Loading...
The URL can be used to link to this page
Your browser does not support the video tag.
Home
My WebLink
About
Drainage Reports - 06/12/2014
I i 1 I AThis Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in its entirety. When a hard copy is absolutely necessary, we recommend double -sided printing. June 10, 2014 City of Ft. Collin pro Plans Approved B Date FINAL DRAINAGE AND EROSION CONTROL REPORT FOR SCOTT PLAZA Fort Collins, Colorado Prepared for: Taylor Fitzpatrick Capital, LLC 7825 E. Gelding St., Suite 102 Scottsdale, AZ 85260 Prepared by: NORTHERN ENGINEERING 200 South College Avenue, Suite 10 Fort Collins, Colorado 80524 Phone: 970.221.4158 Fax: 970.221.4159 w .northemengineering.com Project Number: 948-001 NorthernEnaineerina.com // 970.221.4158 ' (NORTHERN ENGINEERING June 10, 2014 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 ADDRESS: PHONE:970.221.4158 200 S. College Ave. Suite 10 WEBSITE: Fort Collins, CO80524 FAX:970.221.4159 www•northernengineering.com RE: Final Drainage and Erosion Control Report for SCOTT PLAZA ' Dear Staff: Northern Engineering is pleased to submit this Final Drainage and Erosion Control Report for your ' review. This report accompaniesithe Project Development Plan submittal for the proposed Scott Plaza development. This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM), and serves to document the stormwater impacts associated with the proposed project. We understand that review by the City is to assure general compliance with standardized criteria contained in the FCSCM. If you should have any questions as you review this report, please feel free to contact us. ' Sincerely, NORTHERN ENGINEERING SERVICES, INC. Aaron Cvar, PE Project Engineer ■V INORTHERN ENGINEERING Scott Plaza ' TABLE OF CONTENTS ' I. A. GENERAL LOCATION AND DESCRIPTION................................................................... 1 Location..............................................................................................................................................1 B. Description of Property .....................................................................................................................2 C. Floodplain..........................................................................................................................................4 II. DRAINAGE BASINS AND SUB-BASINS....................................................................... 5 A. Major Basin Description....................................................................................................................5 III. DRAINAGE DESIGN CRITERIA................................................................................... 5 A. Regulations........................................................................................................................................5 ' B. Four Step Process 5 .............................................................................................................................. ' C. D. Development Criteria Reference and Constraints............................................................................6 Hydrological Criteria .........................................................................................................................6 ' E. G. Hydraulic Criteria..............................................................................................................................6 Modifications Criteria of ...................................................................................................................7 IV. A. DRAINAGE FACILITY DESIGN.................................................................................... General Concept............................................................................................................................... 7 7 B. Specific Details..................................................................................................................................8 ' V. CONCLUSIONS........................................................................................................9 A. Compliance with Standards..............................................................................................................9 ' B. Drainage Concept..............................................................................................................................9 References....................................................................................................................... 10 APPENDICES: APPENDIX A —Hydrologic Computations APPENDIX B—Detention Calculations APPENDIX C—Water Quality/LID Supporting Documentation ' APPENDIX D —Erosion Control Report Final Drainage Report ' (NORTHERN ENGINEERING LIST OF FIGURES: Figure1 — Aerial Photograph ................... :............................................................................ 2 Figure 2— Proposed Site Plan................................................................................................ 3 Figure3 — Existing Floodplains............................................................................................. 4 i 11 I 1 I MAP POCKET: Proposed Drainage Exhibit Final Drainage Report NORTHERN ENGINEERING Scott Plaza I I. GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map i !I{ �6i''N{ 91ig [l li TG t"n > 1Q I - s it N. li _ ! 1�i,,.�r,r, MOUNTAIN AVEp gg��,,,� 41�t j- -- t �ti��' 1li [fwlo�{t1ft7I 1 �17: �MULBy ERRY SIT lit I N U KT J � G. it '�i'l;Ill`{�j{ ' �j�],��" NEW rEII�jt�] x. tT ,� III1�� J Y Yr Il 3I ' �IYtlt3l.rk� U1Jll' r rrrl�itil I�lt? =alp T D!4_7 Erb 11 L PROJECT „ t r j,<_cn 7� , r�n . • i SITE I PLUM ST' �ELIZABETH ST }1$_ I + i1L�r .3r 1[: r i�� M1 i :i` 1yt t� �izr t�l ili f� i sI a—1_l7-1 II_IJ J : ii Jl rj?.� 7 I�XI t , lil�,^ -! 1 �""� V I i I�ii�i�. - LL I cam' 1 yr3 '.aIT }.. r �', -nr•. ' I iT {,-r.�. _ 1 �tI-4W PROSPECT RD. _ 1 [ r NORTH II� I• t �. T,. II f it 2. The project site is located in the northeast quarter of Section 15, Township 7 North, Range 69 West of the 6`h Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado The project site is located on the south side of West Plum Street, and just west of Shields Street. The project site lies within the Old Town Master Drainage Basin. Per the Old Town Master Drainage Plan, onsite detention is required. Onsite detention is required for the runoff volume difference between the 100 year developed inflow rate and the 2 year historic release rate. It is acknowledged that this is the standard requirement, but since the existing outfall into Plum already floods a home the release rate could be more restrictive. The proposed preliminary design addresses this with a reduced release rate. 3. The proposed project is surrounded by existing and new development. Apartment developments exist to the east and west of the proposed project. Commercial development exists to the south of the proposed project. A new apartment development is currently under construction to the north of the proposed project, Final Drainage Report 1 N NORTHERN ENGINEERING Scott Plaza 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 which was referred to as "The Retreat at 1200 Plum" (Ref. 6). 4. No offsite flows of significance enter the site. B. Description of Property 1. The development area is roughly 1.2 net acres. Figure 1 — Aerial Photograph 2. The subject property currently four multi -family buildings and a gravel drive/parking area along the east side of the development site. Existing ground cover generally consists of residential landscaping and gravel drive. Existing ground slopes are generally mild (i.e., 1 to 5±%) through the interior of the property. A portion of the site topography slopes south to north. The remainder of the existing site slopes to the south, directing existing runoff into a concrete pan located along the south property line. 3. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey website: http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx, the site consists of Nunn clay loam, which falls into Hydrologic Soil Group C. Final Drainage Report 2 (NORTHERN ENGINEERING Scott Plaza Figure 2— Proposed Site Plan Final Drainage Report 3 ' NORTHERN ENGINEERING Scott Plaza t 4. The proposed project will consist of the construction of an apartment complex. Parking areas and associated utilities will be constructed. LID features are provided throughout the project site, with permeable pavers being proposed as the main LID ' feature. It is acknowledged that the current City draft standards require that 50% of the new impervious area be treated by an LID method and 25% of new parking lots must be pervious. The proposed plan exceeds this requirement. ' 5. No major irrigation ditches or related facilities are in the vicinity of the project site. 6. The proposed land use is an apartment complex. ' C. Floodplain 1. The project site is not encroached by any City or FEMA floodplain. Figure 3 —Area Floodplain Mapping 2. No offsite improvements are proposed with the project. Final Drainage Report 4 ■V (NORTHERN ENGINEERING Scott Plaza ' II. DRAINAGE BASINS AND SUB -BASINS A. Major Basin Description 3. The project site is located within the Old Town Master Drainage Basin. Onsite ' detention is required for the runoff volume difference between the 100 year developed inflow rate and the 2 year historic release rate. It is acknowledged that this is the standard requirement, but since the existing outfall into Plum already floods a home the release rate could be more restrictive. The proposed preliminary design addresses this with a reduced release rate. ' B. Sub -Basin Description 4. A portion of the subject property historically drains overland north into the adjacent Plum Street. The remainder of the site historically drains overland south into an ' existing concrete pan located along the south property line. A more detailed description of the project drainage patterns follows in Section IV.A.4., below. III. DRAINAGE DESIGN CRITERIA A. Regulations There are no optional provisions outside of the FCSCM proposed with the proposed project. B. Four Step Process The overall stormwater management strategy employed with the proposed project utilizes the "Four Step Process" to minimize adverse impacts of urbanization on receiving waters. The following is a description of how the proposed development has incorporated each step. Step 1 — Employ Runoff Reduction Practices Several techniques have been utilized with the proposed development to facilitate the reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the current use by implementing multiple Low Impact Development (LID) strategies including: N9 Conserving existing amenities in the site including the existing vegetated areas. Na Providing vegetated open areas throughout the site to reduce the overall impervious area and to minimize directly connected impervious areas (MDCIA). NE Routing flows, to the extent feasible, through vegetated swales to increase time of concentration, promote infiltration and provide initial water quality. Step 2 — Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release The efforts taken in Step 1 will facilitate the reduction of runoff; however, urban development of this intensity will still generate stormwater runoff that will require additional BMPs and water quality. The majority of stormwater runoff from the site will ultimately be intercepted and treated using extended detention methods prior to exiting the site. Final Drainage Report 5 ' (NORTHERN ENGINEERING Scott Plaza ' Step 3 — Stabilize Drainageways There are no major drainageways within the subject property. While this step may not ' seem applicable to proposed development, the project indirectly helps achieve stabilized drainageways nonetheless. By providing water quality where none previously existed, sediment with erosion potential is removed from the downstream drainageway systems. ' Furthermore, this project will pay one-time stormwater development fees, as well as ongoing monthly stormwater utility fees, both of which help achieve City-wide drainageway stability. Step 4 — Implement Site Specific and Other Source Control BMPs. ' The proposed project will improve upon site specific source controls compared to historic conditions: NO Trash, waste products, etc. that were previously left exposed with the historic trailer ' park will no longer be allowed to exposure to runoff and transport to receiving drainageways. The proposed development will eliminate these sources of potential pollution. ' C. Development Criteria Reference and Constraints The subject property is tied currently developed properties adjacent to the site. Thus, ' several constraints have been identified during the course of this analysis that will impact the proposed drainage system including: ' Na Existing elevations along the property lines will generally be maintained. NO As previously mentioned, overall drainage patterns of the existing site will be maintained. NO Elevations of existing downstream facilities that the subject property will release to will be maintained. D. Hydrological Criteria ' 1. The City of Fort Collins Rainfall Intensity -Duration -Frequency Curves, as depicted in Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations ' associated with the proposed development. Tabulated data contained in Table RA-7 has been utilized for Rational Method runoff calculations. 2. The Rational Method has been employed to compute stormwater runoff utilizing ' coefficients contained in Tables RO-11 and RO-12 of the FCSCM. 3. Three separate design storms have been utilized to address distinct drainage ' scenarios. A fourth design storm has also been computed for comparison purposes. The first design storm considered is the 801h percentile rain event, which has been employed to design the project's water quality features. The second event analyzed is the "Minor," or "Initial" Storm, which has a 2-year recurrence interval. The third event considered is the "Major Storm," which has a 100-year recurrence interval. The fourth storm computed, for comparison purposes only, is the 10-year event. 4. No other assumptions or calculation methods have been used with this development that are not referenced by current City of Fort Collins criteria. ' E. Hydraulic Criteria 1. As previously noted, the subject property maintains historic drainage patterns. ' 2. All drainage facilities proposed with the project are designed in accordance with Final Drainage Report 6 ' INORTHERN ENGINEERING Scott Plaza ' criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District ' (UDFCD) Urban Storm Drainage Criteria Manual. 3. As stated above, no part of the subject property is located in a City or FEMA regulatory floodplain. ' 4. The proposed project does not propose to modify any natural drainageways. ' F. Modifications of Criteria 1. The proposed development is not requesting any modifications to criteria at this time. IV. DRAINAGE FACILITY DESIGN ' A. General Concept 1. The main objectives of the project drainage design are to maintain existing drainage patterns, and to ensure no adverse impacts to any adjacent properties. 2. A list of tables and figures used within this report can be found in the Table of Contents at the front of the document. The tables and figures are located within the sections to which the content best applies. 3. The drainage patterns anticipated for proposed drainage basins are described below. ' Basin 1 Basin 1 consists of the apartment building; the basin area is composed primarily of rooftop. This basin will generally drain via parking and drive curb and gutter to the ' permeable paver system within Basin 3, where water quality and detention will be provided for this basin. ' Basin 2 Basin 2 consists of a small area (0.03 Ac.) of frontage along Plum Street. This basin will sheet flow into Plum Street undetained. Compensation for this undetained release ' is discussed below. Basin 3 ' Basin 3 consists of of drive area which will be captured and detained within the permeable paver system designed within this basin. The permeable paver system has been designed per USDCM Volume 3 (Reference 5) methodology. Runoff from Basin 1 is also designed to be conveyed to this permeable paver system and detained within the subgrade of the paver system. Basin 4 Basin 5 consists of drive, parking, and landscaped area. This basin will sheet flow into into an existing concrete pan located along the south property line. Historically, 0.55 Acres of existing development drained to design point 5. Historic development consisted of rooftop and gravel. With the proposed 0.22 Acres now draining to this design point, consisting of permeable pavers and landscaping, there will be a reduction in runoff. Proposed runoff to design point 5 is 2.2 cfs, versus an estimated historic 4.1 cfs in a 100-year storm event. Final Drainage Report 7 ' ■� (NORTHERN ENGINEERING Scott Plaza ' A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of ' this report. B. Specific Details A required detention volume of 0.12 acre-feet has been calculated for the subgrade ' detention provided below the permeable paver system within Basin 3. Basins 1,3, and 4 are directed into the paver system and detained within. Please see detention calculations provided in Appendix B. The release rate determined for the proposed detention facility has been preliminarily set at 0.60 cfs. This release rate has been determined based on the methodology utilized for the approved Final Drainage Report ' for "The Retreat at 1200 Plum" (Ref. 6). The methodology accounts for impervious area that is allowed to be "grandfathered". There is 0.24 acres of impervious area within the development site which drains to Plum Street. A 100-year discharge from this impervious area of 2.27 cfs has been calculated. There is 0.37 acres of pervious ' area within the development site which also drains to Plum Street. A 2-year discharge of 0.74 cfs has been calculated. The sum of "grandfathered" impervious area