PHASE III DRAINAGE REPORT

Transcription

1 PHASE III DRAINAGE REPORT FOR Eastlake Assisted Living & Memory Care April 20, 2016 June 3, 2016 August 5, 2016 Prepared for: 3301 E 120 th Ave, LLC E. Maplewood Ave., Suite 150 Greenwood Village CO Phone: Contact: Bill Lyons, Jr. Prepared by: 6505 S. Paris Street, Suite B Centennial, Colorado Phone: Fax: Contact: Jason Monforton, P.E. Job No

2 Your Project, Our Pride TM CERTIFICATION J3 ENGINEERING CONSULTANTS, LLC. HEREBY CERTIFIES THAT THE DRAINAGE FACILITIES FOR THE EASTLAKE ASSISTED LIVING FACILITY WILL BE CONSTRUCTED ACCORDING TO THE DESIGN PRESENTED IN THIS REPORT. I UNDERSTAND THAT THE CITY OF THORNTON DOES NOT AND SHALL NOT ASSUME LIABILITY FOR THE DRAIANGE FACILITIES DESIGNED AND/OR CERTIFIED BY MY ENGINEER. I UNDERSTAND TJAT THE CITY OF THORNTONGREVIEWS DRAINAGE PLANS BUT CANNOT, ON BEHLAFT OF EASTLAKE ASSISTED LIVING, GUARANTEE THE FINAL DRAINAGE DESIGN REVIEW WILL ABSOLVE 3301 E. 120TH AVENUE llc AND/OR THEIR SUCCESSORS AND/OR ASSIGNS OF FUTURE LIABILITY FOR IMPROPER DESIGN. I FURTHER UNDERSTAND THAT APPORVAL OF THE PLAT AND/OR DEVELOPMENT PERMIT DOEST NOT IMPLY APPORVAL OF MY ENGINEER S DRAINAGE DESIGN. ATTEST: NOTARY PUBLIC AUTHORIZED SIGNATURE I HEREBY CERTIFY THAT THIS REPORT FOR THE FINAL DRAINAGE DESIGN OF EASTLAKE ASSISTED LIVING WAS PREPARED BY ME OR UNDER MY DIRECT SUPERVISION IN ACCORDANCE WITH THE PROVISIONS OF THE CITY OF THORNTON STANDARDS AND SPECFICATIONS FOR THE DEISIGN AND CONSTRUCTION OF PUBLIC AND PRIVATE IMPROVEMENTS FOR THE RESPONSIBLE PARTIES THEROF. I UNDERSTAND THAT THE CITY OF THORNTON DOES NOT AND SHALL NOT ASSUME LIABILITY FOR DRAINAGE FACILTIES DESIGNED BY OTHERS. JASON A. MONFORTON, P.E. J3 ENGINEERING CONSULTANTS, LLC, PRINCIPAL Registered Professional Engineer State of Colorado No

3 Your Project, Our Pride TM TABLE OF CONTENTS Page No. I. INTRODUCTION... 1 A. Location... 1 B. Proposed Development... 1 C. Adjacent Areas... 1 II. HISTORIC DRAINAGE... 1 III. DESIGN CRITERIA... 2 A. References... 2 B. Hydrologic Criteria... 2 IV. DRAINAGE PLAN... 2 A. General Concept... 2 B. Specific Drainage Basins Details... 3 C. Detention / Water Quality Ponds... 7 V. CONCLUSION... 7 VI. REFERENCES... 8 VII. CONTRIBUTORS:... 9 APPENDIX SUPPORTING MATERIAL Vicinity Map....A1 Soils Map.... A2-A4 Development Parcel Data...A5 Parcel Data Table...A6 Composite Imperviousness Calculations...A7 Composite C Factor Calculations...A8 Time of Concentration...A9 Rational Method (2, 5 & 100 Year for Basins B2)... A10 A12 UD Sewer Calculations... A13-21 Full Spectrum Detention Voume...A22 Firm Flood Insurance Map...A23

