no-rise analysis for zidell property remediation...

NO-RISE ANALYSIS FOR ZIDELL PROPERTY REMEDIATION PROJECT

Submitted to: City of Portland

Bureau of Development Services 1900 SW 4th Avenue, Suite 5000

Portland, OR 97201

Prepared for: ZRZ Realty Company

3121 SW Moody Street Portland, OR 97201

Prepared by:

Northwest Hydraulic Consultants Inc. 16300 Christensen Road, Suite 350

Seattle, WA 98188

November 24, 2010

Northwest Hydraulic Consultants, November 24, 2010 No-Rise Analysis for Zidell Property Remediation Project – Portland, OR

ii

EXECUTIVE SUMMARY The proposed Zidell Property Remediation Project includes a sand “cap” to contain contaminated sediments along the left (west) bank of the Willamette River near downtown Portland, Oregon. Because the cap will be constructed inside the limits of the effective (existing) FEMA floodway, a “No Rise” analysis is required to demonstrate that the cap will have no adverse effects on flood water surface elevations. This report herein is explicitly written to provide the City of Portland with the information that staff will need to confirm that the proposed project meets their own and FEMA’s “No-Rise” requirements. FEMA provides guidelines describing the tasks that need to be completed to demonstrate “No-Rise”. The guidelines state that the effective FEMA hydraulic model is the primary tool that should be used to demonstrate “No-Rise”, which for this site is based upon the Army Corps of Engineers’ backwater programs HEC-RAS and its predecessor HEC-2. NHC followed the FEMA guidelines and modified the effective model to create an HEC-RAS model that contains sufficient detail to evaluate existing conditions, a range of project configurations, which ultimately led to a final project configuration that achieves “No-Rise”. The model results demonstrate that the project will not increase 100-year floodplain nor floodway water levels and therefore satisfies the “No-Rise” requirement. Certification of “No-Rise” is provided.


iii

TABLE OF CONTENTS

EXECUTIVE SUMMARY ............................................................................................................ ii

1. INTRODUCTION AND BACKGROUND .............................................................................. 1

1.1. Study Area ..........................................................................................................................1

1.2 Hydrology .............................................................................................................................2

1.3 Datum Information ..............................................................................................................2

1.4 TriMET Bridge .....................................................................................................................2

2. HEC-RAS MODEL DEVELOPMENT ................................................................................... 3

2.1. FEMA Effective, Duplicate Effective, and Existing Condition Models .......................3

2.2. HEC-RAS FEMA Floodway Model .................................................................................3

2.3 HEC-RAS “With-Project” Model .......................................................................................7

3. “NO-RISE” CERTIFICATION, FEMA MAP, CONSTRUCTION PLANS ....................... 14

3.1 No-Rise Certification ........................................................................................................14

3.2 NFIP Existing Floodplain / Floodway Map ....................................................................14

3.3 Construction Plans ...........................................................................................................14

4. CONCLUSION ....................................................................................................................... 15

REFERENCES ........................................................................................................................... 16

LIST OF APPENDICES Appendix A Photographs of the Existing River Bank along the Zidell Property

A1. Typical bank along Downstream Reach A2. Typical bank along Downstream Reach A3. Typical bank along North Bridge Reach A4. Typical bank along South Bridge Reach A5. Typical bank along Slipway Reach

Appendix B FEMA Certification of a No-Rise Determination Appendix C Effective FEMA FIRM


iv

LIST OF FIGURES Figure 1 Zidell Property Remediation Project Vicinity Map Figure 2 Existing condition and with-project model cross-section locations Figure 3 Existing condition topography and bathymetry Figure 4 With-project topography and bathymetry Figure 5 Typical design concept for North Spillway Reach Figure 6 Typical design concept for South Bridge Reach south of Ross Island Bridge Figure 7 Typical design concept for North Bridge Reach north of Ross Island Bridge Figure 8 Typical design concept for Downstream Reach

LIST OF TABLES

Table 1 Existing Condition Model 100-year Flood Water Surface Elevations. Table 2 Existing Condition Model Water Surface Elevations for Base Flood and Floodway