discharge into Plum Street combined with 2-year pervious area discharge is ' 3.01, which is considered as the allowable peak release rate for the site. We have subtracted the 100-year discharge computed from Basin 2, and 4 (0.30 cfs total) for an allowable release rate of 2.71 cfs. We then reduced this release rate to 1.35 cfs, 1 in order to take into consideration the downstream flooding issues that have been identified in the March 2013 City Conceptual Review for this project. ' LID features include the aforementioned sand filter, and permeable pavement systems within Basins 3 and 5. The total area draining to all LID features combined is 1.13 acres, which comprises 97.8% of the site. This exceeds the requirement stating that 50% of the site must pass through an LID feature. The site also exceeds the requirement that 25% of parking and drive area must be composed of permeable ' pavement, with the majority of parking and drive area outside of the parking structure proposed as a permeable pavement. In summary, a total detention volume of 0.12 acre-feet (5086 cubic feet) will be provided within the subgrade of the permeable paver system. V. CONCLUSIONS ' A. Compliance with Standards 1. The drainage design proposed with the proposed project complies with the City of Fort Collins' Stormwater Criteria Manual. ' 2. The drainage design proposed with this project complies with all applicable City of Fort Collins Master Drainage Plans. ' 3. The drainage plan and stormwater management measures proposed with the proposed development are compliant with all applicable State and Federal regulations governing stormwater discharge. ' B. Drainage Concept ' 1. The drainage design proposed with this project will effectively limit any potential Final Drainage Report 8 ■V INORTHERN ENGINEERING Scott Plaza damage associated with its stormwater runoff as all runoff is being captured and routed to offsite drainage facilities which have either been previously approved by the City of Fort Collins or are in the review and approval process with the City of Fort Collins. 2. The drainage concept for the proposed development is consistent with all applicable City of Fort Collins Master Drainage Plans. References Final Drainage Report 9 (NORTHERN ENGINEERING Scott Plaza 1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities, November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services. 2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code. 3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007. 4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright -McLaughlin Engineers, Denver, Colorado, Revised April 2008. 6. Final_Drainaize and Erosion Control Report for The Retreat at 1200 Plum, Northern Engineering, April 22, 2009. Final Drainage Report 10 APPENDIX A HYDROLOGIC COMPUTATIONS !� !! £,a, Ely ° ■� � ( 0 \ (/ §§§§ 2 f(£)( , - \t&m 22//§ // § 3 ; � !■!,k$$$m u f2/J2aaaa � S \ƒ22/\ \/k /00#N )!7 _,,,, 4}\ 7 q22 \ \1 00000 ]§\ \w\ ; cr k ) ;!# :! @/, \ 0 g \ 2jk _ �0 ®# o / ikf k ) : : != q Lu moo -� � Ix:::`! w { �49 - O ;,! - L!@.2 © $$J3)�;/�! 1 1 i 1 1 1 1 i 1 1 1 1 1 i 1 c oo o .q 0 c N N.i d E o i f N~ E in in in m m ¢ � om C c ~E zz z z z z a o u Z, U ;O N > Q z Q z Q z Q z LL m > al 14 L J � H � f 2 1p a m e LL V Y � Y O Cooa* o1�ra (7 o N 2° V Iq UU' U0 Lq „„.... e N 0 0 0 0 Q Id � 2 W J 3 2 u O c m r E 0 o 0 0 0 00 o gu( 'E LLIc 1 ;��$uo ��CVNVV d g33g� ^" LC Q • o % _ r c a ry a a aN E 0 ai 2R 3E dE d° e N ii 0 0 0 0 v W H N N N N Q � � qJ t r , OM a s N J O N O O O O 0 N O O' al O O O1 U V O O O O IL C A iS T O In In In m O 0 Cn 0 0 II t N N eep V o p II II w o z z z z o > > v m A 0 00 m> 3 m F LL ^ ii ; � V C H of J U U 0a o' �` 0 F O g O N N 0 O N N 0 Q T+ CO O a O N N m — 10 10 O C rii .-. O O O LL m Obi Q � m o c o rn rn rn 0)a - d of m m of m c 5 - u V c o f cq ao cq m n CO oq 00 2 c ^ y Zc, ry n m Ln 00 m m in 00 O o N - C N N N N o gp ti �i 0 oa coo O CLId 8y n k O O O O o.�iNN 9 O .00 V C O �pj O o 0 Ol 01 O 1 LO (n 01 O n k 2 � cn 0) 0) LO Q g u v LLI� 0 o 0 0 0 0 00 o J tiNN� p �+1 w ass•• Z s • U rl Y 0 y° O V LL V a C m `u �' F 'E .y U c O m T ` N E 117 In In In o` E `o h Q N c U O N N Q V O O O O r S O C p U L. N N <+1 V w >< A o 0 •~C m N C U n W N UCc II Nmv Qao APPENDIX B DETENTION CALCULATIONS 1 1 1 1 1 1 1 1 DE�TENTLO:NIP:O:NDIC►'ALCU.LrAiTil_ON FJAM ME-�TiHOD Project Number : 948-001 Date :; 1/15/14 Project Location Fort Collins Calculations By: ATC Pond No : 1 - - -- - - - Input Variables Results Design Point! 1 Design Storm' 100-yr Developed "C" =i 1.00 Area(A)= 0.92 acres Max Release Rate =j 1.35 cfs Required Detention Volume _ - i 5055;ft3 0.12, ac-ft Time Time 100-yr Intensity Q100 Inflow (Runoff) Volume Outflow (Release) Volume Storage Detention Volume mins secs in/hr cfs (ft) (ft) (ft ) 5 300 9.950 9.15 2746 405.0 2341.2 10 600 7.720 7.10 4261 810.0 3451.4 15 900 6.520 6.00 5399 1215.0 4183.6 20 1200 5.600 5.15 6182 1620.0 4562.4 25 1500 4.980 4.58 6872 2025.0 4847.4 30 1800 4.520 4.16 7485 2430.0 5055.1 35 2100 4.080 3.75 1 7883 2835.0 5047.6 40 2400 3.740 3.44 8258 3240.0 5017.9 45 2700 3.460 3.18 8595 3645.0 4949.6 50 3000 3.230 2.97 8915 4050.0 4864.8 55 3300 3.030 2.79 9199 4455.0 4744.1 60 3600 2.860 2.63 9472 4860.0 4612.3 65 3900 2.720 2.50 9759 5265.0 4494.4 70 4200 2.590 2.38 10008 5670.0 4337.8 75 4500 2.480 2.28 1 10267 6075.0 4192.2 80 4800 2.380 2.19 10510 6480.0 4030.1 85 5100 2.290 2.11 10745 6885.0 3859.7 90 5400 2.210 2.03 10979 7290.0 3689.3 95 5700 2.130 1.96 11170 7695.0 3474.7 100 6000 2.060 1.90 11371 8100.0 3271.2 105 6300 2.000 1.84 11592 8505.0 3087.0 110 6600 1.940 1.78 11780 8910.0 2869.7 115 6900 1.890 1.74 1 11998 9315.0 2682.7 120 7200 1.840 1.69 1 12188 9720.0 2468.2 OUTLET RATING CURVE Subgrade Detention Orifice Project: 948-001 Date: 1 /15/2014 By: ATC 100-YR ORIFICE RATING Orifice Dia (in) 5.25 Orifice Area (sf 0.1503 Orifice invert (ft) 0.00 Orifice Coefficient 0.65 Orifice Area (SF) Stage (FT) Outlet release (CFS) 0.1503 0.00 0.00 0.1503 0.25 0.39 0.1503 0.50 0.55 0.1503 0.75 0.68 0.1503 1.00 0.78 0.1503 1.25 0.88 0.1503 1.50 0.96 0.1503 1.75 1.04 0.1503 2.00 1.11 0.1503 2.25 1.18 0.1503 2.50 1.24 0.1503 2.75 1.30 0.1503 3.00 1.36 APPENDIX C WATER QUALITY/LID SUPPORTING DOCUMENTATION WATER QUALITY DESIGN CALCULATIONS Permeable Paver System - Subgrade Volume Project: 948-001 Bv: ATC REQUIRED STORAGE & OUTLET WORKS: BASIN AREA = 0.920 <-- INPUT from impervious calcs BASIN IMPERVIOUSNESS PERCENT = 90.00% <-- INPUT from impervious calcs BASIN IMPERVIOUSNESS RATIO = 0.9 <--CALCULATED WQCV (watershed inches) = 0.321 <-- CALCULATED from Figure EDB-2 WQCV (ac-ft) = 0.025 <-- CALCULATED from UDFCD DCM V.3 Section 6.5 1 Permeable Pavement Systems T-10 Description The term Permeable Pavement System, as used in this manual, is a general term to describe any one of several pavements that allow movement of water into the layers below the pavement surface. Depending on the design, permeable pavements can be used to promote volume reduction, provide treatment and slow release of the water quality capture volume (WQCV), and reduce effective imperviousness. Use of permeable pavements is a common Low Impact Development (LID) practice and is often used in combination with other BMPs to provide full treatment and slow release of the WQCV. A number of installations within the UDFCD Photograph PPS-1. The reservoir layer of a permeable pavement provides storage volume for the WQCV. Photo courtesy of Muller Engineering and Jefferson County Open Space. boundary have also been designed with an increased depth of aggregate material in order to provide storage for storm events in excess of the water quality (80th percentile) storm event. This requires some additional design considerations, which are discussed within this BMP Fact Sheet. Site Selection This infiltrating BMP requires consultation with a geotechnical engineer when proposed near a structure. In addition to providing the pavement design, a geotechnical engineer can assist with evaluating the suitability of soils, identifying potential impacts, and establishing minimum distances between the BMP and structures. Permeable pavement systems provide an alternative to conventional pavement in pedestrian areas and lower -speed vehicle areas. They are not appropriate where sediment -laden runoff could clog the system (e.g., near loose material storage areas). This BMP is not appropriate when erosive conditions such as steep slopes and/or sparse vegetation drain to the permeable pavement. The sequence of construction is also important to preserve pavement infiltration. Construction of the pavement should take place only after construction in the watershed is complete. For sites where land uses or activities can cause infiltrating stormwater to contaminate groundwater, special design requirements are required to ensure no -infiltration from the pavement section. Permeable Pavement Functions L1DNolume Red. Yes WQCV Yes W CV+Flood Control Yes Fact Sheet Includes EURV Guidance No Typical Effectiveness for Targeted Pollutants' Sediment/Solids Very Good' Nutrients Good Total Metals Good Bacteria Unknown Other Considerations Life -cycle Costs° High' 1 Not recommended for watersheds with high sediment yields (unless pretreatment is provided). 