4 I. INTRODUCTION The purpose of this report is to provide a guide to the Developer to use for the planning and final design of drainage facilities for the proposed East Lake Assisted Living and Memory Care. The narrative provides a comprehensive description of the project, methodology utilized for analyses and summarizes the final hydrologic and hydraulic design of drainage facilities. The East Lake Assisted Living and Memory Care parcel will also be referred to as the Site for the remainder of this report. A. Location Located in the southeast one-quarter of Section 36, Township 1 South, Range 68 West, of the 6th PM, City of Thornton, Adams County, Colorado. The property comprises of approximately 1.68 acres and is bounded on the south by E. 120th Avenue, on the north, west and east by Madison Park Subdivision. East Lake Assisted Living and Memory Care Facility tributary area resides in the Brantner Gulch Basin. A Vicinity Map is included within the Appendix for reference. The site is located within Zone X as shown on FIRM Map number 08001C0312H which is included in the Appendix. B. Proposed Development The proposed development will be a memory care and assisted living facility consisting of two buildings each with 16 beds, comprising 8761 square feet and 8570 square feet, respectively. The total site is approximately 1.68 acres and will drain to the north into 4 storm inlets and 12 inch and 18 inch RCP storm pipes to one of two water quality ponds that are hydraulically connected via an 18 RCP pipe. Roughly 0.10 acres of predominantly landscaped area will drain off-site un-detained along the northern, western and eastern edges of the property and while the southern edge consists of primarily sidewalk and roadway and will drain to 120 th Ave as it does in the existing condition. The portion entry drives that drain are part of the existing 120 th ROW or areas that Drainage from the Site was divided into a number of sub-basins and analyzed utilizing the rational method outlined in the City of Thornton s Standards and Specification. A reasonable estimate of the composite average percent impervious for the Site after development is 55.0 and 40.5% for the basins draining off-site. The percent impervious was determined using Table 6-3 in the Urban Storm Drainage Criteria Manual (USDCM) Volume 1. On-Site soils consist primarily of Loamy land, as shown on the Natural Resources Conservation Service Soil Map for Adams County, Colorado Area located in the Appendix of this report. These sandy soils are consistent with the characteristics of Hydrologic Soil Group C. Type C soils are identified as having high infiltration rate when thoroughly wetted, moderate runoff, and moderate to severe erosion hazard. Hydrologic analysis for the Site was based on HSG C soils. C. Adjacent Areas The site lies in a residential area bounded on the south by 120 th Ave and an all other sides by the Madison Park Apartments Complex. A Vicinity Map is included within the Appendix of this report. II. HISTORIC DRAINAGE The site is within the major drainage basins of Brantner Gulch. Surrounding land use consists of a combination or urban uses such as commercial and residential. The East Lake Assisted Living parcel is zoned neighborhood services and lies just south of the Madison Park Subdivision Amendment 1, Lot 1, 1

5 Block 1 and north of E. 120 th Avenue. Madison Park receives runoff from a large developed drainage basin south of 120 th Avenue. Runoff from the basin is collected via curb and gutters and storm sewer that are ultimately routed to the south side of 120 th Avenue to a low point and then into an existing 3 x 6 concrete box culvert that crosses 120 th Av to the north and continues north on the Madison Park Subdivision site. The Site currently consists mostly of grassed undeveloped land that currently has one two story framed house and separate garage on the parcel. The site currently drains via sheet flow to the northeast corner of the parcel and onto the Madison Subdivision parcel. III. DESIGN CRITERIA The City of Thornton s Standards and Specification and USDCM provided the basis for all final design recommendations. A drainage plan is presented for the water quality storm events based on City of Thornton s requirements. A. References The City of Thornton s Standards and Specification and the Urban Drainage and Flood Control District (UDFCD), Urban Storm Drainage Criteria Manuals (USDCM) (References 1 and 2, respectively) were the major technical references used for this report. B. Hydrologic Criteria Hydrologic analyses were calculated using the Rational Method. Rainfall intensities were taken from The City of Thornton s Standards and Specification (Reference 1) IDF equation and are based upon the 1-hour point rainfall depths as identified in Table 2. Please refer to the Appendix for the maps illustrating the 1- hr point rainfall depths and the rational calculations sheet for the Intensity calculations. Table 2: 1-hr Point Rainfall Depths Storm Event 1-hr Rainfall Depth (in) 2-yr yr yr 2.69 The proposed sub-basin characteristics were developed and used for the computation of peak flow rates and for the hydraulic design. The time of concentration and peak flow rate calculations for each subbasin are presented in the appendix. The design frequencies analyzed were the 5-year (minor) and the 100-year (major) storm events. The Rational Method procedures and methodology follow the City of Thornton s and Urban Drainage s Criteria outlined in References 1 and 2, respectively. IV. DRAINAGE PLAN A. General Concept The site is designed as one basin that will drain to two hydraulically connected ponds. Pond 1 is the primary pond and is located along the eastern edge of the site. Pond 2 is located in the southern part of 2

