THE TRAILS AT ASPEN RIDGE FILING PRELIMINARY DRAINAGE REPORT EL PASO COUNTY, COLORADO PROJECT NO. 181710415 Prepared for: COLA LLC 555 MIDDLE CREEK PARKWAY COLORADO SPRINGS, CO 80921 Prepared by: STANTEC CONSULTING SERVICES, INC 5725 MARK DABLING BLVD, SUITE190 COLORADO SPRINGS, CO 80919 January 31, 2019 PCD File No:
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Aspen Ridge PDR - Microsoft...U:\181710415\record\reports\drainage_report\PDR - Filings 2 thru 5\Aspen Ridge PDR.doc 6 The western third of the site drains to the Big Johnson Reservoir
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THE TRAILS AT ASPEN RIDGE FILING PRELIMINARY DRAINAGE REPORT EL PASO COUNTY, COLORADO
PROJECT NO. 181710415
Prepared for: COLA LLC 555 MIDDLE CREEK PARKWAY COLORADO SPRINGS, CO 80921
Prepared by: STANTEC CONSULTING SERVICES, INC 5725 MARK DABLING BLVD, SUITE190 COLORADO SPRINGS, CO 80919
January 31, 2019
PCD File No:
CERTIFICATIONS Design 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 County for drainage reports and said report is in conformity with the applicable 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. _____________________________________________ Seal Charlene. M. Durham, P.E. #36727 Owner/Developer’s Statement: I, the owner/developer have read and will comply with all of the requirements specified in this drainage report and plan. By (Signature): Date: By (Printed): Title: Address: 555 Middle Creek Parkway Colorado Springs, CO 80921 El Paso County: Filed in accordance with the requirements of the El Paso County Land Development Code, Drainage Criteria Manual Volumes 1 and 2, and the Engineering Criteria Manual, as amended. _________________________________________ ____________ Jennifer Irvine, P.E., Date County Engineer / ECM Administrator
GENERAL CONCEPT ............................................................................................................................................................. 15 STORM SEWER SYSTEM ....................................................................................................................................................... 16 ON-SITE WATER QUALITY & DETENTION ........................................................................................................................... 16 OFFSITE ANALYSIS .............................................................................................................................................................. 16 FOUR STEP PROCESS ........................................................................................................................................................... 16
EROSION CONTROL ........................................................................................................................................................ 17
PURPOSE The purpose of this Preliminary Drainage Report (PDR) is to identify and analyze on and offsite drainage patterns, locate and identify tributary and downstream drainage features and facilities that impact the proposed site. Runoff quantities and proposed facilities have been calculated using the City of Colorado Springs/El Paso County Drainage Criteria Manual (DCM) revised November 1991; and in accordance with El Paso County ordinance 15-042. The Trails at Aspen Ridge is approximately 117.98 acres and is part of the overall Waterview Development, which is 721.8 acres within El Paso County. This area includes the area east of Powers Boulevard and south of Bradley Road. The entire site 117.98 acres will be single family residential with 516 lots, open space/landscape, tract for future development and public and private streets. The site is bordered by Powers Boulevard to the west, Bradley Road to the north and undeveloped areas to the east and The Trails at Aspen Ridge Filing No. 1 to the south.
GENERAL LOCATION & DESCRIPTION The Trails at Aspen Ridge development site is located within 2 major drainage basins, Big Johnson Reservoir on the west and Jimmy Camp Creek on the east. Big Johnson Reservoir Drainage Basin Planning Study (DBPS) had originally stated that developed flows would be released into the Big Johnson Reservoir and no detention would be required as long as water quality measures were taken within the basin. However, within recent years, this is no longer the case. Detention will be required within all basins. There is currently no approved El Paso County Drainage Basin Planning Study (DBPS) for Jimmy Camp. This report may be updated if/when a DBPS is approved. Design, phasing, responsibility and maintenance of any proposed improvements will be discussed in the final drainage report. Fees will be assessed and paid according to the current rates at the time of platting for each filing.
Description of Property The project site is 117.98 acres of vegetation, consisting of short grasses and weeds. The average slope of the site is between 3 and 8%, with a minimum slope of 1% along Powers Boulevard and a maximum of 19% through the central area and along the eastern boundary of the site. The site is composed of several different soil types. From the NRCS report in Appendix A, the site falls into the following soil types: 8 – Blakeland loamy sand (1-9%) – Type A Soil
52 - Manzanst clay loam (3-8%) – Type C Soil 56 - Nelson Tassel fine sandy loam (3-19%) – Nelson Type B Soil, Tassel Type D Soil 86 - Stoneham sandy loam (3-8%) – Type B Soil 108 - Wiley silt loam (3-9%) – Type B Soil 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.
Climate The climate of the site is typical of a sub-humid to semiarid climate with mild summers and winters. The average temperature is 31 degrees F in the winter and 68.4 degrees in the summer. Total annual precipitation is 15.21 inches.
Floodplain Statement The Flood Insurance Rate Map (FIRM No. 08041C0768-G dated 12/7/18) indicates that there is no floodplain in the vicinity of the proposed site. See Figure 2: FIRM.
Utilities & Other Encumbrances The site is currently undeveloped and there are no known utilities on site.
Drainage Basins and Sub-Basins
Major Basin Description The Trails at Aspen Ridge development lies within 2 major basins, Big Johnson and Jimmy Camp Creek Drainage Basins. This project is part of the overall Waterview Development and design complies with the Amendment to the Master Development Drainage Plan (MDDP) dated July 21, 2014 by Springs Engineering.
The western third of the site drains to the Big Johnson Reservoir and will need to be detained prior to crossing under Powers Boulevard. The remainder of the site is within the Jimmy Camp Creek Basin and will be detained with the detention pond designed as part of Filing No. 1, prior to exiting the site. All developed runoff will meet El Paso County standards for water quality and discharge rates.
Sub-Basin Description
Historic Drainage Patterns The historic drainage patterns of the site were analyzed in the Master Development Drainage Plan for Waterview by Merrick and Company and the Amendment to the Master Development Drainage Plan (MDDP) dated July 21, 2014 by Springs Engineering. No new historic calculations were done.
Off-Site Drainage There is an off-site basin upstream of the Jimmy Camp Creek Basin that affects the site drainage. A twin set of CMP’s under Bradley Road will contribute flow to the proposed site. It is shown in the hydrology calculations for existing and proposed basins. Based on the MDDP, this basin will release at historic flow rates and any developments or improvements to the basin will need to address their own water quality and detention needs. Currently twin 42” cmp’s carry the flow under Bradley Road on site. These existing structures will tie into the proposed on-site storm system. Currently, flows leave offsite at 10 different locations where flows release to Aspen Ridge Filing No. 1 (10 occur within the Jimmy Camp basin and 2 are in the Big Johnson basin). There are two locations, both located along Powers Boulevard, where flows exit the entire Trails at Aspen Ridge development. Flows within the Big Johnson Basin run towards the southwest corner of the site, where they are directed to an existing roadside ditch along Powers Boulevard, which releases to either an existing 48” CMP or 60” CMP. Flows along the south side of Bradley Road, continue to the east and exit at Design Point JCD-C. All of the Jimmy Camp basin flows, will enter into Aspen Ridge Filing No.1. These flows have been accounted for in the design of the storm sewer system and East Detention Pond in Filing No. 1.
DRAINAGE DESIGN CRITERIA
Development Criteria Reference The City of Colorado Springs Drainage Criteria Manual (DCM), El Paso County Engineering Criteria Manual (ECM), El Paso County Ordinance 15-042 and Urban Storm Drainage Criteria Manual (USDCM) by Urban Drainage & Flood Control District was used in preparation of this report. Additional preliminary and final drainage plans, master development drainage plans and drainage basin planning studies used in the preparation of the report are listed in the References Section.
Hydrologic Criteria
Rational Method The rational method was used to determine onsite flows, as required by the current City of Colorado Springs Drainage Criteria Manual (DCM). Both the 5-year and 100-year storm events were considered in this analysis. Runoff coefficients appropriate to the existing and proposed land uses were selected for an SCS type “B” soil from Table 6-6 of the DCM. The time of concentration was calculated per DCM requirements. Rational Method results are shown in the Appendix B & C. USDCM spreadsheets were used to design the detention and water quality pond features.
Storm Sewer Design Storm Sewer systems will be designed to the 100-year storm and checked with the 5-year storm. Inlets will be placed at sump areas and intersections where street flow is larger than street capacity. UDFCD Inlet spreadsheet will be used to determine the size of all at-grade and sump inlets. There will be a minimum of three systems within the site, one which within the Big Johnson Basin, connecting to the Filing No. 1 system and releasing into the West Detention Pond and two, tying into Filing No. 1 storm systems, releasing into the East Pond in the Jimmy Camp Basin. These facilities will be designed as part of the Final Drainage Report (FDR) for the site.
