CA_FLAP_03S11(1)_HydraulicsReport_100_3-26-21.pdf

H Y D R A U L I C S R E P O R T

Hydraulics Report for the Reds Meadow Road Improvements Project

PREPARED FOR: Dustin Robbins/CFLHD

COPY TO: Ed Henderson/Jacobs

Travis Howard/Jacobs

PREPARED BY: Nicole Lapp/Jacobs

DATE: March 26, 2021

PROJECT NUMBER: 704630

Introduction The purpose of this report is to document the existing and proposed hydrologic and hydraulic conditions associated with the Reds Meadow Road Improvement Project and to document the drainage design criteria used for final design.

Project Description The Reds Meadow Road Project consists of improvements to an 8.3-mile corridor of roadway near the community of Mammoth Lakes, California. The road is situated in the southern reaches of the Sierra Nevada mountain range at an elevation that ranges from approximately 8,300’ to 9,200’ above mean sea level. The road begins at the intersection with Highway 203 at the Minaret Vista Entrance Station and terminates at the Reds Meadow Resort and Pack Station. The road is owned by the U.S. Forest Service and serves as the primary access point for the Reds Meadow Resort and Pack Station and Devil’s Postpile National Monument, in addition to providing access to multiple campgrounds, day use parking areas, and trail heads. The roadway is only utilized during the summer tourist season. It is closed in the fall and re-opened in the spring. Winter maintenance activities such as plowing snow are not performed. The roadway has a 15-mph posted speed limit for the first 2.5 miles, then increases to 25 mph for the remainder of the corridor.

For the purposes of this memo, the project is broken into two separate portions: the 4R portion and the 3R portion. The upper 2.5 miles of the project is considered the 4R portion and will involve a complete reconstruction and widening of the roadway to two lanes. The term 4R stands for Resurfacing, Restoration, Rehabilitation and Reconstruction.

The lower 5.8 miles of the project is considered the 3R portion and will involve repair and rehabilitation measures to the existing pavement. Widening, reconstruction, and re-alignment work will not be performed to the 3R portion of the project. The term 3R stands for Resurfacing, Restoration, and Rehabilitation.

There are two additional components to the project: The Devils Postpile re-alignment and the Minaret Vista access road. For the purposes of this memo, the Devils Postpile re-alignment will be considered 4R work and will follow any 4R drainage criteria established for the project. The Minaret Vista access road will be considered 3R work and will follow any 3R drainage criteria established for the project.

See Appendix A for a location map that provides a visual representation of the project components described above. A vicinity map is also included in Appendix A.

thoward2 Rectangle thoward2 Typewritten Text 3-26-21

HYDRAULICS REPORT FOR THE REDS MEADOW ROAD IMPROVEMENTS PROJECT

Existing Conditions 4R (Upper 2.5 Miles). The existing roadway for the 4R portion consists of a paved surface of variable width; often only wide enough for a single vehicle. The roadway operates as a one-lane, two-way road with pullouts spaced periodically along the alignment that allow for vehicles going in opposite directions to pass each other. This 2.5 miles is on a longitudinal grade that averages approximately 8-9% as the roadway descends along the side of the mountain. The roadway moves down the mountain in a side-hill fashion with roadside cut slopes of approximately 1V:1.5H on the inboard side and roadside fill slopes of approximately 1V:1.5H on the outboard side. The surrounding terrain is mountainous with fair vegetative cover ranging from scattered grasses and brush to large coniferous forests.

The existing drainage facilities include informal roadside ditches coupled with multiple cross culverts along the alignment. Existing cross culvert types, sizes, and locations in the 4R segment are identified in the Culvert Discharge Summary in Appendix C. There are no formal gutters, ditches or catch basins.

This roadway receives offsite runoff from the adjacent mountain. The total watershed flowing toward the road is approximately 680 acres. Flow from this watershed is dispersed along the alignment with portions passing under the road via cross culverts and portions passing over the road in a sheet flow manner. Onsite runoff either runs directly off the road or is collected in a roadside ditch and conveyed to a cross culvert where it passes under the road. Roadway cross slope varies along the entire corridor with certain portions super-elevated and certain portions in a normal crown.

3R (Lower 5.8 Miles). The existing roadway for the 3R portion consists of a paved surface that is approximately 22 feet wide. The roadway operates as a two-lane, two-way road with a single centerline stripe and no edge lines or formal shoulders. The surrounding terrain is relatively flat with meadows and forests on either side of the road. The longitudinal grade is relatively flat as the road meanders along the valley floor.

The existing drainage facilities include informal roadside ditches and cross culverts. There are no formal gutters, ditches or catch basins. This roadway receives offsite runoff from the adjacent mountain. Flow from this watershed is dispersed along the alignment with the majority passing under the road via cross culverts. Onsite runoff runs off the road and maintains a sheet flow pattern beyond the edge of pavement. There are no curbs or gutters for the majority of the road.

Proposed Conditions 4R (Upper 2.5 Miles). The proposed project for the upper 2.5 miles involves a complete reconstruction of the roadway. The road will be widened from a one-lane road with turnouts to a two-lane road (11-foot lanes with 1-foot shoulders). A 2-foot wide paved ditch/gutter on the inboard side of the road is being proposed to collect onsite and offsite drainage. Multiple retaining walls are being proposed. All existing cross culverts will be removed and replaced, and additional culverts and inlets will be placed where warranted. The posted speed limit will remain at 15 mph with a design speed of 20 mph.

3R (Lower 5.8 Miles). The proposed project for the 3R portion involves rehabilitating the existing pavement. No widening or re-alignments are proposed. All existing cross culverts were assessed at the 30% field review to determine if they should be replaced, repaired, or left as is. Of the 47 identified culverts, 8 will be kept and the remaining 39 will be replaced. Replaced culverts will be upsized to meet the CFL minimum of 24-inches for cross culverts if adequate cover is available. A summary of the findings from this exercise can be found in Appendix D.

The 30% field review also included an assessment of the overall drainage performance for the 3R corridor. The 30 percent site visit was performed during a rain event. This allowed the team to observe several drainage deficiencies along the corridor. Deficiencies included lack of roadside ditches, roadside berms prohibiting drainage, sags in the roadway that didn’t have cross culverts, and concentrated flows traveling across the roadway. Solutions to these situations that have been included in the 95% design included adding new cross culverts, cutting in new ditches, removing roadside berms that block drainage, incorporation of paved ditches, shoulder breaks, and new curb added in select locations.

Incorporation of the findings from the site visit into the 95% design package represent the extent of the drainage work for the 3R segment. No hydrologic or hydraulic calculations are being performed for this portion of the project.

Hydrology (4R) Design Criteria The Federal Lands Highway Project Development and Design Manual (PDDM) published by the U.S.

Department of Transportation Federal Highway Administration is the primary guideline for Hydrologic criteria on the project. The edition dated March 2018 was used.

A Hydrologic analysis was performed to determine flows entering the proposed drainage facilities for the 4R portion of work. Hydrologic calculations were based on the guidelines presented in the document titled Highway Design Series No. 2, Second Edition, Highway Hydrology (HDS-2), published by the U.S. Department of Transportation Federal Highway Administration. The edition dated October 2002 was used. Peak flows were calculated using the Rational Method (Equation 5.28 from HDS-2). See below for Equation 5.28. Use of the rational method is dependent on the maximum size of watershed.

Per Section 5.3.1 of HDS-2 the maximum drainage area should be smaller than 200 acres for the rational method to work properly. All watersheds within the project are below 200 acres in size. An evaluation of the topography revealed the largest drainage basin to be approximately 120 acres in size.

Rational Formula, Equation 5.28

Below is a summary of the components of the rational method as they relate to this project.

• Runoff Coefficient (C): Runoff coefficients were based on Table 5.7 of HDS-2. A value of 0.3 for the offsite runoff coefficient was used due to the steep un-improved nature of the existing terrain. A value of 0.90 was used for the onsite runoff coefficient, which is typical for paved surfaces such as the proposed roadway. Table 5.7 from HDS-2 is included in Appendix B.

• Rainfall Intensity (i): Values from NOAA Atlas 14 were used for rainfall intensity. A listing of the NOAA Atlas 14 rainfall data specific to this project’s location is included in Appendix B. Rainfall intensity values were selected based on the time of concentration calculated. Time of concentrations for each basin were calculated simultaneous to the flow calculation using the Hydraulic Toolbox.

