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HomeMy WebLinkAboutWPO201400068 Correspondence 2014-11-14 Nee ENGINEERS SURVEYORS PLANNERS ASSOCIATES November 14,2014 Michelle Roberge, P.E. County of Albemarle Department of Community Development 401 McIntire Road, Room 227 Charlottesville, VA 22902-4596 Re: WP02014-00068 Farmington Country Club, Southside Improvements WWA Project No. 214045.03 Dear Ms. Roberge: Enclosed please find two (2) copies of the revised Site Plan Amendment for the above- referenced project. We offer the following responses to your comments dated October 30, 2014 with regard to the Minor Amendment application: A. WPO(WPO2014000068) 1. Comment: Show soil map of site. Comment Addressed. The soils are shown on sheet C-12. 2. Comment: The drainage area A table on sheet C-13 shows a BMP practice to a rain garden #2. The plan does not show a rain garden. Please clarify if you are proposing a rain garden. Comment addressed. There is no rain garden proposed. This has been removed from the table. 3. Comment: The sloped area south of the proposed parking lot all drain to the biofilter, but only.5 acres is shown going to the bioretention practice. It appears more than.5 acres will drain to biofilter. Please revise. Comment addressed. Applicant confirmed the areas going to the biofilter. The existing improvements north of parking lot will drain into an existing stormsewer system that will eventually bypass the biofilter. 4. Comment: Add this note on C-12 for biofilter mix. "Tested for acceptable phosphorus index between 10 and 30 or between 7 and 23 mg/kg of P in soil 44 media. " Comment addressed • 5. Comment: Submit perc rate for biofilter area. (One per 1,000 sq ft offilter surface). Also, verb that the bottom of#57 aggregate is 2'above seasonably high water table. Comment not addressed. The bottom of the biofilter is 601.16 and the 3040 Avemore Square Place •Charlottesville,VA 22911 Telephone(434) 984-2700 •Fax(434) 978-1444 Charlottesville •Lynchburg geotech report states that groundwater is present at test site HA-3. The geotech submitted an email stating that the water is perched at HA-3. The response doesn't clear up my concern about groundwater due to the following reasons: i) The tests were not advanced below 601 (the bottom of the biofilter). If it is perched how far below is the groundwater table? We need to clarify that there is no groundwater at 2'below the biofilter. ii) The response from the geotech states the 6 nearby IT locations were dry as well. Which 6 tests is he referencing? This is useful if tests are within the biofilter area. Here are my recommendations. A) You can resubmit the report addressing the above concerns. We just need the geotech to sign and seal the doc. The email below will not suffice. B) Or revising layout to raise bottom of basin elevation to 603. For example,you can move the biofilter just south of the parking lot to a higher elevation. IfA doesn't work, then unfortunately, we will have to explore option B. Response: Additional soil borings will be done and the updated information will be forwarded to you under separate cover. 6. Comment: Label underdrain with Schedule 40 PVC with cleanouts. Show 12"depth for#57 aggregate. Comment addressed. 7. Comment: The geometry of basin does not meet spec of bioretention design criteria. Short circuiting should be prevented. Please revise. Comment addressed. 8. Comment: Show the 2'gravel diaphragm level spreader at pretreatment area. On profile view, show the lip on level spreader. Comment addressed. 9. Comment: I recommend moving the curb cut location away from the corner of parking lot and shifting layout of gravel spreader to enter far east side of biofilter. Comment addressed. 10. Comment: Two rip rap strips are shown on plan, but only one profile view is shown. Please show both since one is from sidewalk and the other from the culvert under the golf cart path. My concern is that#57 stones will wash away at steeper slopes. The detail shown is for sheet flows off pavement, then into a pretreatment area that is flat. Please clarify design since the detail has been modified. Comment partially 3040 Avemore Square Place •Charlottesville,VA 22911 Telephone(434)984-2700 •Fax(434) 978-1444 Charlottesville •Lynchburg Page 2 of 4 addressed The weir is 5'wide on plan view. Please revise to provide room for weir as it appears to conflict with the gravel level spreader location. Response: The bio-filter has been revised and there is no longer a conflict. 11. Comment: The water quantity analysis for channel protection should show the actual drainage area to the point of analysis, such as drainage area A, B, C and existing areas. The CN should be different to drainage area. The spreadsheet shows how much phosphorus to remove, but channel analysis cannot be determined by the separate disturbed drainage areas alone since the CN is not correct. Channel protection is addressed At our engineering meeting, we directed applicant to show adequate channels further downstream since the energy balance equation at point of discharge was not met. The entire site is owned by Farmington Country Club and applicant was able to look 450'downstream to show adequate channel within their site. 12. Comment: Please clarify the total drainage area to pond. It appears to be larger than what is shown. Comment addressed. 