MEMORANDUM. Corona Subdivision XP Storm Evaluation. Date: March 5, Curt Bates, City of Petaluma. David S. Smith, P.E., WEST Consultants, Inc.

MEMORANDUM Project: Corona Subdivision XP Storm Evaluation Subject: Results Summary Date: March 5, 2013 To: Curt Bates, City of Petaluma No. C056132 EXP. 12/31/14 From: David S. Smith, P.E., WEST Consultants, Inc. This memo summarizes the analysis completed by WEST Consultants, Inc. (WEST) for the City of Petaluma (the City) to evaluate the hydraulic impact of the proposed Corona Subdivision, located between Corona Road and the intersection of Andover Way and Monica Way (see Figure 1). Modeling completed by WEST for the FEMA map revision currently in process includes breakout flows from Corona Creek in the area of the proposed development. Elevating the Corona Subdivision to remove it from the 100 year floodplain will increase the water surface elevation in adjacent residential areas. Therefore, a new detention basin just upstream of Road is planned to mitigate the lost floodplain storage due to development. XP Storm version 2010 (build May 20, 2010) was used in this evaluation. The methods used to evaluate the hydraulic effects of the Corona Subdivision and the Road detention basin are described below along with tabular modeling results for the 10 year and 100 year events and a flood boundary map for the 100 year event. 1 of 7

March 5, 2013 Road Detention Corona Subdivision Modeling Approach Figure 1. Corona Subdivision and Road Detention Location The City s 10 year and 100 year XP Storm models that are the basis of the FEMA remapping effort were used for evaluating the Corona Subdivision (filenames 10yr_9 27 10.xp and 100yr_9 27 10.xp ). The following detail was added to the model(s) in the vicinity of Corona Creek (see Figure 2): 9 nodes were added in the right overbank of Corona Creek in the vicinity of the breakout at node cc_02 (Stonehenge Way, Andover Way, Mauro Pietro Drive, Sonoma Mountain Parkway, and Wellington Place): o cc2_l102 o cc2_l108 o cc2_l012 WEST Consultants, Inc. 2 of 8

March 5, 2013 o cc2_l120 o cc2_l1 o cc2_l1 o cc2_l1 o cc2_l1 o cc2_l170 The 8 x 12 culvert for Corona Creek at Wellington Place was added to the model (along with a weir for overtopping flows). Model nodes cc_0202 and cc_0203 were added, along with the following culvert details: o Upstream invert elevation = 27.5 o Downstream invert elevation = 27.2 o Length =.8 feet o Overtopping flow crest elevation = 36.8 o Overtopping flow weir width = 62 feet The pedestrian bridge for Corona Creek just upstream of Wellington Place was added to the model (along with a weir for overtopping flows). Model nodes cc_0207 and cc_0208 were added, along with the following bridge details: o Upstream invert elevation = 29.38 o Downstream invert elevation = 29.33 o Length = 10.7 feet o Overtopping flow crest elevation = 36.7 o Overtopping flow weir width = feet o The bridge opening is modeled as a user defined conduit with a table of depth, flow area, wetted perimeter, and top width. The low chord of the pedestrian bridge is modeled at a depth of 6.12 feet (corresponds to elevation 35.5), with a flow area of 170.8 ft 2, wetted perimeter of 63.3 feet, and top width of 61.9 feet. WEST Consultants, Inc. 3 of 8

March 5, 2013 Figure 2. Corona Creek XP Model Detail The model filenames including the above detail were renamed Corona_10yr_weir473 _28.xp for the 10 year event and Corona_100yr_weir473_28.xp for the 100 year event. Both models include three scenarios: Base Scenario, Post Project Scenario, and Storage Scenario. The Base Scenario represents existing conditions with the detail described above. The Post Project Scenario is a modification to the Base Scenario with the removal of flood storage at the Corona Subdivision between model nodes cc2_l110 and cc2_l108 to account for placement of fill. The Storage Scenario is a modification to the Post Project Scenario with detention added upstream of Road at model node cc320_l010 (see Figure 3). WEST Consultants, Inc. 4 of 8

March 5, 2013 Road Detention Figure 3. Storage at XP Model Node cc320_l010 The dimensions of the proposed detention basin north of Road are summarized in Table 1 based on data provided by Steven J. Lafrachi and Associates, Inc. The top of the detention basin along Road is elevation 52.1 feet, NAVD based on review of the City s 2003 topography. This elevation is close to the Road elevation on the south side of the basin, and less than the natural ground elevation on the north and west sides of the basin. The bottom of the basin is modeled as elevation 45.1 feet, NAVD with side slopes of two units horizontal to one unit vertical (2H:1V). WEST Consultants, Inc. 5 of 8

March 5, 2013 Table 1. Elevation Area Relationship of the Proposed Road Detention Basin Elevation Depth Area ft, NGVD ft, NAVD ft, NAVD ft 2 ac 42.5 45.12 0.02 145256 3.335 43 45.62 0.52 1469 3.373 44 46.62 1.52 1643 3.458 45 47.62 2.52 154378 3.544 46 48.62 3.52 1581 3.6 47 49.62 4.52 161929 3.717 48.62 5.52 165746 3.805 49 51.62 6.52 1696 3.889 The detention basin connection to Corona Creek is modeled with a 20 foot wide sharp crested weir with a crest elevation of 47.3 feet. The coefficient of discharge for the weir is a function of the weir crest height, the depth of flow over the weir, the channel velocity in Corona Creek, and the angle/shape of the weir relative to flow in Corona Creek. The coefficient of discharge for the lateral weir was calculated based on the following equation which relates the lateral weir coefficient to the normal weir coefficient 1 : C = C n * ((Fw 2 + 2)/(3 Fw 2 + 2)) 0.5 Where: C = discharge coefficient for a lateral weir C n = discharge coefficient for a normal weir = 3.27 + 0. (H / p) for a sharp crested weir 2 H = measured head above the weir crest p = weir crest above invert Fw 2 = v 2 / g (y p) v = channel flow velocity at the cross section where C is being determined y = stage in channel For the 100 year event, the lateral weir coefficient is calculated to range from about 2.4 to 3.2, and for the 10 year event from about 2.2 to 2.9. An average value of 2.8 was used in the model for both events. An 18 inch culvert is included in the model to drain the detention basin, and this was modeled with a flap gate to prevent flow from Corona Creek from filling the detention 1 Hydraulic Engineering, Proceedings of the 1988 National Conference sponsored by the Hydraulics Division of ASCE, Colorado Springs, CO, August 8-12, 1988, pp. 979-985. 2 Chow, V.T., Open-Channel Hydraulics, McGraw-Hill Publishing Company, 1959, p.362 WEST Consultants, Inc. 6 of 8