• Drainage Area (A): The watershed boundaries were determined from the following sources:

– The projects topographic survey (1’ contour interval), limited to within 50’+/- of roadway CL

– USGS Topographic Mapping (10-foot contour interval)

– Site walk performed in fall of 2018

– Google Earth imagery, last updated June 2016

The existing culverts in the 4R portion of work determined the locations of basins within the watershed. Analysis of the contours in the survey and mapping led to the conclusion that some of the collected water within each basin will flow directly to the culvert by bypassing the gutter.

To address this the basins with very limited gutter capacity were separated into a culvert basin and a gutter basin to provide a more accurate representation of the drainage conditions for hydrologic analysis. Each culvert basin and gutter basin was named based on the station of the culvert it drains to.

The culvert basin boundaries were developed by using both the 1’ contours from the topographic survey and the 10’ contours from the USGS maps beyond the topographic survey.

Due to the imprecise nature of the 10’ contour mapping, the site walk photos and Google Earth were referenced to help adjust the boundaries to better reflect the behavior of water on the slope. The interior boundary of each gutter basin was developed by following the 1’ contours to the limits of the topographic survey. The 10’ contour mapping, site visit photos, and Google Earth imagery were then used to help develop the remaining portion of the interior boundary to intersect with the gutter basin. Portions of the roadway which drain toward the inboard side were included in the basins. The basin maps are included in Appendix B. Note, gutter basins were only delineated, and the subsequent hydrologic analysis were only performed for the gutters that did not have enough capacity to pass the entire culvert flow.

• Time of Concentration: The time of concentration was calculated in a manner consistent with Section 2.6, Travel Time, of HDS-2. The total time of concentration used for each basin was a summation of the Sheet Flow travel time (derived from HDS-2, Equation 2.6), Shallow Concentrated Flow travel time (derived from HDS-2, Equation 2.7), and Channel Flow (derived from HDS-2, Equation 2.8). Key values to be used in time of concentration calculations are listed below.

– Maximum Sheet Flow Distance: 300 feet (HDS-2, Section 2.6.2.1)

– Mannings Roughness Coefficient (n) for Sheet Flow: 0.40 (HDS-2, Table 2.1, Woods, Light underbrush). Table 2.1 included in Appendix B.

– Intercept Coefficient (k) for Shallow Concentrated Flow: 0.076 (HDS-2, Table 2.2, Forest with heavy ground litter). Table 2.2 included in Appendix B.

– Mannings Roughness Coefficient (n) for Channels and Pipes: To be based on Table 3-4 of Hydraulic Engineering Circular No. 22 (HEC-22), Third Edition, Urban Drainage Design Manual, published by the U.S. Department of Transportation Federal Highway Administration. Table 3.4 included in Appendix B.

– Minimum time of concentration: 5 minutes (HEC-22, Section 7.2.2)

Calculations

Hydrologic calculations were performed using the FHWA Hydraulic Toolbox software, Version 4.2. A summary of the hydrologic calculations for both the culvert and gutter basins can be found in Appendix B. The Hydraulic Toolbox reports for each basin analyzed are included in Appendix F.

Hydraulics (4R) Design Criteria The Federal Lands Highway Project Development and Design Manual (PDDM) published by the U.S.

Department of Transportation Federal Highway Administration is the primary guideline for Hydraulic criteria on the project. The edition dated March 2018 was used.

Drainage facilities in the 4R portion of the project were analyzed in a manner consistent with the guidelines in the PDDM. For the purposes of hydraulic analysis, the roadway is considered a Low- Standard Road consistent with the guidelines established in Section 7.1.6.1 of the PDDM. Low standard roads have a design speed less than 45 mph or an ADT less than 1,500 or are not designated a critical access road. The Reds Meadow Road has a design speed of 20 mph, an ADT of 450, and is not considered a critical access road, therefore it is classified as a Low-Standard Road.

Exhibit 7.1A in the PDDM provides a quick reference guide to the key pieces of hydraulic criteria associated with commonly encountered drainage facilities. Exhibit 7.1A is included in Appendix C. Key hydraulic criteria that were employed on this project are summarized below.

• Pavement Drainage

– Design Storm: 10-year, 50-year in sumps

– Spread: Shoulder and half of one travel lane

– Inlet Clogging: 50% in sag or sump, 0% on grade

• Cross Culverts

– Design Storm: 25-year

– Minimum Size: 24-inches

• Inlets

– Design Storm: 10-year, 50-year in sumps

Gutters. Gutters were analyzed using the Hydraulic Toolbox. An initial analysis of all gutters was performed using the entire flow going to the culvert. Based on this analysis several gutters did not have adequate capacity. A secondary analysis was performed for the gutters that didn’t meet capacity. The secondary analysis used the capacity based on the gutter basin flow. See the hydrology section for an explanation of the gutter basin. Upon completion of the secondary analysis it was determined that all gutters adequately passed the design flows. A summary of the gutter calculations can be found in Appendix C. The Hydraulic Toolbox reports can be found in Appendix F.

Inlets. Multiple inlet types and configurations were evaluated to determine what types best meet the context of the project. Where the terrain allowed, CFL standard flared culvert ends were selected as the preferred entrance condition. When a flared end section was not feasible, a Caltrans Standard GMP inlet was selected to operate as a sump inlet beyond the edge of pavement. There are several locations where there is not enough space to accommodate a flared end section or a sump inlet. CFL on-grade inlets were utilized in these cases. Any bypass flow from the on-grade inlets was included in the evaluation of the downstream inlet. A CFL Standard 6A-6 inlet is being used for all on grade inlets. On grade inlets were analyzed using the FHWA Hydraulic Toolbox software, Version 4.2. The Caltrans GMP inlet was analyzed using equations 4-26 and 4-27 of HEC-22 for weir and orifice operation respectively.

See Appendix C for a summary of the inlet calculations.

Culverts The minimum proposed culvert diameter is 24 inches. All culverts were analyzed using the culvert Hydraulic Analysis Program HY-8 version 7.5 published by the Federal Highway Administration.

According to the HDS-5, as noted in the FHWA HY-8 User Manual, “flared end sections made of either metal or concrete, are the section commonly available from manufacturers. From limited hydraulic tests they are equivalent in operation to a headwall in both inlet and outlet control.” Based on this equivalency, headwalls were used as the inlet condition for the purposes of the HY-8 cross culvert analysis. Actual headwalls will not be utilized.

A summary of the culvert analysis can be found in Appendix C. All proposed culverts in the 4R segment adequately pass the design flows.

Existing culverts in the 3R portion of the project that are less the 24 inches in diameter will be removed and replaced with a standard sized culvert (24-inch minimum) if there is adequate cover between the crown of the culvert pipe and the roadway surface. If there is not adequate cover to accommodate a 24-inch culvert, the largest feasible culvert will be installed. In most situations this is an 18-inch culvert.

Channel grading and roadway re-profiling will not be performed to accommodate larger culverts. A summary of the 3R culverts can be found in Appendix D.

Riprap/Energy Dissipators. All new culverts in the 4R portion of the project will have an energy dissipator installed at the outlet. If the culvert has a gentle slope (<10%) and is discharging on native ground a standard energy dissipator per CFL Standard Drawing C251-50 was utilized. If the culvert was discharging on a fill slope, a modified version of Standard Drawing C251-50 was used. In the modified version, the riprap class, width, and depth remain the same, but the length of dissipator is extended to the toe of fill slope. If the culvert was discharging on a steep slope (>1:1.5) gabion baskets were used to dissipate the energy. The baskets extend from the culvert outlet to the toe of slope. A detail showing the gabion basket configuration can be found in the G series of the drawing set.

Floodplain The floodplain relative to this project was reviewed. Published FEMA maps (National Flood Hazard Layer FIRMette, dated June 29, 2018) show this project to be entirely in Zone D, which is classified as Area of Undetermined Flood Hazard. No impacts to the floodplain are anticipated as part of this project. The relevant FEMA Flood Maps are attached in Appendix E.

