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HomeMy WebLinkAboutWPO201300008 Review Comments Erosion Control Plan 2013-05-24�pF A vt�r�1Q COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Commonwealth Multi- Family Plan preparer: Dominion Engineering [fax 979 -1681] Owner or rep.: Moores Creek Land, LLC Plan received date: 17 Apr 2013 Date of comments: 24 May 2013 Reviewer: Michelle Roberge I have completed the engineering review for Commonwealth Multi- Family, WP0201300008. Please address my comments for E &S and SWM. A. Erosion Control Plan (WP0201300008) 1. [Comment] Please provide the recorded easement, permission letter, or documention from the Turtle Creek Condominiums and Colonial Realty Limited Partnership for your proposed outfall pipe and future SWM facility. [Revision 11 Comment addressed. 2. [Comment] It appears that you will haul more fill to the site. Please show a stockpile location with silt fence. [Revision 11 Comment addressed. [Comment] The trees to be planted south of site should be included within the limits of disturbance. The proposed waterlines should also be within the LOD. Please revise the LOD. [Revision 11 Comment addressed. 4. [Comment] The sediment trap is undersized. Please revise. [Revision 11 Comment not addressed. I recommend changing the shape to a rectangular 14.8' x 53.3' sediment trap with 1:1 slope for contour 477 -479 and 2:1 slope for contour 479 -481. 5. [Comment] For construction sequence note 2, please provide an outlet protection for the pipe. [Revision 11 Per VESCH Section 3.18, the outlet protection should be right after the pipe at a 0% slope. Please show end of pipe at toe of slope so that the apron is at outfall. A drop manhole might be necessary to reduce pipe slopes. Per comment 2 in SWM section, the BMP layout may change. 6. [Comment] The silt fence is hidden under the LOD line. Please clearly show the location of the silt fence east of site. The LOD should be on the parcel unless easements are provided per comment 1. [Revision 11 Comment addressed. Engineering Review Comments Page 2 of 3 7. [Comment] Please provide the narrative for your project. [Revision 11 Comment addressed. B. Stormwater Management Plan (WP0201300008) 1. [New Comment] The site plan dated SDP2010 -04 that was approved on May 5, 2010 has a parking lot layout slightly different from what is shown on the WPO plan. The approved site plan shows a stacking block retaining wall and 2 additional parking spaces. Please match WPO plans with approved site plans or apply for a minor amendment to the site plan. Prior to applying for a minor amendment, please verify that the parking spaces removed are not required to meet the minimum number of parking spaces per our ordinance. 2. [New Comment]The underground detention is undersized. One option is to change the orientation of the pipe to run horizontally on northern area of parking lot. Our computations indicate at least 160' length of pipe with a minimum of 0.5% pipe slope. (See comment 4 below for additional BMP comments to retain more runoff on site to address MS -19.) Typically, a 6" pvc pipe from the Filterra structure directs runoff into a DI. From the DI, a 15" pipe drains into the detention facility. Please provide these details. Also include the plate detail with grate info to prevent clogging of 4" orifices. 3. [New Comment] Please provide 48" manholes on both ends of the detention facility. The 4" orifice can clog easily. Therefore, please provide enough space behind the plate for a 48" manhole and crawl space when maintenance work is necessary. 4. [Comment] The site is proposed to drain into an existing 48" RCP pipe owned and maintained by VDOT. From there it drains through the townhouse site, then Stonefield shopping center, under Rt. 29 and finally into the city. Adequate channels are required to be demonstrated. The contributing drainage area, from your site, to a point of discharge is one percent or less for the total watershed area. Please provide this analysis. Please be aware that there have been great concerns at the discharge from Stonfield, and this site contributes to that flow directly. [Revision 11 The existing area for outfall has ponding issues that encroaches on the Turtle Creek Condominium's property. Based on the channel adequacy report, please address the following: a) Verify the pipe size is correct. It appears to be 48 ". Please provide photos and state the pipe's conditions. b) 18' of head at the upstream end is already too high, therefore adequate channel has not been met due to existing pipe is undersized. Please design a facility that retains more runoff on site and maximizes groundwater recharge to reduce additional flow to existing culvert. c) Please verify if pipe is maintained by VDOT. Further discussion with VDOT may be necessary to discuss additional runoff due to pipe conditions. 5. [Comment] It appears this WPO application changed from the previously approved WP0200700040. The previous application included a cofferdam with a culvert inlet protection (CIP). Please refer to that plan for guidance. It is our understanding that this was worked out with Greg Harper of the County General Services Department. [Revision 11 Comment addressed. Engineering Review Comments Page 3 of 3 6. [Comment] It appears that you are proposing to install the riser for the future SWM facility. Please show the the size of the basin and provide calculations for this future SWM facility to determine if the pipe and basin are adequately sized. Also show the stormwater management easements that encompasses the 100 year high water mark. These will be required prior to approval. [Revision 11 Comment addressed. 7. [Comment] Please provide your stormsewer and outlet protection calculations. [Revision 11 Per comment 2, the underground detention is undersized. Please provide new calcs. 8. [Comment] Please provide the drainage easement for the proposed 15" HDPE stormsewer pipe and all existing utilities with the DB and page no. [Revision 11 Comment addressed. 9. [Comment] Please provide the manufacturer's certification and approval for your proposed Filterra design. [Revision 11 Comment addressed. 10. [Comment] Also provide the load reduction calculation found on our website to meet the water quality criteria. [Revision 11 Comment addressed. 11. [Comment] The 10' stormwater management access for the future SWM facility can be easily accessed by the existing parking lot east of property. Please provide an approval letter from Colonial Realty Limited Partnership for this use. Also provide the easement on the parking lot. [Revision 11 Comment addressed. 12. [Comment] VDOT, ACSA and Fire Department approvals are required. [Revision 11 Comment addressed. 13. [Comment] Please provide anchors for the pipe sloped at 16 %. Please refer to VDOT standards. [Revision 11 Comment addressed. Sincerely, r"de- Michelle Roberge File: E1_rp,esc,swm,fsp_GEB _ template.doc