Runs. Table 3 100-year Base Flood Water Surface Elevations Existing Condition and With-

Project Table 4 100-year Floodway Water Surface Elevations Existing Condition and With-

Project


1

1. INTRODUCTION AND BACKGROUND ZRZ Realty Company (Zidell) plans to remediate bank and streambed sediments near the Zidell Waterfront Property along the west bank of the Willamette River downstream from Ross Island. The purpose of the project is to prevent exposure or the transport of the contaminated soil that is contained within the river bed and bank along the Zidell property. This objective will be achieved through the use of a sand cap that will be covered by an engineered protective surface layer of vegetation, engineered matting, and/or rock material. As part of preparing the remediation design, NorthWest Ecosystem Services, Inc. (NWES), the firm managing the project, asked Northwest Hydraulic Consultants (NHC) to complete a detailed hydraulic analysis to help the design team develop a plan that will produce “No-Rise” in regulatory flood levels. A “No-Rise” design was achieved.

1.1. Study Area The Zidell Property is located on the left (west) bank of the Willamette River near downtown Portland Oregon (Figure 1). The containment cap, which is identified by the light blue footprint in Figure 1, will extend from the north end of Ross Island downstream to the I-5 (Marquam) Bridge. The study reach for the hydraulic analyses begins just upstream of the confluence of the Willamette and Columbia Rivers and continues several miles upstream of the project. This reach was selected to ensure that the detailed hydraulic analysis along the project reach correctly ties into the hydraulic analysis that was completed for the effective FEMA Flood Insurance Study (FIS) of the Willamette River (FEMA, 2004).

Figure 1. Zidell Property Remediation Project vicinity map.


2

1.2 Hydrology

The 100-year annual instantaneous peak discharge used in all model simulations performed for this investigation is 375,000 cfs. This is the value that was used in the effective FEMA HEC-2 model and is reported in the FEMA FIS for this reach of the Willamette River.

1.3 Datum Information The effective FEMA HEC-2 model uses elevations relative to the National Geodetic Vertical Datum of 1929 (NGVD29); the use of this datum has been continued in this investigation. This was done to ensure that the water surface elevations computed in the hydraulic analysis can be compared directly to the Base Flood Elevations published on the effective FEMA Flood Insurance Rate Maps (FIRMs) and within the FEMA Flood Insurance Study report (FIS). Conversions from elevations with respect to NAVD88 and City of Portland (COP) datums are given below (City of Portland, 2010): NGVD29 = NAVD88 minus 3.475 feet NGVD29 = COP minus 1.375 feet

1.4 TriMET Bridge

Current construction schedules call for the in-water portion of the Zidell Property Remediation Project and the piers and scour protection for the new TriMET bridge to both be constructed in the summer of 2011. The two projects are completely independent of one-another, except in one location where TriMet scour protection is shown overlapping a small area of the Zidell cap; however, TriMet is modifying the bridge scour design and this overlap might not occur in the modified design. . The current TriMET bridge plan calls for a small portion of the proposed scour protection surrounding the west intermediate pier to be placed on top of an area where Zidell will install a “Thin Cap” of sand. This is a 6 to 10 inch thick layer of sand that will be placed for habitat purposes. The “Thin Cap” has no measurable impact on flood levels and thus it is our opinion that there is no need to evaluate the combined effect of the two projects.