6 the site and will drain to Pond 1. There is approximately 0.08 acres along the northern perimeter of the site that will not be able to be graded to capture runoff into the onsite water quality ponds. These minimized areas will sheet flow to adjacent properties undetained. The onsite basins were divided into sub-basins. The sub-basins were designated with a letter B to show each corresponds to the same major basin. Basins were subdivided to route runoff and determine peak flows at critical locations. These sub-basins are identified with consecutive numeric characters added to the basin letter identifiers (i.e. East On-Site Basin is sub-divided in to basins B1, B2, etc.) Sub-basins with the alphanumeric identifier OS1 represent the tributary area that drains off-site. Design Points are consistent with sub-basin designations and refer to points where basin runoff is quantified (i.e. DP1). Storm pipes have been sized using the design points to ensure that they are capable of conveying the necessary flows. B. Specific Drainage Basins Details Sub-basin B1 is located on the northwest corner of the site. Runoff from sub-basin B1 is generated from 0.03 acres of sidewalk, 0.01 acres from the roof and 0.07 acres of landscaped area. The runoff coefficients for sub-basin B1 are 0.45 for a 5-year storm and 0.67 for a 100-year storm. The composite basin imperviousness is 35.1%. The runoffs generated from sub-basin B1 are 0.24 cfs for the 5-year storm event and 0.69 cfs for a 100-year storm event. Runoff from this sub-basin is conveyed as overland flow to the north until it enters the inlet in the northwest corner of the site (DP1). It then flows to the east via a 12 HDPE Pipe to the water quality pond. The proposed graded depression at the inlet is approximately 4 minimum, this will ensure the 100 year water surface elevation is well below the proposed finished floor of the adjacent building. Based on the proposed manufacturer s specifications the grate at this inlet can capture 100% of the anticipated 100 year flows from this area. Sub-basin B2 contains the northwestern portion of the memory care facility building including courtyard. The area is approximately 0.05 acres of rooftop, 0.01 acres of landscaped area, and 0.01 acres of sidewalk. The runoff coefficients for sub-basin B2 are 0.79 for a 5-year storm and 0.87 for a 100-year storm. The composite basin imperviousness is 80.3%. The runoffs generated from sub-basin B2 are 0.26 cfs for the 5-year storm event and 0.56 cfs for a 100-year storm event. Runoff from the roof will be conveyed through downspouts that will be conveyed to the inlet in the courtyard and to the north via a 6 PVC pipe to connect to the 15 PVC pipe at DP2 in the back of the lot. Sub-basin B3 is located in the northern portion of the site and includes the northeast corner of the memory care facility and a portion of the landscape area along the north lot line. Runoff from sub-basin B3 is generated from 0.02 acres of sidewalks, 0.05 acres of the roof, and 0.05 acres of landscaped area. The composite basin imperviousness is 50.9%. The runoff coefficients for sub-basin B3 are 0.29 for a 5- year storm and 0.68 for a 100-year storm. The runoffs generated from sub-basin B3 are 0.33cfs for a 5- year storm event and.74 cfs for a 100-year storm event. Runoff from B3 is conveyed as overland flow until it enters the side walk chase in the northeast corner of the basin which leads to the inlet at DP3 in the northern portion of the sub-basin and flows to the east in an 18 PVC Pipe to the EURV Pond. 3