2 Does not consider the life cycle cost of the conventional pavement that it replaces. 3 Based primarily on data from the International Stormwater BMP Database (www. bmpdatabase. or¢). Based primarily on BMP-REALCOST available at www.udfcd.ore. Analysis based on a single installation (not based on the maximum recommended watershed tributary to each BMP). ' August 2011 Urban Drainage and Flood Control District PPS-1 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems ' Permeable pavements and other BMPs used for infiltration that are located adjacent to buildings, hardscape or conventional pavement areas can adversely impact those structures if protection measures are not provided. Wetting of ' subgrade soil underlying those structures can cause the structures to settle or result in other moisture -related problems. Wetting of potentially expansive soils or bedrock ' can cause those materials to swell, resulting in structure movements. In general, a geotechnical engineer should evaluate the potential impact of the BMP on adjacent ' structures based on an evaluation of the subgrade soil, groundwater, and bedrock conditions at the site. In addition, the following minimum requirements should be met: 1 1 Benefits ■ Permeable pavement systems provide water quality treatment in an area that serves more than one purpose. The depth of the pavement system can also be increased to provide flood control. ■ Permeable pavements can be used to reduce effective imperviousness or alleviate nuisance drainage problems. In locations where subgrade soils do not allow infiltration, Permeable pavements benefit tree the growing medium should be underlain by an health by providing additional air underdrain system. and water to nearby roots. Where infiltration can adversely impact adjacent structures, the filter layer should be underlain by an underdrain system designed to divert water away from the structure. ■ In locations where potentially expansive soils or bedrock 1 exist, placement of permeable pavement adjacent to structures and conventional pavement should only be considered if the BMP includes an underdrain designed to ' divert water away from the structure and is lined with an essentially impermeable geomembrane liner designed to restrict seepage. Designing for Maintenance lJ 1 1 1 Recommended ongoing maintenance practices for all BMPs are provided in the BMP Maintenance chapter of this manual. During design and construction, the following should be considered to ensure ease of maintenance over the long-term: ■ Hold a pre -construction meeting to ensure that the contactor has an understanding of how the pavement is intended to function. Discuss the contractor's proposed sequence of construction and look for activities that may require protection of the permeable pavement system. ■ Permeable pavements are less likely to form ice on the surface than conventional pavements. ■ Some permeable pavements can be used to achieve LEED credits. Limitations Additional design and construction steps are required for placement of any ponding or infiltration area near or upgradient from a building foundation, particularly when potentially expansive soils exist. This is discussed in the design procedure section. ■ In developing or otherwise erosive watersheds, high sediment loads can clog the facility. Ensure that the permeable pavement is protected from construction activities following pavement construction (e.g., landscaping operations). This could include covering areas of the pavement, providing alternative construction vehicle access, and providing education to all parties working on - site. ■ Include an observation well to monitor the drain time of the pavement system over time. This will assist with determining the required maintenance needs. See Figure PPS-8. ' PPS-2 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 I Permeable Pavement Systems T-10 ■ Call for construction fence on the plans around pervious areas where infiltration rates need to be ' preserved and could be reduced by compaction from construction traffic or storage of materials. ' Example Construction Drawing Notes ■ Excavation of subgrade shall not commence until after the pre -construction meeting. ■ Subgrade shall be excavated using low ground pressure (LGP) track equipment to minimize over compaction of the subgrade.' ' ■ Grading and compaction equipment used in the area of the permeable pavement should be approved by the engineer prior to use. ' ■ Loose materials shall not be stored on the permeable pavement area. ■ The contractor shall, at all times during and after system installation, prevent sediment, ' debris, and dirt from any source from entering the permeable pavement system. ■ Placement of the wearing course shall be performed after fine grading and landscaping in ' adjacent areas is complete. If the wearing course becomes clogged due to construction activities, clean the surface with a vacuum machine to restore the infiltration rate after construction is complete. ' For partial and full infiltration sections only. Design Procedure and Criteria Note: This manual includes a variety of specific pavements, which are discussed and distinguished in supplemental BMP Fact Sheets T-10.1, T-10.2, etc. This BMP Fact Sheet outlines the design procedure and other design components and considerations that are common to all of the systems. Review of the supplemental Fact Sheets is recommended to determine the appropriate pavement for a specific site or ' use. 1. Subsurface Exploration and Determination of a No -Infiltration, Partial Infiltration, or Full Infiltration Section: Permeable pavements can be designed with three basic types of sections. The appropriate section will depend on land use and activities, proximity to adjacent structures and soil characteristics. Sections of each installation type are shown in Figure PPS-1. ' No -Infiltration Section: This section includes an underdrain and an impermeable liner that prevents infiltration of stormwater into the subgrade soils. Consider using this section when any ' of the following conditions exist: o Land use or activities could contaminate groundwater if stormwater is allowed to infiltrate. ' o Permeable pavement is located over potentially expansive soils or bedrock that could swell due to infiltration and potentially damage the permeable pavement system or adjacent structures (e.g., building foundation or conventional pavement). August 2011 Urban Drainage and Flood Control District PPS-3 Urban Storm Drainage Criteria Manual Volume 3 I 1 1 1 [] 1 1 I T-10 Permeable Pavement Systems ■ Partial Infiltration Section: This section does not include an impermeable liner, and allows some infiltration. Stormwater that does not infiltrate is collected and removed by an underdrain system. ■ Full Infiltration Section: This section is designed to infiltrate the water stored in the voids of the pavement into the subgrade below. UDFCD recommends a minimum infiltration rate of 2 times the rate needed to drain the WQCV over 12 hours. Subsurface Exploration and Testing for all Sections: A geotechnical engineer should scope and perform a subsurface study. Typical geotechnical investigation needed to select and design the pavement system for handling anticipated traffic loads includes: Prior to exploration review geologic and geotechnical information to assess near -surface soil, bedrock and groundwater conditions that may be encountered and anticipated ranges of infiltration rate for those materials. For example, if the site is located in a general area of known shallow, potentially expansive bedrock, a no -infiltration section will likely be required. It is also possible that this BMP may be infeasible, even with a liner, if there is a significant potential for damage to the pavement system or adjacent structures (e.g., areas of dipping bedrock). Drill exploratory borings or exploratory pits to characterize subsurface conditions beneath the subgrade and develop requirements for subgrade preparation. Drill at least one boring or pit for every 40,000 ftZ, and at least two borings or pits for sites between 10,000 ftZ and 40,000 ftZ. The boring or pit should extend at least 5 feet below the bottom of the base, and at least 20 feet in areas where there is a potential of encountering potentially expansive soils or bedrock. More borings or pits at various depths may be required by the geotechnical engineer in areas where soil types may change, in low-lying areas where subsurface drainage may collect, or where the water table is likely within 8 feet below the planned bottom of the base or top of subgrade. Installation of temporary monitoring wells in selected borings or pits for monitoring groundwater levels over time should be considered where shallow