preliminary drainage report pete lien & sons ready mix concrete … · 2019-02-08 ·...

Preliminary Drainage Report Pete Lien & Sons Ready Mix Concrete Plant – Judge Orr Road

El Paso County, Colorado

Prepared for: Pete Lien & Sons, Inc. 3401 Universal Drive

Rapid City, South Dakota 57702

Prepared by:

Kiowa Project No. 18055

January 29, 2019

i Kiowa Engineering Corporat ion

TABLE OF CONTENTS

Table of Contents ....................................................................................................................... i

Statements and Approvals....................................................................................................... ii

I. General Location and Description ............................................................................. 1

II. Major Drainage Basins and Subbasins ....................................................................... 1

III. Drainage Design Criteria ............................................................................................. 2

IV. Drainage Facility Design .............................................................................................. 2

A. Stormwater Quality and Detention Design ........................................................... 4

V. References .................................................................................................................... 4

Appendix Table of Contents ................................................................................................... 5

ii Kiowa Engineering Corporat ion

STATEMENTS AND APPROVALS

ENGINEER'S STATEMENT: The attached drainage plan and report were prepared under my direction and supervision and are correct to the best of my knowledge and belief. Said drainage report has been prepared according to the criteria established by the City/County for drainage reports and said report is in conformity with the master plan of the drainage basin. I accept responsibility for any liability caused by any negligent acts, errors or omissions on my part in preparing this report.

Kiowa Engineering Corporation, 1604 South 21st Street, Colorado Springs, Colorado 80904

Matthew W. Erichsen, P.E. (PE #36713) Date For and on Behalf of Kiowa Engineering Corporation

DEVELOPER'S STATEMENT: I, the Developer, have read and will comply with all of the requirements specified in this drainage report and plan.

By: Date Pete Lien & Sons, Inc.

Print Name:

Address: Pete Lien & Sons, Inc. 3401 Universal Drive Rapid City, SD 57702

EL PASO COUNTY: Filed in accordance with the requirements of the Drainage Criteria Manual, Volumes 1 & 2, El Paso County Engineering Criteria Manual, and Land Development Code, as amended.

Jennifer Irvine, P.E. Date El Paso County Engineer/ECM Administrator

1 Kiowa Engineering Corporat ion

I. GENERAL LOCATION AND DESCRIPTION

The purpose of this Drainage Report is to address and discuss the drainage patterns and impacts associated with the proposed development of the site. The Pete Lien & Sons Ready Mix Concrete Plant – Judge Orr Road site will be developed as a ready mix concrete plant. The subject site is located at the northeast corner of the intersection of Judge Orr Road and Stapleton Drive to the northeast of the Town of Falcon in El Paso County, Colorado. The site is located in the south half of Section 34, Township 12 South, Range 64 West of the 6th Principal Meridian. The site is bounded to the west by Stapleton Drive, to the south by Judge Orr Road, to the east by an existing drainageway (Geick Ranch West Tributary) and undeveloped land and to the north by undeveloped land. Haegler Ranch Tributary 2 is located along the south side of the site and Geick Ranch West Tributary is located along the east side of the site. Improvements were made to Haegler Ranch Trib when Stapleton Road was constructed. The improvements include a storm sewer crossing under Stapleton Road and drop structures along the drainageway downstream of Stapleton Road. The existing site is undeveloped with no existing utilities other than the drainage improvements along Haegler Ranch Tributary 2. The total property area is 91.86 acres. The location of the site is shown on the Vicinity Map (Figure 1).

The proposed development is planned to include 19.50 acres of the property and will consist of a ready mix concrete plant and associated improvements. The development will include self-determined setbacks on all four sides of the ready mix plant to provide a buffer to the adjacent properties. In addition, wetlands and soils suitable for wetlands have been identified on the eastern half of the property. These areas are planned to be protected as part of the development and will be an undeveloped buffer to the east. This area is identified as the wetland avoidance area on the Drainage Plan.

The existing vegetative cover within the development is in fair condition with grasses throughout the site. The site is currently used for livestock grazing. The existing ground within the property slopes to the east at slopes of 1 to 4 percent. Soils within the subject site are classified to be within Hydrologic Soils Group A and D as shown in the El Paso County Soils Survey, see Appendix for the Soil Map. Specifically, the site includes Columbine gravelly sandy loam (Soil Group A) which makes up the majority of the site and the area planned to be developed. The eastern portion of the site within the proposed wetland preservation area includes soils classified as Fluvaquentic Haplaquolls (Soil Group D). For the purposes of computing the existing and proposed hydrology for the site, Hydrologic Soil Group A was used.

There are no active irrigation ditches or facilities within or adjacent to the site.

II. MAJOR DRAINAGE BASINS AND SUBBASINS

The site lies within the Haegler Ranch drainage basin. The Haegler Ranch Basin, Drainage Basin Planning Study was reviewed and it was determined the subject site is located outside of the DBPS study limits. The Haegler Ranch Tributary 2 is located along the south side of the property, along Judge Orr Road. The drainage enters the site through twin box culverts under Stapleton Drive on the west and continues east in an existing open channel to the southeast over a drop structure and along the Judge Orr Road right of way. The drainageway continues east along the ROW to a low point located east of the subject property where the flows combine with the Geick Ranch West Tributary and flow under Judge Orr Road. The Geick Ranch West Tributary is located along the east side of the property flowing from north to south with some contour berms along the length creating small stock ponds. At the north side of the intersection of Stapleton and Judge Orr Road, existing twin culverts carry roadside swale flows under Stapleton. The flows from these culverts combine with the Haegler


Ranch Trib 2 flows at a point downstream of Stapleton Drive. Other than the flows described above, there are no significant off site flows which enter the site.