3

2. HEC-RAS MODEL DEVELOPMENT 2.1. FEMA Effective, Duplicate Effective, and Existing Condition Models The effective Flood Insurance Study HEC-2 model for Willamette River was obtained from FEMA and reviewed. This is the “FEMA Effective” model. This HEC-2 model was imported into and converted to HEC-RAS version 4.1.0 (USACE, 2010), initially retaining the original cross sections and bridge geometries from the HEC-2 model. This HEC-RAS model is the “Duplicate Effective” model required by FEMA for a “No-Rise” investigation. It was determined that the “Duplicate Effective” model is too coarse to be a reliable and useful tool for assisting the design or evaluating impacts of the remediation project. It was determined that a more refined model was needed to provide a defensible tool for evaluating realistic impacts of project alternatives and demonstrating to agencies “No-Rise” of the final project configuration. New cross-sections were developed within the reach of the proposed project, consisting of 14 additional cross-section locations chosen to appropriately simulate transitions within the cap design, as well as new cross-sections reoccupying the four original cross-sections in the FEMA effective model. The locations and alignments of these cross-sections (18 total) are shown in Figure 2. The additional cross-sections are identified by green lines and the reoccupied FEMA effective cross-sections are the red lines. The cross sections were cut from the detailed topography and bathymetric data shown in Figure 3 which was developed for this investigation under the direction of Maul Foster & Alongi, Inc. (MFA). These figures represent an accurate, up to date depiction of existing elevations within the project area. Model parameters such as Manning’s n values are the same as those used in the FEMA Effective model. The resultant HEC-RAS model is the “Existing Condition” model required by FEMA for a “No-Rise” investigation. The 100-year water surface elevations computed by the model are presented in Table 1. These elevations are referred to as “Base Flood Elevations”.

2.2. HEC-RAS FEMA Floodway Model Once the “Existing Condition” HEC-RAS model was complete, NHC added encroachments to the cross-sections to model the effective FEMA floodway. For cross-sections in the model upstream and downstream of the project site, the encroachment stationing and method was imported from the effective HEC-2 model. Because the cross-sections added by NHC to create the existing and post-project conditions models do not exist in the HEC-2 model, the FEMA Digital Flood Insurance Rate Map (DFIRM) data were used to determine where the floodway extents lie on each of the new cross-sections (FEMA, 2010) To demonstrate that the floodway encroachments in the “Existing Condition” model do not cause flood levels to increase more than one foot, 100-year water surface elevations were computed for the encroached condition and compared to the Base Flood Elevations presented in Table 1. The results, which are shown in Table 2, confirm that the floodway limits as input into the “Existing Condition” model do not cause flood levels to rise more than one foot and therefore, the floodway limits which are used in the model comply with FEMA requirements.


4

Figure 2. Existing condition and with-project model cross-section locations. Note -- those

reoccupying original FEMA effective cross-sections are shown in red. The numbers represent both the HEC-RAS cross section ID and river mile.


5

Figure 3. Existing condition topography and bathymetry. Note -- those reoccupying

original FEMA effective cross-sections are shown in red. The numbers represent both the HEC-RAS cross section ID and river mile.


6

Table 1. Existing Condition Model 100-year Flood Water Surface Elevations.

Note – The cells highlighted in gray are within the Zidell property project reach.

XS

Existing Condition

Base Flood Water Surface

Elevation (ft, NGVD29)

XS

Existing Condition



XS

Existing Condition



0.38 26.7 12.62 28.6 14.22 29.5 1.52 26.8 12.72 28.6 14.90 29.8 2.40 26.9 12.79 28.6 15.66 30.5 3.03 26.9 12.81 28.7 16.01 30.3 3.50 26.9 12.99 28.9 16.33 30.9 4.54 27.0 13.10 29.1 16.58 31.0 5.00 27.0 13.16 29.0 16.62 31.1 6.00 27.1 13.17 29.0 16.63 31.2 6.70 27.2 13.33 29.1 16.74 31.7 6.94 27.3 13.47 29.2 17.36 32.1 7.00 27.3 13.51 29.2 17.83 32.6 7.01 27.3 13.54 29.2 18.31 32.9 7.07 27.3 13.60 29.2 18.63 33.7 7.68 27.6 13.62 29.2 19.10 33.7 8.40 27.7 13.66 29.2 19.88 34.1 9.66 27.7 13.68 29.3 20.02 34.1 11.00 27.8 13.73 29.3 20.03 34.2 11.66 27.9 13.77 29.3 20.16 34.7 11.72 27.9 13.79 29.4 20.89 34.8 11.73 27.9 13.83 29.4 21.20 35.5 11.94 28.0 13.84 29.4 21.40 35.6 12.05 28.1 13.94 29.4 21.50 36.3 12.11 28.2 13.97 29.4 21.65 38.5 12.12 28.3 14.00 29.5 21.80 39.2 12.30 28.5 14.02 29.5 22.15 40.1 12.36 28.6 14.11 29.5 22.25 40.0 12.41 28.5 14.19 29.5 22.30 40.2 12.42 28.6 14.21 29.5


