CA_SEKI_10(10-11)_Final_Hydraulics_Report.pdf

Subject: CA PRA SEKI 10(10) & 10(11) Generals Highway Final Hydraulic Recommendations

From: Kelly Terrell & Scott Hogan

Highway Engineer Hydraulics Team Leader Lakewood, CO

To: Pat Flynn Project Manager Lakewood, CO

This memo provides recommendations for the hydraulic design of Generals Highway, in Sequoia and Kings Canyon National Park, Tulare County, California. The project consists of reconstructing (4R) approximately 0.9 miles and resurfacing (3R) approximately 5.7 miles of Generals Highway, and 2.0 miles of Wolverton Road.

This memo specifically addresses the hydrologic and hydraulic analyses for culverts within the project limits. The resulting recommendations are included after the summary of analysis.

Roadway Hydraulics Design Standards and Criteria

According to the Project Development Design Manual (PDDM), Generals Highway is a high-standard road since the future estimated Average Daily Traffic (ADT) totals more than 1500 vehicles.

Design Standards for Culverts

Capacity and Stability Design: 50-year flood Capacity Check Flood: Evaluate potential for adverse impacts for the overtopping flood

Design Criteria for Culverts

Headwater o New: Water Surface Elevation (WSEL) ≤ bottom of aggregate base layer o Existing: WSEL ≤ shoulder hinge point o Headwater/Diameter (HW/D) ratio for culverts 48” or smaller: HW/D ≤ 1.5 o Headwater/Diameter (HW/D) ratio for culverts larger than 48”: HW/D ≤ 1.2 o WSEL limited by unacceptable hazards to human life or property

Minimum Size: 24” for cross-road culverts

Memorandum

Date: March 23, 2017

In Reply Refer To:

HFHD-16

Slope:

o Stream Crossings: Match streambed o Ditch Relief: Minimum = 2%, Maximum = 25%

Cover: Refer to FLH Standard Drawings for the minimum and maximum cover on pipes

Hydrologic Analysis and Results

The Watershed Modeling System (WMS), version 8.3 was used to delineate the drainage basin for each culvert crossing on the 4R portion of the project and for selected crossings on the 3R portion. Each basin was adjusted to account for the additional runoff from roadside ditches. The peak discharge estimates were computed using NOAA Atlas 2 for the Sierra Nevada region and the Rational Method for the basins up to 90 acres. USGS regression equations for the Sierra Region were used for the basins with areas greater than 90 acres.

The results from the WMS and Rational Method analysis for the 10- through 50-year peak flows for the 4R portion are summarized below in Table 1.

Table 1 Computed peak discharges for culverts on SEKI 10(10)

Drainage

Concentration Point

Drainage Basin Area

(acres)

Drainage Basin Average Slope

(ft/ft)

10-yr Peak Discharge

(cfs)

25-yr Peak Discharge

(cfs)

50-yr Peak Discharge

(cfs) 677+95 0.72 0.643 1.62 2.01 2.31 679+55 0.63 0.664 1.80 2.25 2.59 680+65 1.84 0.610 4.90 6.12 7.06 684+10 3.62 0.555 8.94 11.16 12.86 690+05 10.23 0.697 23.25 28.93 33.30

692+83 2.96 0.608 7.40 9.23 10.64 695+97 0.49 0.231 0.60 0.75 0.86 698+64 1.71 0.670 4.87 6.10 7.04 702+10 2.03 0.623 5.40 6.74 7.78 703+77 4.82 0.720 11.15 13.88 15.98 708+07 49.76 0.650 79.38 97.99 112.31 711+15 11.92 0.712 23.81 29.53 33.92 719+10 2.07 0.385 4.55 5.66 6.51

Not all culverts on the 3R portion were evaluated. All culverts 24” or larger and culverts with a contributing drainage area of greater than ten acres were evaluated. See below for the Sierra Region USGS Regression Equations used to calculate discharges for basins greater than 90 acres. See Table 2 for the peak discharge results for the 3R portion of the project.

2.63 . . .