March 5, 2013 basin during the rising limb of the hydrograph. The modeled pipe is 100 feet long with a 0.1 percent slope (elevation 45.1 upstream to elevation 45 downstream). Design of the weir crest is recommended as an adjustable crest using stop logs or similar modular components at no more than half foot increments to allow for plus or minus 2 feet adjustment. This is recommended because the model is based on a calibration that did not include any stream gages along Corona Creek. In addition, the cross section geometry just upstream of Road is based on low detail USGS topography. In the future, updating the hydrologic modeling assumptions and model cross section geometry in this reach may lead to a different conclusion regarding the preferred weir crest elevation and/or the length of the weir. Results Without detention, the 100 year water surface elevation due to the Corona Subdivision would increase by a maximum of 0.41 feet in the vicinity of the project. Downstream on the Petaluma River, the peak discharge would increase by about 20 cfs and the maximum water surface elevation would increase by about 0.01 feet. Due to these increases, the Road detention area is recommended. Tabular comparisons of model results for the 10 and 100 year event are provided in Tables 2 and 3, respectively. Flood boundary results for existing conditions and project conditions (the Corona Subdivision with the Road detention basin) for the 100 year event are provided as Exhibit 1. The detention basin reduces 100 year event flooding in the vicinity of the Corona Subdivision by an average of about 0.7 feet. This reduction is the result of less flow breaking out from Corona Creek toward Stonehenge Way and Andover Way at model node CC2_L010. The lowest pad elevation of 39.4 feet NAVD is higher than the maximum water surface elevation of 39.27 feet NAVD in this location, therefore the breakout flow would be essentially contained in the street and would not need to be shown on FEMA Flood Insurance Rate Maps during the Map Change processing for this project. The 100 year water surface elevation is also reduced in Corona Creek by an average of about 0.6 feet, and in the Petaluma River by an average of about 0.02 feet. The maximum 100 year water surface elevation in the Road detention basin is 49.71 feet. This corresponds to a maximum depth of 4.61 feet and 2.39 feet of freeboard. For the 10 year event, the maximum water surface elevation is 47.31 feet. This corresponds to a maximum depth of 2.21 feet and 4.79 feet of freeboard. WEST Consultants, Inc. 7 of 8

March 5, 2013 Conclusions The proposed Road detention basin size, weir elevation, and weir width described above represents a maximized detention configuration for the area upstream of Road. According to the model results, the proposed Corona Subdivision project with the Road detention basin reduces water surface elevations below existing elevations not only for the project site vicinity but also Corona Creek and the Petaluma River. WEST Consultants, Inc. 8 of 8

March 5, 2013 Table 2 10 year XP Storm Results for and With Project (Corona Subdivision plus Road

Flooding Source Corona Creek Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation Link1297 cc2_l010 cc2_l020 0 0 38.00 38.00 Link14 cc2_l010 CC2_L012 0 0 38.00 38.00 Link1871 CC2_L012 cc2_l090 0 0 37.70 37.70 Link1872 CC2_L012 CC2_L120 0 0 38.00 38.00 Link1298 cc2_l020 cc2_l0 0 0 39.05 39.05 Link1299 cc2_l0 cc2_l0 0 0.00.00 Link15 cc2_l090 cc2_l100 0 0 38. 38. Link1870 cc2_l090 CC2_L108 0 0 37.70 37.70 Link1869 cc2_l100 CC2_L102 0 0 38. 38. Link16 CC2_L108 cc2_l110 0 0 38.00 0 Link1873 CC2_L120 CC2_L1 0 0 39.00 39.00 Link1874 CC2_L120 CC2_L1 0 0 37.90 37.90 Link1876 CC2_L1 CC2_l1 0 0 37.90 37.90 Link1875 CC2_L1 CC2_L1 0 0 37.90 37.90 Link1877 CC2_l1 CC2_L170 0 0 36. 36. cc0202l CC2_L170 cc_0202 0 0 cc320c cc320_l010 cc_0320-113 cc321c cc320_l010 cc_0320 6 47.31 cc320w cc320_l010 cc_0320-113 LCC1_963.1 cc_00 pr_05n 544 541-3 23.38 23.35-0.02 lcc_00 cc_00 cc_00 347 348 23.45 23.42-0.03 lcc_00 cc_00 cc_00 346 346 23.53 23. -0.03 L1166 cc_00 pr_05 0 0 22.13 22.13 lcc_0070 cc_0070 cc_00 346 346 23.79 23.78-0.01 lcc_0075 cc_0075 cc_0070 346 346 24.11 24.11 UW_ccTP070 cc_0075 cctp070 0 0 lcc_0080 cc_0080 cc_0075 345 346 25.12 25.12 L1124 cc_0080 pr_0580 221 209-12 25.12 25.12 UW_ccTP065 cc_0080 cctp065 0 0 lcc_0085 cc_0085 cc_0080 415 391-24 25.43 25.42-0.01 UW_ccTP0 cc_0085 cctp0 0 0 lcc_0090 cc_0090 cc_0085 415 391-24 25.74 25.66-0.08 L1123 cc_0090 pr_0590n -144-144 26.36 26.36 UW_ccTP045 cc_0090 cctp045 0 0 lcc_0100 cc_0100 cc_0090 497 455-43 27.01 26.86-0.16 UW_ccTP0 cc_0100 cctp0 0 0 lcc_0110 cc_0110 cc_0100 497 455-43 28.20 28.02-0.17 UW_ccTP020 cc_0110 cctp020 10 1-9 lcc_01 cc_01 cc_0110 4 456-47 28.65 28.47-0.18 UW_ccTP010 cc_01 cctp010 16 14-2 lcc_01 cc_01 cc_01 7 4-47 29.28 29.07-0.21 lcc_01 cc_01 cc_01 7 4-47 31.29.84-0.45 lcc_01 cc_01 cc_01 496 448-48 31..86-0.44 lcc_0170 cc_0170 cc_01 510 458-52 31.35.88-0.47 LC1_5475.1 cc_0180 cc_0170 171 153-18 32.17 31.58-0.59 LC1_5475.2 cc_0180 cc_0170 173 154-19 32.17 31.58-0.59 LC1_5475.3 cc_0180 cc_0170 173 154-19 32.17 31.58-0.59 ccrrweir cc_0180 cc_0170 0 0 lcc_0190 cc_0190 cc_0180 539 471-68 32.23 31.76-0.47 lcc_0200 cc_0200 cc_0190 5 475-75 32.39 32.00-0.39 Link1868 cc_0202 cc_0200 556 481-75 32.64 32.23-0.41 lcc_0203.1 cc_0203 cc_0202 0 0 lcc_0203w cc_0203 cc_0202 0 0 lcc_0207 cc_0207 cc_0203 561 488-73 34.53 33.96-0.58 lcc_0208.1 cc_0208 cc_0207 563 494-69 34.59 34.06-0.54 lcc_0208w cc_0208 cc_0207 563 494-69 34.59 34.06-0.54 lcc_0208w2 cc_0208 cc_0207 0 0 lcc_0210 cc_0210 cc_0208 566 499-67 34.71 34.20-0.51 lcc_0220 cc_0220 cc_0210 574 510-64 35.47 35.21-0.26