As described above, the east portion of the property includes wetland type vegetation, based on a field and document investigation by a Professional Wetland Scientist. The wetland avoidance line/area has been identified to keep the proposed improvements out of this area and act as a buffer to the east. Consultation and permitting with the United States Army Corps of Engineers will not be necessary, since the improvements will be located outside of this area. This avoidance line/area is self imposed by the developer/property owner. If the property owner would like to modify the location of this line in the future, it is recommended that a wetland scientist provide input. Consultation with the USACE will be necessary if jurisdictional wetlands are impacted by development.

Portions of the subject property are located within a Zone AE and Zone A FEMA regulated floodplain based on Flood Insurance Rate Map 08041C0558G, effective dated December 7, 2018. A copy of the FIRM panel is provided in the Appendix. The floodplain locations are also located on the Drainage Plan. The proposed development is planned to stay well outside the existing floodplains.

In the existing condition, the majority of the site drains by sheet flow east and southeast to one of the existing drainageways, refer to Exhibit A, the Existing Conditions Drainage Plan. Basin EX-A: The basin is located along the north and northeast sides of the property including the Geick Ranch West Tributary. The runoff from this basin will sheet flow east and southeast into the existing tributary. Basin EX-B: The basin is located along the south and southeast sides of the property. The runoff sheet flows east-southeast towards into the Haegler Ranch Trib which conveys the flows past the southeast corner of the property to a low point where the flows continue under Judge Orr Road.

III. DRAINAGE DESIGN CRITERIA

Hydrologic calculations for the site were performed using the methods outlined in the El Paso County Drainage Criteria Manual. Topography for the site is presented on the Drainage Plan. The hydrologic calculations were made for the existing and proposed site conditions. The Drainage Plans present the drainage patterns for the site, including the sub-basins. The peak flow rates for the sub-basins were estimated using the Rational Method. The 5-year (Minor Storm) and 100-year (Major Storm) recurrence intervals were determined. The drainage basin area, time of concentration, and rainfall intensity were determined for each of the sub-basins within the property. The onsite soils were assumed to be Hydrologic Soil Group A, based on the Soil Survey.

Storm water quality and detention improvements are required as part of the development of the property, refer to the Stormwater Quality and Detention Design section for a description. The stormwater quality and detention improvements will be provided in a Full Spectrum Detention Basin (designed as an Extended Detention Basin) at the east edge of the development. The UD-Detention spreadsheets created by UDFCD were used to size and design the Full Spectrum Detention Basin. The supporting calculations are included in the Appendix of this report.

IV. DRAINAGE FACILITY DESIGN

The drainage of the area to be developed will be accomplished through a combination of sheet flow, swale flow, gutter flow and storm sewer flow. These flows will drain to the proposed stormwater quality and detention basin before outfalling into the historic flow path. The existing drainageways along the south and east side of the property will not be impacted by the proposed development. The proposed drainage basins and patterns for the site are shown on the Drainage Plan (Exhibit B), provided in the map pocket at the end of this report. The hydrologic and stormwater quality/detention calculations are provided in the Appendix.


The County requires a Four Step Process for selection of appropriate permanent BMPs for the site. In this development following are the steps taken to meet this process.

Step 1-Employ Runoff Reduction Practices: Portions of the proposed improvements will sheet flow to a grass lined swale which will reduce the directly connected impervious area and provide the opportunity for infiltration.

Step 2-Stabilize Drainageways: The existing drainageways are located along the edges of the property and will not be directly impacted by the proposed development. The flows from the site will drain through a detention basin to decrease the peak flow to historic levels. The flows from the detention basin will drain across nearly 1,000-feet of grassed area before reaching the drainageways which will minimize the possibility of erosion occurring in the existing drainageways. In addition, at the downstream end of the property is where the drainageways flow through a culvert under Judge Orr Road. The culvert will act as a check structure to hold the drainageway flowline at the downstream end of the property.

Step 3-Provide Water Quality Capture Volume (WQCV): An extended detention basin will be used to provide water quality treatment for the runoff from the developed portion of the site. The extended detention basin will release the WQCV over 40 hours.

Step 4-Consider Need for Industrial and Commercial BMPs: No industrial water will be discharged from the site. Material handling and conveying equipment will be controlled using baghouses and best practices as required by the State of Colorado. These practices minimize migration of any materials from the ready mix site to neighboring lands..

Following is a description of the on-site drainage sub-basins:

Sub-basin A: The sub-basin is located along the northeast portion of the site and is located to the east of the proposed development. The basin is the same as basin EX-A, except for the west portion of that basin which is now a part of Sub-basin C. The runoff from this basin will drain by sheet flow to the existing drainageway. No improvements are planned within this basin.

Sub-basin B: The sub-basin is located along the south portion of the site and to the south and east of the proposed development. The basin is the same as basin EX-B, except for the west portion of that basin which is now a part of Sub-basin C. The runoff from this basin will drain by sheet flow to the existing drainageway. No improvements are planned within this basin.

Sub-basin C: The sub-basin is located in the northwest/central part of the site and includes the area proposed to be developed. The area within the basin will be developed with a ready mix concrete plant along with the associated facilities, office, parking lot, water well, septic system and driveway from Stapleton Drive. The on-site drives will be mainly gravel. Concrete pavement will be used in certain areas within the development. The area within the basin will be graded to generally drain east to the proposed stormwater quality and detention basin, see the Stormwater Quality and Detention Design section for a description of the facility. Grasslined swales will be constructed along the north and south side of the developed area to convey the runoff from the edges of the development to the proposed detention basin. Inlets and storm sewers will also be used within the developed area, to capture and convey flows to the detention basin. The detention basin and outlet pipe have been designed to stay completely out of the wetland avoidance area. The flows leaving the detention basin will follow the historic path to the existing drainageways on the east side of the property.


