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HomeMy WebLinkAboutSYMBIOS LOGIC OVERALL DEVELOPMENT PLAN - 5-94D - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTOVERALL DRAINAGE STUDY AND PHASE I PRELIMINARY DRAINAGE STUDY FOR THE SYMBIOS LOGIC SITE FORT COLLINS, COLORADO OVERALL DRAINAGE STUDY AND PHASE I PRELIMINARY DRAINAGE STUDY FOR THE SYMBIOS LOGIC SITE FORT COLLINS, COLORADO April 22, 1996 Prepared for: Client: RNL Design Seventeenth Street Plaza 1225 Seventeenth Street, Suite 1700 Denver, Colorado 80202 Prepared by: RBD, Inc. Engineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 (970) 482-5922 RBD Job No. 714-001 Engineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 970/482-5922 FAX: 970/482-6368 April 22, 1996 Mr. Basil Hamdan City of Fort Collins Utility Services Stormwater 235 Mathews Fort Collins, Colorado 80522 RE: Overall Drainage Study and Preliminary Phase I Drainage Study for the Symbios Logic Site Dear Basil: We are pleased to submit to you, for your review and approval, this Overall Drainage Study and Phase I Preliminary Drainage Study for the Symbios Logic site. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, RBD Inc. Engineering Consultants Prepared By: ( 41�17 - Patricia Kroetch Project Engineer Reviewed By: "v7- AvalL-A t3ur David K. Thaemert, P.E. Water Resources Project Engineer Denver 303/458-5526 TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION A. LOCATION 1 B. DESCRIPTION OF PROPERTY 1 II. DRAINAGE BASINS A. MAJOR BASIN DESCRIPTION 1 B. SUB -BASIN DESCRIPTION 2 III. DRAINAGE DESIGN CRITERIA A. REGULATIONS 2 B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 3 C. HYDROLOGICAL CRITERIA 3 D. HYDRAULIC CRITERIA 3 E. VARIANCES FROM CRITERIA 3 IV. DRAINAGE FACILITY DESIGN A. GENERAL CONCEPT 4 B. SPECIFIC DETAILS 4 OVERALL SITE DEVELOPMENT 4 PRELIMINARY FIRST FILING DEVELOPMENT 6 V. STORM WATER QUALITY A. GENERAL CONCEPT 6 B. SPECIFIC DETAILS 6 VI. EROSION CONTROL A. GENERAL CONCEPT 7 VII. CONCLUSIONS A. COMPLIANCE WITH STANDARDS 7 B. DRAINAGE CONCEPT 8 C. STORM WATER QUALITY 8 D. EROSION CONTROL CONCEPT 8 REFERENCES 9 `a'PP_ X PAGE 2 VICINITY MAP 4 HYDROLOGY 10 DETENTION AND RETENTION POND CALCULATIONS 15 TABLES AND FIGURES FOX MEADOWS BASIN H DRAINAGE 19 MASTER PLAN INFORMATION EXCERPTS FROM PREVIOUS DRAINAGE REPORTS 36 UPDATED 100—YEAR SWMM MODEL INPUT DATA 50 FOR THE SOUTH FOX MEADOWS BASIN UPDATED 100—YEAR SWMM MODEL OUTPUT FILE 56 FOR THE SOUTH FOX MEADOWS BASIN I OVERALL DRAINAGE STUDY AND PHASE I PRELIMINARY DRAINAGE STUDY ' FOR THE SYMBIOS LOGIC SITE FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The Symbios Logic site is located north of Harmony Road and west of County Road 9 (Minor Road) in southeastern Fort Collins, Colorado. The site is shown on the Vicinity Map in the Appendix. More particularly, the site is situated in the southeasterly portion of Section 22, Township 7 North, Range 68 West of the Sixth P.M., City of Fort Collins, Larimer County, Colorado. B. Description of Property The Symbios Logic site contains 102 acres of land, more or less, of which all of the area is currently undeveloped and being proposed for an Industrial Park for the Symbios Logic Company. The majority of the property currently consists of cultivated farm land. Topography at the site is generally sloping from west to east at approximately 0.8 %. There is a concrete irrigation ditch in the southeast corner of this site which is a portion of the Dixon Canyon Lateral. This ditch will be replaced by a pipe during Phase 1 construction as approved by the ditch company. There is also an irrigation lateral that runs north -south through the west portion of the site. This lateral will be investigated to determine if it should be maintained or if it can be abandoned. If the lateral needs to be maintained, it will be rerouted around the loop road in a future phase. II. DRAINAGE BASINS A. Major Basin Description The Symbios Logic site lies entirely within the Fox Meadows Drainage Master Plan (Basin H) as shown in the Master Plan Report by Resource Consultants Inc., dated 1981. In addition, this area was studied again by Nolte and Associates in May 1990 when they prepared a master drainage plan for the Hewlett-Packard (H-P) site which lies to the East of the Symbios Logic site. This site was recently investigated in the Final Drainage Study for Hewlett-Packard Building 5 by RBD, Inc. in February 1996. Applicable portions of all of these studies are included in the Appendix. The Master Drainage Report which was done by Nolte and Associates did not alter any of the assumptions or conclusions which were made in the Fox Meadows Master Drainage Plan. In effect, this report simply incorporated the recommendations that the Master Drainage Plan for Fox Meadows had called for in the design of the H-P site. These recommendations included the design of a drainage swale which runs along the North side of the H-P site and eventually drains into H-P's North pond. This drainage swale has been sized and final designed