Detention Storage Criteria This report addresses the preliminary design stage of the west detention/water quality feature within the proposed development. Ponds and water quality are based on the UDFCD UD-Detention Version 3.07 spreadsheet for an Extended Detention Basin. Preliminary storage volumes and outflows have been calculated for the West Detention Pond facility. A copy of this design has been included in the appendix, as detention was not considered in the original MDDP report of the Big Johnson/Crus Gulch basin. Final calculations will be completed at the time of final platting for this facility.
DRAINAGE BASINS There is one off site basin (OS-1) (not a part of the Aspen Ridge development area) which contributes flow to the Jimmy Camp Basin of the development (JCD1) via twin 42” cmp’s under Bradley Road (Design Point A). The contributing area of the basin is 12.73 acres, is currently undeveloped and generates 44.4 cfs and 48.3 cfs for the minor and major storm events.
Existing Drainage Analysis
Big Johnson Basin There are three basins which are in the Big Johnson Basin portion of the development. One basin is offsite of the Aspen Ridge boundary and the other two basins release flows under Powers Boulevard via existing culverts to the Big Johnson Reservoir to the west.
Basin OS-13 (15.06 acres) is an offsite portion of Basin BJD-13 shown in the MDDP. Flow is directed to an existing low spot located at Powers Boulevard (Design Point BJD-M) where an existing 60” cmp will release the flow into the open space on the west side of Powers and into the Big Johnson Reservoir. Flows for this basin are 7.1 cfs for the 5-year storm and 37.9 cfs for the 100-year storm.
Basin BJD-13 (29.93 acres) is an onsite portion of Basin BJD-13 from the MDDP. Flow is directed to an existing low spot located at Powers Boulevard (Design Point BJD-M) where an existing 60” cmp will release, combined with flow from OS-13, into the open space on the west side of Powers and into the Big Johnson Reservoir. The existing culvert will release into the open space on the west side of Powers and reach the Big Johnson Reservoir. This basin generates 29.93 cfs and 61.7 cfs for the 5 and 100-year storms.
Basin BJD-13A (6.81 acres) is an onsite portion of Basin BJD-13 from the MDDP. This flow will leave the site at the southwest corner (Design Point B) where it is directed along Powers Boulevard to an existing 48” cmp directly south of the site. The existing culvert will release into
the open space on the west side of Powers and reach the Big Johnson Reservoir. This basin generates 3.6 cfs and 19.2 cfs for the 5 and 100-year storms.
Jimmy Camp Basin There are 7 existing basins which are located within the Jimmy Camp basin for this proposed development.
There is one off site basin (OS-1), north of Bradley Road, which contributes flow to the Jimmy Camp Basin of the development via twin 42” cmp’s under Bradley Road (Design Point A). The contributing area of the basin is 14.40 acres, is currently undeveloped and generates 7.1 cfs and 71.1 cfs for the minor and major storm events.
Basin JCD-2 (9.25 acres) located at Bradley Road and the northeast corner of the site. Flows in
this basin are carried within the roadside ditch and leave the site at Design Point JCD-C (Corresponds to the same design point in the MDDP). Flows for this basin are 5.0 cfs for the 5-year storm and 26.6 cfs for the 100-year storm.
OS-3 (1.50 acres) is within the western portion of the MDDP Basin JCD-1, which is offsite. This Basin is located along the Big Johnson/Jimmy Camp Basin boundary. Flow is conveyed through natural swales till it enters onsite Basin JCD-3 at Design Point D. This basin generates 0.79 cfs and 4.3 cfs for the 5 and 100-year storms.
Basin OS-4 (17.38 acres) is the east portion of the MDDP Basin JCD-1, which is offsite. Flow is conveyed through natural swales till it enters the site along the northern boundary at Design Point E. This basin generates 1.8 cfs and 47.3 cfs for the 5 and 100-year storms.
Basin JCD-3 (23.02 acres) is the onsite portion of the west half of the MDDP basin JCD-1. Flow is conveyed through natural swales till it exits the site along the southeast corner of the site, where it will enter The Trails at Aspen Ridge Filing No. 1 at Design Point B-2. This basin generates 17.8 cfs and 121.2 cfs for the 5 and 100-year storms.
Basin JCD-4 (48.02 acres) is the onsite portion of the remaining portion of the MDDP basin JCD-1. Flow is conveyed through natural swales till it exits the site along the southern boundary, where it will enter The Trails at Aspen Ridge Filing No. 1 at Design Point B-1. This basin generates 12.3 cfs and 58.1 cfs for the 5 and 100-year storms.
Basin JCD-1A (4.91 acres) is the onsite portion of the MDDP Basin JCD-1A and is located along the southern boundary of the site and exits to the south onto The Trails at Aspen Ridge Filing No. 1 at Design Point C-1. Flows for this basin are 2.7 cfs for the 5-year storm and 14.6 cfs for the 100-year storm.
Proposed Drainage Analysis The proposed development lies within two separate basins: Jimmy Camp Creek and the Big Johnson. The eastern two-thirds, which is in the Jimmy Camp Creek Basin, will all head to the east towards the East Pond, designed as part of Filing No. 1. The western third of the site is directed towards the West Pond, prior to exiting under Powers Boulevard vis an existing culvert. Below is a summary of the Design Points within each of these two basins.
Big Johnson Basin The area within the Big Johnson Basin is approximately 37.4 acres. Flows will all be directed via curb and gutter to various inlets through the site, where all flows will into the West Pond or a WQ facility at the southwest corner. Both of these locations direct flows to existing culverts under Powers Boulevard. Below is a summary of the design points within the Big Johnson Basin.
Design Point HHH (Q5=6.0, Q100=67.1) combines flow from Basins BJ-2A and BJ-11 at the northwest corner of Natural Bridge Rail and Sidewinder Drive. Flow will continue to the south as gutter flow in Sidewinder Drive to DP-III. It is anticipated that at-grade inlets will need to be installed along Sidewinder Drive due to street capacity issues.
Design Point III (Q5=6.9, Q100=65.5) combines flow from Basin BJ-2B and Design Point HHH at
the northwest corner of Rainy Creek Trail and Sidewinder Drive. Flow will continue to the south as gutter flow in Sidewinder Drive to DP-JJJ. It is anticipated that at-grade inlets will need to be installed along Sidewinder Drive due to street capacity issues.
Design Point JJJ (Q5=7.6, Q100=65.2) combines flow from Basin BJ-2C and Design Point III at the northwest corner of Turkey Flat Lane and Sidewinder Drive. Flow will continue to the south as gutter flow in Sidewinder Drive to DP-AAA. It is anticipated that at-grade inlets will need to be installed along Sidewinder Drive due to street capacity issues.
Design Point AAA (Q5=8.1, Q100=65.1) consists of flow from Basin BJ-2D along with Design Point JJJ as they enter the Filing No. 1 development, on the west side of Sidewinder Drive. Flow will continue to the south as gutter flow in Sidewinder Drive to DP-DDD.
Design Point KKK (Q5=3.9, Q100=8.0) combines flow from Basins BJ-1A and BJ-1B at the northeast corner of Rainy Creek Drive and Sidewinder Drive. Flow will continue to the south as gutter flow in Sidewinder Drive to DP-BBB. It is anticipated that at-grade inlets will need to be installed along Sidewinder Drive due to street capacity issues.
Design Point BBB (Q5=7.3, Q100=15.0) consists of flow from Basin BJ-1C and Design Point KKK as it enters the Filing No. 1 development, on the east side of Sidewinder Drive. Flows will continue to the south as gutter flow in Sidewinder Drive DP-CCC. It is anticipated that future at-grade inlets will need to be installed due to street capacity issues.
Design Point CCC (Q5=7.4, Q100=15.4) is part of Filing No. 1 and consists of flow from Basin BJ-4 with the flow from DP-BBB. An at-grade inlet will be installed to intercept these flows in Sidewinder Drive. Any flow by will continue to the west in Buffalo Horn Drive to DP-DDD.
Design Point DDD (Q5=16.0, Q100=82.9) falls within Filing No. 1 and consists of flow from
Basin BJ-3 with DP-AAA and flow by from Inlet DP-CCC. Flows are combined at the intersection of Sidewinder Drive and Buffalo Horn Drive and continue to the west as gutter flow in Buffalo Horn Drive to DP-EEE.
Design Point LLL (Q5=5.7, Q100=12.6) combines flow from Basins BJ-22 and BJ-23 at the northwest corner of Turkey Flat Lane and Triple Tree Loop. Flow will continue to the south as gutter flow in Triple Tree Loop to DP-EEE. It is anticipated that at-grade inlets may need to be installed along Triple Tree Loop due to street capacity issues.
Design Point EEE (Q5=23.9, Q100=96.9) consists of flow from Basins BJ-5, BJ-24 and BJ-25 combined with flow from Design Point LLL and flow by from inlet DP-DDD. A sump inlet will be installed to intercept these flows.