A. STORMWATER QUALITY AND DETENTION DESIGN

Storm water quality and detention measures are required by the County as part of the development of the property. The water quality measures to be instituted for the development will include:

1. Construction of an extended detention basin at the east end of the development for the developed runoff to drain through. The water quality enhancements to be included in the water quality basin are presedimentation forebays, minimal sloped low flow channel, outlet structure with an internal micropool, water quality orifice plate to reduce the release rate to a drain time of nearly 40 hours for the Water Quality Capture Volume (WQCV) and a well screen across the orifice plate to minimize the chance of debris blocking the orifice plate.

2. Grass lined swales will be constructed along the north and south sides of the area to be developed. The swales will convey developed runoff and also provide water quality improvement allowing sediment/debris to fall out of the runoff and infiltration to occur before reaching the full spectrum detention basin. A forebay will be installed at the downstream end of the swales to collect sediment and debris.

The Full Spectrum Detention basin will include the elements described above and an emergency spillway and outlet pipe. The outlet structure will be designed to release the WQCV, EURV and 100-year flow at the prescribed rates. The emergency spillway will be constructed along the east edge of the detention area to release flows in excess of the 100-year event and in an emergency situation. The UD-Detention workbook along with UDFCD equations have been used to design the facility. Refer to the Appendix for the calculations. The outlet structure will be designed to drain the WQCV in approximately 40 hours and to drain the EURV in approximately 72 hours. The embankment will be designed to result in an embankment which is non-jurisdictional based on the state engineer’s requirements.

V. REFERENCES

1) Haegler Ranch Basin Drainage Basin Planning Study, prepared by URS, May 2009.

2) El Paso County Drainage Criteria Manual (Volumes 1 and 2) and Engineering Criteria Manual,

current editions.

3) City of Colorado Springs Drainage Criteria Manual, Volumes 1 and 2, May 2014.

4) Urban Storm Drainage Criteria Manual (USDCM) Volumes 1, 2 and 3, Urban Drainage and

Flood Control District, Current Editions

5) Soil Survey of El Paso County Area, Colorado, prepared by United States Department of

Agriculture Soil Conservation Service.


APPENDIX TABLE OF CONTENTS

APPENDIX

Figure 1: Vicinity Map Soils Map FEMA Flood Insurance Rate Map

APPENDIX A

Hydrologic Calculations Runoff Coef, Time of Concentration and Runoff Calcs

APPENDIX A.1

Supporting Tables and Figures

APPENDIX B

Full Spectrum Detention Calculations

APPENDIX C

Exhibit A: Drainage Plan – Existing Conditions Exhibit B: Drainage Plan – Proposed Conditions

Kiowa Eng ineer ing Corporat ion

APPENDIX Figure 1: Vicinity Map

Soils Map FEMA Flood Insurance Rate Map

Hydrologic Soil Group—El Paso County Area, Colorado

Natural ResourcesConservation Service

Web Soil SurveyNational Cooperative Soil Survey

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538700 538800 538900 539000 539100 539200 539300 539400 539500 539600 539700 539800

538700 538800 538900 539000 539100 539200 539300 539400 539500 539600 539700 539800

38° 57' 36'' N10

4° 3

3' 1

3'' W

38° 57' 36'' N

104°

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' W

38° 57' 11'' N

104°

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' W

38° 57' 11'' N

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N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS840 250 500 1000 1500

Feet0 50 100 200 300

MetersMap Scale: 1:5,420 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION

Area of Interest (AOI)Area of Interest (AOI)

SoilsSoil Rating Polygons

A

A/D

B

B/D

C

C/D

D

Not rated or not available

Soil Rating LinesA

A/D

B

B/D

C

C/D

D


Soil Rating PointsA

A/D

B

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C

C/D

D


Water FeaturesStreams and Canals

TransportationRails

Interstate Highways

US Routes

Major Roads

Local Roads

BackgroundAerial Photography

The soil surveys that comprise your AOI were mapped at 1:24,000.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

Please rely on the bar scale on each map sheet for map measurements.

Source of Map: Natural Resources Conservation ServiceWeb Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857)

Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: El Paso County Area, ColoradoSurvey Area Data: Version 16, Sep 10, 2018

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Jun 7, 2016—Aug 17, 2017

The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.




1/28/2019Page 2 of 4

Hydrologic Soil Group

Map unit symbol Map unit name Rating Acres in AOI Percent of AOI

19 Columbine gravelly sandy loam, 0 to 3 percent slopes

A 67.2 69.2%

29 Fluvaquentic Haplaquolls, nearly level

D 29.9 30.8%

Totals for Area of Interest 97.2 100.0%

Description

Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms.

The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows:

Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.

Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission.

Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.

Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.

If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes.




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Rating Options

Aggregation Method: Dominant Condition

Component Percent Cutoff: None Specified

Tie-break Rule: Higher




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USGS The National Map: Orthoimagery. Data refreshed October, 2017.

