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HomeMy WebLinkAboutFile Documents.1230 Snowbunny Ln.0116.2019 (5).ARBKEngineering1_0116.2019.ARBK_1230 Snowbunny Page: C2 SITE PLAN Author: pjm File Name: 1230 Snowbunny CO Civils.pdf A landscape plan was not included in the submittal. What is proposed to be planted in the rain gardens? 1230 Snowbunny CO Civils.pdf (13) Page: C2 SITE PLAN Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Is it not recommended to have the water service line routed below an infiltration BMP system. Page: C2 SITE PLAN Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Is utility work proposed? If a new water service is proposed include the following: - line size and material. - new tap shall be 18" from existing/other fittings. - ensure 10' horizontal separation from sanitary and 18" vertical separation in sanitary crossing. Page: C2 SITE PLAN Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Maximum driveway width permitted for a two car garage is 18' and 10' for single car garage. Revise to meet standards. Page: C4 GRADING & DRAINAGE Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Has a geotech signed off on this design? URMP calls out that there to be a liner for the first 10' from building foundations. A landscape plan was not included in the submittal. What is proposed to be planted in the rain gardens? Is it not recommended to have the water service line routed below an infiltration BMP system. Is utility workproposed? If a new water service is proposed include the following: - line size and material. - new tap shall be 18"from existing/other fittings. - ensure 10' horizontal separation from sanitary and 18"vertical separation in sanitary crossing. Maximum driveway width permitted for a two car garage is 18' and 10' for single car garage. Revise to meet standards. Has a geotech signed off on this design? URMP calls out that there to be a liner for the first 10' from building foundations. Page: C4 GRADING & DRAINAGE Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Provide adequate grading information with spot elevations or contour lines for construction. It is not clearly shown on this plan how drainage is routed to the BMPs. Page: C4 GRADING & DRAINAGE Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Show grade of the driveway. Depending on slopes, a curb perimeter may be desired to prevent shifting of the pavers. Page: C4 GRADING & DRAINAGE Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Show more grading for the berm, include flow line for clarification. Page: C4 GRADING & DRAINAGE Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Show riprap at outlet. The rip rap will prevent erosion, will it function as a point source discharge or will it spread out? Page: C5 DETAIL Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Call out side slopes. Max allowable is 3:1. Provide adequate grading information with spot elevations or contour lines for construction. It is not clearly shown on this plan how drainage is routed to the BMPs. Show grade of thedriveway. Depending on slopes, a curb perimeter may be desired to preventshifting of the pavers. Show more grading for the berm, include flow line for clarification. Show riprap at outlet. The rip rap will prevent erosion, will it function as a point source discharge or will it spread out? Call out side slopes. Max allowable is 3:1. Page: C5 DETAIL Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Slopes called out for the pipe are not consistent. Revise for consistency. Page: C5 DETAIL Author: pjm File Name: 1230 Snowbunny CO Civils.pdf URMP approved filter media is 70% sand, 30% combo off topsoil and largo organic matter. Page: SURVEY Author: pjm File Name: 1230 Snowbunny CO Civils.pdf Survey must be verified within last 12 months. Page: [1] VR-Drainage-Drainage Author: pjm File Name: Valentine-Drainage-Report.pdf If the modified FFA method to release at histroic rates is proposed, existing conditions is not required for the analysis. Show historic grading and flow patterns. Valentine-Drainage-Report.pdf (10) Page: 6 Author: pjm File Name: Valentine-Drainage-Report.pdf APP B shows no infiltration pavers only per the legend, clarify where pervious pavers are used. Slopes called out forthe pipe are notconsistent. Revise forconsistency. URMP approved filtermedia is 70% sand,30% combo offtopsoil and largoorganic matter. Survey must be verified within last 12 months. Existing Drainage Basins PE:QC: 2018-458 JK 4.10.19 RB VR-Drainage AE APP A Project Mil If the modified FFA method to release at histroic rates is proposed, existing conditions is not required for the analysis. Show historic grading and flow patterns. Basin A encompasses the south and east side of the site with a portion that touches the north-east side of the house, generally between the residence and the ditch to the east. Sub-basins 1, 2, 3 and 4 comprise Basin A. This basin is 9674 square feet of which 2779 square feet is impervious. Tree canopy credit is calculated per section 8.4.1 of the COA URMP, a detailed calculation is shown in Appendix C. Grass buffers, pervious pavers, and a rain garden will treat the remaining WQCV. See Appendix B for the proposed location of BMPs in this basin. Table 2 Basin A (Sub-basins 1,2,3, & 4) Basin Area (sf) 9674 % Impervious 29% Required WQCV (cf) 50.4 Credits Pervious Paver Area (sf) 90 Grass Buffer Area (sf) 3275 Tree Canopy Credit Area (sf) 215 Rain Garden Volume (cf) 9.0 Results Effective Impervious Area (sf) -891 Effective % Imperviousness -9.2% Available WQCV (cf) 80.6 Surplus WQCV (cf) 30.2 Sub-basin 1 Sub-basin 1 is located on the south side of the property and has a total and impervious area of 2616 and 685 square feet, respectively. This corresponds to 26% impervious area for the sub-basin. This area is mostly a grassed area containing trees with the south portion of the roof included. The existing site will be impacted by the addition of a living space over the garage, a second story deck, and a covered patio. Storm water will be routed from the roof to grass buffer via roof drainage and gutter downspouts then east and