Environmental Impacts The California Construction General Permit requires best management practices (BMPs) for mitigating hydromodification associated with increases in the impervious area. The 3R segment will not increase the impervious area as the existing pavement is being replaced to the same roadway width. The 4R segment descends from the crest of the mountain to the valley floor and bisects a 1,300 acre drainage basin with steep forested terrain. The 4R segment includes 40 cross culverts that have drainage sub-basins that range in size from 2 acres to 120 acres and convey flows along the steep drainage courses which are accustom to high velocities. The 4R segment will increase the existing impervious area from

5.7 acres to 7.9 acres (+2.2 acres), which represents 0.17% of the overall drainage basin area. The increased impervious area is distributed across the 40 sub-basins resulting in negligible increases to their peak flows; therefore, the project is not anticipated to cause hydromodification impacts.

Conclusions This document provides a summary of the existing and proposed hydrologic and hydraulic conditions associated with the Reds Meadow Road Improvement Project. All proposed drainage facilities adequately comply with the established project criteria. There are no adverse effects to surrounding properties anticipated as a part of this project.

Appendix A – Location and Vicinity Maps

LEGEND

4R

3R

PACK STATION

DEVILS POSTPILE RE-ALIGNMENT (4R)

LIMITS OF 1'

CONTOURS3R PORTION

LIMITS OF 1'

CONTOURS

4R PORTION

MINARET VISTA ACCESS ROAD (3R)

HIGHWAY 203

REDS MEADOW IMPROVEMENTS

LOCATION MAP

JULY 2, 2018

Appendix B – Hydrology

Culvert Basin Hydrology Summary

10yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 11+42 0.3 3.00 43 42 42 1.08 1.38 1.62 1.00 1.20 1.50 16+49 0.3 6.00 45 45 45 1.04 1.33 1.56 1.90 2.40 2.80 27+82 0.3 11.00 45 45 45 1.04 1.33 1.55 3.50 4.40 5.20 29+31 0.3 2.00 33 33 33 1.24 1.59 1.86 0.80 1.00 1.10 33+71 0.3 12.00 42 43 43 1.08 1.37 1.60 3.90 5.00 5.80 38+02 0.3 5.00 29 29 29 1.33 1.71 1.99 2.00 2.60 3.00 40+52 0.3 4.00 29 29 29 1.34 1.71 2.01 1.60 2.10 2.40 45+86 0.3 7.00 31 31 31 1.29 1.65 1.93 2.70 3.50 4.10 47+00 0.3 3.00 30 29 29 1.33 1.70 1.99 1.20 1.50 1.80 48+24 0.3 2.00 33 33 33 1.25 1.60 1.87 0.80 1.00 1.10 50+51 0.3 14.00 58 59 59 0.90 1.13 1.32 3.80 4.80 5.60 51+37 0.3 4.00 48 48 48 1.01 1.29 1.50 1.20 1.60 1.80 52+67 0.3 4.00 44 43 43 1.06 1.35 1.59 1.30 1.60 1.90 54+28 0.3 9.00 48 49 49 1.00 1.27 1.48 2.70 3.50 4.00 60+50 0.3 14.00 38 38 38 1.15 1.46 1.70 4.90 6.20 7.20 63+20 0.3 12.00 120 120 120 0.58 0.74 0.87 2.10 2.70 3.20 67+15 0.3 15.00 24 54 54 0.94 1.19 1.40 4.30 5.40 6.30 67+90 0.3 2.00 26 26 26 1.42 1.82 2.12 0.90 1.10 1.30 71+16 0.3 12.00 54 54 54 0.94 1.19 1.39 3.40 4.30 5.10 78+48 0.3 42.00 61 61 61 0.87 1.11 1.30 11.10 14.10 16.50 83+36 0.3 13.00 53 53 53 0.94 1.20 1.41 3.70 4.70 5.50 86+31 0.3 16.00 51 51 51 0.97 1.23 1.44 4.70 6.00 7.00 90+05 0.3 5.00 45 45 45 1.05 1.33 1.56 1.60 2.00 2.40 92+24 0.3 4.00 37 37 37 1.17 1.49 1.74 1.40 1.80 2.10 94+54 0.3 9.00 45 46 46 1.04 1.32 1.54 2.80 3.60 4.20 96+86 0.3 5.00 47 47 47 1.02 1.30 1.52 1.50 2.00 2.30 99+11 0.3 14.00 43 43 43 1.07 1.37 1.60 4.50 5.80 6.80

104+80 0.3 57.00 104 104 104 0.63 0.80 0.94 10.90 13.90 16.30 109+81 0.3 65.00 78 78 78 0.75 0.96 1.13 14.80 18.90 22.10 112+03 0.3 2.00 25 25 25 1.45 1.86 2.18 0.90 1.10 1.30 115+08 0.3 15.00 35 35 35 1.21 1.54 1.81 5.50 7.00 8.20 119+55 0.3 27.00 90 90 90 0.69 0.88 1.03 5.60 7.20 8.40 121+67 0.3 7.00 33 33 34 1.25 1.58 1.84 2.60 3.30 3.90 124+40 0.3 3.00 28 28 28 1.37 1.75 2.05 1.20 1.60 1.90 133+00 0.3 43.00 104 103 103 0.63 0.81 0.95 8.30 10.50 12.30 133+21 0.3 42.00 69 69 69 0.81 1.03 1.21 10.20 13.10 15.30 137+69 0.3 120.00 105 105 105 0.63 0.80 0.94 22.90 29.10 34.20

C A (acres) tc (min) i (in/h) Basin Q (cfs)

NOAA Atlas 14, Volume 6, Version 2 Location name: Oakhurst, California, USA* Latitude: 37.6736°, Longitude: -119.0644°

Elevation: 9328.04 ft**

* source: ESRI Maps

** source: USGS

POINT PRECIPITATION FREQUENCY ESTIMATES

Sanja Perica, Sarah Dietz, Sarah Heim, Lillian Hiner, Kazungu Maitaria, Deborah Martin, Sandra Pavlovic, Ishani Roy, Carl Trypaluk, Dale Unruh, Fenglin Yan, Michael Yekta, Tan Zhao, Geoffrey

Bonnin, Daniel Brewer, Li-Chuan Chen, Tye Parzybok, John Yarchoan

NOAA, National Weather Service, Silver Spring, Maryland

PF_tabular | PF_graphical | Maps_&_aerials

PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1

Duration Average recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

5-min 1.32 (1.16-1.52)

1.91 (1.68-2.21)

2.70 (2.36-3.13)

3.36 (2.90-3.94)

4.28 (3.53-5.24)

5.00 (4.01-6.31)

5.76 (4.46-7.50)

6.55 (4.90-8.87)

7.68 (5.42-11.0)

8.58 (5.80-12.8)

10-min 0.948 (0.834-1.09)

1.37 (1.20-1.58)

1.94 (1.69-2.24)

2.41 (2.08-2.82)

3.07 (2.53-3.76)

3.59 (2.87-4.52)

4.13 (3.20-5.38)

4.70 (3.51-6.35)

5.50 (3.89-7.85)

6.14 (4.16-9.18)

15-min 0.764 (0.672-0.876)

1.10 (0.968-1.27)

1.56 (1.36-1.81)

1.94 (1.68-2.28)

2.48 (2.04-3.03)

2.89 (2.32-3.64)

3.33 (2.58-4.33)

3.79 (2.83-5.12)

4.44 (3.14-6.33)

4.96 (3.35-7.40)

30-min 0.518 (0.456-0.596)

0.752 (0.658-0.866)

1.06 (0.928-1.23)

1.32 (1.14-1.55)

1.68 (1.39-2.06)

1.97 (1.58-2.48)

2.26 (1.76-2.95)

2.58 (1.93-3.48)

3.01 (2.13-4.30)

3.37 (2.28-5.03)

60-min 0.345 (0.303-0.396)

0.499 (0.438-0.575)

0.706 (0.616-0.816)

0.878 (0.758-1.03)

1.12 (0.922-1.37)

1.31 (1.05-1.65)

1.50 (1.17-1.96)

1.71 (1.28-2.31)

2.00 (1.42-2.86)

2.24 (1.51-3.34)

2-hr 0.258 (0.226-0.296)

0.352 (0.309-0.406)

0.481 (0.420-0.556)