National Flood Hazard Layer FIRMette

0 500 1,000 1,500 2,000250Feet

Ü

104°

33'11

.11"W

38°57'35.40"N

104°32'33.66"W

38°57'7.42"N

SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT

SPECIAL FLOODHAZARD AREAS

Without Base Flood Elevation (BFE)Zone A, V, A99

With BFE or Depth Zone AE, AO, AH, VE, ARRegulatory Floodway

0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone XFuture Conditions 1% AnnualChance Flood Hazard Zone XArea with Reduced Flood Risk due toLevee. See Notes. Zone XArea with Flood Risk due to Levee Zone D

NO SCREEN Area of Minimal Flood Hazard Zone X

Area of Undetermined Flood Hazard Zone D

Channel, Culvert, or Storm SewerLevee, Dike, or Floodwall

Cross Sections with 1% Annual Chance17.5 Water Surface Elevation

Coastal Transect

Coastal Transect BaselineProfile BaselineHydrographic Feature

Base Flood Elevation Line (BFE)

Effective LOMRs

Limit of StudyJurisdiction Boundary

Digital Data AvailableNo Digital Data AvailableUnmapped

This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standardsThe flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 1/29/2019 at 1:00:17 AM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time.This map image is void if the one or more of the following mapelements do not appear: basemap imagery, flood zone labels,legend, scale bar, map creation date, community identifiers,FIRM panel number, and FIRM effective date. Map images forunmapped and unmodernized areas cannot be used forregulatory purposes.

Legend

OTHER AREAS OFFLOOD HAZARD

OTHER AREAS

GENERALSTRUCTURES

OTHERFEATURES

MAP PANELS

8

1:6,000

B 20.2

The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location.


APPENDIX A Hydrologic Calculations

Runoff Coef, Time of Concentration and Runoff Calcs

TCC Ready Mix - Judge Orr SiteRunoff Coeficient and Percent Impervious Calculation

LA PV RO DR HI

C5 C100

EX-A 1,509,525 sf 34.65ac AB 0% 34.65ac 100% 0% 100% 0% 0% 90% 0% 0% 100% 0% 0% 2% 0% 0% 0.0% 0.08 0.35EX-B 2,492,000 sf 57.21ac AB 0% 57.21ac 100% 0% 100% 0% 0% 90% 0% 0% 100% 0% 0% 2% 0% 0% 0.0% 0.08 0.35

DP E1 EX-A, EX-B 91.86ac AB 0% 91.86ac 100% 0% 100% 0% 0% 90% 0% 0% 100% 0% 0% 2% 0% 0% 0.0% 0.08 0.35

A 1,021,340 sf 23.45ac AB 0% 23.45ac 100% 0% 100% 0% 0% 90% 0% 0% 100% 0% 0% 2% 0% 0% 0.0% 0.08 0.35B 1,553,580 sf 35.67ac AB 0% 35.67ac 100% 0% 100% 0% 0% 90% 0% 0% 100% 0% 0% 2% 0% 0% 0.0% 0.08 0.35C 1,426,505 sf 32.75ac AB 0% 15.59ac 48% 0% 100% 17.15ac 52% 52% 90% 0% 0% 100% 0% 0% 2% 0% 0% 52.4% 0.36 0.53

Basin Runoff Coefficient is based on % Imperviousness CalculationRunoffCoefficientsandPercentsImperviousHydrologicSoilType: AB RunoffCoefCalcMethod %ImpLand Use Abb % C2 C5 C10 C25 C50 C100 Weighted

Commercial Area CO 95% 0.79 0.81 0.83 0.85 0.87 0.88 %Imp

Drives and Walks DR 100% 0.89 0.90 0.92 0.94 0.95 0.96 A

Streets - Gravel (Packed) GR 40% 0.23 0.30 0.36 0.42 0.46 0.50 AB

Historic Flow Analysis HI 2% 0.03 0.08 0.17 0.26 0.31 0.36 C

Lawns LA 0% 0.02 0.08 0.15 0.25 0.30 0.35 D

Off-site flow-Undeveloped OF 45% 0.26 0.32 0.38 0.44 0.48 0.51Roofs RO 90% 0.71 0.73 0.75 0.78 0.80 0.81

BasinRunoffCoef

% Im

perv

Land

Use

A

rea

% A

rea

Com

p La

nd

Use

% Im

p

Basin%

Imperv

% Im

perv

Land

Use

A

rea

% A

rea

Com

p La

nd

Use

% Im

p

Com

p La

nd

Use

% Im

p

% Im

perv

Land

Use

A

rea

% A

rea

Com

p La

nd

Use

% Im

p

% Im

perv

Land

Use

A

rea

% A

rea

Runoff Coefficients taken from Table 6-6: Runoff Coefficients for Rational Method from City of Colo Springs DCM

Area5LandUse

Basin/DP

BasinorDPArea(DPcontributing

basins) Soil

Typ

e

% Im

perv

Land

Use

A

rea

Area1LandUse Area2LandUse Area3LandUse Area4LandUse

% A

rea

Com

p La

nd

Use

% Im

p

18055 Drainage Calcs.xlsx Runoff Coef-CSDate Printed: 1/29/2019

Kiowa Engineering Corporation

TCC Ready Mix - Judge Orr SiteTime of Concentration Calculation

Comp.

Length Slope ti Length Slope Land Type K Velocity tt tc

Total Length

tc

(1st DP)

EX-A 34.65ac 0.08 0.0% 400lf 1.8% 30.9 min. 2920lf 2.0% SP 7 1.0 ft/sec 49.2 min. 80.0 min. 3320lf 50.8 min. 50.8min.EX-B 57.21ac 0.08 0.0% 300lf 1.7% 27.2 min. 3060lf 1.8% SP 7 0.9 ft/sec 54.3 min. 81.5 min. 3360lf 52.9 min. 52.9min.

A 23.45ac 0.08 0.0% 200lf 2.3% 20.1 min. 1600lf 1.9% SP 7 1.0 ft/sec 27.6 min. 47.7 min. 1800lf 35.9 min. 35.9min.B 35.67ac 0.08 0.0% 200lf 1.9% 21.4 min. 3140lf 2.0% SP 7 1.0 ft/sec 52.9 min. 74.3 min. 3340lf 50.9 min. 50.9min.C 32.75ac 0.36 52.4% 100lf 2.0% 10.7 min. 2100lf 2.0% GW 15 2.1 ft/sec 16.5 min. 27.2 min. 2200lf 20.7 min. 20.7min.