Flooding Source Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation lcc_02 cc_02 cc_0220 577 510-67 38.57 38.03-0.55 cc02l cc_02 cc2_l010 0 0 cc2r cc_02 cc2_r10 0 0 lcc_02 cc_02 cc_02 459 363-96 39.61 38.82-0.78 cc02- cc_02 cc_02 0 0 1285.1 cc_02 cc_02 456 364-93 41.61.66-0.96 cc02-l cc_02 cc2_l0 0 0 lcc_02 cc_02 cc_02 457 364-93 41.81.92-0.89 lcc_0270 cc_0270 cc_02 464 367-97 42.35 41. -0.75 lcc_0280 cc_0280 cc_0270 469 370-99 43.74 42.79-0.95 lcc_0290 cc_0290 cc_0280 325 213-112 43.75 42.80-0.95 lcc_00 cc_00 cc_0290 320 207-113 45.10 44.53-0.57 lcc_0310 cc_0310 cc_00 321 207-114 46.90 46. -0. UW cc_0320 cc_0310 0 0 1278.1 cc_0320 cc_0310 321 207-114.85 48.83-2.03 lcc_03 cc_03 cc_0320 322 320-1 51.31.92-0.39 lcc_03 cc_03 cc_03 267 264-3 56.08 56.19 0.10 lcc_03 cc_03 cc_03 270 270 65.37 65.37 lcc_03 cc_03 cc_03 274 274 67. 67. lcc_0370 cc_0370 cc_03 275 275 73.35 73.35 lcc_0380 cc_0380 cc_0370 279 279 82.47 82.47 Link1317 cctp010 cctp020 0 0 28.65 28.01-0.64 Link1326 cctp010 cctp180 0 0 28.65 28.47-0.18 Link1318 cctp020 cctp0 0 0 27.18 27.18 Link1319 cctp0 cctp0 0 0 27.18 27.18 Link1338 cctp0 cctp0 0 0 26.05 26.05 Link1339 cctp0 cctp1 0 0 27.58 27.58 Link1337 cctp045 cctp0 0 0 26.47 26.47 Link1320 cctp0 cctp0 0 0 26.05 26.05 Link1334 cctp0 cctp1 0 0 26.05 26.05 Link1321 cctp0 cctp070 0 0 25.90 25.90 Link1342 cctp065 cctp0 0 0 26.41 26.41 Link1322 cctp070 cctp080 0 0 25.90 25.90 Link1333 cctp070 cctp1 0 0 25.90 25.90 Link1323 cctp080 cctp090 0 0 26.75 26.75 Link1324 cctp090 cctp100 0 0 27.03 27.03 Link1329 cctp090 cctp1 0 0 27.03 27.03 Link1325 cctp100 cctp110 0 0 28.83 28.83 Link1336 cctp110 cctp180 0 0 29.29 29.29 Link1332 cctp120 cctp110 0 0 27. 27. Link13 cctp1 cctp1 0 0 27.26 27.26 Link1331 cctp1 cctp120 0 0 27.26 27.26 Link1335 cctp1 cctp1 0 0 27.83 27.83 Link13 cctp1 cctp170 0 0 28.10 28.10 Link1328 cctp170 cctp1 0 0 27.83 27.83 Link1327 cctp180 cctp170 0 0 28.83 28.83 Link1256 Cor-CC_10 pr_06n 0 0 29.20 29.20 Link1736 Cor-CC_10 Cor-CC_20 0 0 28.00 28.00 Link1255 Cor-CC_20 pr_00n 0 0 27.32 27.32 Link1737 Cor-CC_20 Cor-CC_ 0 0 27.00 27.00 Link1826 Cor-CC_ cc_0090 0 0 27.00 27.00 lpc_04 pc_04 pr_07 1703 1703 38.54 38.54 lpc_0800 pc_0800 pc_04 1679 1679 38.57 38.57 lpc_1525 pc_1525 pc_0800 1557 1557 38.58 38.58 lpr_0020 pr_0020 pr_0010 8554 85-15 6.53 6.53 lpr_00 pr_00 pr_0020 8554 8539-15 6.59 6.59 lpr_00 pr_00 pr_00 8553 8538-15 6.65 6.65 lpr_00 pr_00 pr_00 7128 7112-16 6.73 6.73 lpr_00 pr_00 pr_00 7120 7103-17 6.76 6.76