7

Table 2. Existing Condition Model Water Surface Elevations for Base Flood and Floodway Runs.

XS

Existing Conditions

XS

Existing Conditions

XS

Existing Conditions

Floodway (ft, NGVD29)

Base Flood

(ft, NGVD29)

Rise (ft)

Floodway(ft, NGVD29)

Base Flood

(ft, NGVD29)

Rise(ft)

Floodway (ft, NGVD29)

Base Flood

(ft, NGVD29)

Rise(ft)

0.38 25.9 26.7 0.8 12.62 27.8 28.6 0.7 14.22 28.8 29.5 0.7 1.52 26.0 26.8 0.8 12.72 27.8 28.6 0.7 14.90 29.1 29.8 0.7 2.40 26.1 26.9 0.8 12.79 27.9 28.6 0.7 15.66 29.8 30.5 0.7 3.03 26.1 26.9 0.8 12.81 28.0 28.7 0.7 16.01 29.7 30.3 0.7 3.50 26.1 26.9 0.8 12.99 28.2 28.9 0.7 16.33 30.2 30.9 0.7 4.54 26.2 27.0 0.8 13.10 28.4 29.1 0.7 16.58 30.3 31.0 0.7 5.00 26.2 27.0 0.8 13.16 28.3 29.0 0.7 16.62 30.4 31.1 0.7 6.00 26.3 27.1 0.8 13.17 28.3 29.0 0.7 16.63 30.5 31.2 0.7 6.70 26.5 27.2 0.8 13.33 28.3 29.1 0.7 16.74 31.0 31.7 0.7 6.94 26.6 27.3 0.7 13.47 28.4 29.2 0.7 17.36 31.4 32.1 0.6 7.00 26.6 27.3 0.7 13.51 28.4 29.2 0.7 17.83 32.0 32.6 0.6 7.01 26.6 27.3 0.7 13.54 28.5 29.2 0.7 18.31 32.3 32.9 0.6 7.07 26.6 27.3 0.7 13.60 28.5 29.2 0.7 18.63 33.0 33.7 0.6 7.68 26.9 27.6 0.7 13.62 28.5 29.2 0.7 19.10 33.0 33.7 0.6 8.40 26.9 27.7 0.7 13.66 28.5 29.2 0.7 19.88 33.4 34.1 0.7 9.66 27.0 27.7 0.7 13.68 28.5 29.3 0.7 20.02 33.4 34.1 0.7

11.00 27.1 27.8 0.7 13.73 28.6 29.3 0.7 20.03 33.6 34.2 0.6 11.66 27.2 27.9 0.7 13.77 28.6 29.3 0.7 20.16 34.1 34.7 0.6 11.72 27.2 27.9 0.7 13.79 28.6 29.4 0.7 20.89 34.3 34.8 0.5 11.73 27.2 27.9 0.7 13.83 28.7 29.4 0.7 21.20 34.8 35.5 0.8 11.94 27.3 28.0 0.7 13.84 28.7 29.4 0.7 21.40 34.9 35.6 0.7 12.05 27.5 28.1 0.6 13.94 28.7 29.4 0.7 21.50 35.6 36.3 0.7 12.11 27.5 28.2 0.6 13.97 28.7 29.4 0.7 21.65 37.7 38.5 0.7 12.12 27.6 28.3 0.7 14.00 28.8 29.5 0.7 21.80 38.5 39.2 0.7 12.30 27.8 28.5 0.7 14.02 28.8 29.5 0.7 22.15 39.5 40.1 0.6 12.36 27.8 28.6 0.7 14.11 28.8 29.5 0.7 22.25 39.4 40.0 0.6 12.41 27.8 28.5 0.7 14.19 28.8 29.5 0.7 22.30 39.6 40.2 0.6 12.42 27.9 28.6 0.7 14.21 28.8 29.5 0.7 Note – The cells highlighted in gray are within the Zidell property project reach.