7 Sub-basin B4 is comprised of the majority of the open space between the two proposed buildings and captures the runoff from the down spouts along the west side of the Assisted Living Building. Runoff from sub-basin B4 is generated from 0.03 acres from the roof, 0.02 acres of sidewalks, and 0.10 acres of landscaped area. The composite basin imperviousness is 34.4%. The runoff coefficients for sub-basin B4 are 0.45 for a 5-year storm and 0.66 for a 100-year storm. The runoffs generated from sub-basin B4 are 0.30 cfs for a 5-year storm event and.85 cfs for a 100-year storm event. Runoff from B4 is conveyed as overland flow until it enters sidewalk chase and continues on to DP3 in the northern portion of the subbasin and flows to the east in a 18 HDPE Pipe to the EURV Pond. Sub-basin B5 is located on the northwestern edge of the assisted living building. Runoff from sub-basin B5 is generated from the rear portion of this proposed building s rooftop as well as the surrounding landscaped areas and sidewalks. The area is approximately 0.01 acres of roof, 0.02 from the sidewalks, and 0.04 from the landscaped areas. Runoff from the roof will be conveyed through sidewalk chases join the rest of the flow over land to the inlet at DP3. The runoff coefficients for sub-basin B5 are 0.48 for a 5-year storm and 0.68 for a 100-year storm. The composite basin imperviousness is 38.3%. The runoffs generated from sub-basin B5 are 0.15 cfs for the 5-year storm event and 0.42 cfs for a 100-year storm event. During the 100 year storm there is approximately 4 of ponding at the inlet due to the HGL of the pipe network. The surrounding grading has more than enough space to accommodate this ponding Sub-basin B6 contains the portion of the assisted living facility build surrounding the courtyard and the portions of the roof that contribute to the downspouts that discharge in to the courtyard. The area is approximately 0.05 acres of rooftop, 0.01 acres of landscaped area, and 0.01 acres of sidewalk. The runoff coefficients for sub-basin B6 are 0.79 for a 5-year storm and 0.87 for a 100-year storm. The composite basin imperviousness is 80.3%. The runoffs generated from sub-basin B6 are 0.23 cfs for the 5-year storm event and 0.50 cfs for a 100-year storm event. Runoff from the roof will be conveyed through downspouts that will be conveyed to the inlet in the courtyard and to the north via a 6 PVC pipe to connect to the 18 PVC pipe in the rear of the lot. Sub-basin B7 is located in the northeast corner of the site. Runoff from sub-basin B7 is generated from 0.02 acres of sidewalks, <0.01 acres of roof, and 0.03 acres of landscaped area. The composite basin imperviousness is 40.8%. The runoff coefficients for sub-basin B7 are 0.50 for a 2-year storm and 0.69 for a 100-year storm. The runoffs generated from sub-basin B7 are 0.11 cfs for a 5-year storm event and 0.29 cfs for a 100-year storm event. Runoff from B7 is conveyed as overland flow until it enters an inlet in the northeastern portion of the sub-basin, DP4, and flows to the south in a 24 private PVC Pipe. Sub-basin B8 is located in the southeastern portion of the site along eastern property line. Runoff from sub-basin B8 is 0.01 acres of rooftop and 0.05 acres of landscaped area. The calculated runoff coefficients for sub-basin B8 are 0.35 for a 5-year storm and 0.60 for a 100-year storm. The composite basin imperviousness is 20.8%. The runoffs generated from the sub-basin are 0.10 cfs for a 5-year storm event and 0.32 cfs for a 10-year storm event. Runoff from this sub-basin is conveyed as overland flow to the center of the sub-basin and into Pond 1. Sub-basin B9 is located in the southeastern portion of the site along the entrance road and parking area. Sub-basin B9 contains Water Quality Pond 1. Runoff from sub-basin B9 is generated from 0.01 acres of sidewalk, 0.02 acres of rooftop, 0.02 acres of the pond, and 0.07 acres of landscaped area. The calculated runoff coefficients for sub-basin B9 are 0.48 for a 5-year storm and 0.69 for a 100-year storm. The composite basin imperviousness is 19.1%. The runoffs generated from sub-basin B9 are 0.26 cfs for 4