0.588 (0.508-0.688)

0.740 (0.610-0.906)

0.859 (0.689-1.08)

0.984 (0.764-1.28)

1.12 (0.835-1.51)

1.30 (0.922-1.86)

1.45 (0.984-2.17)

3-hr 0.215 (0.189-0.248)

0.289 (0.253-0.333)

0.388 (0.339-0.449)

0.472 (0.407-0.551)

0.588 (0.485-0.720)

0.681 (0.546-0.857)

0.777 (0.603-1.01)

0.880 (0.658-1.19)

1.02 (0.725-1.46)

1.14 (0.772-1.70)

6-hr 0.159 (0.140-0.183)

0.209 (0.184-0.241)

0.277 (0.241-0.320)

0.333 (0.287-0.389)

0.411 (0.340-0.504)

0.474 (0.380-0.597)

0.539 (0.418-0.702)

0.608 (0.454-0.821)

0.704 (0.498-1.00)

0.781 (0.529-1.17)

12-hr 0.112 (0.099-0.129)

0.152 (0.133-0.175)

0.205 (0.179-0.237)

0.249 (0.215-0.291)

0.310 (0.255-0.379)

0.357 (0.286-0.450)

0.406 (0.315-0.528)

0.457 (0.341-0.618)

0.528 (0.373-0.753)

0.584 (0.395-0.872)

24-hr 0.079 (0.070-0.091)

0.110 (0.098-0.126)

0.151 (0.134-0.174)

0.184 (0.162-0.214)

0.230 (0.195-0.276)

0.266 (0.221-0.326)

0.302 (0.245-0.380)

0.340 (0.268-0.439)

0.391 (0.296-0.528)

0.432 (0.316-0.603)

2-day 0.056 (0.049-0.064)

0.074 (0.066-0.086)

0.099 (0.088-0.115)

0.120 (0.105-0.139)

0.148 (0.126-0.178)

0.170 (0.142-0.209)

0.193 (0.156-0.242)

0.216 (0.171-0.280)

0.249 (0.188-0.335)

0.274 (0.200-0.383)

3-day 0.044 (0.039-0.050)

0.057 (0.051-0.066)

0.075 (0.067-0.087)

0.090 (0.079-0.105)

0.111 (0.094-0.133)

0.127 (0.106-0.156)

0.144 (0.117-0.181)

0.161 (0.127-0.208)

0.185 (0.140-0.249)

0.203 (0.149-0.284)

4-day 0.037 (0.033-0.042)

0.048 (0.042-0.055)

0.062 (0.055-0.072)

0.075 (0.066-0.087)

0.091 (0.078-0.110)

0.104 (0.087-0.128)

0.118 (0.096-0.148)

0.132 (0.104-0.170)

0.151 (0.114-0.203)

0.166 (0.121-0.232)

7-day 0.025 (0.023-0.029)

0.033 (0.030-0.038)

0.044 (0.039-0.050)

0.052 (0.046-0.061)

0.064 (0.054-0.077)

0.073 (0.061-0.089)

0.082 (0.067-0.103)

0.092 (0.072-0.119)

0.105 (0.079-0.141)

0.115 (0.084-0.161)

10-day 0.020 (0.018-0.023)

0.026 (0.023-0.030)

0.035 (0.031-0.040)

0.042 (0.037-0.048)

0.051 (0.043-0.061)

0.058 (0.048-0.071)

0.065 (0.053-0.082)

0.073 (0.057-0.094)

0.083 (0.063-0.112)

0.091 (0.066-0.127)

20-day 0.013 (0.011-0.015)

0.017 (0.015-0.020)

0.023 (0.020-0.026)

0.027 (0.024-0.032)

0.033 (0.028-0.040)

0.038 (0.031-0.046)

0.042 (0.034-0.053)

0.046 (0.037-0.060)

0.052 (0.040-0.071)

0.057 (0.042-0.079)

30-day 0.010 (0.009-0.012)

0.014 (0.012-0.016)

0.018 (0.016-0.021)

0.022 (0.019-0.025)

0.026 (0.022-0.032)

0.030 (0.025-0.036)

0.033 (0.027-0.041)

0.036 (0.029-0.047)

0.040 (0.031-0.055)

0.044 (0.032-0.061)

45-day 0.009 (0.008-0.010)

0.011 (0.010-0.013)

0.015 (0.013-0.017)

0.018 (0.016-0.021)

0.021 (0.018-0.025)

0.024 (0.020-0.029)

0.026 (0.021-0.033)

0.029 (0.023-0.037)

0.032 (0.024-0.043)

0.034 (0.025-0.047)

60-day 0.008 (0.007-0.009)

0.010 (0.009-0.012)

0.013 (0.012-0.015)

0.015 (0.014-0.018)

0.018 (0.016-0.022)

0.020 (0.017-0.025)

0.022 (0.018-0.028)

0.024 (0.019-0.031)

0.027 (0.020-0.036)

0.028 (0.021-0.040)

1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).

Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.

Please refer to NOAA Atlas 14 document for more information.

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Maps & aerials

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Large scale terrain

Large scale map

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100km

60mi

100km

60mi

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National Weather Service National Water Center

1325 East West Highway Silver Spring, MD 20910

Questions?: HDSC.Questions@noaa.gov

Disclaimer

100km

60mi

Page 4 of 4Precipitation Frequency Data Server

Gutter Basin Hydrology Summary

2‐foot gutter 10yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr

33+71 Gutter 0.3 4.00 29.07 28.82 28.69 1.34 1.72 2.02 1.60 2.10 2.40 50+51 Gutter 0.3 1.00 19.83 19.41 19.19 1.67 2.15 2.53 0.50 0.70 0.80 60+50 Gutter 0.3 6.00 21.71 22.49 22.95 1.58 1.98 2.29 2.90 3.60 4.20 63+20 Gutter 0.3 2.00 16.37 16.12 15.99 1.85 2.38 2.80 1.10 1.40 1.70 67+15 Gutter 0.3 2.00 18.41 18.03 17.84 1.74 2.24 2.63 1.10 1.40 1.60 71+16 Gutter 0.3 1.00 19.04 18.41 18.09 1.70 2.22 2.61 0.50 0.70 0.80 94+54 Gutter 0.3 2.00 21.27 21.05 20.94 1.60 2.06 2.41 1.00 1.20 1.50 99+11 Gutter 0.3 3.00 23.11 22.95 22.87 1.53 1.96 2.29 1.40 1.80 2.10 104+80 Gutter 0.3 4.00 22.87 22.59 23.83 1.54 1.98 2.24 1.90 2.40 2.70 109+81 Gutter1 0.3 7.00 25.68 25.39 25.24 1.44 1.85 2.17 3.10 3.90 4.60 109+81 Gutter2 0.3 3.00 25.00 24.87 24.80 1.46 1.87 2.19 1.30 1.70 2.00 121+67 Gutter 0.3 1.00 19.86 19.45 19.24 1.67 2.15 2.53 0.50 0.60 0.80 133+21 Gutter 0.3 3.00 26.84 26.51 26.34 1.40 1.80 2.12 1.30 1.60 1.90

C A (acres) tc (min) i (in/h) Q (cfs)

(2.6)

HDS-2, TABLE 2.1

(2.7)

(2.8)

HDS-2, TABLE 2.2

3-14

Table 3-4. Typical Range of Manning's Coefficient (n) for Channels and Pipes.

Conduit Material Manning's n*

Closed Conduits

Concrete pipe 0.010 - 0.015

CMP 0.011 - 0.037

Plastic pipe (smooth) 0.009 - 0.015

Plastic pipe (corrugated) 0.018 - 0.025

Pavement/gutter sections 0.012 - 0.016

Small Open Channels

Concrete 0.011 - 0.015

Rubble or riprap 0.020 - 0.035

Vegetation 0.020 - 0.150

Bare Soil 0.016 - 0.025

Rock Cut 0.025 - 0.045

Natural channels (minor streams, top width at flood stage <30 m (100 ft))

Fairly regular section 0.025 - 0.050

Irregular section with pools 0.040 - 0.150

*Lower values are usually for well-constructed and maintained (smoother) pipes and channels

HEC-22, TABLE 3-4

HDS-2, TABLE 5.7

Appendix C – Hydraulics

Hydrology and Hydraulics December 2012

7-2 General

Exhibit 7.1-A QUICK REFERENCE GUIDE

Topic Standard Criteria Method Reference

HYDROLOGY

Peak Flow Methods

HDS 2,

HEC 22,

NEH Part 630, TR-55, TM 4-A6, Bulletin 17B

Hydrograph Methods

HDS 2,

WinTR-55

ROADWAY HYDRAULICS

Culverts Capacity Design and

Stability Design:

High-Standard road:

50-year flood Low-Standard road:

25-year flood Roadside ditch:

10-year flood

Capacity Check Flood:

Evaluate potential for adverse impacts for the overtopping flood

Exception:

See Floodplain Encroachments

Headwater New: WSEL bottom of aggregate base layer

Existing: WSEL shoulder hinge point.