2.3 HEC-RAS “With-Project” Model The existing condition model was modified to include the initial proposed concept. NHC and MFA worked together to test a series of configurations, refining design details until “No-Rise” was achieved. MFA then created a new “with-project” topographic elevation dataset from which the final HEC-RAS cross section geometries were obtained (Figure 4). Typical cross sections showing the conceptual configuration of the design within each of the four project sub-reaches are presented in Figures 5 to 8. All other model parameters remain the same as in the existing condition model, allowing for simple comparison between existing and post-project conditions. This new model is the “With-Project” model.


8

Figure 4. With-project topography and bathymetry.


9

Figure 5. Typical design concept for North Spillway Reach.

Figure 6. Typical design concept for South Bridge Reach south of the Ross Island Bridge.


10

Figure 7. Typical design concept for North Bridge Reach north of the Ross Island Bridge.

Figure 8. Typical design concept for the Downstream Reach.


11

The “existing condition” versus “with-project” 100-year water surface elevations are compared in Tables 3 and 4. Table 3 compares Base Flood Elevations produced by the existing condition and with-project models. Table 4 compares the Floodway water surface elevations produced by the floodway version of the same two models. The tables demonstrate that, when rounded to the hundredth of a foot as per FEMA criteria, in no place do “with-project” water surface elevations rise above the “existing condition” water levels, for both 100-year Base Flood and Floodway conditions; demonstrating that the project meets the “No-Rise” requirement. Although the project will, in some places, reduce the channel cross-section area slightly, this does not result in a net increase in water surface elevation because a slight constriction can actually reduce water levels. Basic hydraulic theory, based upon the energy equation, suggests that constrictions into a river channel that reduce the cross-sectional area, will cause a rise in the elevation of the Energy Grade Line (EGL), which represents the total energy of the river flow. One component of this total energy is the velocity, and the EGL along a river is higher than the water surface elevation (also called the Hydraulic Grade Line or the HGL) by an amount related to the velocity along the river. Slight constrictions within the river can cause a rise in the EGL but also an increase in the velocity. Because the velocity also increases, the result is often an actual reduction in the water surface elevation (HGL) due to the constriction. The No-Rise condition seen here is due in part to this effect, combined with the fact that some cross-section banks will be laid back in the proposed condition which will result in an increase in cross-section area at these locations. It should be noted that the increases in velocity are negligibly small, and will not have any impact (e.g. scour or erosion), but are sufficient to drop the water surface elevation the small amount needed to maintain “No-Rise”. Furthermore, roughness coefficients were not changed from the effective model, even though the with-project condition is believed to have a slightly lower resistance. This is due mainly to the removal of the hundreds of old wooden pilings and remnant dock parts, and to a lesser extent the smoothing or re-contouring of the river bank and the replacement of thick brush with landscaped vegetation (see existing bank photographs in Appendix A). This was an intentionally conservative assumption so that there would be no dispute over the value of the roughness coefficients used in the model.


12

Table 3. 100-Year Base Flood Water Surface Elevations for Existing Conditions and With-Project.