8 a 5-year storm event and 0.72 cfs for a 100-year storm event. Runoff from this sub-basin is conveyed as overland flow to the center of the sub-basin and into Pond 1. Sub-basin B10 is located in the southeastern portion of the site along the entrance road and parking area. Runoff from sub-basin B10 is generated from 0.19 acres of parking, 0.03 acres of sidewalk, and 0.01 acres of rooftop. The calculated runoff coefficients for sub-basin B10 are 0.92 for a 5-year storm and 0.94 for a 100-year storm. The composite basin imperviousness is 96.8%. The runoffs generated from sub-basin B10 are 0.49 cfs for a 5-year storm event and 0.99 cfs for a 100-year storm event. Runoff from this sub-basin is conveyed as overland flow to a 12 curb chase in the parking lot DP9, where it will be conveyed to Pond 2. There was not enough space available to grade the entire pond into this location so an 18 concrete pipe has been proposed under the parking area to hydraulically connect Pond 2 to the area where Pond 1 has been graded. This pipe will allow the captured runoff in each pond to raise and lower together to effectively deliver one water quality/eurv pond. This Pond discharges into an outlet structure in Pond 1s. No hydraulic sizing of the pipe has been provided as it is not intended to convey a set rate of flow, it is merely intended to link the two ponds together. Sub-basin B11 is located in the southwestern portion of the site along the entrance road and parking area. Runoff from sub-basin B11 is generated from 0.10 acres of parking, 0.05 acres of landscaped area, and 0.03 acres of sidewalk. The calculated runoff coefficients for sub-basin B11 are 0.72 for a 5-year storm and 0.82 for a 100-year storm. The composite basin imperviousness is 70.4%. The runoffs generated from sub-basin B11 are 0.60 cfs for a 5-year storm event and 1.33 cfs for a 100-year storm event. Runoff from this sub-basin is conveyed as overland flow to a 12 curb chase in the parking lot DP8, where it will be conveyed to Pond 1. Sub-basin B12 is located in the western portion of the site. Runoff from sub-basin B12 is generated from 0.01 acres of rooftop and 0.08 acres of landscaped area. The composite basin imperviousness is 70.4%. The runoff coefficients for sub-basin B12 are 0.33 for a 5-year storm and 0.60 for a 100-year storm. The runoffs generated from sub-basin B12 are 0.66 cfs for a 5-year storm event and 2.01 cfs for a 100-year storm event. Runoff from B12 is conveyed as overland flow to an inlet at DP7 which will then run east along the front of the memory care building and continue into Pond 1. Sub-basin B13 is located in the southern portion of the site and contains Pond 1. Runoff from sub-basin B13 is generated from 0.10 acres of pond, and 0.24 acres of landscaped area. The composite basin imperviousness is 2.9%. The runoff coefficients for sub-basin B13 are 0.42 for a 5-year storm and 0.65 for a 100-year storm. The runoffs generated from sub-basin B13s are 0.64 cfs for a 5-year storm event and 1.94 cfs for a 100-year storm event. Runoff from B13 is conveyed as overland flow to Pond 1. Pond 1 discharges to an 18 concrete pipe that connects to Pond 2. Flows from Pond 2 leave the site via an 18 storm pipe and an outlet structure to control the EURV flows and convey undetained 100 year flows. Runoff flows to the existing 3 by 6 RCB storm sewer to the east of the site at a tie-in point near E. 120 th Avenue. Sub-basin B14 is the front portion of the roof of the memory care facility. Runoff from sub-basin B14 is generated from 0.06 acres of rooftop. The composite basin imperviousness is 90.0%. The runoff coefficients for sub-basin B14 are 0.87 for a 5-year storm and 0.91 for a 100-year storm. The runoff generated from sub-basin B14 are 0.23 cfs for a 5-year storm event and 0.46 cfs for a 100-year storm event. Runoff from B14 is conveyed through downspouts directly into the 12 collection pipe and continues in the pipe to Pond 1. 5

9 Sub-basin B15 is the front portion of the roof of the assisted living facility. Runoff from sub-basin B15 is generated from 0.05 acres of rooftop. The composite basin imperviousness is 90.0%. The runoff coefficients for sub-basin B15 are 0.87 for a 5-year storm and 0.91 for a 100-year storm. The runoff generated from sub-basin B15 are 0.19 cfs for a 5-year storm event and 0.39 cfs for a 100-year storm event. Runoff from B15 is conveyed through downspouts directly into the 6 collection pipe and continues in the pipe to Pond 2. Sub-basin OS1 is the western portion of the drive that located in the right of way that will be directed to the water quality pond. Runoff from sub-basin OS1 is generated from 0.04 acres of roadway. The composite basin imperviousness is 100.0%. The runoff coefficients for sub-basin OS1 are 0.94 for a 5- year storm and 0.96 for a 100-year storm. The runoff generated from sub-basin OS1 are 0.16 cfs for a 5- year storm event and 0.31 cfs for a 100-year storm event. Runoff from OS1 is conveyed through curb and gutter to the curb chase at DP8 and into Pond 1. Sub-basin OS2 is the eastern portion of the drive that located in the right of way that will be directed to the water quality pond. Runoff from sub-basin OS2 is generated from 0.02 acres of roadway. The composite basin imperviousness is 100.0%. The runoff coefficients for sub-basin OS2 are 0.94 for a 5- year storm and 0.96 for a 100-year storm. The runoff generated from sub-basin OS2 are 0.07 cfs for a 5- year storm event and 0.15 cfs for a 100-year storm event. Runoff from OS2 is conveyed through curb and gutter to the curb chase at DP9 and into Pond 1. Sub-basin OS3 is the northern edge of the property along the lot line. Runoff from sub-basin OS3 is generated from 0.05 acres of landscaped area. The composite basin imperviousness is 2.0%. The runoff coefficients for sub-basin OS3 are 0.21 for a 5-year storm and 0.52 for a 100-year storm. The runoff generated from sub-basin OS3 are 0.04 cfs for a 5-year storm event and 0.20 cfs for a 100-year storm event. Runoff from OS3 is conveyed by over land flow off site and into the existing storm system in the Madison Park Subdivision. Sub-basin OS4 is the eastern edge of the property along the lot line. Runoff from sub-basin OS4 is generated from 0.04 acres of landscaped area. The composite basin imperviousness is 2.0%. The runoff coefficients for sub-basin OS4 are 0.21 for a 5-year storm and 0.52 for a 100-year storm. The runoff generated from sub-basin OS4 are 0.03 cfs for a 5-year storm event and 0.14 cfs for a 100-year storm event. Runoff from OS4 is conveyed by over land flow off site and into the existing storm system a in the Madison Park Subdivision. Sub-basin OS5 is the western edge of the property along the lot line. Runoff from sub-basin OS5 is generated from 0.01 acres of landscaped area. The composite basin imperviousness is 2.0%. The runoff coefficients for sub-basin OS5 are 0.21 for a 5-year storm and 0.52 for a 100-year storm. The runoff generated from sub-basin OS5 are 0.03 cfs for a 5-year storm event and 0.14 cfs for a 100-year storm event. Runoff from OS5 is conveyed by over land flow off site and into the existing storm system a in the Madison Park Subdivision 6