HW/D ratio:

48” [1200 mm] or smaller

= 1.5 Larger than 48” [1200 mm]

= 1.2

Other: WSEL limited by unacceptable hazards to human life or property.

Minimum Size:

Cross-road culvert =

24” [600 mm] Parallel culvert =

18” [450 mm]

Slope:

Stream Crossings:

Match streambed Ditch Relief:

Min. = 2%, Max. = 10%

Cover

Pipe Anchors:

Concrete > 10% slope, Metal > 25% slope

HDS 5,

HEC 14

nl058442 Highlight nl058442 Highlight nl058442 Highlight nl058442 Highlight

NL058442

Text Box Exhibit 7.1-A PDDM

Exhibit 7.1-A QUICK REFERENCE GUIDE (Continued)

General 7-3

Topic Standard Criteria Method Reference

Ditches Capacity Design:

10-year flood

Stability Design:

Permanent Linings

10-year flood Temporary Linings:

2-year flood

Depth:

New: WSEL bottom of aggregate base layer Existing: WSEL shoulder hinge point

Slope:

Min. = 0.5%

Stability:

Permissible shear stress

HDS 3,

HEC 15

Pavement Drainage

Capacity Design:

10-year flood, 50-year in sumps

Spread:

High-Standard road:

3 ft [900 mm] into one travel lane, Low-Standard road:

Half of one travel lane

Depth:

On-grade and Sags:

Allowable spread, not to exceed curb height, Sumps and Parking Areas:

6” [150 mm].

Inlet Clogging Factor:

Grate Inlets in sag or sump, 50%

HEC 21,

HEC 22

Storm Drains Capacity Design:

10-year flood, 50-year in sumps

Minimum Size:

15” [375 mm].

Minimum Slope:

Pipe- 3 ft/sec [0.9 m/s]

HEC 22

Outlet Protection HEC 14

Alternative Pipe Materials

Service Life:

50-years

Minimum Pipe Classification:

RCP: Class II Metal: 0.064” [1.63 mm]

FHWA-RD-97-

140, Caltrans Chapter 850 nl058442 Highlight nl058442 Highlight nl058442 Highlight nl058442 Highlight nl058442 Highlight nl058442 Highlight nl058442 Highlight

7-4 General

Topic Standard Criteria Method Reference

RIVER HYDRAULICS

Floodplain Encroachment

Design Flood:

100-year

Check Flood:

Overtopping flood, not to exceed 500-year

FEMA Regulated Base Floodplain with Detailed Study:

With floodway defined, no floodway encroachment

With no defined floodway or no detailed study, rise 1.0 ft [0.3 m]

Unregulated Base Floodplain:

Rise 1.0 ft [0.3 m]

HEC-RAS

Scour and Stream Stability

HDS 6, HEC 18,

HEC 20,HEC 23

Bridged Waterways

Capacity Design:

Design Flood:

50-year Check Flood:

Greater of overtopping flood or 100-year, not to exceed 500-year

Stability Design:

Design Flood:

100-year Check Flood:

500-year

Freeboard:

2.0 ft [0.6 m], greater where potential for debris or ice

Stability Design:

Design Flood:

Normal geotechnical and structural safety factors

Check Flood:

Safety Factor 1.0

HEC-RAS,

HEC 18,

HEC 20,

HEC 23

Longitudinal Embankments

Capacity Design:

High-Standard road:

50-year flood Low-Standard road:

25-year flood Check Flood:

Greater of overtopping or 100-year

Stability Design:

High-Standard road:

50-year flood Low-Standard road:

25-year flood

Capacity Design:

Freeboard:

2.0 ft [0.6 m]

HEC 14,

HEC 23

General 7-5

Topic Standard Criteria Method Reference

Retaining Walls Longitudinal Flow Scour:

Wall height > 6.5 ft [2 m]:

100-year Wall height 6.5 ft [2 m] on High-Standard road:

50-year

Wall height 6.5 ft [2 m] on Low-Standard road:

25-year

Pipe Penetrations:

High-Standard road:

50-year Low-Standard road:

25-year

Stability Design:

Normal geotechnical and structural safety factors

HEC 14,

HEC 23

Low-Water Crossings

Allowable Uses:

feature

Capacity Design:

Vented: 10-year

Stability Design:

25-year flood

Capacity Design:

Vented:

No overtopping

Stability Design

Low Volume Roads Engineering, HDS 5, HEC 20, HEC 23

Channel Changes

Capacity Design:

Duplicate existing stream characteristics

Stability Design:

High-Standard road:

50-year Low-Standard road:

25-year

Capacity Design

Stability Design

HDS 6,

HEC 20,

HEC 23

Scour and Stream Instability Counter-measures

HDS 6,

HEC 11,

HEC 14,

HEC 23

Energy Dissipators

Design Standard:

Range of discharges

Design Guidance:

Natural or stable channel velocity

HEC 14

7-6 General

Topic Standard Criteria Method Reference

COASTAL HYDRAULICS

General HEC 25

Hydrology HEC 25, EM 1110-2-

Scour and Stream Stability

HDS 6,

HEC 18,

HEC 20,

HEC 23,

HEC 25

Bridged Waterways

Capacity Design:

50-year storm tide plus wave height

Stability Design:

Design Flood:

100-year Check Flood:

500-year

Design Criteria Same as riverine except freeboard measurement reference datum

HDS 6,

HEC 11,

HEC 23,

HEC 25

Roadway Embankments

Capacity Design:

High-Standard road:

50-year storm tide plus wave height

Low-Standard road:

Highest astronomic tide plus 25-year wave height

Stability Design:

High-Standard road:

50-year storm tide plus wave height

Low-Standard road:

25-year wave

Capacity Design:

High Standard road Freeboard: 2.0 ft [0.6 m]

Stability Design

HEC 14,

HEC 23

Scour and Stream Instability Counter-measures

HDS 6,

HEC 11,

HEC 14,

HEC 23

Gutter Summary ‐ Based on Culvert Basins Design Storm: 10‐year (50‐year for sumps)

10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr Compliant?

