A" or Alternate "B ", described in Section II,B, subject to +r the selection of the alternate and approval by the necessary agencies. 3. Phase III Phase III is that area adjacent to the existing San Sevaine Channel and the area north of Baseline Avenue: Refer to Figure No. 4 for the schematic area. The initiation of Phase III development will depend upon the elimination of the San Sevaine Creek flood hazard and the elimi- nation of the need for the existing San Sevaine Creek Channel traversing the easterly portion of the site. Phase III would require the construction of those facilities described in Alternate "A" or Alternate "b ", Section II,B. The necessary facilities include the storm drain along Baseline Avenue to eliminate the local flows tributary to the existing San Sevaine Channel. Refer to Section II,B for a description of the Alternates and the respective costs. 4. Unrestricted Area The extreme easterly portion of the project area, outside of the San Sevaine Creek overflow area, is not restricted from development from the standpoint of flood hazards. E 28 1 w 1 1 �i An exception would be the area immediately adjacent to and along the San Sevaine Creek overflow area. However, this fringe area can be developed with the provision of those flood protective measures described in Section IV, B -1 above. M 29 BILL MANN & ASSOCIATES 1814 Commercenter West Suite A SAN BERNARDINO, CA 92408 (714) 885-4309 di Sri 7 84- JOB SHEET NO. OF CALCULATED BY DATE.-..// ' 7-64 CHECKED BY DATE SCALE 11 lk Is < L 1 ........... .............. ............. ............. .............. ............... ............ . .. ........ .............. ............. ....... ..... ............. ........... . 12 : L l I e.. r1 ............ . _.v i . .. ....... ............ . . . . . . . . . 13-a! -i? : . ... ... I El I Wl rA f — M - 7 W_ WK MW 1141►. 8A 14 BILL MANN & ASSOCIATES JOB_ - — — 1814 Commercenter West Suite A. 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