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HomeMy WebLinkAboutDrainage Reports - 08/03/1995FINAL DRAINAGE & EROSION CONTROL REPORT FOR RETAIL DEVELOPMENT TAFT HILL ROAD & WEST ELIZABETH STREET April 28, 1995 (Revised July 19, 1995) PREPARED FOR Mr. Paul Santanachote 1401 Pearl Street Boulder, CO. 80302 PREPARED BY: PARSONS AND ASSOCIATES, INC. CONSULTING ENGINEERS 432 LINK LANE PLAZA FORT COLLINS, COLORADO 80524 (303) 221-2400 PROJECT NUMBER: 95.13 TEL TABLE OF CONTENTS Introduction Site Description Hydrologic Analysis Erosion Control Wind Erosion Water Erosion Conclusions and Recommendations Figure 1 Vicinity Map Figure 2 Existing Conditions Appendix A Drainage Calculations Appendix B Erosion Calculations 1 2 3,4 5 5 5 6 Exhibit 1 Drainage and Erosion Control Plan Back Pocket FINAL DRAINAGE AND EROSION CONTROL REPORT FOR RETAIL DEVELOPMENT TAFT HILL ROAD & WEST ELIZABETH STREET INTRODUCTION The purpose of this study is to provide drainage and erosion control information for the development of a .54 acre (legally described) commercial site which will include a restaurant and office space on Taft Hill Road at West Elizabeth. All design specifications are prepared in accordance with the "City of Fort Collins Drainage Design and Construction Standards". This site has historically been used as a convenience store/gas station. However, the lot is currently vacant and no buildings or improvements are present. SITE DESCRIPTION The site currently drains to the curb line on the north flowline of West Elizabeth. Existing vegetation on the site consists of scattered shrubs and is surrounded by concrete walks or asphalt surfaces and gravel. The historic and proposed development for the tract is commercial as outlined above. The entire project will be developed in one phase with all improvements proposed for construction. The site is located in the Northwest Quarter of Section 15, Township 7 North, Range 69 West of the Sixth Principal Meridian, Larimer County, Colorado. The project area consists of three parcels, combined to form a new minor subdivision. The project is located at the northeasterly corner of the intersection of Taft Hill Road and West Elizabeth Street (See Figure 1, Vicinity Map). ' The area to the north is a small commercial building with an asphalt parking lot. The area to the east is an existing ' residential subdivision. The southerly and westerly portions front I West Elizabeth and Taft Hill Road, respectively. J I Pi VICINITY MAP 1 " = 1400' FIGURE 1 HYDROLOGIC ANALYSIS The Rational Method has been used to calculate the stormwater run-off for the 10-year and 100-year return period events for the Historic and proposed improvements to the site. HISTORIC• The historic (existing) 10-year and 100-year events were developed to compare existing (historic) conditions to the fully developed (proposed) conditions. The composite "C" coefficients for the historic show a C=0.86, or approximately 4300 square feet of mixed landscape and gravel area on the existing site with approximately 29,200 square feet of impervious surface, please refer to Figure 2. All storm flows concentrate south and east from the northwest corner of the project which is an existing high point on the site. An existing asphalt curb head on the eastern perimeter of the site directs flows to the south (West Elizabeth). Basin C collects to the east and a shallow swale per historic conditions. Concentrated