with the H-P Building 5 drainage report. The drainage swale to be constructed across the H-P site has been final designed by H-P and is anticipated to be constructed this spring. The Master Drainage Plan for the H-P site is shown in the Appendix. The Symbios Logic site currently drains to two' existing 18" RCP and onto the H-P site. According to the Master Drainage Plan done for the H-P site the Symbios Logic site falls within both basins 31 and 23. However, the shape and area of these basins does not correspond to the shape of the Symbios Logic site. It appears that Symbios Logic would have pond #215 on their site and pond #214 also. The total area draining to these two ponds on the master plan is equal to 149.2 acres. This area includes the Symbios site and the area to the west of this site. Both ponds #215 and #214 were shown as having an allowable release rate of 24 cfs each or a total release of 48 cfs. B. Sub -Basin Description Historic drainage patterns on the subject site are in an easterly direction per Figure 2 (Fox Meadows Drainage Master Plan) on page 31 in the appendix. Upstream off -site areas lying west of Corbett Drive contribute storm water runoff which crosses the Symbios Logic site at the present time. When the Symbios Logic site is developed, off -site flows will be conveyed in a drainage swale around the site and onto the H-P site by a proposed culvert under County Road 9. This culvert will discharge those off -site flows into the proposed drainage swale on the north side of the Hewlett-Packard site. No off -site runoff from properties north and south of the Symbios Logic site traverse through the site. III. DRAINAGE BASIN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. Oil B. Development Criteria Reference and Constraints The Fox Meadows Basin (Basin H) Drainage Master Plan and the subsequent H-P Master Drainage Plan criteria and constraints are being utilized in this Overall Drainage Study. The recent Final Drainage Study for H-P Building 5 is also being used to determine criteria for this site. Since the Symbios Logic site is currently being utilized as agricultural land, the Fox Meadows Master Plan for the site included on -site detention facilities for the future development. As can be seen from the Fox Meadows Drainage Master Plan report (Figure 5), detention was planned for 3 locations on the West side of County Road 9. Two of those ponds, which are labeled as pond #3 and #4 in the Fox Meadows Drainage Master Plan, are located entirely within the Symbios Logic site. However, the drainage area which drains to those ponds in the Fox Meadows Master Plan does not correspond to the area of the Symbios Logic .site. In fact, the area which was proposed to drain to ponds #3 and #4 is larger than the Symbios Logic site by approximately 47.2 acres. These ponds will be sized to accept runoff from the entire 149.2 acres and both ponds will have a combined restricted release rate of 48 cfs. C. Hydrologic Criteria The SWMM hydrologic model was previously used in the Fox Meadows Basin Master Drainage Plan. The Hewlett-Packard Master Drainage Plan report utilized the Fox Meadows Basin Master Drainage Plan SWMM model and simply expanded on it. The SWMM model was updated recently for the H-P Building 5 project. This SWMM model has again been updated to include the two detention ponds which are proposed for the Symbios Logic site. A copy of the SWMM model for the 100-year storm is included in the Appendix. D. Hydraulic Criteria All calculations within this study have been prepared in accordance with the City of Fort Collins Storm Drainage Criteria and are included in the appendix. E. Variances from Criteria No variances from the City of Fort Collins Storm Drainage Criteria are being sought for this project. IIV. DRAINAGE FACILITY DESIGN A. General Concept As development occurs within the Symbios Logic site, the drainage concepts shown on the Overall Drainage Plan in the back pocket of this report should be followed. There are three ponds shown within the site to handle the stormwater runoff. One of these ponds is proposed as a permanent wet pond which will be fed by irrigation water and runoff from the adjacent area. Water in this pond will be utilized for irrigating the site. The retention pond will need to be sized in excess of the required amount of permanent water storage to allow for the periodic inflows of stormwater and the ultimate inflow of the 100 year storm. Even though this pond is a permanent retention pond, it will need some overflow mechanism to allow for a situation where complete inundation of the pond volume occurs. The other two ponds will discharge under County Road 9 and onto the H-P site at the allowable release rate of 48 cfs combined. On -site stormwater will be conveyed to the three on -site ponds through the use of drainage swales, storm drain pipes, inlets, curb cuts and cross pans. For the updated SWMM model, the sub -basins within and tributary to the Symbios Logic site were revised to match proposed developed