8460 W Ken Caryl Avenue, Littleton Colorado, 80128 | 720-258-6836 | www.pnt-llc.com

October 13, 2016 Nate Hatleback Project Manager City of Thornton 9500 Civic Center Drive Thornton, CO 80229 RE: Drainage Conformance Letter Hilton Garden Inn @ The Grove

The Grove Filing No 1, lot 5E Thornton, CO. Dear Mr. Hatleback, The Grove, Lot 5E is a 3.18 acre commercial hotel center located at The Grove in Thornton, Colorado. The site plan and general layout of Lot 5E is in conformance with the original site plan layout for The Grove project. This property will include a five-story structure, encompassing approximately 138,000 square feet with 122 guest rooms; 5,000 square foot restaurant and patio; and 4,000 square foot conference meeting facility. The storm water for Lot 5E will be directed to The Grove detention pond as described in the Drainage Report for The Grove, Thornton, Colorado and Dated March 8, 2013, prepared for Thornton Development, LLC by CLC Associates, Inc. See attached the Final Master Drainage map from the above referenced approved drainage report. This map shows the storm water for Lot 5E, Basin F, being conveyed to the detention pond in Basin B via a storm sewer system. See attached sheet from the above referenced report that describes the specific details of drainage Basins B & F. The entire project is within Basin F which is designated to be commercial buildings, drive aisles, parking spaces, and landscaped areas. In the original drainage report for The Grove, Basin F has a 5 year storm coefficient of 0.82 and 100 year storm coefficient of 0.89. The proposed coefficients for the Hilton Garden Inn are 0.70 and 0.75 for the 5 and 100 year storm, respectively. The calculations for these coefficients are shown in this letter. These coefficients are less than the original planned coefficients and therefore less storm water will runoff the site than originally planned. The site is divided into drainage basins as shown on the attached drainage map and basin summary calculations. Basins A1, A2, A3, A4, and A6 all drain off the site and will be conveyed to the detention pond via existing storm sewer system. Basins A5 and A7 are collected by a 5ft Type R inlet within each basin. The attached inlet calculations show that there is sufficient capacity in the inlets for both the 5 and 100 year storm event. The drainage improvements proposed with the construction of The Grove, Lot 13F is in conformance with the above referenced drainage report. Sincerely,  

 

Nick Sheremeta Point Consulting, LLC

Basin Summary Calculated By: NWSHilton Garden @ The Grove Checked By: TDWJob Number: 16.01.005 Date: 10-13-2016

Basin Design Pt Area Area Tc Composite I - 5Yr Q -5Yr Composite I - 100 Yr Q- 100Yr C100A C5ADesignation Designation (SF) (Acres) (Min) C(5Yr) (in/hr) (CFS) C (100 Yr) (in/hr) (CFS)

A1 1 28579 0.66 5.0 0.63 4.5 1.89 0.67 9.0 3.98 0.44 0.42A2 2 10181 0.23 5.0 0.62 4.5 0.66 0.66 9.0 1.39 0.15 0.15A3 3 4996 0.11 5.6 0.21 4.4 0.11 0.25 8.7 0.25 0.03 0.02A4 4 13737 0.32 5.0 0.68 4.5 0.98 0.73 9.0 2.07 0.23 0.22A5 5 33770 0.78 6.8 0.76 4.2 2.45 0.80 8.3 5.15 0.62 0.59A6 1 27375 0.63 9.2 0.85 3.7 2.00 0.90 7.4 4.20 0.57 0.54A7 6 20038 0.46 7.3 0.67 4.1 1.26 0.72 8.1 2.67 0.33 0.31

Design Pt Contributing Q-5Yr Q-100 YrDesignation Basins (CFS) (Cfs)

1 A1+A6 3.89 8.192 A2 0.66 1.39

3=(A3+A5+A7) A3+A5+A7 3.82 8.074 A4 0.98 2.075 A5 2.45 5.156 A5+A7 3.71 7.82

Summation of Routed Flows

Weighted Runoff Coefficients Calculated By: NWSHilton Garden @ The Grove Checked By: TDWJob Number: 16.01.005 Date: 10-13-16

Proposed C5 C2 C10 C100 IMP%Roof 0.85 0.80 0.90 0.90 90

Concrete Drive/Walk 0.87 0.87 0.88 0.89 96Landscaping 0.06 0.05 0.08 0.10 5Paved Street 0.88 0.87 0.90 0.93 100