13. Comment: Clarify the surface elevation of the bioretention area. The profile shows 607, but the plan view shows 606. Comment addressed. The surface elevation is 606. 14. Comment: Relabel bioretention facility#2 under the Bioretention Facility sizing calculations. It should be bioretention facility#1. Comment addressed. 15. Comment: Submit a Pollution Prevention Plan and a Stormwater Pollution Prevention Plan. Comment addressed. 16. Comment: The disturbed acreage on sheet C10 should match the registration statement in the SWPP. Response: The registration statement has been updated. 17. Comment: The forebay area is in addition to the bioretention area required. It is sized to at least 15% of the total Treatment Volume. Please revise. Response: The bio-filter has been resized. 18. Comment: For future reference,please use the Albemarle County SWPP template. For example, you can use/create the tables from section 6 B), C), D), E), F) and G). Response: Noted. 3040 Avemore Square Place •Charlottesville,VA 22911 Telephone(434) 984-2700 •Fax(434) 978-1444 Charlottesville •Lynchburg Page 3 of 4 Salle *40100. Erosion and Sediment Control Plan(ESCP) 1. Comment: Sediment trap outlet needs to be extended to the bottom of the slope/disturbed soil area to prevent additional sediment loss during trap overflows. Comment addressed. 2. Comment: Paved construction entrance detail needs to be on the plan. The Albemarle County Temporary Paved Construction Entrance detail can be found in the County Design Standards Manual. Comment addressed. 3. Comment: Please remove the bio-filter components from the E&SC plan sheets. Bio-filter components should be shown on the SWMpages. Comment addressed. We trust that the above responses and revised plans properly address the outstanding items. If you have any questions, please contact me. Sincerely, WW Associates, Inc. /7/1 c . ,1 2,2\ Robert C. Umberger Project Manager 3040 Avemore Square Place •Charlottesville,VA 22911 Telephone(434) 984-2700 •Fax(434) 978-1444 Charlottesville •Lynchburg Page 4 of 4 , ...se W A ENGINEERS ileSURVEYORS PLANNERS ASSOCIATES October 22,2014 Michelle Roberge, P.E. County of Albemarle Department of Community Development 401 McIntire Road, Room 227 Charlottesville, VA 22902-4596 Re: WP02014-00068 Farmington Country Club, Southside Improvements WWA Project No. 214045.03 Dear Ms. Roberge: Enclosed please find two (2) copies of the revised Site Plan Amendment for the above- referenced project. We offer the following responses to your comments dated September 12, 2014 with regard to the Minor Amendment application: Stormwater Pollution Prevention Plan(SWPPP) The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and(4) any TMDL measures necessary. 1. Comment: Please provide a copy of the DEQ Coverage Letter with the expiration date of June 30, 2019. Response: A copy of the DEQ Coverage Letter will be provided once it has been received. 2. Comment: The plan must demonstrate compliance with quality and quantity requirements using the Runoff Reduction Method. Please use the VRRM spread sheet from VDEQ. Response: The Virginia Runoff Reduction Method has been used. The spread sheets are located on Drawing No. C-13. A. Pollution Prevention Plan(PPP) The PPP content requirements can be found in County Code section 17-404. 1. Comment:A PPP was not found. Please submit a Pollution Prevention Plan (PPP) for review. Requirements can be found in County Code 17-404. 3040 Avemore Square Place •Charlottesville,VA 22911 Telephone(434) 984-2700 •Fax(434) 978-1444 Charlottesville •Lynchburg Response: The PPP is part of the SWPPP. An updated SWPPP has been included with this submission. B. Stormwater Management Plan(SWMP) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved, and the reasons are provided in the comments below. The stormwater management plan content requirements can be found in County Code section 17-403. WPO(WPO2014000068) "1. Comment: Show soil map of site. Response: The soil types and legend is located on Site Plan (SDP2014-00060) Drawing Nos. C-4 and C-5. They have also been added to WPO201400068 Drawing No. C-12 for clarity. Comment: The drainage area A table on sheet C-13 shows a BMP practice to a rain garden #2. The plan does not show a rain garden. Please clarify if you are proposing a rain garden. Response: The rain garden reference has been removed. V3. Comment: The sloped area south of the proposed parking lot all drain to the biofilter, but only.5 acres is shown going to the bioretention practice. It appears more than.5 acres will drain to biofilter. Please revise. Response: The .5 acre shown on the plan is the area going to new storm drain structure 3. The area (1.60 acres) going to the biofilter has been clarified with drainage area flow arrows for clarity (see Drawing No. C-12A). ✓4. Comment: Add this note on C-12 for biofilter mix. "Tested for acceptable phosphorus index between 10 and 30 or between 7 and 23 mg/kg of P in soil media. " Response: The requested note has been added to Drawing No. C-12. 