conditions. This included revising sub -basin areas to match proposed site layout and revising the theoretical detention pond rating curves for ponds 214 and 215. Both of these ponds were previously master -planned to discharge 24 cfs each. Because of the changes in tributary area upstream of each pond, these peak release rates were modified proportionally to the respective tributary area. However, the peak combined release rate from the two ponds still does not exceed 48 cfs. The sub -basin to the west of the proposed Symbios Logic site was modeled in its existing undeveloped condition. Historic runoff for the 100-year event from this sub -basin is accounted for in the detention provided on the Symbios Logic site. Note that any increase of impervious area within this off -site basin will have to detain the difference between developed and historic flows before releasing these flows downstream to the Symbios Logic site. Refer to the Appendix for supporting calculations for the supporting calculations for this SWMM model update. B. Specific Details Overall Site Development Per the Fox Meadows Basin Drainage Master Plan and the approved Hewlett- Packard Master Drainage Plan the Symbios Logic site must have on -site detention. The Fox Meadows Master Plan showed two ponds within the Symbios Logic site 4 Iwhich each release 24 cfs. In addition, the Hewlett-Packard site is constructing a drainage swale which has been sized to accommodate Symbios Logic's off -site flows as well as its' own. The Overall Drainage Plan for the Symbios Logic site includes utilizing a proposed permanent pool pond within the site for retention. An additional volume above the permanent pool will be provided within this pond which allows for the permanent retention of the 100-year runoff for the drainage area which drains to it. There will however, be an emergency overflow provided for this pond. The additional stormwater volume needed in pond # 1 will be approximately 0.58 acre-feet plus one foot of freeboard. This is in addition to whatever "wet pond" volume is needed for irrigation purposes and to maintain an attractive water feature for the Symbios Logic site. The second pond will be located in the northeast corner of this site. This pond will outlet under County Road 9 through a proposed storm pipe which will outlet into the Hewlett-Packard drainage channel with a restricted release of 30.5 cfs. The release rate was adjusted from 24 cfs based on the proportional tributary area. This pond will need a minimum volume of approximately 6.9 acre-feet plus one foot of freeboard. The third pond proposed on the Symbios Logic site is located to the west of County Road 9. Because of the desire which Symbios Logic has to be environmentally sensitive, this pond will contain a wetlands area which will help filter out pollutants from the site. The pond itself will be on both sides of the main entrance off of County Road 9, with a storm pipe located under the entry -way which will allow 17.5 cfs to pass through and access the two existing 18" RCP's (designed with the County Road 9 project, excerpts in appendix) which are located on the North side of the entryway. These pipes will be restricted to a release of 17.5 cfs to bring the total site release to 48 cfs. The release from this pond was adjusted from 24 cfs based on the proportional tributary area. This pond will need a minimum volume of approximately 6.7 acre-feet plus one foot of freeboard. The City of Fort Collins Stormwater Utility has requested that a SWMM Model be submitted and include the three proposed on -site ponds. The Hewlett-Packard site developed a SWMM Model for the entire area, and we have updated this model for the Overall Symbios Site and used this model to size the detention ponds on the Symbios Site. The SWMM Model is a conservative approach to ensure all detention ponds within the City of Fort Collins have sufficient capacity. 5 Preliminary First Filing Development The first phase of the Symbios Logic site will include the construction of a portion of detention pond #3. The storm water runoff from the site will reach this pond by overland methods, i.e. grass swales, pipe, curb cuts, cross pans etc. The runoff from those areas which would have drained into ponds #1 and #2, is being diverted into pond #3 at this time. Therefore, detention pond #3 is being built to accommodate runoff from Phase 1 under developed conditions and the remainder of the site under undeveloped conditions. As this site develops, pond #3 will be enlarged and ponds #1 and #2 will be constructed to accommodate the increased runoff. The outlet culvert for pond #2 was not installed with the recent reconstruction of County Road 9 and therefore this pond will not be constructed with Phase I. This pond will be constructed when the north portion of this site develops or when the site to the west is developed. Pond #1 will be used primarily for irrigation water and as a water feature. This pond will be constructed as the site is developed around the proposed