Equations: Table6‐2

ti (Overland) = 0.395(1.1-C5)L 0.5 S -0.333 (USDCM Eqn 6-3) tt = Lt / 60KS0.5 (USDCM Eqn 6-4) TypeofLandSurface LandType K

C5 = Runoff coefficient for 5-year tt = Channelized flow time (travel time)(min.) Grassed Waterway GW 15

L = Length of overland flow (ft) Lt = Waterway length (ft) Heavy Meadow HM 2.5

S = Average slope of overland flow path (ft/ft) K = Conveyance Factor (see Table 6-2) Nearly Bare Ground NBG 10

tc (1st DP) = (18-15i) + Lt / (60 (24i+12)S0.5) (USDCM Eqn 6-5) S = Watercourse slope (ft/ft) Paved Area PV 20

tc (1st DP) = First DP Time of Concentration in urban catchments Riprap (Not Buried) RR 6.5

Lt = Length of Flow Path Short Pasture/Lawns SP 7

i = imperviousness (expressed as a decimal) Tillage/Fields TF 5

Travel Time (tt)Sub‐BasinData TimeofConcentrationEstimate tc (1st DP in Urban

Catchments) FinaltcBasin/DesignPoint

ContributingBasins Area C5 i

Initial/Overland Time (ti)

18055 Drainage Calcs.xlsx TcDate Prepared: 1/29/2019


TCC Ready Mix - Judge Orr SiteRunoff Calculation

DesignStorm: 5Year

C*A i Sum L VelC Tc (acre) (in/hr) Q Tc C*A i Q Slope Q Q Slope (ft) (ft/s) Tt Remarks

EX-A 34.65 ac 0.08 50.8min 2.60 1.7 4.4 cfsDP E1 EX-B 57.21 ac 0.08 52.9min 4.29 1.6 7.0 cfs 52.9min 6.89 1.6 11.2cfs

A 23.45 ac 0.08 35.9min 1.76 2.2 3.9 cfsB 35.67 ac 0.08 50.9min 2.67 1.7 4.5 cfsC 32.75 ac 0.36 20.7min 11.90 3.0 36.1 cfs

TravelTimePipe Size

TotalRunoff

Street

DirectRunoff PipeStreetDesignPoint

Area Designation Area

18055 Drainage Calcs.xlsx Runoff SF2-5yrDate Prepared: 1/29/2019


TCC Ready Mix - Judge Orr SiteRunoff Calculation

DesignStorm: 100Year

C*A i Sum L VelC Tc (acre) (in/hr) Q Tc C*A i Q Slope Q Q Slope (ft) (ft/s) Tt Remarks

EX-A 34.65 ac 0.35 50.8min 12.13 2.8 34.4 cfsDP E1 EX-B 57.21 ac 0.35 52.9min 20.02 2.7 54.8 cfs 52.9min 32.15 2.7 88.0cfs

A 23.45 ac 0.35 35.9min 8.21 3.7 30.4 cfsB 35.67 ac 0.35 50.9min 12.48 2.8 35.4 cfsC 32.75 ac 0.53 20.7min 17.45 5.1 89.0 cfs

Street DesignPoint

Area Designation Area

Pipe Size

DirectRunoff TotalRunoff Street Pipe TravelTime

18055 Drainage Calcs.xlsx Runoff SF2-100yrDate Prepared: 1/29/2019



APPENDIX A.1 Supporting Tables and Figures

Chapter 6 Hydrology

May 2014 City of Colorado Springs 6-17

Drainage Criteria Manual, Volume 1

Table 6-6. Runoff Coefficients for Rational Method (Source: UDFCD 2001)

3.2 Time of Concentration

One of the basic assumptions underlying the Rational Method is that runoff is a function of the average

rainfall rate during the time required for water to flow from the hydraulically most remote part of the

drainage area under consideration to the design point. However, in practice, the time of concentration can

be an empirical value that results in reasonable and acceptable peak flow calculations.

For urban areas, the time of concentration (tc) consists of an initial time or overland flow time (ti) plus the

travel time (tt) in the storm sewer, paved gutter, roadside drainage ditch, or drainage channel. For non-

urban areas, the time of concentration consists of an overland flow time (ti) plus the time of travel in a

concentrated form, such as a swale or drainageway. The travel portion (tt) of the time of concentration

can be estimated from the hydraulic properties of the storm sewer, gutter, swale, ditch, or drainageway.

Initial time, on the other hand, will vary with surface slope, depression storage, surface cover, antecedent

rainfall, and infiltration capacity of the soil, as well as distance of surface flow. The time of concentration

is represented by Equation 6-7 for both urban and non-urban areas.

HSG A&B HSG C&D HSG A&B HSG C&D HSG A&B HSG C&D HSG A&B HSG C&D HSG A&B HSG C&D HSG A&B HSG C&D

Business

Commercial Areas 95 0.79 0.80 0.81 0.82 0.83 0.84 0.85 0.87 0.87 0.88 0.88 0.89

Neighborhood Areas 70 0.45 0.49 0.49 0.53 0.53 0.57 0.58 0.62 0.60 0.65 0.62 0.68