groundwater that could impact the pavement system area is encountered. Perform laboratory tests on samples obtained from the borings or pits to initially characterize the subgrade, evaluate the possible section type, and to assess subgrade conditions for supporting traffic loads. Consider the following tests: moisture content (ASTM D 2216); dry density (ASTM D 2936); Atterberg limits (ASTM D 4318); gradation (ASTM D 6913); swell - consolidation (ASTM D 4546); subgrade support testing (R-value, CBR or unconfined compressive strength); and hydraulic conductivity. A geotechnical engineer should determine the appropriate test method based on the soil type. For sites where a full infiltration section may be feasible, perform on -site infiltration tests using a double -ring infiltrometer (ASTM D 3385). Perform at least one test for every 160,000 Wand at least two tests for sites between 40,000 ftZ and 160,000 ftZ. The tests should be located near completed borings or pits so the test results and subsurface conditions encountered in the borings can be compared, and at least one test should be located near the boring or pit showing the most unfavorable infiltration condition. The test should be performed at the planned top of subgrade underlying the permeable pavement system, and that subgrade should be prepared similar to that required for support of the permeable pavement system. Be aware that actual infiltration rates are highly variable dependent on soil type, density and moisture content and degree of compaction as well as other environmental and construction influences. Actual rates can differ an order of magnitude or more from those indicated by PPS-4 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 I 1 [] 1 1 1 Permeable Pavement Systems T-10 infiltration or permeability testing. Selection of the section type should be based on careful assessment of the subsurface exploration and testing data. 2. Required Storage Volume: Provide the WQCV based on a 12-hour drain time. ■ Find the required WQCV (watershed inches of runoff). Using the effective impervious area of the watershed area, use Figure 3-2 located in Chapter 3 to determine the WQCV based on a 12- hour drain time. The maximum recommended ratio for tributary impervious area to permeable pavement area is 2.0. Higher loading is not recommended, as it may increase the required maintenance interval. ■ Calculate the design volume as follows: WQCV I Equation PPS-1 V—JAA Where: A = watershed area tributary to the permeable pavement (ft) V = design volume (ft) ■ Add flood control volume if desired. When designing for flood control volumes, provide an overflow that will convey runoff in excess of the WQCV directly into the reservoir. A gravel strip or inlet that is connected to the reservoir can provide this overflow. August 2011 Urban Drainage and Flood Control District PPS-5 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems PERMEABLE PAVEMENT AND ' 8' MIN. LEVELING COURSE (IF APPLICABLE) DEPTH DEPENDANT ON TYPE 6' MIN. RESERVOIR (AASHTO f57 OR 167) CEOMEMBRANE LINER = ' CONNECTION TO .: g• LTAB�R Mph CONCRETE MEETINGLE PPS ' (SEE DETAIL PPS-4)' 12' SEPARATOR FABRIC UNDERDRAIN MEETING ' TABLE PPS-2 30 MIL (MIN.) SEPARATOR FABRIC (ONLY ' ENSURE INSTALLATION IS CONSISTENT GEOMEMBRANE WHEN SUBGRADE CONTAINS WITH MANUFACTURER RECOMMENDATIONS LINER PER TABLE PPS-4 ANGULAR ROCK OR OTHER MATERIAL THAT MAY PUNCTURE NO -INFILTRATION SECTION THE GEOMEMBRANE LINER' ' PERMEABLE PAVEMENT AND 6' MIN. LEVELING COURSE (IF APPLICABLE) ' DEPTH DEPENDANT ON TYPE PERIMETER BARRIER W MIN. RESERVOIR (IF APPLICABLE) (AASHTO #57 OR #67)� ' PERIMETER BARRIER PERMEABLE PAVEMENT AND LEVELING COURSE (IF APPLICABLE) 8' MIN. (IF APPLICABLE) DEPTH DEPENDANT ON TYPE 6' MIN. RESERVOIR ' (AASHTO #57 OR #67) i 1. t FILTER MATERIAL MEETING TABLE PPS-1 OR SEPARATOR FABRIC ' IF NEEDED FOR MATERIAL COMPATIBILITY. TO BE DETERMINED BY A GEOTECHNICAL ENGINEER FULL INFILTRATION SECTION. Figure PPS-1. Permeable Pavement Sections PPS-6 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 Permeable Pavement Systems T-10 3. Depth of Reservoir: The minimum recommended depth of AASHTO No. 57 or No. 67 coarse aggregate is 6 inches. Additional depth may be required to support anticipated loads or to provide additional storage, (i.e., for flood control). This material should have all fractured faces. UDFCD recommends that void storage be calculated only for the reservoir, assuming the aggregate filter layer ' is saturated. With the exception of porous gravel pavement, use a porosity of 40% or less for both No. 57 and No. 67 coarse aggregate. For porous gravel pavement use a porosity of 30% or less to account for reduced volume due to sediment. Porous gravel pavements typically allow greater ' sediment volumes to enter the pavement. See Figures PPS-2 and PPS-3 for alternative pavement profiles. Calculate available storage using equation PPS-2 for a flat subgrade installation, and PPS-3 for a sloped subgrade installation. These equations allow for one inch of freeboard. Flat installations ' are preferred as the design spreads infiltration evenly over the subgrade. For sloped subgrade installations, the increased storage depth located upstream of the lateral barrier (see step 7) can increase lateral movement (parallel to the flow barrier) of water into areas adjacent to the pavement ' section. When used for vehicular traffic, a pavement design should be performed by a qualified engineer experienced in the design of permeable pavements and conventional asphalt and concrete pavements. ' The permeable pavement should be adequately supported by a properly prepared subgrade, properly compacted filter material and reservoir material. ' Reservoir aggregate should have all fractured faces. Place the aggregate in 6-inch (maximum) lifts, compacting each lift by using a 10-ton, or heavier, vibrating steel drum roller. Make at least four passes with the roller, with the initial passes made while vibrating the roller and the final one to two ' passes without vibration. ■ For flat or stepped installations (0% slope at the reservoir/subgrade interface): ' F12 — 1 Equation PPS-2 V—p ]A Where: V = volume available in the reservoir (ft) ' P = porosity, 50.30 for porous gravel, 50.4 for all other pavements using AASHTO No. 57 or No. 67 coarse aggregate in the reservoir ' D = depth of reservoir (in) A = area of the permeable pavement (ft) 1 August 2011 Urban Drainage and Flood Control District PPS-7 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems 2-T1*1ra1n i~(TrP.) AASHTO #57 OR #67 LATERAL FLOW BARRIERS L ® VOLUME AVAILABLE FOR STORAGE Figure PPS-2. Permeable Pavement Profile, Stepped Installation ■ For sloped installations (slope of the reservoir/subgrade interface > 0%): - p f D — 6sL — 1l A Equation PPS-3a L 12 J Wei M L < 2 WQCV sAP Equation PPS-3b Where: V = volume available in the reservoir (ft3) P = porosity, <_0.30 for porous gravel, 50.4 for all other pavements using AASHTO No. 57 or No. 67 coarse aggregate in the reservoir S = slope of the reservoir/subgrade interface (ft/ft) D = depth of the reservoir (in) L = length between lateral flow barriers (see step 4) (11) A = area of the permeable pavement (ftZ) WQCV = water quality capture volume (ft) PPS-8 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 Permeable Pavement Systems T-10 LATERAL FLOW BARRIERS L ' ® VOLUME AVAILABLE FOR STORAGE Figure PPS-3. Permeable Pavement Profile, Sloped Installation. ' 4. Lateral Flow Barriers: Construct lateral flow cutoff barriers using concrete walls or a 30 mil (minimum) PVC geomembrane. Lateral flow barriers should be placed parallel to contours (normal to flow). This will preserve the volume available for storage and ensure that stormwater will not ' resurface, washing out infill material. See Figure PPS-6 and Table PPS4 when using a PVC geomembrane for this purpose. Also include a separator fabric, per Table PPS-3, between the geomembrane and all aggregate materials. Lateral flow barriers should be installed in all permeable pavement installations that have a reservoir/subgrade interface greater than 0%. Lateral flow barriers should be spaced, as necessary, to satisfy equations PPS-3a and PPS-3b. One exception is reinforced grass pavement. Infill washout is not a concern with reinforced grass pavement ' 5. Perimeter Barrier: For all no -infiltration sections, provide a reinforced concrete barrier on all sides of the pavement system. Perimeter barriers may also be recommended for other permeable pavement installations depending on the type or use of the pavement. For PICP and concrete grid pavement, a ' barrier is required to restrain movement of the pavers or grids. Precast, cast -in -place concrete or cut stone barriers are required for commercial vehicular areas. For residential use and commercial pedestrian use, a metal or plastic edge spiked with 3/8-inch-diameter, 10-inch-long nails provides a ' less expensive alternative for edge restraint. For all pavements, consider the section