Flooding Source Petaluma River Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation lpr_0070 pr_0070 pr_00 7115 7099-16 6.94 6.94 lpr_0080 pr_0080 pr_0070 7112 7095-16 6.99 6.99 lpr_0090 pr_0090 pr_0080 7108 7093-15 7.06 7.05 lpr_0100 pr_0094 pr_0090 6563 6547-17 7.08 7.08 Link12 pr_0096 pr_0094 6562 6546-17 7.19 7.19 Link1229 pr_0098 pr_0096 6561 6545-17 7.24 7.24 Link1228 pr_0100 pr_0098 65 6543-17 7.28 7.28 lpr_0110 pr_0110 pr_0100 6526 6510-17 7.34 7.33 lpr_0120 pr_0120 pr_0110 6523 67-17 7.34 7.34 lpr_01 pr_01 pr_0120 6521 65-16 7.39 7.38 lpr_01 pr_01 pr_01 6522 63-19 7.44 7.43 lpr_01 pr_01 pr_01 6523 64-19 7.52 7.51 lpr_01 pr_01 pr_01 66 6289-17 7.62 7.62 lpr_0170 pr_0170 pr_01 65 6289-16 7.68 7.68 lpr_0180 pr_0180 pr_0170 6283 6267-16 7.73 7.72 lpr_0190 pr_0190 pr_0180 6283 6267-16 7.77 7.76 lpr_0195 pr_0195 pr_0190 6233 6206-27 7.88 7.88 lpr_0200 pr_0200 pr_0195 5715 5684-31 7.96 7.95 Link1239 pr_0206 pr_0200 5685 5653-32 7.97 7.97 lpr_0208 pr_0208 pr_0206 5683 5652-31 8.05 8.04 lpr_0210 pr_0210 pr_0208 5681 5651-8.04 8.03 lpr_0220 pr_0220 pr_0210 5663 5633-31 8.08 8.08 lpr_02 pr_02 pr_0220 5661 56-31 8.09 8.08 lpr_02 pr_02 pr_02 5658 5627-31 8.09 8.09 lpr_02 pr_02 pr_02 5654 5623-32 8.10 8.09 lpr_02 pr_02 pr_02 5652 5619-33 8.10 8.09 lpr_0270 pr_0270 pr_02 5651 5617-34 8.11 8.10 lpr_0280 pr_0280 pr_0270 5649 5615-34 8.12 8.11 lpr_0290 pr_0290 pr_0280 5648 5614-34 8.01 8.00 lpr_0298 pr_0298 pr_0290 5531 5514-17 8.41 8. lpr_00 pr_00 pr_0298 5531 5514-17 8.54 8.53-0.01 lpr_08 pr_08 pr_00 5531 5514-17 8.75 8.74-0.01 lpr_0310 pr_0310 pr_08 5531 5514-17 8.87 8.86-0.02 lpr_0320 pr_0320 pr_0310 5531 5514-17 8.79 8.77-0.01 lpr_03 pr_03 pr_0320 5531 5514-17 8.90 8.89-0.02 lpr_0338 pr_0338 pr_03 59 5492-17 9.20 9.18-0.02 lpr_03 pr_03 pr_0338 59 5492-17 9.46 9.44-0.02 lpr_03 pr_03 pr_03 59 5492-17 9.80 9.78-0.02 lpr_03 pr_03 pr_03 59 5492-17 11.00 10.98-0.01 lpr_0370 pr_0370 pr_03 5458 5441-17 11.71 11.69-0.02 lpr_0380 pr_0380 pr_0370 5458 5441-17 12.21 12.20-0.02 lpr_0390 pr_0390 pr_0380 4962 49-12 13.08 13.06-0.01 lpr_00 pr_00 pr_0390 4422 4416-6 13.27 13.26-0.01 lpr_0420 pr_0420 pr_00 4422 4415-6 13.52 13.51-0.01 lpr_04 pr_04 pr_0420 4422 4415-6 13.71 13.70-0.01 lpr_04 pr_04 pr_04 4421 4415-6 15.15 15.13-0.01 lpr_0445 pr_0445 pr_04 4421 4415-6 16.10 16.09 lpr_0448 pr_0448 pr_0445 4420 4414-6 16.34 16.34 lpr_04 pr_04 pr_0448 4420 4415-6 16.57 16.56 lpr_0452 pr_0452 pr_04 4420 4415-5 16.72 16.72 lpr_0458 pr_0458 pr_0452 4421 4416-5 17.00 17.00 lpr_04 pr_04 pr_0458 4422 4416-5 17.12 17.12 lpr_0465 pr_0465 pr_04 4391 4386-5 17.36 17.35 lpr_0470 pr_0470 pr_0465 4392 4387-5 17.48 17.48 lpr_0480 pr_0480 pr_0470 4394 4389-5 17.74 17.74 lpr_0490 pr_0490 pr_0480 4395 4390-5 18.23 18.22 lpr_0496 pr_0496 pr_0490 4397 4392-5 18.44 18.44 lpr_0498 pr_0498 pr_0496 4398 4394-4 18.99 18.98 lpr_00 pr_00 pr_0498 4398 4394-4 19.05 19.05