XS ID

Existing (ft, NGVD29)

With Project

(ft, NGVD29) Rise

(ft) Rise

Rounded(ft)

XS ID

Existing(ft, NGVD29)

With Project

(ft, NGVD29) Rise

(ft) Rise

Rounded(ft)

12.62 27.8178 27.8178 0.0000 0.00 14.22 28.8275 28.8312 0.0037 0.00

12.72 27.8475 27.8475 0.0000 0.00 14.9 29.0768 29.0805 0.0037 0.00

12.79 27.8774 27.8774 0.0000 0.00 15.66 29.8036 29.8072 0.0036 0.00

12.81 27.9670 27.9670 0.0000 0.00 16.01 29.6616 29.6651 0.0035 0.00

12.99 28.1593 28.1593 0.0000 0.00 16.33 30.1957 30.1991 0.0034 0.00

13.1 28.3707 28.3707 0.0000 0.00 16.58 30.3297 30.3331 0.0034 0.00

13.16 28.2868 28.2868 0.0000 0.00 16.62 30.4016 30.4049 0.0033 0.00

13.17 28.3046 28.3046 0.0000 0.00 16.63 30.4888 30.4921 0.0033 0.00

13.33 28.3326 28.3326 0.0000 0.00 16.74 31.0150 31.0182 0.0032 0.00

13.47 28.4381 28.4381 0.0000 0.00 17.36 31.4157 31.4188 0.0031 0.00

13.51 28.4497 28.4497 0.0000 0.00 17.83 31.9730 31.9760 0.0030 0.00

13.54 28.4708 28.4708 0.0000 0.00 18.31 32.2809 32.2839 0.0030 0.00

13.6 28.4594 28.4588 -0.0006 0.00 18.63 33.0257 33.0286 0.0029 0.00

13.62 28.4623 28.4550 -0.0073 -0.01 19.1 33.0328 33.0357 0.0029 0.00

13.66 28.5328 28.5186 -0.0142 -0.01 19.88 33.4195 33.4223 0.0028 0.00

13.68 28.5416 28.5334 -0.0082 -0.01 20.02 33.4022 33.4050 0.0028 0.00

13.73 28.5994 28.5891 -0.0103 -0.01 20.03 33.5911 33.5939 0.0028 0.00

13.77 28.5964 28.5858 -0.0106 -0.01 20.16 34.0864 34.0891 0.0027 0.00

13.79 28.6318 28.6190 -0.0128 -0.01 20.89 34.2715 34.2741 0.0026 0.00

13.83 28.7212 28.7094 -0.0118 -0.01 21.2 34.7539 34.7565 0.0026 0.00

13.84 28.7232 28.7106 -0.0126 -0.01 21.4 34.8929 34.8955 0.0026 0.00

13.94 28.6693 28.6667 -0.0026 0.00 21.5 35.5884 35.5908 0.0024 0.00

13.97 28.7382 28.7283 -0.0099 -0.01 21.65 37.7247 37.7269 0.0022 0.00

14 28.7636 28.7518 -0.0118 -0.01 21.8 38.5112 38.5133 0.0021 0.00

14.02 28.7931 28.7836 -0.0095 -0.01 22.15 39.4538 39.4558 0.0020 0.00

14.11 28.8018 28.7908 -0.0110 -0.01 22.25 39.3653 39.3672 0.0019 0.00

14.19 28.7938 28.7871 -0.0067 -0.01 22.3 39.6192 39.6211 0.0019 0.00

14.21 28.8019 28.8008 -0.0011 0.00 Note – The cells highlighted in gray are within the Zidell property project reach.


13

Table 4. 100-year Floodway Water Surface Elevations for Existing Conditions and With-Project.

XS ID

Existing (ft,

NGVD29)

With Project

(ft, NGVD29) Rise

(ft) Rise

Rounded(ft)

XS ID

Existing(ft,

NGVD29)

With Project (ft, NGVD29)

Rise (ft)