Design Point FFF (Q5=5.9, Q100=12.9) consists of flow from Basins BJ-6 and BJ-21. A sump inlet will be installed to intercept this flow.
Design Point GGG (Q5=2.0, Q100=6.3) consists of flow from Basins BJ-7 and BJ-26. Flow from
this basin drains to the southwest corner of the site, where a proposed rain garden will treat the flow, prior to exiting the site and entering the existing roadside ditch along Powers Boulevard, running to the south.
Design Point MMM (Q5=5.6, Q100=11.95) combines flow from Basin BJ-15 and BJ-16 at the northeast corner of Golden Rout Street and Natural Bridge Rail. Flow will continue to the west as gutter flow in Natural Bridge Rail to DP-NNN. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point NNN (Q5=14.1, Q100=30.45) combines flow from Basins BJ-17 and BJ-18 with
Design Point at the east side of the knuckle between Blue Miner Street and Natural Bridge Rail. A sump inlet will be installed at this location to intercept the flows.
Design Point OOO (Q5=8.7, Q100=18.9) combines flow from Basins BJ-13, BJ-14 and BJ-20 at
the west side of the knuckle between Blue Miner Street and Natural Bridge Rail. A sump inlet will be installed at this location to intercept the flows.
Design Point PPP (Q5=22.6, Q100=48.9) combines flow from Design Points NNN and OOO.
Flow will be released at this location into the West Pond.
Design Point QQQ (Q5=59.4, Q100=186.4) combines flow from Basins BJ-10 and BJ-27 with Design Points EEE, FFF and PPP. This is the combined flow from 2 storm systems within the Big Johnson basin, releasing into the West Pond.
Jimmy Camp Creek Basin The area within the Jimmy Camp Creek Basin is approximately 80.5 acres. The proposed development is located at the upstream end of the drainage basin, and will release onto Filing No. 1 of The Trails at Aspen Ridge, at various locations, which will eventually release into the East Pond, designed in the FDR for Filing No. 1. Drainage for Filing No. 1 took into account the flows from this area. Flows will all be directed via curb and gutter to various inlets through the site. Below is a summary of the design points within the Jimmy Camp Creek Basin.
Design Point A (Q5=3.8, Q100=7.8) consists of flow from Basin JC-1. This basin collects flow from Bradley Road, west of the intersection with Legacy Drive.
Design Point B (Q5=11.5, Q100=22.8) consists of flow from Basins JC-2 and JC-3 combined DP-A. Flows will continue to the east, to the future intersection of Blackmer Drive.
Design Point JCD-C is the location on the east side of the project at the north corner where flows exit the site along Bradley Road. This includes Basin JC-4 combined with DP-B, which flow east
in existing roadside ditch on the south side of Bradley Road, until improvements are made to the roadway. Flows at this location are 13.4 and 26.6 cfs for the minor and major storms. Existing flows are 5.0 cfs and 26.6 cfs. Even though there is a small increase in the 5-year storm, due to the over detention with the East Pond, overall discharge in the Jimmy Camp Creek Basin will be less than historic and there will be no negative impacts to downstream facilities. Upgraded drainage facilities will be designed with future Bradley Road improvements.
Design Point C (Q5=11.5, Q100=23.3) combines flow from Basins JC-5A and JC-5E at the northeast corner of Bull Run Drive and Frontside Drive. Flow will continue to the east as gutter flow in Frontside Drive to DP-D. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point D (Q5=12.9, Q100=26.0) combines flow from Basin JC-5D and Design Point C at the northwest corner of Frontside Drive and Big Johnson Drive. Flow will continue to the north as gutter flow in Big Johnson Drive to DP-E. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point E (Q5=20.9, Q100=42.9) combines flow from Basins JC-6B and JC-6C with Design Point D at the low point on the south side of Winner Creek Drive. A sump inlet will be installed to intercept these flows.
Design Point F (Q5=13.0, Q100=11.95) consists of flow from Basins JC-5F and JC-6A at the low point on the north side of Winner Creek Drive, just west of Blackmer Street. A sump inlet will be installed to intercept these flows.
Design Point G (Q5=0.8, Q100=1.7) is flow from Basin JC-5G located with the north half of Frontside Drive, east of Big Johnson Drive. Design point is located at a low point in the road. A sump inlet will be installed to intercept the flows.
Design Point H (Q5=1.7, Q100=3.5) is flow from Basin JC-5H located with the south half of Frontside Drive, east of Big Johnson Drive. Design point is located at a low point in the road. A sump inlet will be installed to intercept the flows.
Design Point I (Q5=6.3, Q100=11.7) consists of flow from Basins JC-5B and JC-5E at the southwest corner of Frontside Drive and Big Johnson Drive. Flow will continue to the south as gutter flow in Big Johnson Drive to DP-N. It is anticipated that at-grade inlets may need to be installed along Big Johnson Drive due to street capacity issues.
Design Point J (Q5=5.0, Q100=9.3) consists of flow from Basin JC-12, which is where the west
side of Frontside Drive will enter Filing No. 1. Flows will continue as street flow, til they are intercepted by the storm system in Filing No. 1.
Design Point K (Q5=5.5, Q100=10.3) consists of flow from Basin JC-13, which is where the east
side of Frontside Drive will enter Filing No. 1. Flows will continue as street flow, til they are intercepted by the storm system in Filing No. 1.
Design Point L (Q5=3.8, Q100=8.1) consists of flows from Basins JC-8A and JC-8C at the northwest corner of Schoonover Drive and Bull Run Drive. Flow will continue to the east as
gutter flow in Schoonover Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point M (Q5=4.2, Q100=8.7) combines flow from Basin JC-8D with Design Point L at the
northeast corner of Schoonover Drive and Bull Run Drive. Flow will continue to the east as gutter flow in Schoonover Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point N (Q5=13.0, Q100=25.9) combines flow from Basin JC-8E with Design Points I and M at the northwest corner of Schoonover Drive and Big Johnson Drive. Flow will continue to the south as gutter flow in Big Johnson Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues in Big Johnson Drive.
Design Point O (Q5=15.5, Q100=30.6) combines flow from Basins JC-8B and JC-8F with Design Point N at the southwest corner of Schoonover Drive and Big Johnson Drive. Flow will continue to the south as gutter flow in Big Johnson Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues in Big Johnson Drive.
Design Point SS (Q5=7.2, Q100=15.3) consists of flow from Basins JC-16B and JC-16C. Flows
combine at the north corner of Little Boulder Loop and Moose Meadow Street. Flow will continue to the northeast as gutter flow in Moose Meadow Street. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point TT (Q5=7.8, Q100=17.1) consists of flow from Basins JC-16A and JC-16D. Flows combine at the northwest corner of Drinking Horse Court and Moose Meadow Street. Flow will continue to the northeast as gutter flow in Moose Meadow Street. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point UU (Q5=18.1, Q100=38.1) combines flow from Basin JC-16E with flows from Design Points SS and TT at the northwest corner of Legacy Drive and Moose Meadow Street. Flow will continue to the south as gutter flow in Legacy Drive.
Design Point P (Q5=21.4, Q100=51.3) combines flow from Basin JC-17 and Design Pont UU.
Flows will enter Filing No. 1, where an at-grade inlet, designed as part of the Storm System 3 in the FDR for Filing No. 1, will be installed at the southwest corner of Legacy Drive and Moose Meadow Street. Flow by from the inlet will continue along Legacy Drive to the south.
Design Point R (Q5=1.2, Q100=2.3) consists of flow from Basins JC-19G and JC-19H. Flows
combine at the northeast corner of Hazelton Drive and Bear Track Point. Flow will continue to the south as gutter flow in Bear Track Point.
Design Point S (Q5=5.1, Q100=102.2) combines flow from Basins JC-19I and JC-19J with Design Point R. This is a low point in the north side of Bear Track Point, just east of Bird Ridge Drive. A sump inlet will be installed to intercept the street flows.
Design Point T (Q5=8.8, Q100=18.9) consists of flow from Basins JC-19e and JC-19F. This is a low point in the south side of Bear Track Point, just east of Bird Ridge Drive. A sump inlet will be installed to intercept the street flows.