Residential

1/8 Acre or less 65 0.41 0.45 0.45 0.49 0.49 0.54 0.54 0.59 0.57 0.62 0.59 0.65

1/4 Acre 40 0.23 0.28 0.30 0.35 0.36 0.42 0.42 0.50 0.46 0.54 0.50 0.58

1/3 Acre 30 0.18 0.22 0.25 0.30 0.32 0.38 0.39 0.47 0.43 0.52 0.47 0.57

1/2 Acre 25 0.15 0.20 0.22 0.28 0.30 0.36 0.37 0.46 0.41 0.51 0.46 0.56

1 Acre 20 0.12 0.17 0.20 0.26 0.27 0.34 0.35 0.44 0.40 0.50 0.44 0.55

Industrial

Light Areas 80 0.57 0.60 0.59 0.63 0.63 0.66 0.66 0.70 0.68 0.72 0.70 0.74

Heavy Areas 90 0.71 0.73 0.73 0.75 0.75 0.77 0.78 0.80 0.80 0.82 0.81 0.83

Parks and Cemeteries 7 0.05 0.09 0.12 0.19 0.20 0.29 0.30 0.40 0.34 0.46 0.39 0.52

Playgrounds 13 0.07 0.13 0.16 0.23 0.24 0.31 0.32 0.42 0.37 0.48 0.41 0.54

Railroad Yard Areas 40 0.23 0.28 0.30 0.35 0.36 0.42 0.42 0.50 0.46 0.54 0.50 0.58

Undeveloped Areas

Historic Flow Analysis--

Greenbelts, Agriculture2

0.03 0.05 0.09 0.16 0.17 0.26 0.26 0.38 0.31 0.45 0.36 0.51

Pasture/Meadow 0 0.02 0.04 0.08 0.15 0.15 0.25 0.25 0.37 0.30 0.44 0.35 0.50

Forest 0 0.02 0.04 0.08 0.15 0.15 0.25 0.25 0.37 0.30 0.44 0.35 0.50

Exposed Rock 100 0.89 0.89 0.90 0.90 0.92 0.92 0.94 0.94 0.95 0.95 0.96 0.96

Offsite Flow Analysis (when

landuse is undefined)45

0.26 0.31 0.32 0.37 0.38 0.44 0.44 0.51 0.48 0.55 0.51 0.59

Streets

Paved 100 0.89 0.89 0.90 0.90 0.92 0.92 0.94 0.94 0.95 0.95 0.96 0.96

Gravel 80 0.57 0.60 0.59 0.63 0.63 0.66 0.66 0.70 0.68 0.72 0.70 0.74

Drive and Walks 100 0.89 0.89 0.90 0.90 0.92 0.92 0.94 0.94 0.95 0.95 0.96 0.96

Roofs 90 0.71 0.73 0.73 0.75 0.75 0.77 0.78 0.80 0.80 0.82 0.81 0.83

Lawns 0 0.02 0.04 0.08 0.15 0.15 0.25 0.25 0.37 0.30 0.44 0.35 0.50

Land Use or Surface

Characteristics

Percent

Impervious

Runoff Coefficients

2-year 5-year 10-year 25-year 50-year 100-year

Hydrology Chapter 6

6-10 City of Colorado Springs May 2014


For Colorado Springs and much of the Fountain Creek watershed, the 1-hour depths are fairly uniform

and are summarized in Table 6-2. Depending on the location of the project, rainfall depths may be

calculated using the described method and the NOAA Atlas maps shown in Figures 6-6 through 6-17.

Table 6-2. Rainfall Depths for Colorado Springs

Return

Period

1-Hour

Depth

6-Hour

Depth

24-Hour

Depth

2 1.19 1.70 2.10

5 1.50 2.10 2.70

10 1.75 2.40 3.20

25 2.00 2.90 3.60

50 2.25 3.20 4.20

100 2.52 3.50 4.60

Where Z= 6,840 ft/100

These depths can be applied to the design storms or converted to intensities (inches/hour) for the Rational

Method as described below. However, as the basin area increases, it is unlikely that the reported point

rainfalls will occur uniformly over the entire basin. To account for this characteristic of rain storms an

adjustment factor, the Depth Area Reduction Factor (DARF) is applied. This adjustment to rainfall depth

and its effect on design storms is also described below. The UDFCD UD-Rain spreadsheet, available on

UDFCD’s website, also provides tools to calculate point rainfall depths and Intensity-Duration-Frequency

curves2 and should produce similar depth calculation results.

2.2 Design Storms

Design storms are used as input into rainfall/runoff models and provide a representation of the typical

temporal distribution of rainfall events when the creation or routing of runoff hydrographs is required. It

has long been observed that rainstorms in the Front Range of Colorado tend to occur as either short-

duration, high-intensity, localized, convective thunderstorms (cloud bursts) or longer-duration, lower-

intensity, broader, frontal (general) storms. The significance of these two types of events is primarily

determined by the size of the drainage basin being studied. Thunderstorms can create high rates of runoff

within a relatively small area, quickly, but their influence may not be significant very far downstream.

Frontal storms may not create high rates of runoff within smaller drainage basins due to their lower

intensity, but tend to produce larger flood flows that can be hazardous over a broader area and extend

further downstream.

§ Thunderstorms: Based on the extensive evaluation of rain storms completed in the Carlton study

(Carlton 2011), it was determined that typical thunderstorms have a duration of about 2 hours. The

study evaluated over 300,000 storm cells using gage-adjusted NEXRAD data, collected over a 14-

year period (1994 to 2008). Storms lasting longer than 3 hours were rarely found. Therefore, the

results of the Carlton study have been used to define the shorter duration design storms.

To determine the temporal distribution of thunderstorms, 22 gage-adjusted NEXRAD storm cells

were studied in detail. Through a process described in a technical memorandum prepared by the City

of Colorado Springs (City of Colorado Springs 2012), the results of this analysis were interpreted and

normalized to the 1-hour rainfall depth to create the distribution shown in Table 6-3 with a 5 minute

time interval for drainage basins up to 1 square mile in size. This distribution represents the rainfall

Hydrology Chapter 6

6-52 City of Colorado Springs May 2014


Figure 6-5. Colorado Springs Rainfall Intensity Duration Frequency

IDF Equations

I100 = -2.52 ln(D) + 12.735

I50 = -2.25 ln(D) + 11.375

I25 = -2.00 ln(D) + 10.111

I10 = -1.75 ln(D) + 8.847

I5 = -1.50 ln(D) + 7.583

I2 = -1.19 ln(D) + 6.035

Note: Values calculated by

equations may not precisely

duplicate values read from figure.