Flooding Source Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation lpr_0510 pr_0510 pr_00 40 4395-4 19.35 19.35 lpr_0520 pr_0520 pr_0510 4371 4367-4 19.80 19.79 lpr_05 pr_05n pr_0520 4374 4371-4 20.22 20.21 lpr_05 pr_05n pr_05n 4377 4374-3 21.02 21.02 lpr_05 pr_05 pr_05n 3888 3885-3 21.56 21.56 lpr_0552 pr_0552 pr_05 3889 3886-3 21.67 21.66 3876.1 pr_0554 pr_0552 3890 3887-3 21.63 21.63 3876.2 pr_0554 pr_0552 0 0 21.63 21.63 lpr_05 pr_05 pr_0554 3890 3888-3 22.13 22.13 lpr_0570 pr_0570 pr_05 3901 3900-2 24.16 24.16 lpr_0580 pr_0580 pr_0570 3902 3901-2 25.14 25.14 lpr_0590 pr_0590n pr_0580 3938 3935-3 26.86 26.86 lpr_00 pr_00n pr_0590n 88 85-3 27.32 27.32 lpr_06 pr_06n pr_00n 37-3 28.04 28.04 UWCorona pr_07n pr_06n 0 0 21.1 pr_07n pr_06n 43-3 28. 28. lpr_08 pr_08n pr_07n 43 41-3 28.33 28.32 lpr_0610 pr_0610n pr_08n 3595 3595 28.69 28.69 lpr_0612 pr_0612n pr_0610n 3588 3588 28.84 28.84 lpr_0614 pr_0614n pr_0612n 3582 3582 28.99 28.99 lpr_0616 pr_0616n pr_0614n 3559 3559 29.09 29.08 lpr_0618 pr_0618n pr_0616n 35 35 29.34 29.34 lpr_0620 pr_0620n pr_0618n 3543 3543.05.05 lpr_06 pr_06n pr_0620n 3541 35.55.55 lpr_06 pr_06n pr_06n 35 35 31.45 31.45 lpr_06 pr_06 pr_06n 3541 3541 31.52 31.52 lpr_06 pr_06 pr_06 3551 3551 31.66 31.66 lpr_0670 pr_0670n pr_06 3566 3566 32.35 32.35 lpr_0680 pr_0680n pr_0670n 3555 3555 32. 32. 682lob pr_0682 pr_0680n 0 0 2792.1 pr_0682 pr_0680n 35 35 32.52 32.52 684lob pr_0684 pr_0682 0 0 2791.1 pr_0684 pr_0682 3561 3561 32.64 32.64 lpr_0690 pr_0690n pr_0684 3562 3562 32.58 32.58 lpr_0700 pr_0700 pr_0690n 3568 3568 32.76 32.76 lpr_0710 pr_0710 pr_0700 3570 3570 34.73 34.73 lpr_0720 pr_0720 pr_0710 3536 3536 35.70 35.70 lpr_0723 pr_0723 pr_0720 3536 3536 36.93 36.93 3663.1 pr_0725 pr_0723 1095 1095 37. 37. 3663.2 pr_0725 pr_0723 31 37. 37. lpr_07 pr_07 pr_0725 3536 3536 37.65 37.65 lpr_07 pr_07 pr_07 3759 3593-166 37.74 37.74 2526.1 pr_0745 pr_07 3241 3241 38.06 38.06 2526.2 pr_0745 pr_07 3 3 38.06 38.06 lpr_07 pr_07 pr_0745 3590 3590 38.19 38.20 lpr_07 pr_07 pr_07 3590 3590 38.33 38.33 Notes: (1) Change due to project--negative values indicate a decrease, and positive values an increase. Differences in discharge less than 1 cfs and water surface elevation less than 0.01 feet are left blank. Legend: = removed for project conditions (storage in empty field) = added for project conditions (detention basin)

March 5, 2013 Table 3 100 year XP Storm Results for and With Project (Corona Subdivision plus Road

Flooding Source Corona Creek Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation Link1297 cc2_l010 cc2_l020-41 7 48 39.94 39.27-0.67 Link14 cc2_l010 CC2_L012 162 52-110 39.94 39.27-0.67 Link1871 CC2_L012 cc2_l090 123 34-89 39.75 39.15-0.59 Link1872 CC2_L012 CC2_L120 34 6-28 39.75 39.15-0.59 Link1298 cc2_l020 cc2_l0-38 0 38.01 39.29-0.72 Link1299 cc2_l0 cc2_l0 7 0-7.77.00-0.77 Link15 cc2_l090 cc2_l100 23 4-20 39.76 39.16-0. Link1870 cc2_l090 CC2_L108 113 9-105 39.76 39.16-0. Link1869 cc2_l100 CC2_L102 0 0 39.77 39.12-0.65 Link16 CC2_L108 cc2_l110 106 0-106 39.77 0 Link1873 CC2_L120 CC2_L1 9 0-9 39.70 39.17-0.54 Link1874 CC2_L120 CC2_L1 28 0-27 39.70 39.17-0.54 Link1876 CC2_L1 CC2_l1 6 0-6 39. 38.25-1.35 Link1875 CC2_L1 CC2_L1-3 0 3 39. 39.00-0. Link1877 CC2_l1 CC2_L170 5 0-5 cc0202l CC2_L170 cc_0202 4 0-4 cc320c cc320_l010 cc_0320-289 cc321c cc320_l010 cc_0320 5 49.71 cc320w cc320_l010 cc_0320-289 LCC1_963.1 cc_00 pr_05n 765 763-1 27.21 27.17-0.04 lcc_00 cc_00 cc_00 477 474-3 27. 27.25-0.04 lcc_00 cc_00 cc_00 522 514-8 27.34 27. -0.04 L1166 cc_00 pr_05 422 410-12 27.34 27. -0.04 lcc_0070 cc_0070 cc_00 909 893-16 27.68 27. -0.08 lcc_0075 cc_0075 cc_0070 938 915-23 27.72 27.64-0.08 UW_ccTP070 cc_0075 cctp070-195 -182 13 lcc_0080 cc_0080 cc_0075 977 948-29 27.90 27.83-0.06 L1124 cc_0080 pr_0580 578 570-8 27.90 27.83-0.06 UW_ccTP065 cc_0080 cctp065-127 -157 - lcc_0085 cc_0085 cc_0080 1495 1456-39 28.39 28.35-0.04 UW_ccTP0 cc_0085 cctp0 234 249 14 lcc_0090 cc_0090 cc_0085 1462 1436-26 28.79 28.76-0.04 L1123 cc_0090 pr_0590n 521 512-9 28.79 28.76-0.04 UW_ccTP045 cc_0090 cctp045 208 182-26 lcc_0100 cc_0100 cc_0090 823 772-52 29.12 29.06-0.07 UW_ccTP0 cc_0100 cctp0-117 136 254 lcc_0110 cc_0110 cc_0100 699 681-17 29.66 29.58-0.08 UW_ccTP020 cc_0110 cctp020 191 177-14 lcc_01 cc_01 cc_0110 586 568-18 29.82 29.71-0.11 UW_ccTP010 cc_01 cctp010 145 112-33 lcc_01 cc_01 cc_01 611 584-27.14 29.97-0.16 lcc_01 cc_01 cc_01 611 584-27 32.52 32.03-0.49 lcc_01 cc_01 cc_01 596 568-28 32.52 32.04-0.48 lcc_0170 cc_0170 cc_01 6 579-27 32.53 32.05-0.48 LC1_5475.1 cc_0180 cc_0170 204 196-8 33.82 33.21-0.61 LC1_5475.2 cc_0180 cc_0170 204 196-8 33.82 33.21-0.61 LC1_5475.3 cc_0180 cc_0170 204 196-8 33.82 33.21-0.61 ccrrweir cc_0180 cc_0170 0 0 lcc_0190 cc_0190 cc_0180 649 625-25 33.83 33.22-0.61 lcc_0200 cc_0200 cc_0190 691 661-33.94 33. -0.65 Link1868 cc_0202 cc_0200 702 673-34.05 33.41-0.64 lcc_0203.1 cc_0203 cc_0202 0 0 lcc_0203w cc_0203 cc_0202 0 0 lcc_0207 cc_0207 cc_0203 711 680-31 35.82 35.42-0. lcc_0208.1 cc_0208 cc_0207 714 684-31 35.89 35.46-0.43 lcc_0208w cc_0208 cc_0207 714 684-31 35.89 35.46-0.43 lcc_0208w2 cc_0208 cc_0207 0 0 lcc_0210 cc_0210 cc_0208 717 687-35.96 35.55-0.41 lcc_0220 cc_0220 cc_0210 725 696-29 36.34 36.06-0.28