11+42 4.13% ‐2.30% 12.5% 26 2 2 1.0 1.2 1.5 1.51 1.66 1.76 3.00 3.00 3.00 Yes 16+49 7.71% 3.40% 12.5% 26 2 8.5 1.9 2.4 2.8 1.72 1.89 2.02 2.89 2.96 3.01 Yes 27+82 7.51% 2.00% 12.5% 26 2 8.5 3.5 4.4 5.2 3.11 4.19 4.97 3.27 3.53 3.71 Yes 29+31 7.84% 2.00% 12.5% 26 2 8.5 0.8 1.0 1.1 1.3 1.7 2.2 2.1 2.7 3.3 1.79 1.97 2.73 2.95 2.99 3.18 Yes 33+71 7.83% ‐2.43% 12.5% 26 2 2 3.9 5.0 5.8 0.2 0.8 1.2 4.1 5.8 7.0 Infinite Infinite Infinite 3.14 3.20 3.23 No, see gutter basin analysis 38+02 7.84% ‐0.16% 12.5% 26 2 2 2.0 2.6 3.0 0.0 0.9 1.0 2.0 3.5 4.0 1.76 Infinite Infinite 3.00 3.10 3.13 Yes 40+52 6.30% 3.50% 12.5% 26 2 8.5 1.6 2.1 2.4 1.6 2.1 2.4 1.68 1.84 1.95 2.86 2.93 2.98 Yes 45+86 8.99% 2.40% 12.5% 26 2 8.5 2.7 3.5 4.1 0.0 0.1 0.5 2.7 3.6 4.6 1.92 2.82 3.98 2.98 3.20 3.48 Yes 47+00 8.62% 2.40% 12.5% 26 2 8.5 1.2 1.5 1.8 1.2 1.5 1.8 1.43 1.56 1.66 2.86 2.90 2.92 Yes 48+24 8.03% 2.00% 12.5% 26 2 8.5 0.8 1.0 1.1 1.21 1.33 1.41 2.81 2.84 2.86 Yes 50+51 9.37% ‐0.05% 12.5% 26 2 2 3.8 4.8 5.6 Infinite Infinite Infinite 3.02 3.03 3.03 No, see gutter basin analysis 51+37 9.84% 3.80% 12.5% 26 2 8.5 1.2 1.6 1.8 1.40 1.53 1.62 2.97 2.97 2.98 Yes 52+67 8.85% ‐3.80% 12.5% 26 2 2 1.3 1.6 1.9 1.45 1.59 1.69 3.00 3.00 3.00 Yes 54+28 9.36% ‐2.27% 12.5% 26 2 2 2.7 3.5 4.0 1.91 Infinite Infinite 3.00 3.02 3.02 Yes 60+50 8.63% ‐2.00% 12.5% 26 2 2 4.6 6.2 7.2 Infinite Infinite Infinite 3.16 3.20 3.22 No, see gutter basin analysis 63+20 6.80% ‐2.00% 12.5% 26 2 2 2.1 2.7 3.2 0.0 1.1 1.0 2.1 3.8 4.2 Infinite Infinite Infinite 3.17 3.26 3.28 No, see gutter basin analysis 67+15 6.58% ‐3.60% 12.5% 26 2 2 4.3 5.4 6.3 0.8 2.5 2.9 5.1 7.9 9.2 Infinite Infinite Infinite 3.19 3.26 3.28 No, see gutter basin analysis 67+90 7.60% ‐3.60% 12.5% 26 2 2 0.9 1.1 1.3 0.4 2.4 3.6 1.3 3.5 4.9 1.50 Infinite Infinite 3.00 3.10 3.17 Yes 71+16 8.01% ‐3.60% 12.5% 26 2 2 3.4 4.3 5.1 0.0 0.6 2.0 3.4 4.9 7.1 Infinite Infinite Infinite 3.09 3.16 3.22 No, see gutter basin analysis 78+48 9.34% 5.00% 12.5% 26 2 8.5 11.1 14.1 16.5 0.0 0.0 0.9 11.1 14.1 17.4 4.80 5.43 6.01 4.68 5.06 5.40 Yes 83+36 8.47% 3.00% 12.5% 26 2 8.5 3.6 4.7 5.5 2.75 3.55 4.07 3.27 3.56 3.75 Yes 86+31 1.30% 3.57% 12.5% 26 2 8.5 4.7 6.0 7.0 6.15 6.98 7.55 4.78 5.13 5.38 Yes 90+05 2.52% 5.20% 12.5% 26 2 8.5 1.6 2.0 2.4 1.6 2.0 2.4 1.99 2.43 2.74 2.99 3.27 3.46 Yes 92+24 3.50% ‐2.62% 12.5% 26 2 2 1.4 1.8 2.1 0.00 0.05 0.10 1.4 1.8 2.2 1.79 1.98 Infinite 3.00 3.00 3.08 Yes 94+54 3.73% ‐4.80% 12.5% 26 2 2 2.8 3.6 4.2 2.8 3.6 4.2 Infinite Infinite Infinite 3.14 3.18 3.20 No, see gutter basin analysis 96+86 5.33% ‐2.40% 12.5% 26 2 2 1.5 2.0 2.3 0.8 1.5 2.1 2.3 3.5 4.4 1.99 Infinite Infinite 3.00 3.14 3.18 Yes 99+11 5.55% ‐3.20% 12.5% 26 2 2 4.5 5.8 6.8 0.3 1.0 1.9 4.8 6.8 8.7 Infinite Infinite Infinite 3.19 3.25 3.29 No, see gutter basin analysis

104+80 6.60% ‐4.80% 12.5% 26 2 2 10.9 13.9 16.3 10.9 13.9 16.3 Infinite Infinite Infinite 3.06 3.06 3.07 No, see gutter basin analysis 109+81 8.13% ‐4.80% 12.5% 26 2 2 14.8 18.9 22.1 14.8 18.9 22.1 Infinite Infinite Infinite 3.34 3.38 3.41 No, see gutter basin analysis 112+03 7.30% 2.00% 12.5% 26 2 2 0.9 1.1 1.3 0.9 1.1 1.3 1.30 1.43 1.52 3.00 2.99 3.00 Yes 115+08 8.51% 2.00% 12.5% 26 2 8.5 5.5 7.0 8.2 5.5 7.0 8.2 4.94 6.06 6.79 3.70 3.97 4.15 Yes 119+55 7.56% 2.00% 12.5% 26 2 8.5 5.6 7.2 8.4 5.33 6.46 7.20 3.80 4.07 4.25 Yes

119+55 inlet 1 7.47% 2.00% 12.5% 26 2 8.5 2.6 3.2 3.8 5.36 6.48 7.26 3.81 4.08 4.26 Yes 121+67 5.32% ‐3.80% 12.5% 26 2 2 2.6 3.3 3.9 0.6 1.3 1.8 3.2 4.6 5.7 Infinite Infinite Infinite 3.12 3.19 3.22 No, see gutter basin analysis 124+40 8.33% 2.00% 12.5% 26 2 8.5 1.2 1.6 1.9 1.2 1.6 1.9 1.48 1.62 1.72 2.88 2.91 2.93 Yes 133+00 4.65% 3.50% 12.5% 26 2 8.5 8.3 10.5 12.3 0.4 0.6 0.8 8.7 11.1 13.1 6.15 6.99 7.59 4.74 5.10 5.35 Yes 133+21 5.43% ‐4.54% 12.5% 26 2 2 10.2 13.1 15.3 10.2 13.1 15.3 Infinite Infinite Infinite 3.06 3.06 3.07 No, see gutter basin analysis 137+69 2.90% 0.34% 12.5% 26 2 8.5 22.9 29.1 34.2 4.23 4.63 4.91 12.68 13.88 14.75 Yes

NOTE: Where spread width is infinite, a secondary analysis was performed with just the gutter basin flow.

Road Longitudinal Slope

Road Cross‐ slope

Gutter Cross‐slope

Depth at Curb (in)Spread Width (ft)Gutter Width (ft)

Allowable Spread (ft)

Road Width (ft)

Basin Q (cfs) Bypass Q From Upstream (cfs) Total Q (cfs)

Gutter Summary ‐ Based on Gutter Basins Design Storm: 10‐year (50‐year for sumps)

10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr Compliant?

33+71 7.83% ‐2.43% 12.5% 26 2 2 1.60 2.10 2.40 0.21 0.80 1.24 1.81 2.90 3.64 1.69 Infinite Infinite 3.00 3.02 3.11 No Yes 50+51 9.37% ‐0.05% 12.5% 26 2 2 0.50 0.70 0.80 0.50 0.70 0.80 1.01 1.11 1.18 3.00 3.00 3.00 No Yes 60+50 8.63% ‐2.00% 12.5% 26 2 2 2.90 3.60 4.20 2.90 3.60 4.20 1.98 Infinite Infinite 3.00 3.09 3.13 No Yes 63+20 9.61% ‐2.00% 12.5% 26 2 2 1.10 1.40 1.70 0.00 1.14 0.98 1.10 2.54 2.68 1.36 1.85 1.89 3.00 3.00 3.00 No Yes 67+15 6.58% ‐3.60% 12.5% 26 2 2 1.10 1.40 1.60 0.82 2.49 2.88 1.92 3.89 4.48 1.78 Infinite Infinite 3.00 3.14 3.17 No Yes 71+16 6.58% ‐3.60% 12.5% 26 2 2 0.50 0.70 0.80 0.00 0.58 1.96 0.50 1.28 2.76 1.04 1.47 1.96 3.00 3.00 3.00 No Yes 94+54 3.73% ‐4.80% 12.5% 26 2 2 1.00 1.20 1.50 1.00 1.20 1.50 1.54 1.69 1.79 3.00 3.00 3.00 No Yes 99+11 5.50% ‐4.80% 12.5% 26 2 2 1.40 1.80 2.10 0.34 1.04 1.93 1.74 2.84 4.03 1.78 Infinite Infinite 3.00 3.09 3.16 No Yes