Design Point W (Q5=7.2, Q100=12.7) consists of flow from Basins JC-9A and JC-9B. Flows
combine at the southwest corner of Lowline View and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point X (Q5=13.2, Q100=25.0) combines flows from Basins JC-20A and JC-20B with Design Point W. Flows combine at the northwest corner of Hazelton Drive and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point Y (Q5=15.5, Q100=29.9) combines flow from Basin JC-19L with Design Point X. Flows combine at the southwest corner of Hazelton Drive and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point FF (Q5=16.4 Q100=31.9) combines flow from Basin JC-19M with Design Point Yp. Flows combine at the northwest corner of Bear Track Point and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point GG (Q5=16.5, Q100=32.1) combines flow from Basin JC-19K and Design Point FF. Flows combine at the northeast corner of Roundhouse Drive and Bird Ridge Drive. Flow will continue to the east as gutter flow in Roundhouse Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point HH (Q5=4.1, Q100=8.4) consists of flow from Basins JC-9C, JC-20D and JC-20E. Flows combine at the northeast corner of Hazelton Drive and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point II (Q5=5.3, Q100=10.8) combines flow from Basin JC-19O and Design Point HH. Flows combine at the southeast corner of Hazelton Drive and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point JJ (Q5=7.1, Q100=14.5) combines flow from Basins JC-19N and JC-19Q with Design Point II . Flows combine at the northeast corner of Nutter Butter Point and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point KK (Q5=8.0, Q100=16.5) combines flow from Basin JC-19S with Design Point JJ . Flows combine at the southeast corner of Nutter Butter Point and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point LL (Q5=8.9, Q100=18.1) combines flow from Basins JC-19R and JC-19T with Design Point KK . Flows combine at the northeast corner of Turtle Lake Way and Bird Ridge
Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point MM (Q5=10.4, Q100=121.1) combines flow from Basins JC-19U with Design Point LL . Flows combine at the southeast corner of Turtle Lake Way and Bird Ridge Drive. Flow will continue to the south as gutter flow in Bird Ridge Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point NN (Q5=10.4, Q100=21.0) combines flow from Basin JC-19V with Design Point MM . Flows combine at the northeast corner of Roundhouse Drive and Bird Ridge Drive. Flow will continue to the east as gutter flow in Roundhouse Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point RR (Q5=3.6, Q100=6.6) consists of flow from Basins JC-19B and JC-19D. Flows combine at the northwest corner of Roundhouse Drive and Bird Ridge Drive. Flow will continue to the east as gutter flow in Roundhouse Drive.
Design Point OO (Q5=27.1, Q100=53.1) combines flow from Design Points GG, NN and RR at the southwest corner of Schoonover Drive and Big Johnson Drive. Flow will continue to the south as gutter flow in Big Johnson Drive. It is anticipated that at-grade inlets may need to be installed due to street capacity issues.
Design Point PP (Q5=16.0, Q100=32.5) combines flow from Basin JC-21 with Design Point O. Flows combine at the northwest corner of Turtle Lake Way and Big Johnson Drive. Flow will continue to the south as gutter flow in Big Johnson Drive. It is anticipated that at-grade inlets may need to be installed in Big Johnson Drive due to street capacity issues.
Design Point QQ (Q5=45.7, Q100=91.1) combines flow from Basin JC-19W with Design Points PP and OO. Flows combine at the northwest corner of Roundhouse Drive and Big Johnson Drive. Flow will continue to the south as gutter flow in Big Johnson Drive. It is anticipated that at-grade inlets may need to be installed in Big Johnson Drive due to street capacity issues.
Design Point YY (Q5=13.4, Q100=26.6) consists of Basin JC-22. Flow is conveyed as street flow to the south on the east side of Big Johnson Drive, prior to entering Filing No. 1. Flows will be intercepted by one of the storm systems designed in the FDR for Filing No. 1.
Design Point ZZ (Q5=51.2, Q100=102.4) combines flow from Basins JC-19A and JC19-C with Design Point QQ at the northwest corner of Big Johnson Drive and Legacy Drive, prior to entering Filing No. 1. Flows will continue as street flow onto Filing No. 1, where they will eventually be intercepted as part of the storms systems designed in the Filing No. 1 FDR.
Design Point U (Q5=3.6, Q100=15.3) consists of flow from Basin JC-28, residential development, as it enters Filing No. 1 at the northwest corner of Falling Rock Drive and Sunday Gulch Drive. It is anticipated that an at-grade inlet will be needed at this location due to the street capacity limits and flows are included in the design of the Storm System 3 design in Filing No. 1 FDR.
Design Point V (Q5=3.3, Q100=6.4) consists of flow from Basin JC-7, residential development, as it enters Filing No. 1 at the southwest corner of Falling Rock Drive and Sunday Gulch Drive.
Flows from this basin do not exceed street capacity requirements and will be directed around the intersection and continue south as gutter flow along Sunday Gulch Drive. These flows were accounted for in the Filing No. 1 FDR.
Design Point Z (Q5=3.4, Q100=8.1) consists of flow from Basin JC-40, which is residential and
road basin entering the site on the west side of Lazy Ridge Drive, entering Filing No. 1, just north of the Buffalo Horn intersection.
Design Point AA (Q5=1.2, Q100=2.4) consists of flow from Basin JC-46, which is a road basin entering the site on the east side of Lazy Ridge Drive. Flows will enter Filing No. 1, just north of the intersection with Buffalo Horn Drive.
Design Point BB (Q5=7.4, Q100=17.5) consists of flow from Basins JC-38 and JC-39. This is a
low point located on the west side of Lazy Ridge Drive. A sump inlet will be installed to intercept these flows and connect to Storm System 2, designed as part of Filing No. 1 FDR.
Design Point CC (Q5=7.4, Q100=24.2) consists of flow from Basins JC-44 and JC-45 with any flow by from Design Point BB. A sump inlet will be installed to intercept these flows and connect to Storm System 2, designed as part of Filing No. 1 FDR.
Design Point DD (Q5=2.3, Q100=5.4) consists of flow from Basin JC-74, flow from the north portion of Wagon Hammer Drive on the west half of the street. This flow enters Filing No. 1 development. An at-grade inlet will be installed due to street capacity requirements. This has been designed as part of Storm System 2 in the Filing No. 1 FDR.
Design Point EE (Q5=1.5, Q100=3.4) consists of flow from Basin JC-75, flow from the north
portion of Wagon Hammer Drive on the east half of the street. This flow enters the Filing No. 1 development. An at-grade inlet will be installed due to street capacity requirements. This has been designed as part of Storm System 2 in the Filing No. 1 FDR.
DRAINAGE FACILITY DESIGN
General Concept The Trails at Aspen Ridge is located within the Big Johnson and Jimmy Camp Creek Drainage Basins. Approximately one-third of the site drains towards the west in the Big Johnson Basin and the remaining area drains towards the east in the Jimmy Camp Basin.
Storm Sewer System All development is anticipated to be urban and will include storm sewer and street inlets. Storm sewers collect storm water runoff and convey the runoff to water quality/detention facilities prior to discharging. As commercial and residential development continues in this area, there will be a need for storm system design. Final Plat submittals will include details concerning inlet location, storm sewer sizing and locations as part of the Final Drainage Report for each submittal.
On-Site Water Quality & Detention There are two water quality/detention ponds for the Trails at Aspen Ridge development. These facilities will provide water quality and detention for proposed improvements. These structures are private and will be maintained by Waterview II Metropolitan District. The East Pond is being designed as part of the Filing No. 1 development, which is currently under review. The West Pond will have final design calculations done at time of Final Plat. Outlet structures, fore bays, trickle channels, etc. will be constructed when final construction drawings are approved with the Final Plat submittal. Temporary Sediment Basins shown will remain in place until full construction of the Extended Detention Basins and final stabilization has been achieved. There are two proposed water quality facilities (Rain Gardens) to treat areas which could not reach either of the two detention ponds, prior to exiting the development, to treat the smaller “edge” areas which cannot make it to the detention facilities prior to exiting the site. These facilities are private and will be maintained by Waterview II Metropolitan District. Dam Breach Analysis A Non-Jurisdictional Water Impoundment Structure application to the Colorado State Engineer has been sent to the state for review. A copy of this application and state review letter has been included in the appendix with the design calculations for the detention pond. The state review had no negative impact to the proposed design.
Offsite Analysis The Jimmy Camp Basins, will all release into Filing No. 1 for The Trails as Aspen Ridge Filing No. 1. The Final Plat and Final Drainage Report for this site addresses the offsite issues for this drainage basin. The Big Johnson Basins, release at two different locations. The first will be at the southwest corner of the site. Flows will release through a proposed rain garden, to achieve the necessary water quality and then continue through the existing road side ditch along Powers Boulevard to the south. The second location is the existing 60” cmp under Powers Boulevard. The West Pond will release rates, less than existing directly to the culvert crossing location. Based on these conditions, there would be no adverse impacts to any downstream facilities within the Big Johnson Drainage Basin.
Four Step Process In accordance with the El Paso County Engineering Criteria Manual, Appendix I, this site has implemented the four-step process to minimize adverse impacts of urbanization and helps with the management of smaller, frequently occurring events. The four-step process includes reducing runoff volumes, treating and slowly releasing the water quality capture volume (WQCV), stabilizing drainageways, and implementing long-term source controls.