Flooding Source Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation lcc_02 cc_02 cc_0220 7 702-28.24 39.92-0.31 cc02l cc_02 cc2_l010 149-89 cc2r cc_02 cc2_r10 0 0 lcc_02 cc_02 cc_02 685 533-152.76. -0.36 cc02- cc_02 cc_02 84 0-84 1285.1 cc_02 cc_02 598 534-64 42.91 42.32-0.59 cc02-l cc_02 cc2_l0 48 0-48 lcc_02 cc_02 cc_02 731 534-197 43.11 42.48-0.63 lcc_0270 cc_0270 cc_02 731 539-192 43.68 42.95-0.73 lcc_0280 cc_0280 cc_0270 731 544-187 46.59 44.56-2.04 lcc_0290 cc_0290 cc_0280 529 285-244 46.61 44.56-2.04 lcc_00 cc_00 cc_0290 542 275-267 46.80 44.92-1.88 lcc_0310 cc_0310 cc_00 551 272-279 47.70 46.70-1.00 UW cc_0320 cc_0310 167 0-167 1278.1 cc_0320 cc_0310 398 273-126 52.55 49.98-2.58 lcc_03 cc_03 cc_0320 566 561-5 52.90 51.97-0.93 lcc_03 cc_03 cc_03 455 451-4 57.11 57.19 0.08 lcc_03 cc_03 cc_03 461 461 66.18 66.18 lcc_03 cc_03 cc_03 462 462 68. 68. lcc_0370 cc_0370 cc_03 464 464 74. 74. lcc_0380 cc_0380 cc_0370 470 470 83.19 83.19 Link1317 cctp010 cctp020 135 108-27 29.78 29.67-0.10 Link1326 cctp010 cctp180 5 0-5 29.78 29.67-0.10 Link1318 cctp020 cctp0 323 281-43 29.62 29.54-0.08 Link1319 cctp0 cctp0 316 293-23 29.11 29.06-0.05 Link1338 cctp0 cctp0 4 3-27 28.73 28.70-0.04 Link1339 cctp0 cctp1 22 18-3 28.73 28.70-0.04 Link1337 cctp045 cctp0 121 116-5 28.79 28.76-0.04 Link1320 cctp0 cctp0 320 6-14 28.39 28.35-0.04 Link1334 cctp0 cctp1 16 13-3 28.39 28.35-0.04 Link1321 cctp0 cctp070 186 173-13 27.98 27.94-0.04 Link1342 cctp065 cctp0-142 -137 4 27.92 27.86-0.06 Link1322 cctp070 cctp080 29 23-7 27.73 27.65-0.08 Link1333 cctp070 cctp1 18 13-6 27.73 27.65-0.08 Link1323 cctp080 cctp090 20 14-6 27.73 27.65-0.08 Link1324 cctp090 cctp100 0 0 27.73 27.65-0.08 Link1329 cctp090 cctp1-5 -3 2 27.73 27.65-0.08 Link1325 cctp100 cctp110 0 0 28.84 28.83-0.01 Link1336 cctp110 cctp180 0 0 29.34 29.29-0.05 Link1332 cctp120 cctp110 0 0 27.74 27.66-0.08 Link13 cctp1 cctp1-5 -4 1 27.73 27.65-0.08 Link1331 cctp1 cctp120 3 1-2 27.73 27.65-0.08 Link1335 cctp1 cctp1 6 4-2 28.39 28.35-0.04 Link13 cctp1 cctp170 0 0 28.74 28.70-0.04 Link1328 cctp170 cctp1 0 0 28.86 28.83-0.03 Link1327 cctp180 cctp170 0 0 29.78 28.83-0.95 Link1256 Cor-CC_10 pr_06n 0 0 29.20 29.20 Link1736 Cor-CC_10 Cor-CC_20 0 0 29.20 29.20 Link1255 Cor-CC_20 pr_00n 0 0 28.81 28.77-0.04 Link1737 Cor-CC_20 Cor-CC_ -14-13 1 28.81 28.77-0.04 Link1826 Cor-CC_ cc_0090-32 - 2 28.81 28.77-0.04 lpc_04 pc_04 pr_07 3531 3532 39.62 39.62 lpc_0800 pc_0800 pc_04 3142 3142 39.67 39.67 lpc_1525 pc_1525 pc_0800 3236 3237 39.68 39.68 lpr_0020 pr_0020 pr_0010 11987 11976-10 6.53 6.53 lpr_00 pr_00 pr_0020 11987 11976-11 6.66 6.66 lpr_00 pr_00 pr_00 11986 11976-11 6.77 6.77 lpr_00 pr_00 pr_00 10883 10862-21 6.99 6.98 lpr_00 pr_00 pr_00 10875 10854-21 7.07 7.07