6.55 . . .

10.4 . . .

Where, Table 2 Computed peak discharges for culverts on SEKI 10(11)

Drainage Concentration

Point

Drainage Basin Area

(acres)

Drainage Basin Average Slope

(ft/ft)

10-yr Peak Discharge

(cfs)

25-yr Peak Discharge

(cfs)

50-yr Peak Discharge

(cfs) 727+80 10.8 0.574 11.1 13.6 15.6 730+50 13.6 0.529 19.1 23.8 27.3 740+30 4.8 0.587 5.1 6.3 7.2 770+40 5.3 0.347 6.2 7.7 8.8 772+60 419 0.314 81* 137* 187* 784+90 59 0.345 53 64.5 73.5 791+30 305 0.425 64* 108.6* 148*

793+25 4.1 0.393 4.0 4.9 5.6 843+50 145 0.243 33.5* 57.4* 79.0* 845+90 68 0.233 50.9 61.6 69.9 857+80 17.1 0.297 14.4 17.5 19.9 863+00 25.5 0.263 20.8 25.2 28.9 879+30 16.4 0.235 13.7 16.7 19.0 904+60 7.2 0.257 5.7 6.9 7.9 907+40 35 0.222 26.3 31.8 36.1 910+50 191 0.301 41.0* 70.3* 95.6* 921+50 13.3 0.336 10.2 12.4 14.0 929+40 439 0.185 77.6* 132* 180* 962+85 16.2 0.275 11.2 13.5 15.4 970+50 29.6 0.184 20.6 25.0 28.3 980+50 6.7 0.227 9.7 12.0 13.8 987+00 10.9 0.251 8.30 10.1 11.4 990+55 40.0 0.239 30.4 36.8 41.8 998+50

370 0.270 66.0* 113* 155* 998+65

*Calculated using USGS Regression Equations for the Sierra Region

Culvert Hydraulic Analysis and Results

A total of 14 culverts cross the 4R portion of Generals Highway, and all were included in the following analysis. During the scoping trip, the Park expressed that many of the culverts frequently overtop. The locations and descriptions of the existing culverts are summarized in Table 3.

The culverts collect flow from the drainages east of the roadway and discharge onto steep slopes towards the Marble Fork Kaweah River. Given the steep culvert slopes and steep slopes at the culvert outlets, each culvert was assumed to operate under inlet control. As noted in Table 3, locations of some inlets and outlets were not found. For the hydraulic analysis, the inlet and outlet locations were estimated based on the other culvert layouts and elevations were estimated from two-foot contour mapping.

Table 3 Existing Culvert Conditions SEKI 10(10)

Culvert Location

Culvert Description Culvert length

(ft)

Culvert Slope

Upstream invert elevation (ft)

Road overtopping elevation (ft)

Design Discharge

(50-yr) (cfs)

677+64 18” CMP 34 8.6 4908.16 4910.5 2.31

679+25

18” CMP

Concrete Headwall Drop Inlet

36 11.7 4918.52 4920 2.6

680+39

12” CMP

Drop Inlet

35* 10.0* 4924.34* 4926 7.1

683+83

18” CMP

Drop Inlet

31 9.3 4945.96 4947.58 12.9

689+75

15” CMP

Stone Headwall 37* 5.0* 4990.18 4992.42

33.3 689+91

18” CMP

Stone Headwall

60 4.6 4989.67 4992.42

692+59

24” CMP

Stone headwall with concrete facing

48 12.5 5009.01 5012.74 10.6

695+64

18” CMP

Stone headwall 45* 28.8* 5030* 5035.26 0.9

698+32

18” CMP

Concrete headwall 48 9.3 5052.62 5054.1 7.0

701+78

15” CMP

Concrete headwall 35 11.6 5076.47 5079.9 7.8

703+44

18” CMP

Drop Inlet

32 7.5 5086.96 5089.12 16.0

707+74

24” CMP

Stone headwall 61 15.2 5122.64 5125.45 112

710+83

18” CMP

Concrete headwall 39 9.1 5143.29 5146.76 33.9

716+45 18” CMP

718+82 18” CMP 34 7.4 5202.8 5204.72 6.5

* Inlet or outlet not found. Locations and elevations were estimated from contour mapping.