APPENDIX B Full Spectrum Detention Calculations

Project:

Basin ID:

Depth Increment = ft

Required Volume Calculation Top of Micropool -- 0.00 -- -- -- 0 0.000

Selected BMP Type = EDB -- 0.30 -- -- -- 20 0.000 3 0.000

Watershed Area = 32.75 acres -- 1.30 -- -- -- 5,700 0.131 2,806 0.064

Watershed Length = 2,200 ft -- 2.30 -- -- -- 28,570 0.656 19,998 0.459Watershed Slope = 0.020 ft/ft -- 3.30 -- -- -- 52,220 1.199 60,393 1.386

Watershed Imperviousness = 52.40% percent -- 4.30 -- -- -- 70,080 1.609 121,543 2.790Percentage Hydrologic Soil Group A = 100.0% percent -- 5.30 -- -- -- 75,460 1.732 194,313 4.461Percentage Hydrologic Soil Group B = 0.0% percent -- 6.30 -- -- -- 80,930 1.858 272,508 6.256

Percentage Hydrologic Soil Groups C/D = 0.0% percent -- -- -- --Desired WQCV Drain Time = 40.0 hours -- -- -- --

Location for 1-hr Rainfall Depths = User Input -- -- -- --Water Quality Capture Volume (WQCV) = 0.581 acre-feet -- -- -- --

Excess Urban Runoff Volume (EURV) = 2.005 acre-feet -- -- -- --2-yr Runoff Volume (P1 = 1.19 in.) = 1.370 acre-feet 1.19 inches -- -- -- --5-yr Runoff Volume (P1 = 1.5 in.) = 1.799 acre-feet 1.50 inches -- -- -- --

10-yr Runoff Volume (P1 = 1.75 in.) = 2.210 acre-feet 1.75 inches -- -- -- --25-yr Runoff Volume (P1 = 2 in.) = 2.740 acre-feet 2.00 inches -- -- -- --

50-yr Runoff Volume (P1 = 2.25 in.) = 3.391 acre-feet 2.25 inches -- -- -- --100-yr Runoff Volume (P1 = 2.52 in.) = 4.155 acre-feet 2.52 inches -- -- -- --

500-yr Runoff Volume (P1 = 0 in.) = 0.000 acre-feet inches -- -- -- --Approximate 2-yr Detention Volume = 1.292 acre-feet -- -- -- --Approximate 5-yr Detention Volume = 1.699 acre-feet -- -- -- --

Approximate 10-yr Detention Volume = 2.068 acre-feet -- -- -- --Approximate 25-yr Detention Volume = 2.523 acre-feet -- -- -- --Approximate 50-yr Detention Volume = 2.809 acre-feet -- -- -- --

Approximate 100-yr Detention Volume = 3.148 acre-feet -- -- -- ---- -- -- --

Stage-Storage Calculation -- -- -- --Zone 1 Volume (WQCV) = 0.581 acre-feet -- -- -- --

Zone 2 Volume (EURV - Zone 1) = 1.424 acre-feet -- -- -- --Zone 3 (100yr + 1 / 2 WQCV - Zones 1 & 2) = 1.433 acre-feet -- -- -- --

Total Detention Basin Volume = 3.438 acre-feet -- -- -- --Initial Surcharge Volume (ISV) = user ft 3̂ -- -- -- --Initial Surcharge Depth (ISD) = user ft -- -- -- --

Total Available Detention Depth (Htotal) = user ft -- -- -- --Depth of Trickle Channel (HTC) = user ft -- -- -- --Slope of Trickle Channel (STC) = user ft/ft -- -- -- --

Slopes of Main Basin Sides (Smain) = user H:V -- -- -- --Basin Length-to-Width Ratio (RL/W) = user -- -- -- --

-- -- -- --Initial Surcharge Area (AISV) = user ft 2̂ -- -- -- --

Surcharge Volume Length (LISV) = user ft -- -- -- --Surcharge Volume Width (W ISV) = user ft -- -- -- --

Depth of Basin Floor (HFLOOR) = user ft -- -- -- --Length of Basin Floor (LFLOOR) = user ft -- -- -- --Width of Basin Floor (WFLOOR) = user ft -- -- -- --

Area of Basin Floor (AFLOOR) = user ft 2̂ -- -- -- --Volume of Basin Floor (VFLOOR) = user ft 3̂ -- -- -- --

Depth of Main Basin (HMAIN) = user ft -- -- -- --Length of Main Basin (LMAIN) = user ft -- -- -- --Width of Main Basin (WMAIN) = user ft -- -- -- --

Area of Main Basin (AMAIN) = user ft 2̂ -- -- -- --Volume of Main Basin (VMAIN) = user ft 3̂ -- -- -- --

Calculated Total Basin Volume (Vtotal) = user acre-feet -- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- ---- -- -- --

Optional User Override1-hr Precipitation

Volume (ft 3̂)

Volume (ac-ft)

Area (acre)

DETENTION BASIN STAGE‐STORAGE TABLE BUILDER

Optional Override

Area (ft 2̂)Length

(ft)

Optional Override Stage (ft)

Stage(ft)

Stage - StorageDescription

Area (ft 2̂)

Width (ft)

Pete Lien & Sons Ready Mix - Judge Orr Site

UD-Detention, Version 3.07 (February 2017)