Flooding Source Petaluma River Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation lpr_0070 pr_0070 pr_00 10875 10854-21 7.38 7.38 lpr_0080 pr_0080 pr_0070 10874 10853-21 7.49 7.48 lpr_0090 pr_0090 pr_0080 10873 10852-21 7.82 7.81-0.01 lpr_0100 pr_0094 pr_0090 109 10485-24 7.86 7.85-0.01 Link12 pr_0096 pr_0094 109 10486-24 8.11 8.09-0.01 Link1229 pr_0098 pr_0096 10510 10486-24 8.20 8.19-0.01 Link1228 pr_0100 pr_0098 10510 10486-24 8.28 8.27-0.01 lpr_0110 pr_0110 pr_0100 10491 10467-24 8.39 8.38-0.01 lpr_0120 pr_0120 pr_0110 10492 10467-24 8.39 8.38-0.01 lpr_01 pr_01 pr_0120 10492 10468-24 8.49 8.47-0.01 lpr_01 pr_01 pr_01 10493 10469-25 8.58 8.56-0.01 lpr_01 pr_01 pr_01 10494 10470-25 8.73 8.71-0.01 lpr_01 pr_01 pr_01 10354 10328-26 8.93 8.92-0.01 lpr_0170 pr_0170 pr_01 10356 103-26 9.03 9.02-0.01 lpr_0180 pr_0180 pr_0170 10342 10316-26 9.12 9.11-0.01 lpr_0190 pr_0190 pr_0180 10343 10317-26 9.20 9.19-0.01 lpr_0195 pr_0195 pr_0190 10344 10318-26 9.45 9.43-0.02 lpr_0200 pr_0200 pr_0195 10011 9985-26 9.61 9.59-0.02 Link1239 pr_0206 pr_0200 9991 9964-27 9.65 9.63-0.02 lpr_0208 pr_0208 pr_0206 9992 9965-27 9.87 9.86-0.02 lpr_0210 pr_0210 pr_0208 9993 9966-27 9.90 9.88-0.02 lpr_0220 pr_0220 pr_0210 9982 9955-27 10.07 10.05-0.02 lpr_02 pr_02 pr_0220 9985 9958-27 10.10 10.08-0.02 lpr_02 pr_02 pr_02 9988 9961-27 10.11 10.09-0.02 lpr_02 pr_02 pr_02 9990 9962-28 10.11 10.09-0.02 lpr_02 pr_02 pr_02 9992 9964-28 10.12 10.10-0.02 lpr_0270 pr_0270 pr_02 9992 9965-28 10.13 10.11-0.02 lpr_0280 pr_0280 pr_0270 9993 9965-28 10.15 10.13-0.02 lpr_0290 pr_0290 pr_0280 9994 9966-28 9.95 9.93-0.02 lpr_0298 pr_0298 pr_0290 9864 9836-28 10.65 10.64-0.02 lpr_00 pr_00 pr_0298 9865 9836-28 10.88 10.86-0.02 lpr_08 pr_08 pr_00 9866 9838-28 11.28 11.26-0.02 lpr_0310 pr_0310 pr_08 9868 98-28 11.46 11.44-0.02 lpr_0320 pr_0320 pr_0310 9868 98-28 11.31 11.29-0.02 lpr_03 pr_03 pr_0320 9869 9841-28 11. 11.48-0.02 lpr_0338 pr_0338 pr_03 9838 9809-28 12.05 12.03-0.02 lpr_03 pr_03 pr_0338 9838 9810-28 12.42 12. -0.02 lpr_03 pr_03 pr_03 9839 9810-28 12.81 12.79-0.02 lpr_03 pr_03 pr_03 9839 9811-28 14.20 14.18-0.02 lpr_0370 pr_0370 pr_03 9765 9737-28 15.03 15.01-0.02 lpr_0380 pr_0380 pr_0370 9765 9737-28 15.65 15.63-0.02 lpr_0390 pr_0390 pr_0380 8680 86-31 16.53 16.51-0.02 lpr_00 pr_00 pr_0390 7783 7757-26 16.77 16.74-0.02 lpr_0420 pr_0420 pr_00 7781 7755-26 17.09 17.07-0.02 lpr_04 pr_04 pr_0420 7780 7754-26 17.33 17. -0.02 lpr_04 pr_04 pr_04 7775 77-26 19.03 19.01-0.02 lpr_0445 pr_0445 pr_04 7772 7747-26 19.41 19.39-0.02 lpr_0448 pr_0448 pr_0445 7771 7745-26 19.54 19.52-0.02 lpr_04 pr_04 pr_0448 7770 7744-26 19.65 19.64-0.02 lpr_0452 pr_0452 pr_04 7770 7744-26 19.74 19.72-0.02 lpr_0458 pr_0458 pr_0452 7771 7745-27 19.94 19.93-0.02 lpr_04 pr_04 pr_0458 7773 7746-27 20.03 20.01-0.02 lpr_0465 pr_0465 pr_04 7731 7704-27 20.20 20.19-0.02 lpr_0470 pr_0470 pr_0465 7734 7706-28 20.29 20.27-0.02 lpr_0480 pr_0480 pr_0470 7738 7710-28 20.56 20.54-0.02 lpr_0490 pr_0490 pr_0480 7742 7714-28 20.94 20.92-0.02 lpr_0496 pr_0496 pr_0490 7748 7719-29 21.06 21.04-0.02 lpr_0498 pr_0498 pr_0496 77 7721-29 21.93 21.91-0.02 lpr_00 pr_00 pr_0498 7751 7722-29 22.01 21.99-0.02