The road segment is classified as a high standard road according to criteria in the Project Development Design Manual (PDDM) since the future estimated Average Daily Traffic (ADT) totals more than 1500 vehicles. Consequently, the design standard for culvert discharge is a 50-year flow event, with a maximum headwater to depth ratio (HW/D) of 1.5 for culverts 48” or smaller. A summary of the HY-8 culvert hydraulic analysis for the existing culverts is presented below in Table 4 and Table 5.

Table 4 Summary of Existing Culverts Hydraulic Analysis SEKI 10(10)

Culvert Location

Existing Culvert

Description

Computed Headwater Elevation

(ft)

HW

(ft)

HW

/D

Comments

677+95 18” CMP 4908.96 0.80 0.53

679+55 18” CMP 4919.36 0.84 0.56

680+65 12” CMP 4926.05 1.71 1.71

Exceeds HW/D criteria

Overtops roadway 684+10 18” CMP 4947.66 1.70 1.13 Overtops roadway

690+05 15” CMP

4992.55 2.37 1.90

Exceeds HW/D criteria Overtops roadway

690+05 18” CMP

4992.55 2.88 1.92

Exceeds HW/D criteria Overtops roadway

692+83 24” CMP 5010.80 1.79 0.89

695+97 18” CMP 5030.40 0.40 0.27

698+64 18” CMP 5054.13 1.51 1.01 Overtops roadway 702+10 15” CMP 5079.35 2.88 2.30 Exceeds HW/D criteria 703+77 18” CMP 5089.20 2.24 1.49 Overtops roadway 707+74 24” CMP 5125.19 2.55 1.27 Overtops roadway

711+15 18” CMP 5147.43 4.14 2.76

Exceeds HW/D criteria

Overtops roadway

719+10 18” CMP 5204.46 1.66 1.11

Table 5 Summary of Existing Culverts Hydraulic Analysis SEKI 10(11)

Culvert Location

Existing Culvert

Description

Design Discharge

(50-yr) (cfs)

HW (ft) HW/D Road Overtopping

Discharge (cfs) Comments

727+80 18" CMP 15.60 3.6 2.40 12.54

Exceeds HW/D criteria Overtops roadway

730+50 24" CMP 27.30 3.92 1.96 22.49

Exceeds HW/D criteria Overtops roadway

740+30 24" CMP 7.20 1.42 0.71 22.1

770+40 60" CMP 195.98 7.07 1.41 509.62

60" CMP exceeds HW/D criteria 772+60 18" CMP 0 0.00

784+90 24" CMP 73.50 5.48 2.74 27.45

Exceeds HW/D criteria Overtops roadway

791+30 18" CMP 153.36 15.4 10.27 189.71 Exceeds HW/D criteria

793+25 48" CMP 7.64 1.91

843+50 30" CMP 148.88 19.14 7.66 115.81 Exceeds HW/D criteria

845+90 18" CMP 3.86 2.57 Overtops roadway

857+80 18" CMP 19.90 2.56 1.71 9.73

Exceeds HW/D criteria Overtops roadway

863+00 18" CMP 28.87 3.91 2.61 13

Exceeds HW/D criteria Overtops roadway

879+30 18" CMP 19.00 4.55 3.03 14.55

Exceeds HW/D criteria Overtops roadway

904+60 36" CMP 7.90 1.28 0.43 78.75

907+40 36" HDPE 36.10 2.97 0.99 50.04

910+50 30" CMP 95.59 6.98 2.79 48.61

Exceeds HW/D criteria Overtops roadway

921+50 18" CMP 14.00 4.28 2.85 14.81 Exceeds HW/D criteria

929+40 30" CMP 180.47 9.46 3.78 58.28

Exceeds HW/D criteria Overtops roadway

962+85 18" CMP 15.40 1.94 1.29 7.82 Overtops roadway

970+50 18" CMP 28.30 3.11 2.07 11.38

Exceeds HW/D criteria Overtops roadway

980+50 24" CMP 13.80 2.08 1.04 20.53

987+00 24" CMP 11.40 1.52 0.76 27.69

990+55 18" CMP 41.80 2.87 1.91 10.53

Exceeds HW/D criteria Overtops roadway

998+50 36" CMP 154.59 5.23 1.74 434.82 36" CMP exceeds HW/D criteria 998+65 72" CMP 3.54 0.59