Multi-family 0.65 0.60 0.70 0.80 75Commercial 0.87 0.87 0.88 0.89 95

Gravel 0.25 0.15 0.35 0.65 40

Land Use (Acres) Weighted Runoff CoefficientTotal Concrete Paved

Basin Area Roof Drive/Walk Landscape Street Multi-family Commercial Gravel C2 C5 C10 C100 %ImpA1 0.66 0.000 0.066 0.198 0.264 0.000 0.132 0.000 0.63 0.63 0.65 0.67 70.5A2 0.23 0.000 0.069 0.069 0.092 0.000 0.000 0.000 0.61 0.62 0.64 0.66 69.2A3 0.11 0.000 0.022 0.088 0.000 0.000 0.000 0.000 0.21 0.21 0.23 0.25 22.3A4 0.32 0.000 0.048 0.080 0.192 0.000 0.000 0.000 0.67 0.68 0.70 0.73 76.8A5 0.78 0.000 0.117 0.117 0.546 0.000 0.000 0.000 0.75 0.76 0.78 0.80 85.7A6 0.63 0.630 0.000 0.000 0.000 0.000 0.000 0.000 0.80 0.85 0.90 0.90 90.2A7 0.46 0.000 0.023 0.115 0.322 0.000 0.000 0.000 0.66 0.67 0.69 0.72 76.0

TOTAL 3.18 0.630 0.345 0.667 1.416 0.000 0.132 0.000 0.69 0.70 0.73 0.75 77.7

Project:Inlet ID:

Gutter Geometry (Enter data in the blue cells)Maximum Allowable Width for Spread Behind Curb TBACK = 0.0 ftSide Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = ft/ftManning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012

Height of Curb at Gutter Flow Line HCURB = 6.00 inchesDistance from Curb Face to Street Crown TCROWN = 2.0 ftGutter Width W = 2.00 ftStreet Transverse Slope SX = 0.083 ft/ftGutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ftStreet Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ftManning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012

Minor Storm Major StormMax. Allowable Spread for Minor & Major Storm TMAX = 2.0 2.0 ftMax. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches

Allow Flow Depth at Street Crown (leave blank for no) check = yes

Maximum Capacity for 1/2 Street based On Allowable Spread Minor Storm Major StormWater Depth without Gutter Depression (Eq. ST-2) y = 1.99 1.99 inchesVertical Depth between Gutter Lip and Gutter Flowline (usually 2") dC = 2.0 2.0 inchesGutter Depression (dC - (W * Sx * 12)) a = 0.00 0.00 inchesWater Depth at Gutter Flowline d = 1.99 1.99 inchesAllowable Spread for Discharge outside the Gutter Section W (T - W) TX = 0.0 0.0 ftGutter Flow to Design Flow Ratio by FHWA HEC-22 method (Eq. ST-7) EO = 1.000 1.000Discharge outside the Gutter Section W, carried in Section TX QX = 0.0 0.0 cfsDischarge within the Gutter Section W (QT - QX) QW = 0.0 0.0 cfsDischarge Behind the Curb (e.g., sidewalk, driveways, & lawns) QBACK = 0.0 0.0 cfsMaximum Flow Based On Allowable Spread QT = SUMP SUMP cfsFlow Velocity within the Gutter Section V = 0.0 0.0 fpsV*d Product: Flow Velocity times Gutter Flowline Depth V*d = 0.0 0.0

Maximum Capacity for 1/2 Street based on Allowable Depth Minor Storm Major StormTheoretical Water Spread TTH = 6.0 6.0 ftTheoretical Spread for Discharge outside the Gutter Section W (T - W) TX TH = 4.0 4.0 ftGutter Flow to Design Flow Ratio by FHWA HEC-22 method (Eq. ST-7) EO = 0.659 0.659Theoretical Discharge outside the Gutter Section W, carried in Section TX TH QX TH = 0.0 0.0 cfsActual Discharge outside the Gutter Section W, (limited by distance TCROWN) QX = 0.0 0.0 cfsDischarge within the Gutter Section W (Qd - QX) QW = 0.0 0.0 cfsDischarge Behind the Curb (e.g., sidewalk, driveways, & lawns) QBACK = 0.0 0.0 cfsTotal Discharge for Major & Minor Storm (Pre-Safety Factor) Q = 0.0 0.0 cfsAverage Flow Velocity Within the Gutter Section V = 0.0 0.0 fpsV*d Product: Flow Velocity Times Gutter Flowline Depth V*d = 0.0 0.0Slope-Based Depth Safety Reduction Factor for Major & Minor (d > 6") Storm R = SUMP SUMPMax Flow Based on Allowable Depth (Safety Factor Applied) Qd = SUMP SUMP cfsResultant Flow Depth at Gutter Flowline (Safety Factor Applied) d = inchesResultant Flow Depth at Street Crown (Safety Factor Applied) dCROWN = inches

MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major StormMAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs

ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)

Hilton Garden @ The GroveInlet For Drainage Basin A5

Storm_inlet_Calculations 7_22_16.xlsm, Inlet 1 10/13/2016, 1:46 PM

Design Information (Input) MINOR MAJORType of Inlet Type =Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inchesNumber of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inchesGrate Information MINOR MAJORLength of a Unit Grate Lo (G) = N/A N/A feetWidth of a Unit Grate Wo = N/A N/A feetArea Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/AClogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/AGrate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/AGrate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/ACurb Opening Information MINOR MAJORLength of a Unit Curb Opening Lo (C) = 5.00 5.00 feetHeight of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inchesHeight of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inchesAngle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degreesSide Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feetClogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67

Low Head Performance Reduction (Calculated) MINOR MAJORDepth for Grate Midwidth dGrate = N/A N/A ftDepth for Curb Opening Weir Equation dCurb = 0.33 0.33 ftCombination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.77 0.77Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A

MINOR MAJOR

Total Inlet Interception Capacity (assumes clogged condition) Qa = 5.4 5.4 cfsInlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 2.5 5.2 cfs

INLET IN A SUMP OR SAG LOCATION

CDOT Type R Curb Opening

H-VertH-Curb

W

Lo (C)

Lo (G)

WoWP

CDOT Type R Curb Opening

Override Depths

Storm_inlet_Calculations 7_22_16.xlsm, Inlet 1 10/13/2016, 1:46 PM

Project:Inlet ID:

Gutter Geometry (Enter data in the blue cells)Maximum Allowable Width for Spread Behind Curb TBACK = 0.0 ftSide Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = ft/ftManning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012

Height of Curb at Gutter Flow Line HCURB = 6.00 inchesDistance from Curb Face to Street Crown TCROWN = 2.0 ftGutter Width W = 2.00 ftStreet Transverse Slope SX = 0.083 ft/ftGutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ftStreet Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ftManning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012

Minor Storm Major StormMax. Allowable Spread for Minor & Major Storm TMAX = 2.0 2.0 ftMax. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches

Allow Flow Depth at Street Crown (leave blank for no) check = yes

Maximum Capacity for 1/2 Street based On Allowable Spread Minor Storm Major StormWater Depth without Gutter Depression (Eq. ST-2) y = 1.99 1.99 inchesVertical Depth between Gutter Lip and Gutter Flowline (usually 2") dC = 2.0 2.0 inchesGutter Depression (dC - (W * Sx * 12)) a = 0.00 0.00 inchesWater Depth at Gutter Flowline d = 1.99 1.99 inchesAllowable Spread for Discharge outside the Gutter Section W (T - W) TX = 0.0 0.0 ftGutter Flow to Design Flow Ratio by FHWA HEC-22 method (Eq. ST-7) EO = 1.000 1.000Discharge outside the Gutter Section W, carried in Section TX QX = 0.0 0.0 cfsDischarge within the Gutter Section W (QT - QX) QW = 0.0 0.0 cfsDischarge Behind the Curb (e.g., sidewalk, driveways, & lawns) QBACK = 0.0 0.0 cfsMaximum Flow Based On Allowable Spread QT = SUMP SUMP cfsFlow Velocity within the Gutter Section V = 0.0 0.0 fpsV*d Product: Flow Velocity times Gutter Flowline Depth V*d = 0.0 0.0

Maximum Capacity for 1/2 Street based on Allowable Depth Minor Storm Major StormTheoretical Water Spread TTH = 6.0 6.0 ftTheoretical Spread for Discharge outside the Gutter Section W (T - W) TX TH = 4.0 4.0 ftGutter Flow to Design Flow Ratio by FHWA HEC-22 method (Eq. ST-7) EO = 0.659 0.659Theoretical Discharge outside the Gutter Section W, carried in Section TX TH QX TH = 0.0 0.0 cfsActual Discharge outside the Gutter Section W, (limited by distance TCROWN) QX = 0.0 0.0 cfsDischarge within the Gutter Section W (Qd - QX) QW = 0.0 0.0 cfsDischarge Behind the Curb (e.g., sidewalk, driveways, & lawns) QBACK = 0.0 0.0 cfsTotal Discharge for Major & Minor Storm (Pre-Safety Factor) Q = 0.0 0.0 cfsAverage Flow Velocity Within the Gutter Section V = 0.0 0.0 fpsV*d Product: Flow Velocity Times Gutter Flowline Depth V*d = 0.0 0.0Slope-Based Depth Safety Reduction Factor for Major & Minor (d > 6") Storm R = SUMP SUMPMax Flow Based on Allowable Depth (Safety Factor Applied) Qd = SUMP SUMP cfsResultant Flow Depth at Gutter Flowline (Safety Factor Applied) d = inchesResultant Flow Depth at Street Crown (Safety Factor Applied) dCROWN = inches

MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major StormMAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs

ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)

Hilton Garden @ The GroveInlet For Drainage Basin A7

Storm_inlet_Calculations 7_22_16.xlsm, Inlet 2 10/13/2016, 1:47 PM

Design Information (Input) MINOR MAJORType of Inlet Type =Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inchesNumber of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inchesGrate Information MINOR MAJORLength of a Unit Grate Lo (G) = N/A N/A feetWidth of a Unit Grate Wo = N/A N/A feetArea Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/AClogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/AGrate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/AGrate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/ACurb Opening Information MINOR MAJORLength of a Unit Curb Opening Lo (C) = 5.00 5.00 feetHeight of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inchesHeight of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inchesAngle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degreesSide Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feetClogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67

Low Head Performance Reduction (Calculated) MINOR MAJORDepth for Grate Midwidth dGrate = N/A N/A ftDepth for Curb Opening Weir Equation dCurb = 0.33 0.33 ftCombination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.77 0.77Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A

MINOR MAJOR

Total Inlet Interception Capacity (assumes clogged condition) Qa = 5.4 5.4 cfsInlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 2.0 4.2 cfs

INLET IN A SUMP OR SAG LOCATION

CDOT Type R Curb Opening

H-VertH-Curb

W

Lo (C)

Lo (G)

WoWP

CDOT Type R Curb Opening

Override Depths

Storm_inlet_Calculations 7_22_16.xlsm, Inlet 2 10/13/2016, 1:47 PM

WTR

S

S

WT

RW

TR

WT

R

ST

MS

TM

STMSTM

W

T

R

ST

M

82

8

1

8

0

7

9

7

8

7

7

78

80

81

7

9

83

7

7

7

6

5175

5180

5180

5180

517651

77

5178

5179

5181

5182

5183

5184

5184

5175

5180

5174

5174

5174

5176

5177

5178

5179

5181

5182

5183

5184

5185

5185

51865186

-6.51%

-11.24%

A60.63 0.85

0.90

A10.66 0.63

0.67

A20.23 0.62

1.66

A30.11 0.21

0.25

A40.32 0.68

0.73

A50.780.76

0.80

A70.46 0.67

0.72

PATIOAREA

LINCOLN WAY

LINCOLN

STREE

T

HILTONGARDEN

INNFFE=5184.00

LOT 140.775 AC

MURPHY'SOIL &GAS

CANDLEWOODSUITES

LINCOLN WAY

FREDDY'S

2

1

5

6

4

3

518351835183

5183

5182

5183

5182

5183

5182

51835182

5181

5183

5182

51795178

5177

51845183 5182

-1.01%

-0.6

4%

-0.51%

-0.5

5%

-4.1

0%-0.22%

-3.54%

-3.93%

-4.27%

PROPOSEDSTORM INLET

PROPOSEDSTORM PIPE

PROPOSEDSTORM INLET

DRA

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1/1

GENERAL NOTE

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5-YEAR RUNOFF COEFFICIENTDRAINAGE BASIN DESIGNATIONA1.1

0.13 0.560.71 100-YEAR RUNOFF COEFFICIENT

AREA IN ACRES

BASIN SUMMARY TABLE

BASIN ACRES

Design PointQ5 CFS Q100 CFS

A1 0.66 1 1.89 3.98

A2 0.23 2 0.66 1.39

A3 0.11 3 0.11 0.25

A4 0.32 4 0.98 2.07

A5 0.78 5 2.45 5.15

A6 0.63 1 2.00 4.20

A7 0.46 6 1.26 2.67

LEGEND

1

PROPERTY LINE

EXISTING CONCRETE CURB

PROPOSED CURB AND GUTTER

PROPOSED CONTOUR

EXISTING CONTOUR

DRAINAGE SLOPE/FLOW ARROW

PROPOSED DESIGN POINT

BASIN BOUNDARY

2.00%

SUMMARY OF ROUTED FLOWS

DESIGN

POINT

CONTRIBUTING

BASINS

Q5 CFS Q100 CFS

1

A1+A6 3.89 8.19

2

A2 0.66 1.39

3

A3+A5+A7 3.82 8.07

4

A4 0.98 2.07

5

A5 2.45 5.15

6

A5+A7 3.71 7.82

PROPOSED STORM SEWER

EXISTING STORM LINE