beyond the permeable pavement when evaluating the perimeter design. The perimeter barrier helps force water into the underdrain and reduces lateral flow ' of water. Lateral flow can negatively impact the adjacent conventional pavement section, structure, or embankment (especially when the subgrade is sloped). Also consider material separation. Consider construction of the interface between the permeable pavement and the adjacent materials ' and how the design will prevent adjacent materials from entering the permeable pavement section. Depending on the soils, depth of pavement, and other factors, this may be achieved with fabric or may require a more formalized barrier. ' When a permeable pavement section is adjacent to conventional pavement, a vertical liner may be required to separate the reservoir of the permeable pavement system from dense -graded aggregates and soils within the conventional pavement. An impermeable linear can be used to provide this vertical barrier and separate these two pavement systems. No -Infiltration Section: For this type of section, the perimeter barrier also serves to attach the ' impermeable membrane. The membrane should extend up to the top of the filter layer and be firmly August 2011 Urban Drainage and Flood Control District PPS-9 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems ' attached to the concrete perimeter barrier using batten bars to provide a leak -proof seal. A nitrile- based vinyl adhesive can be used when the need for an impermeable liner is less critical. See Figures PPS-4 and PPS-5 for installation details. For ease of construction, including the placement of geotextiles, it is suggested that the barrier extend to the bottom of the filter layer. ' Partial and Full Infiltration Section: The perimeter barrier for these sections also restricts lateral flow to adjacent areas of conventional pavement or other structures where excessive moisture and/or ' hydrostatic pressure can cause damage. When this is of particular concern, the perimeter barrier should be extended to a depth 12 inches or more below the underdrain. Otherwise, extend the barrier to the bottom of the filter layer. ' 6. Filter Material and Underdrain System: An aggregate filter layer and underdrain are required for all partial and no -infiltration sections. Without this filter layer, the section will not provide adequate pollutant removal. This is based on research performed by UDFCD monitoring sites with and ' without this component. A filter or separator fabric may also be necessary under the reservoir in a full infiltration section if the subgrade is not filter compatible with the reservoir material such that finer subgrade soils could enter into the voids of the reservoir. ' In previous versions of the USDCM, UDFCD recommended that the underdrain be placed in an aggregate drainage layer and that a geotextile separator fabric be placed between this drainage and the ' filter layer. This version of the USDCM replaces that fabric, which could.more easily plug or be damaged during construction, with aggregate filter material that is filter -compatible with the reservoir, and a drainpipe with perforations that are filter -compatible with the filter material. This ' eliminates the need for a separator fabric between the reservoir and the underdrain.layer. The filter material provided below should only be used with the underdrain pipe specified within this section. The underdrain should be placed below a 6-inch-thick layer of CDOT Class C filter material meeting ' the gradation in Table PPS -I. Extend the filter material around and below the underdrain as shown in Figure PPS -I. Provide clean -outs to allow inspection (by camera) of the drainpipe system during and after construction to ensure that the pipe was not crushed or disconnected during construction and to allow for maintenance of the underdrain. ' Use of Class C Filter material with a slotted PVC pipe that meets the slot dimensions provided in Table PPS-2 will eliminate the need for an aggregate layer wrapped geotextile fabric. ' Design Opportunity Pollutant removal occurs in the filter material layer of the section. The basic permeable pavement ' section may be considered with other wearing courses to provide water quality as long as: ■ the filter layer is included in the section, ' ■ the wearing course provides adequate permeability, and ■ the new section does not introduce new pollutants to the runoff. PPS-10 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 r 1 Permeable Pavement Systems T-10 Table PPS-1. Gradation Specifications for Class C Filter Material (Source: CDOT Table 703-7) Sieve Size Mass Percent Passing Square Mesh Sieves 19.0 into (3/4") 100 4.75 mm (No. 4) 60 — 100 300 gin (No. 50) 10 — 30 150 m o. 100 0 — 10 75 jim o. 200 0-3 Table PPS-2. Dimensions for Slotted Pipe Pipe Diameter Slot Length' Maximum Slot Width Slot Centers' Open Area' (per foot) 4" 1-1/16" 0.032" 0.413" 1.90 in 6" 1-3/8" 0.032" 0.516" 1.98 in' ' ' Some variation in these values is acceptable and is expected from various pipe manufacturers. Be aware that both increased slot length and decreased slot centers will be beneficial to hydraulics but detrimental to the structure of the pipe. ' Compact the filter layer using a vibratory drum roller or plate. The top of each layer below the leveling course must be uniform and should not deviate more than a''/z inch when a 10-foot straight edge is laid on its surface. The top of the leveling course should not deviate more than 3/8 inch in 10 ' feet. 7. Impermeable Geomembrane Liner and Geotextile Separator Fabric: For no -infiltration sections, ' install a 30 mil (minimum) PVC geomembrane liner, per Table PPS4, on the bottom and sides of the basin, extending up at least to the top of the filter layer. Provide at least 9 inches (12 inches if possible) of cover over the membrane where it is attached to the wall to protect the membrane from UV deterioration. The geomembrane should be field -seamed using a dual track welder, which allows for non-destructive testing of almost all field seams. A small amount of single track and/or adhesive seaming should be allowed in limited areas to seam around pipe perforations, to patch seams removed for destructive seam testing, and for limited repairs. The liner should be installed with slack to ' prevent tearing due to backfill, compaction, and settling. Place CDOT Class B geotextile separator fabric, per Table PPS-3, above the geomembrane to protect it from being punctured during the placement of the filter material above the liner. If the subgrade contains angular rocks or other ' material that could puncture the geomembrane, smooth -roll the surface to create a suitable surface. If smooth -rolling the surface does not provide a suitable surface, also place the separator fabric between the geomembrane and the underlying subgrade. This should only be done when necessary because fabric placed under the geomembrane can increases seepage losses through pinholes or other geomembrane defects. Connect the geomembrane to perimeter concrete walls around the basin perimeter, creating a watertight seal between the geomembrane and the walls using a continuous ' batten bar and anchor connection (see Figure PPS-5). Where the need for the impermeable August 2011 Urban Drainage and Flood Control District PPS-11 Urban Storm Drainage Criteria Manual Volume 3 I I 1 F u 1 T-10 Permeable Pavement Systems membrane is not as critical, the membrane can be attached with a nitrile-based vinyl adhesive. Use watertight PVC boots for underdrain pipe penetrations through the liner (see Figure PPS-4). Table PPS-3. Physical Requirements for Separator Fabric' Property Class B Test Method Elongation < 50%z Elongation > 50%z Grab Strength, N (lbs) 800 (180) 510 (115) ASTM D 4632 Puncture Resistance, N (lbs) 310 (70) 180 (40) ASTM D 4833 Trapezoidal Tear Strength, N (lbs) 310 (70) 180 (40) ASTM D 4533 Apparent Opening Size, mm S Sieve Size AOS < 0.3mm (US Sieve Size No. 50) ASTM D 4751 Permittivity, sec' 0.02 default value, must also be greater than that of soil ASTM D 4491 Permeability, cm/sec k fabric > k soil for all classes ASTM D 4491 Ultraviolet Degradation at 500 hours 50% strength retained for all classes ASTM D 4355 ' Strength values are in the weaker principle direction 2 As measured in accordance with ASTM D 4632 Table PPS4. Physical Requirements for Geomembrane Property Thickness 0.76 min (30 mil) Test Method Thickness, % Tolerance f5 ASTM D 1593 Tensile Strength, kN/m (lbs/in) width 12.25 (70) ASTM D 882, Method B Modulus at 100% Elongation, kN/m (lbs/in) 5.25 (30) ASTM D 882, Method B Ultimate Elongation, % 350 ASTM D 882, Method A Tear Resistance, N (lbs) 38(8.5) ASTM D 1004 Low Temperature Impact, °C ff) -29 (-20) ASTM D 1790 Volatile loss, % max. 0.7 ASTM D 1203, Method A Pinholes, No. Per 8 mZ (No. per 10 sq. yds.) max. 1 N/A Bonded Seam Strength, % of tensile strength 80 N/A 8. Outlet: The portion of the WQCV in each cell should be slowly released to drain