Summary of Recommendations for SEKI 10(10)

All culverts should be replaced although some of the replacements will need to be analyzed for constructability in the field. See Table 6 for a complete list of proposed culvert replacements.

All 18” culverts should be replaced with 24” culverts. According to the design criteria in the PDDM, the minimum recommended culvert size is 24”.

A 24” CMP should be installed at a new location of approximately 716+45.

End sections should be included on all replacements without headwalls.

All outlets should have standard riprap aprons unless the outlet slope is greater than

1.5:1 and then revet mattresses should be considered.

Per the design criteria in the PDDM, all culverts must have a minimum cover of one foot from the culvert crest to the bottom of the subgrade. Several culverts will require dropping the inlet invert in order meet the minimum cover requirement. These inlets will need to be examined in the field during the next site visit.

Table 6 Summary of Proposed Culverts SEKI 10(10)

Culvert Location

Proposed Culvert

Description

Proposed Upstream

Invert Elevation (ft)

Computed Headwater Elevation

(ft)

HW

(ft)

HW/D Comments

677+62 24” CMP 4907.16 4907.90 0.74 0.37 Replace existing 679+26 24” CMP 4917.02 4917.80 0.78 0.39 Replace existing 680+35 24” CMP 4922.84 4924.24 1.40 0.70 Replace existing 683+79 24” CMP 4944.21 4946.39 2.18 1.09 Replace existing

689+75 30” CMP 4988.93 4992.38 3.45 1.38

Keep existing 18” CMP

Replace 15” with 30” CMP 692+57 24” CMP 5009.01 5010.80 1.79 0.89 Replace existing 695+65 24” CMP 5030 5030.36 0.36 0.18 Replace existing 698+31 24” CMP 5051.62 5052.92 1.30 0.65 Replace existing 701+77 24” CMP 5076.47 5077.91 1.44 0.72 Replace existing 703+43 24” CMP 5085.96 5088.61 2.65 1.32 Replace existing 707+73 48” CMP 5120 5125.30 5.30 1.33 Replace existing 710+82 30” CMP 5143.29 5146.31 3.02 1.21 Replace existing 716+44 24” CMP 5184 5185.74 1.74 0.87 Install new 24” CMP 718+80 24” CMP 5201.3 5202.66 1.36 0.68 Replace existing

Summary of Recommendations for SEKI 10(11)

Some of the culverts on this route need to be replaced or supplemented with new culverts due to capacity while others need to be lined due to poor condition. See Table 7 for a complete list of proposed culvert replacements and linings.

End sections should be included on all replacements without headwalls. Headwalls should be installed on new culverts 48” or greater in size.

All outlets at new culvert installations should have standard riprap aprons unless the outlet slope is greater than 1.5:1 and then revet mattresses should be considered.

Several culverts were identified as in poor condition by the CFL survey team. These culverts are noted as “indicated as poor condition” in Table 7. These culverts should be inspected and replaced or lined as necessary.

Per the design criteria in the PDDM, all culverts must have a minimum cover of one foot from the culvert crest to the bottom of the subgrade. Several culvert replacements will require dropping the inlet invert in order meet the minimum cover requirement. These inlets will need to be examined in the field during the next site visit.

Table 7 Summary of Culverts SEKI 10(11)

Station Size Type Notes and Recommendations

726+12 18" CMP Indicated as poor condition. Replace with 24".

727+55 18" CMP Insufficient capacity, replace with 24".