In order to reduce runoff volume, the new impervious area for the site was minimized. Existing features will be preserved as all of the offsite basins which are undeveloped open space will continue to be so, and all developable areas will be required to release existing flows and handle their own detention and water quality needs. Existing drainage paths have been maintained as much as possible to also help reduce overall impacts from the site. The WQCV is treated through extended detention basins. The outlet structures for both ponds have been designed according to the FSD spreadsheet by UDFCD to ensure the release times of the facilities meet the requirements. There are no proposed major drainageways for the site that would need to be stabilized. Downstream of the project, all flows enter into existing storm swales, which are adequate to handle existing release flows, which will be the case as both ponds are designed to release less than existing flows. Therefore, those downstream channel/facilities would also, not see any increase or adverse effects to their functionality. Some site-specific source control BMPs that will be implemented include, but are not limited to, silt fencing placed around downstream areas of disturbance, construction vehicle tracking pads at the entrances, sediment ponds, designated concrete truck washout basin, designated vehicle fueling areas, covered storage areas, spill containment and control, etc.
DRAINAGE FEES & MAINTENANCE Both the Big Johnson and Jimmy Camp Creek Drainage Basins are part of the El Paso County drainage basin fee program. All applicable fees will be presented in the Final Drainage Reports.
Drainage Infrastructure Costs A presentation of accurate, complete and current estimate of cost proposed facilities will be presented with the Final Drainage Report.
EROSION CONTROL
General Concept During construction, best management practices for erosion control will be employed based on El Paso County criteria and the erosion control plan. The erosion control plan is included at the end of this report. Ditches will be designed to meet El Paso County criteria for slope and velocity, keeping velocities below scouring levels. During construction, best management practices (BMP) for erosion control will be employed based on El Paso County Criteria. BMP’s will be utilized as deemed necessary by contractor and/or engineer and are not limited to measure shown on construction drawing set. The contractor shall minimize amount of area disturbed during all construction activities. In general, the following shall be applied in developing the sequence of major activities: Install downslope and sideslope perimeter BMP’s before the land disturbing activity occurs.
Do not disturb an area until it is necessary for the construction activity to proceed. Cover or stabilize as soon as possible. Time the construction activities to reduce the impacts from seasonal climatic changes or weather
events. The construction of filtration BMP’s should wait until the end of the construction project when
upstream drainage areas have been stabilized. Do not remove temporary perimeter controls until after all upstream areas are stabilized.
Silt Fence Silt fence will be placed along downstream limits of disturbed areas. This will prevent suspended sediment from leaving the site during infrastructure construction. Silt fencing is to remain in place until vegetation is reestablished.
Erosion Bales Erosion bales will be placed ten (10) feet from the inlet of all culverts and inlets during construction to prevent culverts from filling with sediment. Erosion bales will remain in place until vegetation is reestablished in graded roadside ditches. Erosion bale ditch checks will be used on slopes greater than 1% to reduce flow velocities until vegetation is reestablished.
Vehicle Tracking Control This BMP is used to stabilize construction entrances, roads, parking areas and staging areas to prevent the tracking of sediment from the construction site. A vehicle tracking control (VTC) is to be used at all locations where vehicles exit the construction site onto public roads, loading and unloading areas, storage and staging areas, where construction trailers are to be located, any construction area that receives high vehicular traffic, construction roads and parking areas. VTC’s should not be installed in areas where soils erode easily or are wet.
Sedimentation Pond This BMP is used to detain runoff which has become laden with sediment long enough to allow the sediment to settle out. As the construction area is larger than 1 acre, a temporary sediment basin is required per Volume 2 of the Drainage Criteria Manual. These basins were designed and approved as part of the Early Grading Permit for Waterview East. These facilities will remain until permanent ponds/WQ facilities have been built.
SUMMARY Development within the site is to be single family residential. Approximately 1/3 of the site is within the Big Johnson Basin. Flows will release through 1 of two existing culverts under Powers Boulevard. The West Pond will be located directly upstream of one of the two Powers Boulevard crossings to ensure flows are being kept at historic levels prior to reaching the Big Johnson Reservoir. The Jimmy Camp Basins will have several locations where flows are being released onto The Trails at Aspen Ridge Filing No. 1 development. Filing No. 1 will have a detention pond to ensure only historic flows are being released offsite.
A product of the NationalCooperative Soil Survey,a joint effort of the UnitedStates Department ofAgriculture and otherFederal agencies, Stateagencies including theAgricultural ExperimentStations, and localparticipants
Custom Soil ResourceReport for
El Paso CountyArea, Colorado
NaturalResourcesConservationService
June 21, 2017
Soil MapThe soil map section includes the soil map for the defined area of interest, a list ofsoil map units on the map and extent of each map unit, and cartographic symbolsdisplayed on the map. Also presented are various metadata about data used toproduce the map, and a description of each soil map unit.
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS840 300 600 1200 1800
Feet0 50 100 200 300
MetersMap Scale: 1:6,740 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
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Map Unit Legend
El Paso County Area, Colorado (CO625)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
8 Blakeland loamy sand, 1 to 9percent slopes
17.1 8.3%
31 Fort Collins loam, 3 to 8 percentslopes
0.0 0.0%
52 Manzanst clay loam, 0 to 3percent slopes
21.0 10.2%
56 Nelson-Tassel fine sandyloams, 3 to 18 percent slopes
137.8 67.0%
86 Stoneham sandy loam, 3 to 8percent slopes
5.7 2.8%
108 Wiley silt loam, 3 to 9 percentslopes
24.3 11.8%
Totals for Area of Interest 205.8 100.0%
Map Unit DescriptionsThe map units delineated on the detailed soil maps in a soil survey represent thesoils or miscellaneous areas in the survey area. The map unit descriptions, alongwith the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or moremajor kinds of soil or miscellaneous areas. A map unit is identified and namedaccording to the taxonomic classification of the dominant soils. Within a taxonomicclass there are precisely defined limits for the properties of the soils. On thelandscape, however, the soils are natural phenomena, and they have thecharacteristic variability of all natural phenomena. Thus, the range of someobserved properties may extend beyond the limits defined for a taxonomic class.Areas of soils of a single taxonomic class rarely, if ever, can be mapped withoutincluding areas of other taxonomic classes. Consequently, every map unit is madeup of the soils or miscellaneous areas for which it is named and some minorcomponents that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in themap unit, and thus they do not affect use and management. These are callednoncontrasting, or similar, components. They may or may not be mentioned in aparticular map unit description. Other minor components, however, have propertiesand behavioral characteristics divergent enough to affect use or to require differentmanagement. These are called contrasting, or dissimilar, components. Theygenerally are in small areas and could not be mapped separately because of thescale used. Some small areas of strongly contrasting soils or miscellaneous areasare identified by a special symbol on the maps. If included in the database for agiven area, the contrasting minor components are identified in the map unitdescriptions along with some characteristics of each. A few areas of minorcomponents may not have been observed, and consequently they are not
Custom Soil Resource Report
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mentioned in the descriptions, especially where the pattern was so complex that itwas impractical to make enough observations to identify all the soils andmiscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes theusefulness or accuracy of the data. The objective of mapping is not to delineatepure taxonomic classes but rather to separate the landscape into landforms orlandform segments that have similar use and management requirements. Thedelineation of such segments on the map provides sufficient information for thedevelopment of resource plans. If intensive use of small areas is planned, however,onsite investigation is needed to define and locate the soils and miscellaneousareas.
An identifying symbol precedes the map unit name in the map unit descriptions.Each description includes general facts about the unit and gives important soilproperties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except fordifferences in texture of the surface layer, all the soils of a series have majorhorizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,salinity, degree of erosion, and other characteristics that affect their use. On thebasis of such differences, a soil series is divided into soil phases. Most of the areasshown on the detailed soil maps are phases of soil series. The name of a soil phasecommonly indicates a feature that affects use or management. For example, Alphasilt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricatepattern or in such small areas that they cannot be shown separately on the maps.The pattern and proportion of the soils or miscellaneous areas are somewhat similarin all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils ormiscellaneous areas that are shown as one unit on the maps. Because of presentor anticipated uses of the map units in the survey area, it was not consideredpractical or necessary to map the soils or miscellaneous areas separately. Thepattern and relative proportion of the soils or miscellaneous areas are somewhatsimilar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areasthat could be mapped individually but are mapped as one unit because similarinterpretations can be made for use and management. The pattern and proportionof the soils or miscellaneous areas in a mapped area are not uniform. An area canbe made up of only one of the major soils or miscellaneous areas, or it can be madeup of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soilmaterial and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
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El Paso County Area, Colorado
8—Blakeland loamy sand, 1 to 9 percent slopes
Map Unit SettingNational map unit symbol: 369vElevation: 4,600 to 5,800 feetMean annual precipitation: 14 to 16 inchesMean annual air temperature: 46 to 48 degrees FFrost-free period: 125 to 145 daysFarmland classification: Not prime farmland
Map Unit CompositionBlakeland and similar soils: 85 percentEstimates are based on observations, descriptions, and transects of the mapunit.