Rise Rounded

12.62 28.5622 28.5622 0.0000 0.00 14.22 29.5406 29.5456 0.0050* 0.00

12.72 28.5925 28.5925 0.0000 0.00 14.9 29.7808 29.7857 0.0049 0.00

12.79 28.6213 28.6213 0.0000 0.00 15.66 30.4784 30.4832 0.0048 0.00

12.81 28.7078 28.7078 0.0000 0.00 16.01 30.3234 30.3281 0.0047 0.00

12.99 28.8957 28.8957 0.0000 0.00 16.33 30.8775 30.8820 0.0045 0.00

13.1 29.1002 29.1002 0.0000 0.00 16.58 31.0093 31.0138 0.0045 0.00

13.16 29.0197 29.0197 0.0000 0.00 16.62 31.0778 31.0823 0.0045 0.00

13.17 29.0368 29.0368 0.0000 0.00 16.63 31.1614 31.1659 0.0045 0.00

13.33 29.0646 29.0646 0.0000 0.00 16.74 31.6693 31.6736 0.0043 0.00

13.47 29.1623 29.1623 0.0000 0.00 17.36 32.0657 32.0699 0.0042 0.00

13.51 29.1757 29.1757 0.0000 0.00 17.83 32.6206 32.6247 0.0041 0.00

13.54 29.1959 29.1959 0.0000 0.00 18.31 32.9267 32.9308 0.0041 0.00

13.6 29.1831 29.1825 -0.0006 0.00 18.63 33.6674 33.6713 0.0039 0.00

13.62 29.1865 29.1795 -0.0070 -0.01 19.1 33.6537 33.6576 0.0039 0.00

13.66 29.2487 29.2345 -0.0142 -0.01 19.88 34.0733 34.0771 0.0038 0.00

13.68 29.2584 29.2506 -0.0078 -0.01 20.02 34.0611 34.0648 0.0037 0.00

13.73 29.3171 29.3082 -0.0089 -0.01 20.03 34.2381 34.2418 0.0037 0.00

13.77 29.3154 29.3065 -0.0089 -0.01 20.16 34.7162 34.7198 0.0036 0.00

13.79 29.3506 29.3380 -0.0126 -0.01 20.89 34.7900 34.7937 0.0037 0.00

13.83 29.4351 29.4248 -0.0103 -0.01 21.2 35.5279 35.5314 0.0035 0.00

13.84 29.4378 29.4261 -0.0117 -0.01 21.4 35.5657 35.5691 0.0034 0.00

13.94 29.3860 29.3837 -0.0023 0.00 21.5 36.2880 36.2913 0.0033 0.00

13.97 29.4221 29.4114 -0.0107 -0.01 21.65 38.4584 38.4614 0.0030 0.00

14 29.4785 29.4647 -0.0138 -0.01 21.8 39.2170 39.2198 0.0028 0.00

14.02 29.5068 29.4954 -0.0114 -0.01 22.15 40.0811 40.0838 0.0027 0.00

14.11 29.5138 29.5025 -0.0113 -0.01 22.25 40.0106 40.0133 0.0027 0.00

14.19 29.5036 29.4968 -0.0068 -0.01 22.3 40.2306 40.2333 0.0027 0.00

14.21 29.5168 29.5168 0.0000 0.00 *actual rise is 0.00497, which rounds to 0.00


14

3. “NO-RISE” CERTIFICATION, FEMA MAP, CONSTRUCTION PLANS

3.1 No-Rise Certification NHC certifies that the analysis described here-in was completed using methods that are consistent with industry standards and adhere to FEMA guidelines and requirements. A signed and stamped copy of the FEMA form “Certification of a “No-Rise” Determination for a Proposed Floodway Development” is presented in Appendix B.

3.2 NFIP Existing Floodplain / Floodway Map FEMA typically asks that a copy of the effective FEMA Floodplain / Floodway Map for the project area is included with a No-Rise submittal. This is attached as Appendix C.

3.3 Construction Plans Construction plans for the remediation project will be submitted by Maul Foster Alongi, Inc as a separate document.


15

4. CONCLUSION NHC, working with MFA, has developed a design for the soil containment cap that will create “No-Rise” in Base Flood and Floodway regulatory water surface elevations within the Willamette River. FEMA methods and procedures were followed to demonstrate “No-Rise”, and therefore NHC has prepared a “Certification of a “No-Rise” Determination for a Proposed Floodway Development” as required by FEMA.