ultimately north by existing vegetated topography to the proposed detention at the north-east corner of the site. Grass buffer area is at or above a 1:1 ratio to impervious area, after applying the tree APP B shows no infiltration pavers only per the legend, clarify where pervious pavers are used. Page: 8 Author: pjm File Name: Valentine-Drainage-Report.pdf It is my understanding that no runoff is being routed to the pavers for treatment other than what falls directly on them, is that correct? Page: 10 Author: pjm File Name: Valentine-Drainage-Report.pdf Runoff shall be released at historic rate in a historic manner, revise to not have point discharge. Page: 15 Author: pjm File Name: Valentine-Drainage-Report.pdf Provide a table with grass buffer areas to verify 1:1 ratio. Page: 15 Author: pjm File Name: Valentine-Drainage-Report.pdf This information shall be provided on the civil sheets as well. This sheet will not be onsite during construction. Ensure all pertinent information regarding construction, grading and drainage is provided on the civil sheets. Page: 18 Author: pjm File Name: Valentine-Drainage-Report.pdf Provide peak flow calcs for historic site in order to use modified FAA method for detention per requirements of a major engineering review checklist. way and garage and routed by 4” PVC ge. All other storm water in sub-basin 6 o pervious pavers and eventually grass to impervious area, after applying the asin contains a surplus of 505 square ted runoff from the driveway that is tion 3.2.3). ng the rational method as explained in as explained in Section 2 of the URMP. It is my understanding that no runoff is being routed to the pavers for treatment other than what falls directly on them, is that correct? 1230 Snowbunny Lane, Aspen, Colorado April 17, 2019 Rain gardens were installed in both basins to treat the remaining required WQCV. Locations and WQCV calculations for the rain gardens can be found in Appendix B and C, respectively. 6.0 Detention Methodology The required detention volume was calculated using the Rational Volume Method for Detention Volume (Watershed <90acres) as outlined in Chapter 5 the URMP. Calculations of the required detention volume can be seen in Appendix E. After consideration of the site and the importance of minimizing disturbance to the existing lawn, localized detention is sized and located based on existing drainage paths. The most effective approach that remains aesthetically pleasing is to build berms around the downstream discharge points of each basin. The detention areas will rely on berms and the existing grading to hold the developed runoff from the site. The detention areas will incorporate an outlet pipe that will release runoff at, or below, historic rates. Using positive drainage away from the house and preserving as much healthy vegetation as possible, the detention areas only needed berms built up on two sides to store runoff. Utilizing quantities calculated from the Rational Volume Method for Detention Volume, the berms would only need to be built up 6” from the existing ground. This approach will satisfy not only the detention requirements but also be minimally invasive to the existing landscaping. Outfall discharge of the detention area was calculated using Equation 5-10 of the URMP and can be seen in Appendix F. The outlet pipe was sized to drain the detention area at the historic 10-year flow rate, while storing the 100-year storm. This approach was used to avoid multiple stage discharge, thus eliminating a larger impact to the site. 7.0 Maintenance Runoff shall be released at historic rate in a historic manner, revise to not have point discharge. Provide a table with grass buffer areas to verify 1:1 ratio. 3 (A) 4 (A) Graphic Scale In Feet: 1" = 6' 0 3 6 12 Line Architectsnowbunny Lane118 West Sixth Street, Suite 200Glenwood Springs, CO 81601970.945.1004 www.sgm-inc.com This information shallbe provided on thecivil sheets as well.This sheet will not beonsite duringconstruction. Ensureall pertinentinformation regardingconstruction, gradingand drainage isprovided on the civilsheets. 1230 Snowbunny Lane, Aspen, Colorado Peak Flow Calculations for Project Site – Proposed Condit Historical Flow Calculations Seen in Appendix E with Dete · Watershed Area, 4)RJ1* )v* = = . · Percent Imperviousness, B B = 4wxy4z{z|}× 1 B = 2779 HCM 9674 HCM = ~.~ % · Maximum Watershed Length, = 0 ,routing on property from SW · Watershed Slope, 2o79:CB?> :C E?GCℎ 7>A − Provide peak flow calcs for historic site in order to use modified FAA method for detention per requirements of a major engineering review checklist. Page: 18 Author: pjm File Name: Valentine-Drainage-Report.pdf Where is design point 1? Clarify this is basin A. Page: 27 Author: pjm File Name: Valentine-Drainage-Report.pdf How is the headwater depth provided? It appears that the pipe is flush with the ground in the detail. Page: 27 Author: pjm File Name: Valentine-Drainage-Report.pdf Release rate shall be equal to or less than 100 year event, not 10 year event. Where are historic rates calculated in this report? April 17, 2019 Appendix D Conditions Design Point 1 h Detention Calculations . xy {z|}× 100 79 HCM 74 HCM × 100 .~ % Where is design point 1? Clarify this is basin A. C₀g H₀A₀ - DP1 D₀ - DP1 A₀ - DP1 D₀ - DP2 Q - DP1 Q - DP2 -ft/sec²ft ft²in.ft²in.cfs cfs 0.6 32.2 0.33 0.037 2.6 0.018 1.8 0.092 0.039 *** Use Sch *** Use Sch Discharge Coefficient Headwater Depth Gravitational Constant Orifice Area Orifice Area Orifice Diameter Orifice Diameter Actual Outflow Actual Outflow How is the headwater depth provided? It appears that the pipe is flush with the ground in the detail. Q - DP1 Q - DP2 C₀g H₀A₀ - DP1 D₀ - DP1 A₀ - DP1 D₀ - DP2 Q - DP1 Q - D cfs cfs -ft/sec²ft ft²in.ft²in.cfs cfs 0.103 0.051 0.6 32.2 0.33 0.037 2.6 0.018 1.8 0.092 0 Historic 10 year Flow Rate (Q) Discharge Coefficient Headwater Depth Gravitational Constant Orifice Area Orifice Area Orifice Diameter Orifice Diameter Actual Outflow Actu Outfl Release rate shall be equal to or less than 100 year event, not 10 year event. Where are historic rates calculated in this report?