Description of Blakeland
SettingLandform: Flats, hillsLandform position (three-dimensional): Side slope, talfDown-slope shape: LinearAcross-slope shape: LinearParent material: Alluvium derived from sedimentary rock and/or eolian deposits
derived from sedimentary rock
Typical profileA - 0 to 11 inches: loamy sandAC - 11 to 27 inches: loamy sandC - 27 to 60 inches: sand
Properties and qualitiesSlope: 1 to 9 percentDepth to restrictive feature: More than 80 inchesNatural drainage class: Somewhat excessively drainedRunoff class: LowCapacity of the most limiting layer to transmit water (Ksat): High to very high (5.95
to 19.98 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 5 percentAvailable water storage in profile: Low (about 4.5 inches)
Other soilsPercent of map unit: Hydric soil rating: No
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PleasantPercent of map unit: Landform: DepressionsHydric soil rating: Yes
31—Fort Collins loam, 3 to 8 percent slopes
Map Unit SettingNational map unit symbol: 3684Elevation: 5,200 to 6,500 feetMean annual precipitation: 14 to 16 inchesMean annual air temperature: 48 to 52 degrees FFarmland classification: Not prime farmland
Map Unit CompositionFort collins and similar soils: 85 percentEstimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
SettingLandform: HillsLandform position (three-dimensional): Side slopeDown-slope shape: LinearAcross-slope shape: LinearParent material: Loamy alluvium
Typical profileA - 0 to 9 inches: loamBt - 9 to 16 inches: clay loamBk - 16 to 21 inches: clay loamCk - 21 to 60 inches: loam
Properties and qualitiesSlope: 3 to 8 percentDepth to restrictive feature: More than 80 inchesNatural drainage class: Well drainedRunoff class: MediumCapacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.57 to 2.00 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 15 percentSalinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)Available water storage in profile: High (about 10.1 inches)
Land capability classification (nonirrigated): 6eHydrologic Soil Group: BEcological site: Loamy Plains (R067BY002CO)Other vegetative classification: LOAMY PLAINS (069AY006CO)Hydric soil rating: No
Minor Components
PleasantPercent of map unit: Landform: DepressionsHydric soil rating: Yes
Other soilsPercent of map unit: Hydric soil rating: No
52—Manzanst clay loam, 0 to 3 percent slopes
Map Unit SettingNational map unit symbol: 2w4nrElevation: 4,060 to 6,660 feetMean annual precipitation: 14 to 16 inchesMean annual air temperature: 50 to 54 degrees FFrost-free period: 130 to 170 daysFarmland classification: Prime farmland if irrigated
Map Unit CompositionManzanst and similar soils: 85 percentMinor components: 15 percentEstimates are based on observations, descriptions, and transects of the mapunit.
Description of Manzanst
SettingLandform: Terraces, drainagewaysLandform position (three-dimensional): TreadDown-slope shape: LinearAcross-slope shape: Linear, concaveParent material: Clayey alluvium derived from shale
Typical profileA - 0 to 3 inches: clay loamBt - 3 to 12 inches: clayBtk - 12 to 37 inches: clayBk1 - 37 to 52 inches: clayBk2 - 52 to 79 inches: clay
Properties and qualitiesSlope: 0 to 3 percentDepth to restrictive feature: More than 80 inches
Custom Soil Resource Report
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Natural drainage class: Well drainedCapacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 15 percentGypsum, maximum in profile: 3 percentSalinity, maximum in profile: Slightly saline (4.0 to 7.0 mmhos/cm)Sodium adsorption ratio, maximum in profile: 10.0Available water storage in profile: High (about 9.0 inches)
RitoazulPercent of map unit: 7 percentLandform: Drainageways, interfluvesLandform position (three-dimensional): RiseDown-slope shape: LinearAcross-slope shape: LinearEcological site: Clayey Plains (R067BY042CO)Hydric soil rating: No
ArvadaPercent of map unit: 6 percentLandform: Drainageways, interfluvesDown-slope shape: LinearAcross-slope shape: LinearEcological site: Salt Flat (R067XY033CO)Hydric soil rating: No
WileyPercent of map unit: 2 percentLandform: InterfluvesDown-slope shape: LinearAcross-slope shape: LinearEcological site: Loamy Plains (R067BY002CO)Hydric soil rating: No
56—Nelson-Tassel fine sandy loams, 3 to 18 percent slopes
Map Unit SettingNational map unit symbol: 3690Elevation: 5,600 to 6,400 feet
Custom Soil Resource Report
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Mean annual precipitation: 12 to 14 inchesMean annual air temperature: 48 to 52 degrees FFrost-free period: 135 to 155 daysFarmland classification: Not prime farmland
Map Unit CompositionNelson and similar soils: 45 percentTassel and similar soils: 30 percentEstimates are based on observations, descriptions, and transects of the mapunit.
Description of Nelson
SettingLandform: HillsLandform position (three-dimensional): Crest, side slopeDown-slope shape: LinearAcross-slope shape: LinearParent material: Calcareous residuum weathered from interbedded sedimentary
rock
Typical profileA - 0 to 5 inches: fine sandy loamCk - 5 to 23 inches: fine sandy loamCr - 23 to 27 inches: weathered bedrock
Properties and qualitiesSlope: 3 to 12 percentDepth to restrictive feature: 20 to 40 inches to paralithic bedrockNatural drainage class: Well drainedRunoff class: MediumCapacity of the most limiting layer to transmit water (Ksat): Moderately low to high
(0.06 to 2.00 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 10 percentSalinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)Available water storage in profile: Very low (about 2.8 inches)
SettingLandform: HillsLandform position (three-dimensional): Crest, side slopeDown-slope shape: LinearAcross-slope shape: LinearParent material: Calcareous slope alluvium over residuum weathered from
sandstone
Custom Soil Resource Report
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Typical profileA - 0 to 4 inches: fine sandy loamC - 4 to 10 inches: fine sandy loamCr - 10 to 14 inches: weathered bedrock
Properties and qualitiesSlope: 3 to 18 percentDepth to restrictive feature: 6 to 20 inches to paralithic bedrockNatural drainage class: Well drainedRunoff class: MediumCapacity of the most limiting layer to transmit water (Ksat): Moderately high (0.20
to 0.60 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 10 percentAvailable water storage in profile: Very low (about 1.2 inches)
Other soilsPercent of map unit: Hydric soil rating: No
PleasantPercent of map unit: Landform: DepressionsHydric soil rating: Yes
86—Stoneham sandy loam, 3 to 8 percent slopes
Map Unit SettingNational map unit symbol: 36b2Elevation: 5,100 to 6,500 feetMean annual precipitation: 13 to 15 inchesMean annual air temperature: 48 to 52 degrees FFrost-free period: 135 to 155 daysFarmland classification: Not prime farmland
Map Unit CompositionStoneham and similar soils: 85 percent
Custom Soil Resource Report
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Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Stoneham
SettingLandform: HillsLandform position (three-dimensional): Side slopeDown-slope shape: LinearAcross-slope shape: LinearParent material: Calcareous loamy alluvium
Typical profileA - 0 to 4 inches: sandy loamBt - 4 to 8 inches: sandy clay loamBtk - 8 to 11 inches: sandy clay loamCk - 11 to 60 inches: loam
Properties and qualitiesSlope: 3 to 8 percentDepth to restrictive feature: More than 80 inchesNatural drainage class: Well drainedRunoff class: MediumCapacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 15 percentSalinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)Available water storage in profile: High (about 9.5 inches)
PleasantPercent of map unit: Landform: DepressionsHydric soil rating: Yes
Other soilsPercent of map unit: Hydric soil rating: No
Custom Soil Resource Report
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108—Wiley silt loam, 3 to 9 percent slopes
Map Unit SettingNational map unit symbol: 367bElevation: 5,200 to 6,200 feetMean annual precipitation: 12 to 14 inchesMean annual air temperature: 48 to 52 degrees FFrost-free period: 135 to 155 daysFarmland classification: Not prime farmland
Map Unit CompositionWiley and similar soils: 85 percentEstimates are based on observations, descriptions, and transects of the mapunit.