in approximately 12 hours. An orifice at the outlet of the underdrain can be used for each cell to provide detention and slow release of the WQCV to offset hydromodification. Use a minimum orifice size of 3/8 inch to avoid clogging. If lateral walls are required, each cell should be considered a separate system and be PPS-12 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 I Permeable Pavement Systems T-10 t controlled independently. See Figure PPS-6 for underdrain system layout and outlet details showing a multi -cell configuration. Equations PPS-4 and PPS-5 can be used to determine the depth of the WQCV within the pavement section (based either on the stepped/flat installation shown in Figure PPS-2 or the sloped installation shown in Figure PPS-3) and Equation PPS-6 can be used to size the ' WQCV orifice. If the design includes multiple cells, these calculations should be performed for each cell substituting WQCV and VTo,ai with the volumes provided in each cell. The UD-BMP workbook available at www.udfcd.org can be used when multiple cells are similar in area. The workbook ' assumes that the WQCV is distributed evenly between each cell. For calculating depth of the WQCV using a flat/stepped installation, see Figure PPS-2: ' _ 12 WQCV Equation PPS-4 d PA ' Where: d = depth of WQCV storage in the reservoir (in) P = porosity, 50.30 for porous gravel, <_0.4 for all other pavements using AASHTO No. 57 or No. 67 coarse aggregate in the reservoir ' A = area of permeable pavement system (ft) ' WQCV = water quality capture volume (ft) For calculating depth of the WQCV using a sloped installation, see Figure PPS-3: ' d = 6 �2 WPA WQCV + sL Equation PPS-5 L Where: d = depth of WQCV storage in the reservoir (in) ' A = area of permeable pavement system (ft) s = slope of the reservoir/subgrade interface (ft/ft) tL = length between lateral flow barriers (see step 4) (ft) I 1 ' August 2011 Urban Drainage and Flood Control District PPS-13 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems ' For calculating the diameter of the orifice for a 12-hour drain time (Use a minimum orifice size of 3/8 inch to avoid clogging.): p12 hour drain time — 1414 — Vyo.41 Equation PPS-6 ' Where: D = diameter of the orifice to drain a volume in 12 hours (in) ' Y = distance from the lowest elevation of the storage volume (i.e. the bottom of the reservoir) to the center of the orifice (ft) ' V = volume (WQCV or the portion of the WQCV in the cell) to drain in 12 hours (ft) Additional Design Considerations ' Subgrade Preparation ' Partial Infiltration and Full Infiltration Installations: The subgrade should be stripped of topsoil or other organics and either excavated or filled to the final subgrade level. Unnecessary compaction or over - compaction will reduce the subgrade infiltration rate. However, a soft or loosely compacted subgrade will settle, adversely impacting the performance of the entire permeable pavement system. The following recommendations for subgrade preparation are intended to strike a balance between those competing objectives: ' For sites, or portions thereof, requiring excavation to the final subgrade level, compaction of the subgrade may not be needed, provided that loose materials are removed from the excavation, and a firm subgrade is provided for the support of the pavement system. A geotechnical engineer should observe the prepared subgrade. Local soft areas should be excavated and replaced with properly compacted fill. As an alternative to excavating and replacing material, stabilization consisting of geogrid and compacted granular fill material can be used to bridge over the soft area. Fill material ' should be free draining and have a hydraulic conductivity significantly higher than the subgrade soil. Fill is typically compacted to a level equivalent to 95% Standard Proctor compaction (ASTM D 698). The designer should specify the level of compaction required to support the pavement system. ' For sites (or portions thereof), requiring placement of fill above the existing subgrade to reach the final subgrade level, the fill should be properly compacted. Specify the hydraulic conductivity for the material that is to be placed. This should be at least one order of magnitude higher than the native material. If the type or level of compaction of fill material available for construction is different than that considered in design, additional testing should be performed to substantiate that the design ' infiltration rate can be met. However, additional infiltrometer testing may not be necessary, provided that it can be demonstrated by other means that the compacted fill material is more permeable than that considered for design. ' Low ground pressure (LGP) track equipment should be used within the pavement area to limit over - compacting the subgrade. Wheel loads should not be allowed. 1 ' PPS-14 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 Permeable Pavement Systems T-10 ' No -Infiltration Sections: Unless otherwise indicated by the geotechnical engineer, the subgrade for this section should be scarified and properly compacted to support the liner and pavement system. A level of compaction equivalent to 95% of the Standard Proctor density (ASTM D 698) is typically used. The designer should specify the level of compaction. No -infiltration sections should be smooth rolled with a roller compactor, and the prepared subgrade surface should be free of sharp objects that could puncture the liner. Both the designer and the liner installer should inspect the subgrade for acceptance prior to liner placement. ' Filter and Reservoir Layer Compaction 1 n L J I l l I 1 Filter material placed above the prepared subgrade should be compacted to a relative density between 70% and 75% (ASTM D4253 and ASTM D4254) using a walk -behind vibratory roller, vibratory plate compactor or other light compaction equipment. Do not over -compact; this will limit unnecessary infiltration into the underlying subgrade. The reservoir layer may not be testable for compaction using a method based on specified density (e.g., nuclear density testing). The designer should consider a method specification (e.g., number of passes of a specified vibratory compactor) for those materials. The number of passes appropriate is dependent on the type of equipment and depth of the layer. STAINLESS STEEL CLAMP BUYTL TAC TAPE PROVIDE SLACK TO OUTLET 30 MIL (MIN.) PVC LINER PVC PIPE BOOT SKIRT - (FlELD SEAM ALL SIDES) SOLID PIPE . SLOTTED NOTE: BACKFlLL NOT SHOWN Figure PPS-4. Geomembrane Liner/Underdrain Penetration Detail August 2011 Urban Drainage and Flood Control District PPS-15 Urban Storm Drainage Criteria Manual Volume 3 I T-10 Permeable Pavement Systems TEMPORARILY ATTACH FABRIC TO WALL DURING BACKFILL PROCESS DO NOT WRAP AROUND BA BAR) p' MIN. « • • w ��, STAINLESS WASHER OR GALVANIZEDSTEEL ' BATTEN BARI I' GEOTEXTILE SEPARATOR �i // CONCRETE PERIMETER BARRIER �Cctt� PREPARED SUBGRADE 'PROVIDE SLACK IN LINER PLACEMENT TO ENSURE GEOTEXTILE SEPARATOR FABRIC (IF SUBGRADE CONTAINS ANGULAR PROPER INSTALLATION AND BACKFILL WITHOUT ROCKS OR OTHER MATERIAL THAT DAMAGE COULD PUNCTURE THE LINER) NITRILE POLYMER BASED VINYL MEMBRANE SEAMING ADHESIVE MAY BE USED AS AN NOTE: ALTERNATIVE TO THE BOLTED BATTEN BAR AND IN AREAS WHERE THE NEED FOR AN UNDERD N SYSTEM NER IS LESS CRITICAL. IMPERMEABLE LINER NOT SHOWN SHOW Figure PPS-5. Geomembrane Liner/Concrete Connection Detail PPS-16 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 Permeable Pavement Systems T-10 ' 1) SHAPE SUB —GRADE TO FINAL GRADE 2) LAY DOWN PVC MEMBRANE (LINER) ON SUB —GRADE e 3) INSTALL PIPE AND PLACE FILTER MATERIAL IN TRENCH ' 4) FOLD MEMBRANE LAYERS OVER FILTER MATERIAL I 5) PLACE FILTER MATERIAL BERM ALONG DOWNSTREAM EDGE OF TRENCH 6) FOLD MEMBRANE LAYERS BACK OVER BERM I 7) PLACE ADDITIONAL MATERIAL AS REQUIRED Figure PPS-6. Lateral Barrier Installation ' August 2011 Urban Drainage and Flood Control District PPS-17 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems 4' SOLID PPE STORM MANHOLE Y A OR VAULT (TYP.) TO ww i PLAN VIEW NTS PLACE LARGER ROCK B TO OVERSEER TO CONFINE RESERVOIR MATERIAL RISER SUPORTED WITH METAL STRAPS ANCHORED TO WALL UNDERDRAIN FLOW, FROM CELL LTE BOTTOM SUBCRADE of ITWJ'aO SLOTTED PVC MEETING TABLE PPS-2 �-CONCRETE EDGE (WHERE APPLICABLE) PROVIDE OVERFLOW FROM RESERVOIR r1' OF RESERVOIR LAYER TO D BACKWASHING PAVEMENT 1�► J Figure PPS-7. Underdrain System Layout and Outlet Details Tap OF RISER ELEVATION SET AT WOCV AND NO HIGHER THAN 1' BELOW THE TOP (IF THE RESERVOIR LAYER PPS-18 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 Permeable Pavement Systems T-10 PERMEABLE PAVEMENT BASE COURSE FILTER LAYER SUBGRADE CAST IRON VALVE BOX WITH LOCKING LID REMOVABLE PVC THREADED PLUG & COUPLER 3" MIN. THICK CONCRETE COLLAR a; CONCRETE RESTRAINT Figure PPS-8. Observation Well 400 SLOTTED PVC PIPE MEETING TABLE PPS-2 (TERMINATE PIPE AT THE BOTTOM OF THE FILTER LAYER WITH A NO INFILTRATION SECTION) ABBLLE) IER WELL R August 2011 Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual Volume 3 PPS-19 L I 1 1 T-10 Permeable Pavement Systems Construction Considerations Proper construction of permeable pavement systems requires measures to preserve natural infiltration rates (for full and partial infiltration sections) prior to placement of the pavement, as well as measures to protect the system from the time that pavement construction is complete to the end of site construction. Supplemental Fact Sheets on the specific pavements provide additional construction considerations. The following recommendations apply to all permeable pavement systems: ■ When using an impermeable liner, ensure enough slack in the liner to allow for backfill, compaction, and settling without tearing the liner. ■ Provide necessary quality assurance and quality control (QA/QC) when constructing an impermeable geomembrane liner system, including, but not limited to fabrication testing, destructive and non- destructive testing of field seams, observation of geomembrane material for tears or other defects, and air lace testing for leaks in all field seams and penetrations. QA/QC should be overseen by a professional engineer. Consider requiring field reports or other documentation from the engineer. ■ Keep mud and sediment -laden runoff away from the pavement area. ■ Temporarily divert runoff or install sediment control measures as necessary to reduce the amount of sediment run-on to the pavement. ■ Cover surfaces with a heavy impermeable membrane when construction activities threaten to deposit sediment onto the pavement area. Design Example The UD-BW workbook, designed as a tool for both designer and reviewing agency is available at www.udfcd.ore. This section provides a completed design form from this workbook as an example. PPS-20 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 I Permeable Pavement Systems T-10 ' Design Procedure Form: Permeable Pavement Systems (PPS) Shoot f of 2 ' Designer: Company: Date: Project: Location: 1 1 1 1 J 1 G. Fm,-r BMP Inc. November 29, 2010 Strops at 511th Ave. SE comer of 56th Ave. and 83rd at 1. Type of Permeable Pavement Section Goose One O No Infiltration A) What type of section of permeable pavement is used? partial hsibration Section (Based on the land use and activities, pmpmity to adjacent O Full Infiltration Section structures and soil characteristics.) B) What type of wearing course? 0 PIIP O Conaete Grid pavement O Parvbla CDnvete O porous Gravel 2. Required Storage Volume A) Effective Imperviousness of Area Tributary to Permeable Pavement, I, I, = 65.0 % B) Tributary Area's Imperviousness Ratio (I = I, / 100) 1 = 0� 650 C) Tributary Watershed Area AT" = 55,000 sgff (including area of permeable pavement system) D) Area of Permeable Pavement System A� = 15,000 sq It (Minimum recommended permeable pavement area = 13491 act it) E) Impervious Tributary Ratio RT=F 1.7 (Contributing Impervlum Area / Permeable Pavement Ratio) F) Water Quality Capture Volume (W QCV) Based on 12-hour Drain Time WO CV = 932 cu it (WQCV=(0.8'(0.91'is-1.19'i'* 0.78-1)/12)' Area) G) Is flood control volume being added? Choose Ore YES Provide overflow to carry runoff directly ONO Into the reservoir layer to ensure use of flood control volume regardless H) Total Volume Needed VTaw = 6,340 w ff of infiltration rates. 3. Depth of Reservoir A) Minimum Depth of Reservoir Dm„ = 18.0 Inches (Minimum recommended depth Is 6 inches) Chose One B) Is the slope of the reservoir/subgrade Interface equal to 0%7 Q YES- Rat or Stepped In0lbtian O NO- Sloped Installation C) Porosity (Porous Gravel Pavement < 0.3, Others < 0.40) P = 0.40 D) Slope of the Base Course(Subgrade Interlace S = O / it E) Length Between Lateral Flow Bariers L = fl F) Volume Provided Based on Depth of Base Course V = 8,500 cu ff Flat or Stepped: V = P' ((Dmkryl2)' Area Sloped: V = P' ((Don„- (Don„ - 6-SL-1)) / 121Area 4. Lateral Flow Barriers Chase Ore A) Type of Lateral Flow Barters O Conaere wars O PVC geomembrsne Installed normal to flow O WA- Flat installation O Other (Describe): B) Number of Permeable Pavement Cells Cells = 1 S. Perimeter Barrier A) Is a perimeter barrier provided on all sides of Ore Choose One YES pavement system? (Recommeded for PICP, concrete grid pavement or for any ONO no4rdlitration section.) August 2011 Urban Drainage and Flood Control District PPS-21 Urban Storm Drainage Criteria Manual Volume 3 T-10 Permeable Pavement Systems Design Procedure Form: Permeable Pavement Systems (PPS) Designer. G. Frazer Sheet 2 of 2 Company: BNIP Inc. Daft: November 29, 2010 Project: Shops at 56th Ave. Location: SE comer of Stith Ave. and 83rd St 6. Filter Material and Underdraln System A) Is the undardmin placed below a 6-inch thick layer of otiose Ore YES CDOT Class C fitter material? ONO 10 O N/A B) Diameter of Slotted Pipe (slot dimensions per Table PPs-2) Oaase One Q 4-inch O 6-Itch C) Distance from the Lowest Elevation of the Storage Volume y = 3.8 it (i.e. the bottom of the base course to tire center of the mince) 7. Impermeable Geomembmne Uner and Geotextile Separator Fabric A) Is there a minimum 30 mil thick impermeable PVC geomembrane home One liner on the bottom and sides of the basin, extending up to the top YES 160 of the base course? NO Dxxn One B) COOT Class B Separator Fabric O Placed above the finer O Plaoed above and below the hw 8. Outlet (Assumes each cell has similar area, subgrade slope, and length between lateral barriers (unless subgrade is flat). Calculate cells individually where this "des.) A) Depth of WOCV in the Reservoir Dwncv = —1.86 w inches (Fevation of the Flood Control Outlet) B) Diameter of Orifice for 12-hour Drain Time D� = 0.62 Inches (Use a minimum orifice diameter of 3/84nches) Notes: PPS-22 Urban Drainage and Flood Control District August 2011 Urban Storm Drainage Criteria Manual Volume 3 APPENDIX D EROSION CONTROL REPORT' B E e '9 tT ;i ' ' ■V INORTHERN ENGINEERING Scott Plaz ' EROSION CONTROL REPORT ' A comprehensive Erosion and Sediment Control Plan (along with associated details) HAS BEEN PROVIDED BY SEPARATE DOCUMENT. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of ' the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. ' It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. ' The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3, Chapter 7 — Construction BMPs will be utilized. Measures may include, but are ' not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at existing and proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site ' restrooms shall also be provided by the Contractor. Grading and Erosion Control Notes can be found on the Utility Plans. The Final Plans contain a ' full-size Erosion Control sheet as well as a separate sheet dedicated to Erosion Control Details. In addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere to, the applicable requirements outlined in the Development Agreement for the development. Also, the Site Contractor for this project will be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — Stormwater Program, prior to any earth disturbance activities. Prior to securing ' said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and document the ongoing activities, inspections, and maintenance of construction BMPs. ^I n MAP POCKET DRAINAGE EXHIBITS 1 -��0��� PW it 00] I I 1 ; T TOWNSGUARECONCOS EXISTING D(MtWMUMST- I� FORTCOLUNS. BUILDING I GO W521-- II I; I; I I [IN LID SUMMARY TABLES:In Otltlln am Ina PDEWIW I ��` 1 Om P.arlw Pares 003 m eve (I* WOIaI tl e3a WN S Pm.tlY PAa�a NO mB Dn PsnrPe... >' to f I rw 1.19 advR am Pa-Am tan a EXISTING BUILDING c+uww \\\ B I I 0 N MENOMONIE i i - i C I EUSnxGAYIML PMu1G LOT 1 II� i Rm�o�u�i �I PROPOSED UNDERORNN UNDERORNN IJI� EXISTING BUILDING CAMMIDGE III` NOusElm n1JWPLUMST 'CRT COLLINS. GO 80521 EXISTING BUILDING NORTH n O aD 40 Go F"t ( IN FEET) nm - DD rl. LEGEND: fRGPOSEO STORK SENIOR P GPI CADMIUM" PMWSED CONTOUR E arm; CDMDUP —4953 PRWGSED CURB h GUMR — — — PRWERTY BOUNDARY PROPOSED RICNT OF NAY E%ISnNG RIGHT OF MAY — PROPOMID WY N4L O DEWCAN %MNT Q FLOW ARROW m DRAINAGE BASIN UBM O.al w un MANAGE BASIN BOUNDARY • � � � • PRCPoSED PERUEAeIE PAWNS ZU' R NOTES: Wg w 1. PEFCR To THE 'RxAL DAMAGE AND wosou caNma PEPCtT FOR = w SCOU PLAZe BY NORTHERN ExGNIEGwG. DAM JUNE 10, 2014 FOR L A ASgMMUL INFOPNAMON. 1� Z O" $ BENCHMARK Z w 0 BENCHMPRKtl1: BmCnreM 149T CR/ W FM Clog At tln ewMaul wnm of Weal Elizabeth stl SM1IeMs Bbeal. on a r B: Sign R Ekwatn=54Y.55 UNGVD 1991naGuxM) BENCHMARK 42. p Ciry WFWt Col BanMmaM 3097 k At nn WRammsl comer of weal EambAn and GMStiWtion Avenue. M {'f miatAIS UWMC swral Ueae. .$ EI&CA 5We BY(NGw 19N unadluema) _ FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTIONI I m m $ kQ R D] � c'uuruTrxonFlrnTwmRmcR caowoD W • O KmwatWrsbelow. �alnmmm�aq�. Q _ City of Fort Collins, Colorado UTnM PLAN APPROVAL ApPACI cur T.S.m..r D.1. CHECRm BY nm s rut...le. Gwly nn. CHECKED BY �thl� M Cc mBY: M Sheet CHEGKM BY: aM C600 GRECRm By Of'14 Sheets -. I I'^, a.+r.VIA 0MFtiMW