Flooding Source Link ID U/S Node D/S Node Peak Discharge (cfs) U/S Node Water Surface Elevation lpr_0510 pr_0510 pr_00 7755 7725-22.26 22.24-0.02 lpr_0520 pr_0520 pr_0510 7711 7681-31 22.75 22.73-0.02 lpr_05 pr_05n pr_0520 7727 7695-32 23.45 23.43-0.02 lpr_05 pr_05n pr_05n 7736 7703-32 24.03 24.01-0.02 lpr_05 pr_05 pr_05n 7072 7046-27 25.14 25.12-0.02 lpr_0552 pr_0552 pr_05 7088 7061-27 25.26 25.24-0.02 3876.1 pr_0554 pr_0552 7176 7169-7 25.28 25.26-0.02 3876.2 pr_0554 pr_0552 1188 1098-89 25.28 25.26-0.02 lpr_05 pr_05 pr_0554 7120 7091-29 25.61 25.59-0.02 lpr_0570 pr_0570 pr_05 6835 6824-10 25.93 25.91-0.01 lpr_0580 pr_0580 pr_0570 6878 6868-10 26.45 26.44 lpr_0590 pr_0590n pr_0580 6469 6469 28.04 28.04 lpr_00 pr_00n pr_0590n 67 67 28.38 28.38 lpr_06 pr_06n pr_00n 6411 6411 29.01 29.01 UWCorona pr_07n pr_06n 0 0 21.1 pr_07n pr_06n 68 68 29.62 29.62 lpr_08 pr_08n pr_07n 67 67 29.67 29.67 lpr_0610 pr_0610n pr_08n 5328 5329.05.05 lpr_0612 pr_0612n pr_0610n 5323 5324.15.15 lpr_0614 pr_0614n pr_0612n 5318 5319.38.38 lpr_0616 pr_0616n pr_0614n 5288 5288.48.48 lpr_0618 pr_0618n pr_0616n 5284 5284.63.63 lpr_0620 pr_0620n pr_0618n 5282 5283 31.11 31.11 lpr_06 pr_06n pr_0620n 5283 5284 31.89 31.89 lpr_06 pr_06n pr_06n 5274 5275 33.57 33.57 lpr_06 pr_06 pr_06n 5277 5278 33. 33. lpr_06 pr_06 pr_06 5288 5289 33.64 33.64 lpr_0670 pr_0670n pr_06 56 57 34.06 34.06 lpr_0680 pr_0680n pr_0670n 57 58 1 34.10 34.10 682lob pr_0682 pr_0680n 1452 1454 1 2792.1 pr_0682 pr_0680n 4789 4789 34.31 34.31 684lob pr_0684 pr_0682 1978 1979 1 2791.1 pr_0684 pr_0682 4527 4528 34.49 34.49 lpr_0690 pr_0690n pr_0684 5375 5375 34.43 34.43 lpr_0700 pr_0700 pr_0690n 5389 5390 34. 34. lpr_0710 pr_0710 pr_0700 55 55 35.48 35.48 lpr_0720 pr_0720 pr_0710 5372 5373 1 36.46 36.46 lpr_0723 pr_0723 pr_0720 5377 5379 2 37.42 37.42 3663.1 pr_0725 pr_0723 3772 3775 2 37.62 37.62 3663.2 pr_0725 pr_0723 27 27 37.62 37.62 lpr_07 pr_07 pr_0725 5378 5379 1 37.78 37.78 lpr_07 pr_07 pr_07 5362 5363 38.02 38.02 2526.1 pr_0745 pr_07 37 37 38.62 38.62 2526.2 pr_0745 pr_07 12 12 38.62 38.62 lpr_07 pr_07 pr_0745 5362 5362 39.09 39.09 lpr_07 pr_07 pr_07 5363 5363 39.29 39.29 Notes: (1) Change due to project--negative values indicate a decrease, and positive values an increase. Differences in discharge less than 1 cfs and water surface elevation less than 0.01 feet are left blank. Legend: = removed for project conditions (storage in empty field) = added for project conditions (detention basin)

March 5, 2013 Exhibit 1 Flood Boundary Comparison Map for 100 year Storm in vicinity of Corona Creek

90 70 110 cc_03 cc_03 nn ha ac ro n Co ee k Cr Co ro na 80 cc_0320 cc_0310 N. cc_03 cc_03 el Reisling Road Detention cc_00 cc02_l0 cc02_l070 cc02_l0 N OW SH T NO AI N PL EK RE IC PR CA CaC_R52 Parcels Buildings City Limits Proposed Detention Basin Project - Corona Subdivision and Detention CaC_R1 CaC_R2 0 µ 100 200 0 Corona Subdivision and Proposed Condition Flood Boundary Comparison CaC_R1 CaC_TP80 CaC_R190 CaC_R1 1 10 10-foot Contours CaC_R110 CaC_TP70CaC_R1 cc_00 cc_0020 XP-SWMM Nodes pr_05 Stream Centerlines CaC_R76 CaC_TP CaC_TP cc_00 1 FL 4 O O0 D 20 pr_0570 CaC_0047 CaC_R54 Legend 20 CaC_TP pr_0580 CaC_R90 CaC_L120CaC_L04 CaC_R80 CaC_L1 CaC_L02 CaC_R20 CaC_L1 CaC_0584 CaC_R CaC_R70 CaC_L1 CaC_TP10 CaC_L1 CaC_R72 CaC_R CaC_L170 CaC_03CaC_R100 CaC_R74 CaC_TP20 cc_00 CaC_R94 CaC_R92 TE : cc_00 CaC_R96 CaC_L110 CaC_L CaC_L CaC_L100 20 20 CaC_L cc_0070 CaC_L70 cctp080 CaC_L CaC_L80 cc_0075 CaC_L90 cctp1 cctp070 cctp100 cctp090 cctp120 20 20 cctp1 70 cctp170 cc_0080 cctp110 cctp065 pr_0590 CaC_28 cctp0 cctp180 cctp1 cctp0 cc_0085 cc_0090 CaC_36 CaC_32 cctp1 cctp045 80 CaC_3898 McDow85 McDow83 cc_0100 cctp0 CaC_4446 McDow82 McDow86 pr_00 cc_0202 McDow81 cc_0110 cctp020 CaC_4448 CaC_3900 Cor-CC_ CaC_44 cctp010 CaC_44 CaC_4848 CaC_4846 McDow80 Cor-CC_10 cc_01 cc_01 cc_01 cc_01 70 NO cc_0170 Holm_55 cc2_r CaC_48 cc2_r cc_0190 McDow56 Holm cc2_r10 cc_0200 McDow70 McDow54 McDow58 cc02_l170 cc2_r cc2_r20 McDow48 cc_02 cc_0208cc_0207 McDowMcDow62 McDow45 CaC_5171 cc_0220 McDow cc02_l012 cc02_l120 cc02_l010 cc02_l1 McDow46 RR78 cc_02 cc02_l1 cc02_l1 RR80 cc02_l0 cc_02 cc02_l020 RR76 RR90 cc_02 Corona Subdivision McDow42 cc02_l0 RR74 RR70 cc02_l080cc_0270 80 cc_0280 70 70 cc_0290 0 Feet Vertical Datum = NAVD 1988 February 2013