10 C. Water Quality Ponds Pond 2 is along the southern edge of the site in the center of the semicircular entry drive. Pond 1 is located in the southeastern corner of the site. The ponds will be hydraulically connected via an 18 concrete pipe. The total required water quality volume for this site is ac-ft. The ponds have been sized to capture and treat the amount of runoff generated by the 1.68 acres of developed site. It should be noted that a portion approximately.4 acres of existing ROW (landscaped area) drains to the ponds but this is not accounted for in the treatment volume. Approximately 60% of the volume will be provided in Pond 1 at ac-ft and 40% in Pond 2ss with ac-ft. Both ponds will have a water quality surface elevation of ft NGVD. The required volume for the on-site water quality pond is based upon the calculation spreadsheet Detention Basin Volume Estimating Workbook by the Urban Drainage and Flood Control District. Calculations can be found in the Appendix. The outfall from Pond 1s will discharge to the existing 3 ft by 6 ft reinforced box culvert (RBC) via a Type C outlet structure and 18 rcp. The outlet structure will restrict flows in the EURV events and will discharge 100 year flows through the top grate at developed rates. These flow will be conveyed to the 3 x6 RBC that carries public flow and is designed for the 100 year developed stormwater flows from the major drainage basin including this parcel. An analysis of the system from the 3 x 6 RBC installed beginning in the 120 th right of way to the regional detention facility determined that the HGL at the proposed Eastlake Pond 1 would be Even though the Madison Park Drainage Report determined the 3 x 6 RBC is surcharged the HGL would be below the water surface at the proposed Pond 1 and there will be no back flow. In event of an emergency the 100 year flow will spill over the East retaining wall (elevation of Pond 1. The spillway will convey two times the 100 year storm (21 cfs) with a pond depth of

11 IV. CONCLUSION The Phase III (final) drainage plan provided in this report is intended to fully comply with the City of Thornton Storm Drainage Design and Technical Criteria Manual (Reference 1) and the Urban Drainage and Flood Control District, Urban Storm Drainage Criteria Manuals (Reference 2.) The drainage plan provides the required water quality volume for the proposed development on this Site, has considered impacts on downstream neighbors and infrastructure. The planned improvements outlined in this phase III report will minimize any adverse effects on the water quality of the associated basin. VI. REFERENCES 1. City of Thornton s Standards and Specification, City of Thornton; Revised, October Urban Storm Drainage Criteria Manuals, Volumes 1, 2, and 3, Urban Drainage and Flood Control District; June 2001; Revised January Web Soil Survey of Adams County, Colorado, Natural Resources Conservation Service (NRCS), April Flood Insurance Rate Map (FIRM) Map Community-Panel Number H, National Flood Insurance Program, Federal Emergency Management Agency (FEMA), Panel 312 of 1150, Effective Date March 5, Phase III Drainage Report Madison Park, Phase One, DHM Design Corporation, December Phase III Drainage Report, Madison Park, EMK Consultants, Inc., September

12 VII. CONTRIBUTORS: Contribution Name, Title Initials Report Prepared By: David Hoesly, P.E. Staff Engineer II Report Reviewed By: Donna Barrentine, P.E. Project Manager Note: Contributors to initial each prepared report prior to FINAL submittal. 9

13 APPENDIX Supporting Material 10