Description of Wiley
SettingLandform: HillsLandform position (three-dimensional): Side slopeDown-slope shape: LinearAcross-slope shape: LinearParent material: Calcareous silty eolian deposits
Typical profileA - 0 to 4 inches: silt loamBt - 4 to 16 inches: silt loamBk - 16 to 60 inches: silt loam
Properties and qualitiesSlope: 3 to 9 percentDepth to restrictive feature: More than 80 inchesNatural drainage class: Well drainedRunoff class: MediumCapacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 in/hr)Depth to water table: More than 80 inchesFrequency of flooding: NoneFrequency of ponding: NoneCalcium carbonate, maximum in profile: 15 percentSalinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)Available water storage in profile: High (about 11.5 inches)
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 PlateInvert of Lowest Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = 2.764E-02 ft2
Depth at top of Zone using Orifice Plate = 2.03 ft (relative to basin bottom at Stage = 0 ft) Elliptical Half-Width = N/A feetOrifice Plate: Orifice Vertical Spacing = 8.50 inches Elliptical Slot Centroid = N/A feet
Orifice Plate: Orifice Area per Row = 3.98 sq. inches (use rectangular openings) 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 0.70 1.40Orifice Area (sq. inches) 3.98 3.98 3.98
User Input: Vertical Orifice (Circular or Rectangular) Calculated Parameters for Vertical OrificeZone 2 Circular Not Selected Zone 2 Circular Not Selected
Invert of Vertical Orifice = 2.03 N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area = 0.01 N/A ft2
Depth at top of Zone using Vertical Orifice = 4.37 N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = 0.04 N/A feetVertical Orifice Diameter = 1.00 N/A inches
User Input: Overflow Weir (Dropbox) and Grate (Flat or Sloped) Calculated Parameters for Overflow WeirZone 3 Weir Not Selected Zone 3 Weir Not Selected
Overflow Weir Front Edge Height, Ho = 4.37 N/A ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = 5.37 N/A feetOverflow Weir Front Edge Length = 4.00 N/A feet Over Flow Weir Slope Length = 4.12 N/A feet
Overflow Weir Slope = 4.00 N/A H:V (enter zero for flat grate) Grate Open Area / 100-yr Orifice Area = 9.22 N/A should be > 4Horiz. Length of Weir Sides = 4.00 N/A feet Overflow Grate Open Area w/o Debris = 11.54 N/A ft2
Overflow Grate Open Area % = 70% N/A %, grate open area/total area Overflow Grate Open Area w/ Debris = 5.77 N/A ft2
Debris Clogging % = 50% 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 PlateZone 3 Restrictor Not Selected Zone 3 Restrictor Not Selected
Depth to Invert of Outlet Pipe = 2.50 N/A ft (distance below basin bottom at Stage = 0 ft) Outlet Orifice Area = 1.25 N/A ft2
User Input: Emergency Spillway (Rectangular or Trapezoidal) Calculated Parameters for SpillwaySpillway Invert Stage= 5875.00 ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= 0.83 feet
Spillway Crest Length = 50.00 feet Stage at Top of Freeboard = 5876.83 feetSpillway End Slopes = 4.00 H:V Basin Area at Top of Freeboard = 1.44 acres
Freeboard above Max Water Surface = 1.00 feet
Routed Hydrograph ResultsDesign Storm Return Period = WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 YearOne-Hour Rainfall Depth (in) = 0.53 1.07 1.19 1.50 1.75 2.00 2.25 2.52 3.55
Storm Inflow HydrographsThe user can override the calculated inflow hydrographs from this workbook with inflow hydrographs developed in a separate program.
Sheet 1 of 4Designer:Company:Date:Project:Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 67.0 %
B) Tributary Area's Imperviousness Ratio (i = Ia / 100 ) i = 0.670
C) Contributing Watershed Area Area = 37.440 ac
D) For Watersheds Outside of the Denver Region, Depth of Average d6 = in Runoff Producing Storm
E) Design Concept (Select EURV when also designing for flood control)
F) Design Volume (WQCV) Based on 40-hour Drain Time VDESIGN= 0.818 ac-ft (VDESIGN = (1.0 * (0.91 * i3 - 1.19 * i2 + 0.78 * i) / 12 * Area )
G) For Watersheds Outside of the Denver Region, VDESIGN OTHER= ac-ft Water Quality Capture Volume (WQCV) Design Volume (VWQCV OTHER = (d6*(VDESIGN/0.43))
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VDESIGN USER= ac-ft (Only if a different WQCV Design Volume is desired)
I) Predominant Watershed NRCS Soil Group
J) Excess Urban Runoff Volume (EURV) Design Volume For HSG A: EURVA = 1.68 * i1.28 EURV = 2.753 ac-f t For HSG B: EURVB = 1.36 * i1.08
For HSG C/D: EURVC/D = 1.20 * i1.08
2. Basin Shape: Length to Width Ratio L : W = 5.0 : 1(A basin length to width ratio of at least 2:1 will improve TSS reduction.)
3. Basin Side Slopes
A) Basin Maximum Side Slopes Z = 4.00 ft / ft (Horizontal distance per unit vertical, 4:1 or flatter preferred)
4. Inlet
A) Describe means of providing energy dissipation at concentrated inflow locations:
Charlene DurhamStantecJanuary 30, 2019Trails at Aspen RidgeBig Johnson Basin - West Pond
Aluminum Amico-Klemp SR Series with Cross Rods 2" O.C.B) Type of Screen (If specifying an alternative to the materials recommended in the USDCM, indicate "other" and enter the ratio of the total open are to the total screen are for the material specified.)
West Pond Forebay.xlsm, EDB 1/30/2019, 4:34 PM
Sheet 4 of 4Designer:Company:Date:Project:Location:
10. Overflow Embankment
A) Describe embankment protection for 100-year and greater overtopping:
B) Slope of Overflow Embankment (Horizontal distance per unit vertical, 4:1 or flatter preferred)
Total Available Detention Depth (Htotal) = user ft -- -- -- --Depth of Trickle Channel (HTC) = N/A ft -- -- -- --Slope of Trickle Channel (STC) = N/A 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 -- -- -- --
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 PlateInvert of Lowest Orifice = ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = N/A ft
2
Depth at top of Zone using Orifice Plate = ft (relative to basin bottom at Stage = 0 ft) Elliptical Half‐Width = N/A feet
User Input: Vertical Orifice (Circular or Rectangular) Calculated Parameters for Vertical OrificeNot Selected Not Selected Not Selected Not Selected
Invert of Vertical Orifice = ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area = ft2
Depth at top of Zone using Vertical Orifice = ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = feet
Vertical Orifice Diameter = inches
User Input: Overflow Weir (Dropbox) and Grate (Flat or Sloped) Calculated Parameters for Overflow WeirNot Selected Not Selected Not Selected Not Selected
Overflow Weir Front Edge Height, Ho = ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = feet
Overflow Weir Front Edge Length = feet Over Flow Weir Slope Length = feet
Overflow Weir Slope = H:V (enter zero for flat grate) Grate Open Area / 100‐yr Orifice Area = should be > 4
Horiz. Length of Weir Sides = feet Overflow Grate Open Area w/o Debris = ft2
Overflow Grate Open Area % = %, grate open area/total area Overflow Grate Open Area w/ Debris = ft2
Debris Clogging % = %
User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice) Calculated Parameters for Outlet Pipe w/ Flow Restriction PlateNot Selected Not Selected Not Selected Not Selected
Depth to Invert of Outlet Pipe = ft (distance below basin bottom at Stage = 0 ft) Outlet Orifice Area = ft2
Half‐Central Angle of Restrictor Plate on Pipe = N/A N/A radians
User Input: Emergency Spillway (Rectangular or Trapezoidal) Calculated Parameters for SpillwaySpillway 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 ResultsDesign Storm Return Period = WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year
Ratio Peak Outflow to Predevelopment Q = N/A N/A N/A 1.1 0.1 0.0 0.0 0.0 #N/A
Structure Controlling Flow = Filtration Media Filtration Media Filtration Media Filtration Media Filtration Media Filtration Media Filtration Media Filtration Media #N/A
Max Velocity through Grate 1 (fps) = N/A N/A N/A N/A N/A N/A N/A N/A #N/A
Max Velocity through Grate 2 (fps) = N/A N/A N/A N/A N/A N/A N/A N/A #N/A
Time to Drain 97% of Inflow Volume (hours) = 12 37 32 41 49 58 64 73 #N/A
Time to Drain 99% of Inflow Volume (hours) = 13 38 33 42 51 59 66 75 #N/A
From: Hunyadi - DNR, JohnTo: Charles CothernCc: Cothern, CharlesSubject: Re: Waterview East Subdivision Detention Pond Classification/Breech AnalysisDate: Monday, May 14, 2018 9:19:20 AM
Good Morning Charles,
Excellent! This is exactly the level of analysis needed for these small structuresand I reviewed and agree with your assessments for hazard classifications forthese 2 ponds.
When you are closer to construction, please plan to submit the NOI form about 45days in advance and our water commissioner and division engineer will alsoreview/approve. The water commissioner will be looking for the SDI data sheetshowing how quickly the structures will drain out. When you submit that, pleasere-include this hazard memo as part of the package to keep it all together.
Thanks so much for your efforts. I think it is a valuable process.
John H.
John Hunyadi, PE | Dam Safety EngineerState of Colorado | 4255 Sinton Road, CO Springs, CO T: 719.227.5294 | C: [email protected]
On Thu, May 10, 2018 at 4:45 PM, Charles Cothern<[email protected]> wrote:
John,
Attached is my memorandum providing classification of the pond embankments forthe Waterview East Subdivision. I also included the two spreadsheets in case youwanted to review/modify, etc.
As I have explained before, I have not had to do this previously so consequently Ido not know if I have provided everything you need to prepare a determination onyour end.
So I am open to criticism, if need be, and can make any changes necessary sothat I provide you exactly what you need and will be better at the process nexttime this comes up.