104+80 6.60% ‐4.80% 12.5% 26 2 2 1.90 2.40 2.70 1.90 2.40 2.70 1.77 1.94 Infinite 3.00 3.00 3.01 No Yes 109+81 (1) 8.19% ‐4.80% 12.5% 26 2.7 2.7 3.10 3.90 4.60 3.10 3.90 4.60 2.04 2.24 2.38 4.05 4.05 4.05 No Yes 109+81 (2) 7.22% 0.00% 12.5% 26 2 2 1.30 1.70 2.00 1.30 1.70 2.00 1.53 1.68 1.78 3.00 3.00 3.00 No Yes

121+67 5.30% ‐3.80% 12.5% 26 2 2 0.50 0.60 0.80 0.57 1.29 1.80 1.07 1.89 2.60 1.48 1.84 Infinite 3.00 3.00 3.06 No Yes 129+60 4.80% 1.00% 12.5% 26 2 8.5 2.60 3.30 3.90 0.00 0.00 0.03 2.60 3.30 3.93 3.45 5.55 6.93 3.17 3.43 3.59 No Yes 133+21 5.43% ‐4.54% 12.5% 26 2 2 1.30 1.60 1.90 1.30 1.60 1.90 1.59 1.75 1.85 3.00 3.00 3.00 No Yes

*Allowable spread per the PDDM is shoulder plus 1/2 travel lane. Due to super elevation of roadway actual spread will be infinite once it exceeds capacity of gutter. In these situations allowable spread is defined as gutter width.

Spread Width (ft) Depth at Curb (in) Flow Overtopping Road

Road Longitudinal Slope

Road Cross‐slope

Gutter Cross‐slope

Road Width (ft)

Gutter Width (ft)

Allowable Spread (ft)*

Basin Q (cfs) Bypass Q From Upstream (cfs) Total Q (cfs)

GMP Inlet Summary ‐ 4R Section Design Storm: 50‐year

10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 11+42 GMP 1.43 9162.08 9161.50 0.58 1.0 1.2 1.5 1.0 1.2 1.5 7.6 Yes 16+49 GMP 1.12 9124.69 9124.13 0.56 1.9 2.4 2.8 1.9 2.4 2.8 7.2 Yes 27+82 On‐grade See on grade inlet summary 29+31 On‐grade See on grade inlet summary 33+71 On‐grade 1st See on grade inlet summary 33+71 On‐grade 2nd See on grade inlet summary 38+02 GMP 0.88 8959.88 8959.33 0.55 2.0 2.6 3.0 0.0 0.9 1.0 2.0 3.5 4.0 7.1 Yes 40+52 GMP 1.53 8945.16 8943.63 1.53 1.6 2.1 2.4 1.6 2.1 2.4 17.6 Yes 45+86 GMP 1.09 8897.48 8896.39 1.09 2.7 3.5 4.1 0.0 0.1 0.5 2.7 3.6 4.6 14.8 Yes 47+00 GMP 0.27 8887.27 8887.00 0.27 1.2 1.5 1.8 1.2 1.5 1.8 2.4 Yes 48+24 On‐grade See on grade inlet summary 50+51 GMP 1.87 8857.99 8856.12 1.87 3.8 4.8 5.6 3.8 4.8 5.6 19.4 Yes 51+37 On‐grade See on grade inlet summary 52+67 GMP 0.90 8839.04 8838.21 0.83 1.3 1.6 1.9 1.3 1.6 1.9 13.0 Yes 54+28 GMP 1.34 8825.30 8823.96 1.34 2.7 3.5 4.0 2.7 3.5 4 16.5 Yes 60+50 On‐grade 1st See on grade inlet summary 60+50 On‐grade 2nd See on grade inlet summary 63+20 On‐grade See on grade inlet summary 67+15 On‐grade 1st See on grade inlet summary 67+15 On‐grade 2nd See on grade inlet summary 67+90 On‐grade See on grade inlet summary 71+16 On‐grade 1st See on grade inlet summary 71+16 On‐grade 2nd See on grade inlet summary 78+48 GMP 1.69 8622.94 8621.25 1.69 11.1 14.1 16.5 0.0 0.0 0.6 11.1 14.1 17.1 18.5 Yes 83+36 GMP 1.97 8584.29 8582.32 1.97 3.7 4.7 5.5 3.7 4.7 5.5 20.0 Yes 86+31 GMP 1.89 8583.35 8582.80 0.55 4.7 6.0 7.0 4.7 6 7 7.1 Yes 90+05 On‐grade See on grade inlet summary 92+24 GMP 0.98 8567.90 8566.92 0.98 1.4 1.8 2.1 0.0 0.0 0.1 1.4 1.8 2.2 14.1 Yes 94+54 On‐grade See on grade inlet summary 96+86 On‐grade See on grade inlet summary 99+11 GMP 1.11 8535.50 8534.39 1.11 4.5 5.8 6.8 0.3 1.0 1.9 4.8 6.8 8.73 15.0 Yes

104+80 GMP 0.93 8500.55 8497.86 2.69 10.9 13.9 16.3 10.9 13.9 16.3 23.1 Yes 109+81 Flaired End See culvert summary 112+03 On‐grade See on grade inlet summary 115+08 GMP 1.73 8420.73 8419.00 1.73 5.5 7.0 8.2 5.5 7.0 8.2 18.7 Yes 119+55 On‐grade 1st See on grade inlet summary 119+55 On‐grade 2nd See on grade inlet summary 121+67 GMP 0.91 8376.00 8375.09 0.91 2.6 3.3 3.9 0.6 1.3 1.8 3.2 4.6 5.68 13.6 Yes 124+40 On‐grade See on grade inlet summary 129+60 On‐grade See on grade inlet summary 133+00 GMP 2.23 8317.20 8316.31 0.89 8.3 10.5 12.3 0.4 0.6 0.8 8.7 11.1 13.1 13.4 Yes 133+21 GMP 2.68 8317.20 8316.00 1.20 10.2 13.1 15.3 10.2 13.1 15.3 15.6 Yes 137+69 Flaired End See culvert summary

Inlet capacity (cfs)

Capacity > Flow?Culvert STA Inlet Type d (ft) @ inlet High (min) Elev Inlet Elev d min (ft) Total Q (cfs)Basin Q (cfs) Additional Q (cfs) From Bypass

On‐grade Inlet Summary ‐ 4R Section Design Storm: 10‐year Grate Type: Curved Vane