pond location. A storm drain system is being proposed with Phase 1. Inlets will be located in the parking areas and storm drain pipes will convey runoff to the detention area. These inlets and storm drain will be sized at the time of final design. V. STORM WATER QUALITY A. General Concept The State of Colorado requires Stormwater Management Plans as part of their permit process. The Symbios Logic site development is anticipating construction beginning in the Fall of 1996. Therefore for this study, we have sought to find various Best Management Practices for the treatment of storm water runoff at this preliminary design phase which could be implemented in the final design process. B. Specific Details It is our understanding at this preliminary phase, that the concept of storm water quality should address the treatment of the initial first flush runoff. By capturing the initial first flush runoff, the pollutants can be filtered out of the storm water runoff. The Symbios Logic site is being proposed with a wetlands area within the on -site detention pond. This wetlands area will serve many purposes. Because the area is held flat, the runoff will be slowed down in these areas and this will allow pollutants and other transported materials to be filtered out. In addition, the wetlands native grass species also "treat" the polluted runoff water and allow for a much cleaner discharge from the Symbios Logic site onto H-P. Also, the Symbios Logic site is being designed with numerous drainage swales to transport the storm water runoff to the on -site ponds. The drainage swales will probably average less than 1 % in slope. These relative flat slopes are ideal from a water quality standpoint as these slopes allow storm water to filter out pollutants into the grass as the storm water is transported to the detention ponds. Because water quality is of such importance, we are not proposing to construct concrete trickle pans in the bottom of any drainage swales. The natural grass lined drainage swales are being proposed as an important water quality feature. At the time of final design, the City Stormwater Utility minimum velocity requirements must be met or an underdrain pipe system will need to be installed beneath each swale which does not meet the minimum velocity requirements. The underdrain systems would outlet into the ponds. VI. EROSION CONTROL A. General Concept The Symbios Logic site lies within the Moderate Rainfall Erodibility Zone and the Moderate Wind Erodibility Zone per the City of Fort Collins zone maps. Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites, at the time of final design of the site, the erosion control performance standard will need to be calculated and appropriate measures taken to control erosion from the site. All construction activities must also comply with the State of Colorado permitting process for Stormwater Discharges Associated with Construction Activity. A Colorado Department of Health NPDES Permit will be required before any construction grading can begin within this development. VII. CONCLUSIONS A. Compliance with Standards All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. The City of Fort Collins Stormwater Utility will not maintain the on -site storm drainage facilities within the 1h Symbios Logic site. The owners of the Symbios Logic site will need to maintain their on -site storm drainage facilities on a regular basis. B. Drainage Concept The proposed drainage concepts adequately provide for the transmission of developed on -site runoff to the three proposed retention/detention ponds. The sizes, location and release rates of each pond will allow the Symbios Logic site to develop in conformance with the Fox Meadows Basin Drainage Master Planning concepts accepted by the City of Fort Collins and the H-P Master Drainage Plan. Each of the on -site ponds shall provide one foot of freeboard and an emergency overflow outlet in the event the outlet becomes plugged. C. Storm Water Quality The wetlands area proposed within the on -site detention pond is an excellent way to allow storm water pollutants an opportunity to be filtered out of the storm water as the pollutants are carried by the storm water across the site. Periodic maintenance may be required to remove sediment deposits as they accumulate in the main on -site detention pond. D. Erosion Control Concept Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites, at the time of final design of the site, the erosion control performance standard will need to be calculated and appropriate measures taken to control erosion from the site. REFERENCES 1 2 3. 0 5. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991. Fox Meadows Basin (Basin H) Drainage Master Plan, Fort Collins, Colorado, by Resource Consultants Ind., 1981. Master Drainage Report, Hewlett Packard Site, Preston Kelly Subdivision, Fort Collins, Colorado by Nolte and Associates, May 1990. Final Drainage Study for Hewlett-Packard Company Building 5, Fort Collins, Colorado by RBD, Inc., February 1996. 9