The notice you provided I assumed would be completed and sent in some time inthe future when construction is eminent; however, if you need those now I can
complete and forward. If you need construction drawings prior to the notices oras part of the review of the attached memorandum, I can also send those rightover.
Just let me know what I need to do next so I can keep my submittal processmoving forward with El Paso County.
Thanks for your help.
Charles K. Cothern, P.E.
Springs Engineering, LLC
31 N. Tejon Street, Suite 500
Colorado Springs, CO 80903
719-227-7388 (P)
719-227-7392 (F)
This e-mail message is the property of Springs Engineering, LLC and is for the sole use of the intended recipient(s) andmay contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution isprohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of theoriginal message.
Z:\0001-Dakota Springs\02-Waterview Partners\16-02 Springs at Waterview East\Reports\Preliminary Plan\Drainage\Dam Breach Analysis\SEStantecMemoDamClassification050918.doc
Memorandum Stantec 31 North Tejon Street Suite 500 Colorado Springs, Colorado 80903 Phone: 719-227-7388 Fax: 719-227-7392 Date: May 9, 2018 To: Mr. John Hunyadi Dam Safety Engineer State of Colorado 4255 Sinton Road Colorado Springs, CO 80919 From: Charles K. Cothern, P.E. Subject: Waterview East Detention Pond Embankment Hazard Classification This memorandum has been prepared to determine the classification and the potential for breech for the detention pond embankments for Waterview East. There are two ponds to consider. They are identified as Waterview East Subdivision, East Detention Pond and Waterview East Subdivision, West Detention Pond. Guidelines for Hazard Classification, Office of the State Engineer, Colorado Dam Safety Branch, November 15, 2010 was used to determine the pond embankment classification. The characteristics of each pond are as follows: East Detention Pond The East Detention Pond is located on the east side of the property near the southeast corner and discharges onto neighboring property east of the site. Discharge eventually reaches Jimmy Camp Creek. Drainage Area 138.98 acres Height of Water (Hw) 8.51 ft. Stoarge;100-year design storm 16.51 ac-ft. Surface Area; 100-year design storm 3.83 acres Crest Width of Dam 8 ft. Height of dam to Base Elevation 11.35 ft. Slope of Upstream dam face 3 H:V Slope of Downstream dam face 2 H:V Dam Size Class Minor
Z:\0001-Dakota Springs\02-Waterview Partners\16-02 Springs at Waterview East\Reports\Preliminary Plan\Drainage\Dam Breach Analysis\SEStantecMemoDamClassification050918.doc
West Detention Pond The West Detention Pond is located on the west side of the property and discharges into Powers Boulevard right-of-way. Discharge eventually reaches Big Johnson Reservoir. Drainage Area 42.4 acres Height of Water (Hw) 7.42 ft. Stoarge;100-year design storm 5.04 ac-ft. Surface Area; 100-year design storm 1.38 acres Crest Width of Dam 10 ft. Height of dam to Base Elevation 9.35 ft. Slope of Upstream dam face 3 H:V Slope of Downstream dam face 2 H:V Dam Size Class Minor Classification Analysis Both pond embankments based on proposed embankment construction dimensions are identified as Non-Jurisdictional. Following The Guidelines for Hazard Classification document previously referred to, the conclusions are as follows: East Pond The East Detention pond is classified as a Low Hazard Dam based on the following determinations under a failure scenario:
• No loss of Human life would be expected. The drainage follows a swale downstream that crosses open prairie most recently used for grazing. Fontaine Boulevard is approximately ¾ mile downstream and the nearest housing development is approximately 1.25 miles downstream. The drainage swale is well defined and can contain any potential breech flows.
• Only minor damage, if any, would be expected to unimproved roads or minor irrigation facilities across the open prairie property.
• No reservoirs are downstream however, there are some minor berms across the drainage downstream; these berms could capture pond discharge or breech flows.
• Downstream, near Fontaine Boulevard, there is evidence of potential wetlands that could be affected.
Based on these factors the classification is Low Hazard. West Pond The West Pond is classified as a No Public Hazard Dam. The discharge from the pond and any potential breech discharge would enter the Powers Boulevard right-of-way and a
Z:\0001-Dakota Springs\02-Waterview Partners\16-02 Springs at Waterview East\Reports\Preliminary Plan\Drainage\Dam Breach Analysis\SEStantecMemoDamClassification050918.doc
“sump” location for the Powers Boulevard roadside ditch. The sump is drained west under Powers Boulevard by a 60-inch CMP. The Powers Boulevard Road embankment essentially serves as a second dam embankment that cannot fail under any normal scenario. The CMP pipe would provide a controlled discharge under Powers Boulevard. The discharge under Powers Boulevard drains on to the Blue Stem Open Space, across open praire conveyed by a swale to Big Johnson Reservoir.
• No loss of human life expected. • No damage would occur downstream including erosion of the Powers Boulevard
road side ditch because flow would enter the ditch at the sump location. The Estimate of Dam Breech Parameters spread sheet is included for both ponds for reference. A cross section of the swale daonstream from the East Pond is included along with a flow analysis to show complete capture of the Breech flow. Please let me know if you have any questions. If you can provide an acknowledgement of this analysis which we could use with our submittal to El Paso County, we would appreciate it. Non-Jurisdictional Water Impoundment Structure notifications are being prepared to submit to the State per Section 37-87-125, CRS.
AP
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Stantec Consulting Inc.
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80.99'
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107.94'
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TRACT 'I' 6,684.16 s.f.
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N74°20'48"E
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545.14'
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N00°29'10"W
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3037.92'
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S89°33'39"W
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2495.46'
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S00°19'33"E
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3638.41'
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R=2759.79' L=730.29' Δ=15°09'41"
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Δ=12°59'05"R=2969.79' L=673.03'
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N74°20'48"E
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1062.13'
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N00°29'10"W
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R=2074.21'
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L=552.21'
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289.88'
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N89%%D40'37"E
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N74°20'48"E
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N00°29'10"W
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N00°29'10"W
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S89°33'39"W
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2495.46'
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S00°19'33"E
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3638.41'
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STATE OF COLORADO C/O DIVISION OF PURCHASING
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OPEN SPACE
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BLUESTEM PRAIRIE OPEN SPACE
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PUD KIEMELE FAMILY PARTNERSHIP CITY OF COLORADO SPRINGS
Full Path & Drawing File Name: V:\1817\active\181710214\CAD\Plansheets
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Index of Revisions
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181710214
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Sheet Number
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4-28-18
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BG
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Grading Plan
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see plan
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www.stantec.com
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Fax.
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Tel.
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1110 Elkton Drive
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Suite B
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Colorado Springs, CO 80907
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(719) 432-6889
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CMD/BG
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WATERVIEW EAST PRE-DEVELOPMENT GRADING AND EROSION CONTROL PLAN
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ccothern
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West Detention Pond
ccothern
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East Detention Pond
Waterview East Subdivision
WVE East Pond MLM-WAv2_0.xlsm
PROJECT:
8.516.53.88.0
11.43.02.00.1
0.61Minor
140.5001168.936.511.09.8
0.131.9739
0.9686.510.2
Breach Formation Time (Tf) =
Peak Breach Discharge (Qp) = Cubic Feet per Second
Erosion Rate (ER), Calculated as (Bavg/Tf) =Average Breach Width Divided by Height of Breach (Bavg/Hb ) = If (Bavg/Hb) > 0.6, Full Breach Development is Anticipated
Acre Feet/FootStorage Intensity (SI) =
Feet
Piping Orifice Coefficient (Cp) = Used To Calculate Peak Discharge Through Piping Hole
RESULTS CHECK:
Erosion Rate Divided by Height of Water Over Base of Breach (ER/Hw) = If 1.6 < (ER/Hw) < 21, Erosion Rate is Assumed Reasonable
Height of breach from dam crest to base elevation of breach (Hb) =Slope of upstream dam face (Zu) =
Slope of downstream dam face (Zd) =
FeetVolume Eroded in Piping Hole =
*Piping Hole Width (D) =Cubic YardsCubic Feet Per SecondEstimated Peak Discharge Through Pipe =
Feet
Reservoir Evacuation May Occur Prior to Full Breach Development - Piping Hole Characteristics calculated below.
Piping Orifice Coefficient (Cp) = Used To Calculate Peak Discharge Through Piping Hole
RESULTS CHECK:
Erosion Rate Divided by Height of Water Over Base of Breach (ER/Hw) = If 1.6 < (ER/Hw) < 21, Erosion Rate is Assumed Reasonable
Assumes Full Reservoir At Time of Breach
Bottom Width of Breach (Bb) = FeetBreach Formation Time (Tf) =
Peak Breach Discharge (Qp) = Cubic Feet per Second
Erosion Rate (ER), Calculated as (Bavg/Tf) =Average Breach Width Divided by Height of Breach (Bavg/Hb ) = If (Bavg/Hb) > 0.6, Full Breach Development is Anticipated