10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 10 yr 25 yr 50 yr 27+82 On‐grade 3 1.833 3 2 3.5 4.4 5.2 3.5 4.4 5.2 2.2 2.7 3.0 1.3 1.7 2.2 63% 60% 58% 29+31 On‐grade 3 1.833 3 2 0.8 1.0 1.1 1.3 1.7 2.2 2.1 2.7 3.3 1.9 1.9 2.1 0.2 0.8 1.2 90% 70% 63% 33+71 On‐grade 1st 3 1.833 3 2 3.9 5.0 5.8 0.2 0.8 1.2 4.1 5.8 7.0 3.0 3.0 3.0 1.1 2.8 4.0 73% 52% 43% 33+71 On‐grade 2nd 3 1.833 3 2 0.0 0.0 0.0 1.1 2.8 4.0 1.1 2.8 4.0 1.1 1.9 3.0 0.0 0.9 1.0 100% 67% 75% 48+24 On‐grade 3 1.833 3 2 0.8 1.0 1.1 0.8 1.0 1.1 0.8 1.0 1.1 0.0 0.0 0.0 100% 100% 100% 51+37 On‐grade 3 1.833 3 2 1.2 1.6 1.8 1.2 1.6 1.8 1.2 1.6 1.8 0.0 0.0 0.0 100% 100% 100% 60+50 On‐grade 1st 3 1.833 3 2 4.9 6.2 7.2 4.9 6.2 7.2 3.1 3.1 3.2 1.7 3.0 4.1 64% 51% 44% 60+50 On‐grade 2nd 3 1.833 3 2 0.0 0.0 0.0 1.7 3.0 4.1 1.7 3.0 4.1 1.7 2.0 3.1 0.0 1.0 0.9 100% 67% 77% 63+20 On‐grade 3 1.833 3 2 2.1 2.7 3.2 0.0 1.0 0.9 2.1 3.7 4.1 1.9 2.8 2.8 0.2 1.1 1.3 92% 75% 67% 67+15 On‐grade 1st 3 1.833 3 2 4.3 5.4 6.3 0.2 1.1 1.3 4.5 6.5 7.6 2.7 2.8 2.8 1.7 3.7 4.9 61% 43% 36% 67+15 On‐grade 2nd 3 1.833 3 2 0.0 0.0 0.0 1.7 3.7 4.9 1.7 3.7 4.9 1.7 2.7 2.7 0.0 1.0 2.1 100% 74% 56% 67+90 On‐grade 3 1.833 3 2 0.9 1.1 1.3 0.0 1.0 2.1 0.9 2.1 3.4 0.9 1.9 2.9 0.0 0.1 0.5 100% 94% 86% 71+16 On‐grade 1st 3 1.833 3 2 3.4 4.3 5.1 0.0 0.1 0.5 3.4 4.4 5.6 3.0 3.1 3.1 0.4 1.3 2.5 89% 69% 55% 71+16 On‐grade 2nd 3 1.833 3 2 0.0 0.0 0.0 0.4 1.3 2.5 0.4 1.3 2.5 0.4 1.3 2.0 0.0 0.0 0.6 100% 100% 78% 90+05 On‐grade 3 1.833 3 2 1.6 2.0 2.4 1.6 2.0 2.4 1.6 2.0 2.3 0.0 0.0 0.1 100% 98% 96% 94+54 On‐grade 3 1.833 3 2 2.8 3.6 4.2 2.8 3.6 4.2 2.1 2.1 2.1 0.8 1.5 2.1 73% 58% 49% 96+86 On‐grade 3 1.833 3 2 1.5 2.0 2.3 0.8 1.5 2.1 2.3 3.5 4.4 2.0 2.5 2.5 0.3 1.0 1.9 85% 70% 56%

112+03 On‐grade 3 1.833 3 2 0.9 1.1 1.3 0.9 1.1 1.3 0.9 1.1 1.3 0.0 0.0 0.0 100% 100% 100% 119+55 On‐grade 1st 3 1.833 3 2 5.6 7.2 8.4 5.6 7.2 8.4 3.2 3.7 4.0 2.5 3.5 4.4 56% 51% 47% 119+55 On‐grade 2nd 3 1.833 3 9 0.0 0.0 0.0 2.5 3.5 4.4 2.5 3.5 4.5 1.9 2.2 2.7 0.6 1.3 1.8 78% 63% 60% 124+40 On‐grade 3 1.833 3 2 1.2 1.6 1.9 1.2 1.6 1.9 1.2 1.6 1.8 0.0 0.0 0.0 100% 100% 98% 129+60 On‐grade 3 1.833 3 2 2.6 3.3 3.9 0.00 0.00 0.03 2.6 3.3 3.9 2.2 2.7 3.1 0.4 0.6 0.8 85% 83% 80%

Inlet Type Bypass Q From Upstream (cfs)Basin Q (cfs)

Culvert STA EfficiencyTotal Q (cfs)

Grate Length (ft) Grate Width (ft) Gutter Width (ft) Intercepted Flow (cfs) Bypass Flow (cfs)

Inlet Length (ft)

Culvert Discharge Summary ‐ 4R Section

Design Storm: 25‐year

11+42 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 48.20 1.2 1.2 1.2 0.0 9157.20 9156.72 9157.76 0.51 9162.08 2.95 No

16+49 Corrugated Steel, Circular, Straight NA 24 0.024 1.00% 34.18 2.4 2.4 2.4 0.0 9120.63 9120.28 9121.44 0.74 9124.69 3.56 No

27+82 Corrugated Steel, Circular, Straight 18 24 0.024 5.87% 32.22 2.7 2.7 2.7 0.0 9036.91 9035.03 9037.65 0.74 9040.83 5.91 No

29+31 Corrugated Steel, Circular, Straight 18 24 0.024 9.59% 36.30 1.9 1.9 1.9 0.0 9025.98 9022.24 9026.58 0.60 9029.90 6.42 No

33+71 (up sta) Corrugated Steel, Circular, Straight ‐

24 0.024 1.00% 5.00 3.0 3.0 3.0 0.0 8990.26 8990.21 8991.18 0.83 8995.55 3.77 No

33+71 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 31.27 1.9 3.0 4.9 4.9 0.0 8990.18 8989.87 8991.38 1.08 8994.86 4.36 No

37+75 Corrugated Steel, Circular, Straight 15 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

38+02 Corrugated Steel, Circular, Straight 12 24 0.024 5.34% 41.04 3.5 3.5 3.5 0.0 8955.55 8953.37 8956.41 0.86 8959.88 6.14 No

40+52 Corrugated Steel, Circular, Straight NA 24 0.024 4.84% 49.24 1.9 1.9 1.9 0.0 8939.94 8937.56 8940.57 0.63 8944.98 5.02 No

45+86 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 35.07 3.5 0.1 3.6 3.6 0.0 8892.89 8892.54 8893.91 0.92 8897.48 4.00 No

47+00 Corrugated Steel, Circular, Straight NA 24 0.024 1.00% 34.59 1.5 1.5 1.5 0.0 8883.50 8883.15 8884.14 0.58 8888.27 3.12 No

48+24 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 29.98 1.0 1.0 1.0 0.0 8873.82 8873.52 8874.34 0.47 8878.18 2.83 No

50+51 Corrugated Steel, Circular, Straight 15 24 0.024 6.01% 39.56 4.8 4.8 4.8 0.0 8852.27 8851.84 8853.45 1.07 8857.99 4.34 No

51+37 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 35.45 1.6 1.6 1.6 0.0 8846.98 8846.59 8847.64 0.60 8850.91 3.17 No

52+67 Corrugated Steel, Circular, Straight 15 24 0.024 1.00% 33.64 1.6 1.6 1.6 0.0 8834.71 8834.34 8835.37 0.60 8839.11 3.17 No

54+28 Corrugated Steel, Circular, Straight 18 24 0.024 6.96% 43.13 3.5 3.5 3.5 0.0 8819.98 8816.77 8820.83 0.85 8825.30 6.78 No

60+50 (up sta) Corrugated Steel, Circular, Straight ‐

24 0.024 1.60% 5.00 3.1 3.1 3.1 0.0 8766.51 8766.43 8767.35 0.84 8771.26 3.74 No

60+50 Corrugated Steel, Circular, Straight 18 24 0.024 1.65% 29.97 1.9 3.1 5.0 5.0 0.0 8766.37 8765.82 8767.46 1.09 8770.29 4.46 No

63+20 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 29.71 1.3 1.3 1.3 0.0 8741.84 8741.55 8742.43 0.54 8745.77 3.02 No

67+15 (up sta) Corrugated Steel, Circular, Straight ‐

24 0.024 1.00% 5.00 2.8 2.8 2.8 0.0 8716.40 8716.07 8717.35 0.80 8720.68 3.70 No

67+15 Corrugated Steel, Circular, Straight 18 24 0.024 1.00% 32.07 2.7 2.8 5.5 5.5 0.0 8716.40 8716.07 8717.67 1.16 8720.68 4.50 No

67+90 Corrugated Steel, Circular, Straight 15 24 0.024 1.00% 31.67 2.9 2.9 2.9 0.0 8710.60 8710.28 8711.50 0.82 8715.57 3.75 No

71+16 (up sta) Corrugated Steel, Circular, Straight ‐

24 0.024 1.00% 5.00 3.1 3.1 3.1 0.0 8683.60 8683.55 8684.53 0.84 8688.20 3.80 No

71+16 Corrugated Steel, Circular, Straight 15 24 0.024 1.00% 32.80 1.8 3.1 4.9 4.9 0.0 8683.53 8683.20 8684.73 1.08 8687.45 4.36 No

78+48 Corrugated Steel,…