16

REFERENCES City of Portland (2010). Bureau of Transportation datum conversion table, website http://www.portlandonline.com/transportation/index.cfm?a=70676&c=35705 FEMA (2004). “Flood Insurance Study: City of Portland Oregon, Multnomah, Clackamas, and Washington Counties, 410183V000A. Federal Emergency Management Agency, Revised October 19, 2004. FEMA (2010). Effective Digital Flood Insurance Rate Map Database 410183, S_FLD_HAZ_AR.shp USACE (2010). HEC-RAS. Hydrologic Engineering Center’s River Analysis System, U.S. Army Corps of Engineers.


17

APPENDIX A

Photos

File

: X:\8

014

.01

ZR

Z R

eal

ty C

ompa

ny\1

7\0

3A\P

roje

cts\

Ban

k P

hoto

s\B

ank

Pho

to a

t Sta

tion

23+

00.m

xdP

roje

ct: 8

014

.01

.17/

03A

Pro

duce

d B

y: R

. Ma

ron

nA

ppr

ove

d B

y: A

. C

lary

Pri

nt D

ate:

05-

15-2

009

SW

WH

ITA

KE

R S

T

Station23+00

Return toLocator Map

2323

Appendix A. Photographs of existing river banks on the Zidell Property

jbrown

Typewritten Text

jbrown

Typewritten Text

jbrown

Text Box

Photo A1 - Typical bank along downstream reach

File

: X:\8

014

.01

ZR

Z R

eal

ty C

ompa

ny\1

7\0

3A\P

roje

cts\

Ban

k P

hoto

s\B

ank

Pho

to a

t Sta

tion

20+

00.m

xdP

roje

ct: 8

014

.01

.17/

03A

Pro

duce

d B

y: R

. Ma

ron

nA

ppr

ove

d B

y: A

. C

lary

Pri

nt D

ate:

05-

15-2

009

SW

WH

ITA

KE

R S

T

Station20+00


2020


jbrown

Text Box

typical bank along downstream reach

jbrown

Text Box

Photo A2 - Typical bank along downstream reach

File

: X:\8

014

.01

ZR

Z R

eal

ty C

ompa

ny\1

7\0

3A\P

roje

cts\

Ban

k P

hoto

s\B

ank

Pho

to a

t Sta

tion

10+

00.m

xdP

roje

ct: 8

014

.01

.17/

03A

Pro

duce

d B

y: R

. Ma

ron

nA

ppr

ove

d B

y: A

. C

lary

Pri

nt D

ate:

05-

18-2

009

SW

WH

ITA

KE

R S

T

Station10+00


1010


jbrown

Text Box

Photo A3 - Typical bank along north bridge reach

File

: X:\8

014

.01

ZR

Z R

eal

ty C

ompa

ny\1

7\0

3A\P

roje

cts\

Ban

k P

hoto

s\B

ank

Pho

to a

t Sta

tion

6+00

.mxd

Pro

ject

: 80

14.0

1.1

7/03

AP

rodu

ced

By:

R. M

aro

nn

Ap

pro

ved

By:

A.

Cla

ryP

rint

Dat

e: 0

5-18

-200

9

SW

WH

ITA

KE

R S

T

Station6+00


66


jbrown

Text Box

Photo A4 - Typical bank along south bridge reach

File

: X:\8

014

.01

ZR

Z R

eal

ty C

ompa

ny\1

7\0

3A\P

roje

cts\

Ban

k P

hoto

s\B

ank

Pho

to a

t Sta

tion

1+00

.mxd

Pro

ject

: 80

14.0

1.1

7/03

AP

rodu

ced

By:

R. M

aro

nn

Ap

pro

ved

By:

A.

Cla

ryP

rint

Dat

e: 0

5-18

-200

9

SW

WH

ITA

KE

R S

T

Station1+00


11


jbrown

Text Box

Photo A5 - Typical bank along slipway reach


18

APPENDIX B

FEMA Certification of a No-Rise Determination

Appendix B. FEMA Certification of No-Rise Determination


19

APPENDIX C

Effective FEMA FIRM

Appendix C. Effective FEMA FIRM

no-rise analysis for zidell property remediation...

Documents