flows from this small basin is below the minimum mathematical tolerance of the rational formula. K� e — z—� gg� a" (� ~ W 1 / a � W GVO& 77/H 1-4d1 �\ DEVELOPED• The composite "C" for the developed (proposed) site was calculated as 0.83, with approximately 5440 square feet of landscape and 28,830 square feet of impervious surface, as shown in back pocket exhibit. This represents a net decrease in impervious area from historic conditions and should have no adverse effect on storm drainage patterns or maximum surface elevations during any frequency storm event. Drainage patterns will follow historic spill locations to West Elizabeth combined concentration points 1 and 2 (Exhibit back pocket. The 100-yr. fully developed event storm flows will not increase the historic run-off volumes from the site. The downstream basin (canal importation) has historically been receiving the equivalent of fully developed flows from this site. Basin modeling accounted for the historic conditions from this parcel. Basin C will drain to the northeast, per historic conditions. The developed release rate is equal to the historic release due to the small contributing area. 4 EROSION CONTROL This project is located within an area of moderate wind ' erosion and moderate rainfall erosion according to the City of Fort Collins wind and rainfall erodibility maps. WIND EROSION Wind erosion protection will be provided by existing buildings on the northern perimeter of the project. Asphalt paving of the parking area and seeding and mulching (or landscaping) of all disturbed areas will provide final stabilization upon completion of this project. WATER EROSION Net effectiveness calculations included in Appendix B of this report show that methods proposed for this development will be adequate at minimizing the erosion potential of rainfall events. As stated above, final stabilization will occur with completion of paving and landscaping features. All erosion control calculations and cost estimates are included in Appendix B of this report. 11 CONCLUSIONS AND RECOMMENDATIONS After review of historic and proposed drainage information and existing drainage information, the following conclusions can be made. 1) Run-off from the site will collect to a common outfall point. The minor flows will be conveyed in gutter pans, shallow drain pans or street flow across impervious surfaces. 2) Proposed development will actually decrease (slightly) the storm flows from the initial (10 year) storm. 3) The proposed development will have no impact or increase on downstream conveyance elements during the major (100-yr) storm event. Run-off from the site will have no net increase in f low. 7 DRAINAGE CALCULATIONS APPENDIX A PARSONS & CLIENT B V z r�^�-`/^ JOB NO. Irk- ASSOCIATES PROJECT �Cti�� >�- CALCULATIONS FOR A'5- JY`1_,C- CONSULTING ENGINEERS � FL Collm, Colorado 90524 MADE BY `�7 AO DATE 10 CHECKED DATE SHEET OF 1 cci 4- C� bl� .ti n� C to m Ci W .� l4 C'� m Q o U `o os 3 O J Q U w O U w m Q rn N J j W -� ♦ LL Q H c E cc 3 c LL Z CS a c L R S c C 0 E O C C N ns m O U y m C N M O lO U v N O M a a C C L r M N In lA lA 1n CC C C 0 O � m C _C M O N M E a)E �n In U') LO U C O U m E E v r N o O H U 0 0 (D V n m N N O O ^ 0. p 0 o 0 0 Cn - o O O L c N o O m N M J m p C 0A N m E v uO C v N N CD 0- O O O o in o 0 0 L N Ln m J v c U ODD OORR N co OR o 0 0 0 0 U M N N O CA f� O m CDtf) Q O O O O C � Q ca E Q m U m Z U C 0) O ZC p N M N O fl J p U ~ t° U ro R m m U tC6 E c r rn m 0 R 3 0 m p c cu __ p U C o c m t° U m ,cc cm y > O r o mO C LL p E m E Lo O r C V O v y r M r U o Q m O + m LL C LL 5 m E rn r II c O LL ri o w E c o U c ° ° 0 ur m (D 6 m UA E m E m m E U CO CO)30 O_ 3 U r N O O m c U m CD LL N O .a m E C c c m `m _E m R •� c 0 o F0- � U W F- O Z C C a 3 c LL U O y C st O O j U v N O (D � � lC m C OD aJ CD C6 � C C O O CD C E m E O 6 O ui O 6 O ui U .. 