Example Zone Configuration (Retention Pond)

18055 UD-Detention_v3.07.xlsm, Basin 1/29/2019, 12:52 AM

Project:

Basin ID:

Stage (ft) Zone Volume (ac‐ft) Outlet Type

Zone 1 (WQCV) 2.48 0.581 Orifice Plate

Zone 2 (EURV) 3.78 1.424 Orifice Plate

Z3 (100+1/2WQCV) 4.70 1.433 Weir&Pipe (Restrict)

3.438 Total

User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP) Calculated Parameters for Underdrain

Underdrain Orifice Invert Depth = N/A ft (distance below the filtration media surface) Underdrain Orifice Area = N/A ft2

Underdrain Orifice Diameter = N/A inches Underdrain Orifice Centroid = N/A feet

User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP) Calculated Parameters for Plate

Invert of Lowest Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = N/A ft2

Depth at top of Zone using Orifice Plate = 3.78 ft (relative to basin bottom at Stage = 0 ft) Elliptical Half‐Width = N/A feet

Orifice Plate: Orifice Vertical Spacing = 15.10 inches Elliptical Slot Centroid = N/A feet

Orifice Plate: Orifice Area per Row = sq. inches Elliptical Slot Area = N/A ft2

User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest)

Row 1 (required) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional)Stage of Orifice Centroid (ft) 0.00 1.26 2.52

Orifice Area (sq. inches) 0.00 0.00 0.00

Row 9 (optional) Row 10 (optional) Row 11 (optional) Row 12 (optional) Row 13 (optional) Row 14 (optional) Row 15 (optional) Row 16 (optional)Stage of Orifice Centroid (ft)

Orifice Area (sq. inches)

User Input: Vertical Orifice (Circular or Rectangular) Calculated Parameters for Vertical Orifice

Not Selected Not Selected Not Selected Not Selected

Invert of Vertical Orifice = N/A N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area = N/A N/A ft2

Depth at top of Zone using Vertical Orifice = N/A N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = N/A N/A feet

Vertical Orifice Diameter = N/A N/A inches

User Input: Overflow Weir (Dropbox) and Grate (Flat or Sloped) Calculated Parameters for Overflow Weir

Zone 3 Weir Not Selected Zone 3 Weir Not Selected

Overflow Weir Front Edge Height, Ho = 3.78 N/A ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = N/A feet

Overflow Weir Front Edge Length = N/A feet Over Flow Weir Slope Length = N/A feet

Overflow Weir Slope = N/A H:V (enter zero for flat grate) Grate Open Area / 100‐yr Orifice Area = N/A should be > 4

Horiz. Length of Weir Sides = N/A feet Overflow Grate Open Area w/o Debris = N/A ft2

Overflow Grate Open Area % = N/A %, grate open area/total area Overflow Grate Open Area w/ Debris = N/A ft2

Debris Clogging % = N/A %

User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice) Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate

Zone 3 Restrictor Not Selected Zone 3 Restrictor Not Selected

Depth to Invert of Outlet Pipe = N/A ft (distance below basin bottom at Stage = 0 ft) Outlet Orifice Area = N/A ft2

Outlet Pipe Diameter = N/A inches Outlet Orifice Centroid = N/A feet

Restrictor Plate Height Above Pipe Invert = inches Half‐Central Angle of Restrictor Plate on Pipe = N/A radians

User Input: Emergency Spillway (Rectangular or Trapezoidal) Calculated Parameters for Spillway

Spillway Invert Stage= ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= feet

Spillway Crest Length = feet Stage at Top of Freeboard = feet

Spillway End Slopes = H:V Basin Area at Top of Freeboard = acres

Freeboard above Max Water Surface = feet

Routed Hydrograph Results

Design Storm Return Period = WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year

One-Hour Rainfall Depth (in) = 0.53 1.07 1.19 1.50 1.75 2.00 2.25 2.52 0.00

Calculated Runoff Volume (acre-ft) = 0.581 2.005 1.370 1.799 2.210 2.740 3.391 4.155 0.000

OPTIONAL Override Runoff Volume (acre-ft) =Inflow Hydrograph Volume (acre-ft) = 0.580 2.005 1.370 1.799 2.211 2.741 3.392 4.156 #N/A

Predevelopment Unit Peak Flow, q (cfs/acre) = 0.00 0.00 0.00 0.00 0.01 0.02 0.16 0.38 0.00

Predevelopment Peak Q (cfs) = 0.0 0.0 0.0 0.1 0.3 0.7 5.1 12.5 0.0

Peak Inflow Q (cfs) = 8.2 27.9 19.1 25.1 30.7 38.0 46.8 57.2 #N/A

Peak Outflow Q (cfs) = #N/A

Ratio Peak Outflow to Predevelopment Q = #N/A

Structure Controlling Flow = #N/A

Max Velocity through Grate 1 (fps) = #N/A

Max Velocity through Grate 2 (fps) = #N/A

Time to Drain 97% of Inflow Volume (hours) = #N/A

Time to Drain 99% of Inflow Volume (hours) = #N/A

Maximum Ponding Depth (ft) = #N/A

Area at Maximum Ponding Depth (acres) = #N/A

Maximum Volume Stored (acre-ft) = #N/A

Detention Basin Outlet Structure Design

UD‐Detention, Version 3.07 (February 2017)Pete Lien & Sons Ready Mix Plant - Judge Orr Site

Example Zone Configuration (Retention Pond)


APPENDIX C Exhibit A: Drainage Plan – Existing Conditions

Exhibit B: Drainage Plan – Proposed Conditions

preliminary drainage report pete lien & sons ready mix concrete … · 2019-02-08 ·...

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