730+26 24" CMP Insufficient capacity, replace with 30".

733+52 18" CMP

737+02 18" CMP

740+04 24" CMP Replace with new 24” and add drop inlet

742+71 18" CMP Indicated as poor condition. Line with close fit lining

745+12 18" CMP

750+61 18" CMP

754+13 18" CMP

757+10 18" CMP

759+16 18" CMP

761+33 18" CMP

763+65 18" CMP

770+13 60" CMP

772+31 18" CMP Insufficient capacity, replace with 24"

780+38 18" CMP

784+60 24" CMP Insufficient capacity, replace with 48” and headwall.

787+90 18" CMP

790+96 18" CMP Insufficient capacity, replace with 24".

792+94 48" CMP Line with close fit HDPE or CIPP (70ft)

795+04 18" CMP

798+92 18" CMP Poor condition. Line with CIPP and add drop inlet

801+72 18" CMP Poor condition. Line with CIPP and add drop inlet

804+72 18" CMP

815+45 18" CMP Poor condition. Replace with 24".

821+46 18" CMP

826+43 18" CMP

832+42 18" CMP Poor condition. Replace with 24".

835+97 18" CMP

840+60 18" CMP

843+45 30" CMP Line with close fit HDPE or CIPP (90ft).

845+57 18" CMP Replace with 24”

853+37 18" CMP

857+47 18" CMP Insufficient capacity, replace with 30".

862+72 18" CMP Insufficient capacity, replace with 30".

870+29 18" CMP

874+14 18" CMP

879+02 18" CMP Insufficient capacity, replace with 30".

881+32 18" CMP

884+76 18" CMP

895+44 18" CMP

899+56 18" CMP

900+21 18" CMP

902+42 12" CMP

Insufficient capacity, replace with 24". Consider a combo drop inlet.

904+26 36" CMP

Line culvert with CIPP or Close-fit HDPE. Length =105 ft. This culvert crosses the intersection at the Big Trees Trail parking area. The last 20 ft +/- is covered with timbers and earth and will need to be excavated to access for the lining.

907+11 36" CIPP

910+20 30" CMP

Replace existing 30” CMP with double 30” CMP and headwall

916+00 18" CMP

921+20 18" CMP

Insufficient capacity, replace with 24”, higher in the embankment.

923+78 24” CMP

929+09 30" CMP

Line culvert with CIPP or Close-fit HDPE.

Length=approx. 60 ft. Add additional culvert. Large as possible up to 60”.

933+55 18" CMP

940+14 18" CMP Add drop inlet

946+59 18" CMP

949+59 18" CMP

955+77 18" CMP

962+53 18" CMP Insufficient capacity, replace with 24".

970+21 18" CMP

Insufficient capacity, replace with 30" and add drop inlet

975+50 Add 24” CMP with drop inlet

979+85 24" CMP Line culvert with CIPP or Close-fit HDPE

986+69 24" CMP

990+25 18" CMP Insufficient capacity, replace with 36".

998+17 36" CMP

Line 36” Culvert with CIPP or Close-fit HDPE liner

998+17 72" CMP

1003+56 Add 24” CMP

1016+51 18" CMP Install riprap apron

1019+95 18” CMP

1026+08 18" CMP

Wolverton Road

10+25 24” CMP

13+33 24” CMP Line culvert with CIPP or Close-fit HDPE

17+45 24” CMP Line culvert with CIPP or Close-fit HDPE

21+54 24” CMP

24+54 24” CMP

28+64 24” CMP

32+48 24” CMP Remove end section

37+99 24” CMP

39+03 24” CMP

41+98 24” CMP

46+95 24” CMP

51+75 24” CMP

56+70 36” CMP

Line culvert with CIPP or Close-fit HDPE, new end section rt

62+29 96” CMP

65+95 24” CMP

68+77 24” CMP

72+36 24” CMP

77+36 24” CMP

80+88 24” CMP

83+38 24” CMP

Wolverton

Parking Replace inlet grate on Southwest drop inlet and middle drop inlet