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E E \ m \ 0 y R @ o @ § G ® a C6 49 q & % A j f m V) It a _ Zk§ ?— E a m c a 2¥ / > E y / R # w g o »2 8 CD7 7 G z cli cli a ° E S o y e G o G 0 o 0 cy 8 o 0 % j E ¥ CO Cl CD \ f § 0 0 m ® o 0 6 g Q £ ƒ O G k 2 Cl) � 0 6 0 0 0 0 k Cl) 0 p § « ) o a a 6 �CD j < / E < m 0 7 z m &�f # 7 m co N 0 \ _ E 0 G \ } d k , Q � W co f � 2 \ / r f a)e 0 / m = � c 2 = r _ _ _ c o f o § ƒ > 2 C) e ° / ± a c 5 E § E r ° / % ƒ ® C.) ¥ C)/ } £ - 0 + e % � 2 E & § \ C) { E E w — E E rz \ 0 § e $ % / 65 E C /_ k / � 5 \ / § ] \ (D � 0 3 N _ ( f CD C E E — \ k 2 k C _ > a W Q 0 e I Ir § 0 z J Q U m w O U F- w m Q LO N J j W � rn F- LL Q F- C 0 z E `o C C m Q O ^ p O O O O (n O O O t o O_ N O m CV M J m F- _C CM m E O (O a N CV N O �? O O O (A O O O £ _ 0 N N J c o U O O N O m U o U V: C.) N O CA I� Q O O O O c n (u E Q m U m Z co c 0) to C '0 N M N O O J p m E 0 0 N N CD C C U � � L m C _ 7 m U E c m rn _5 o p co— N C m C c c > m Q _N O c o m - w p `o y E U) 0 r C V O v y r Cl) r U o p m m LOi + IL E r Il O W M O w E c c U c O O O Y y CDC m - 41 U) E 0 E m O 0 O 3 O 7 - a 0 o m m w N o CD E E C R1 C 7 _ R( w m E c_ C - U O �°- tr ;:, N C7 V. u) I EROSION CONTROL CALCULATIONS APPENDIX B RAINFALL PERFORMANCE STANDARD EVALUATION'-- - PROJECT:�A;� ) ,.� ��'����;�� STANDARD FORMA ICOMPLETED BY: GAO DATE: i l 95 I--------------- ----------------- ------------------------------------- IDEVELOPED ERODIBILITY SUBBASIN --------- + ZONE ----------- 3 I H� ti A56 (ac) 0.41 Lib (ft) + 3z,0 Ssb- (%) � 2 -o Lb (feet 0-79 II I 137-1 1 f 5.1 ---------------------------- ------------------------ )T/SF-A:1989 � I � I EFFECTIVENESS CALCULATIONS PROJECT:, i�eu: ten{-----�i;z��-----STANDARD FORM B COMPLETED By `GAO DATE: i `Z5 Erosion Control Method - C-Factor Value P-Factor Value Comment = --------- ------ a��h� wa1kS I�-F►� ---------------------------- ------ , 01. 1.00. 1.00 cG- Ion( la„ds�aP of 1.00 4AJOR 3ASIN(J �i13 I PS (b) SUB BASIN 111 AREA (Ac) 0.41 � i ---------------------- --------------- CALCULATIONS ------------------- --- ---------------- ----- C = 1c). 3- ��� �- tacAor 0•6oX 0 ,� 0.40 ? : 0,q0 4 D -, Co. 15 0:40�1 34A G►a,� - 313�1 �4 �� C 0.07 f,'llc ) �AYC f �Q�KS foo 13,350Y�' 44 ( 0,31 C - 0.111- w+,k fJor ©. fD �-- 0L --------------------------------- HDI/SF-B:1989 F 1 ENGINEER'S COST ESTIMATE Page: FINAL 1 OF 1 Project Number: Project Title: Date: 95.13TEL RETAIL DEVELOPMENT 01-May-95 Estimator: G.A. ODEHNAL P.E. File: TAEL.ECE.WQ1 Item #1: ALTERNATE #1 #2: ALTERNATE #2 Numbe Description of Item Unit Cost* Unit erosion control as designs all disturbed areas seeded Quantity Item Cost Quantity Item Cost A EROSION CONTROL Straw Bales (5 bales) $100.00 LS 1 $100.00 Silt Fence $3.00 LF 220 $660.00 Native Seeding w/ 2 Tons of $1,300.00 AC 0.54 $702.00 Straw Mulch (Crimped) $760.00 $702.00 SUBTOTAL MULTIPLIER 1.5 1.5 TOTAL DEPOSIT $1,140.00 $1,053.00 TOTAL SECURITYREQ'D. $1,140.00 unn cows are mstaUeo costs. inclu�da,1 �4bo*i 1