5. Comment: Submit perc rate for biofilter area. (One per 1,000 sq ft of filter surface). Also, verify that the bottom of#57 aggregate is 2'above seasonably high water table. Response: The geotechnical report has been supplied with this submission. The bottom of the#57 aggregate is greater than 2' above the seasonably high water table (see communication from geotechnical engineer). 3040 Avemore Square Place •Charlottesville,VA 22911 Telephone(434) 984-2700 • Fax(434) 978-1444 Charlottesville •Lynchburg Page 2 of 5 6. Comment: Label underdrain with Schedule 40 PVC with cleanouts. Show 12"depth for#57 aggregate. Response: The underdrain has been labeled on Drawing No. C-12, cleanouts labeled in plan view on Drawing No. C-12, and cleanout detail added to Drawing No. C-12. 7. Comment: The geometry of basin does not meet spec of bioretention design criteria. Short circuiting should be prevented. Please revise. Response: A forebay has been added to the bio-filter(see Drawing No. C-12). In addition, calculations along with graphical presentation demonstrating adequate basin geometry have been added to Drawing No. C-12. Comment: Show the 2'gravel diaphragm level spreader at pretreatment area. On profile view, show the lip on level spreader. Response: A 2' gravel diaphragm with lip is located in the pretreatment area along with a detail on Drawing No. C-12. 9. Comment: I recommend moving the curb cut location away from the corner of parking lot and shifting layout of gravel spreader to enter far east side of biofilter. Response: The curb cut has been removed and a drop inlet storm drain structure 3 has been added. 10. Comment: Two rip rap strips are shown on plan, but only one profile view is shown. Please show both since one is from sidewalk and the other from the culvert under the golf cart path. My concern is that#57 stones will wash away at steeper slopes. The detail shown is for sheet flows off pavement, then into a pretreatment area that is flat. Please clarify design since the detail has been modified. Response: This area has been modified. The culvert has been replaced with a piped outfall with rip-rap apron. 11. Comment: The water quantity analysis for channel protection should show the actual drainage area to the point of analysis, such as drainage area A, B, C and existing areas. The CN should be different to drainage area. The spreadsheet shows how much phosphorus to remove, but channel analysis cannot be determined by the separate disturbed drainage areas alone since the CN is not correct. Response: The analysis has been revised to address the adequacy of the downstream channel. See drawing number C-12A for the Post-Development drainage area map and drawing number C-13 for the downstream channel 3040 Avemore Square Place • Charlottesville,VA 22911 Telephone(434) 984-2700 •Fax(434) 978-1444 Charlottesville •Lynchburg Page 3 of 5 NNW' *Mlle calculations. The post developed 2-year flow is contained within the existing drainage way and the velocity is less than 4 fps for a grassed channel. 12. Comment: Please clarify the total drainage area to pond. It appears to be larger than what is shown. Response: The drainage areas have been clarified on plan (see Drawing C-12 and C-12A). V13. Comment: Clarify the surface elevation of the bioretention area. The profile shows 607, but the plan view shows 606. Response: The profile on the site plan (SDP201400060) has been updated to reflect facility surface at elevation 6Details on Drawing No. C-12 WPO201400068 has been revised to denote facility surface at elevation 606. V 14. Comment: Relabel bioretention facility#2 under the Bioretention Facility sizing calculations. It should be bioretention facility#1. Response: The bioretention facility has been numbered accordingly on Drawing No. C-13. /15. Comment: Submit a Pollution Prevention Plan and a Stormwater Pollution Prevention Plan. Response: The PPP and SWPPP are included in this submission. C. Erosion and Sediment Control Plan(ESCP) Virginia Code§62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved, and the reasons are provided in the comments below. The erosion control plan content requirements can be found in County Code section 17- 402. 1. Comment: Sediment trap outlet needs to be extended to the bottom of the slope/disturbed soil area to prevent additional sediment loss during trap overflows. Response: The sediment trap outlet has been extended to the bottom of slope/disturbed soil as requested (see Drawing No. C-9). 2. Comment: Paved construction entrance detail needs to be on the plan. The Albemarle County Temporary Paved Construction Entrance detail can be found in the County Design Standards Manual. Response: The detail has been added to Drawing No. C-11. 3040 Avemore Square Place • Charlottesville,VA 22911 Telephone(434) 984-2700 • Fax(434) 978-1444 Charlottesville •Lynchburg Page 4 of 5 • 7 3. Comment: Please remove the bio-filter components from the E&SC plan sheets. Bio-filter components should be shown on the SWMpages. Response: The bio-filter underdrains and media have been screened for clarity (see Drawing No. C-9). This is agreed upon during our 10/9/14 meeting. We trust that the above responses and revised plans properly address the outstanding items. If you have any questions,please contact me. Sincerely, WW Associates, Inc. Robert C. Umberger Project Manager 3040 Avemore Square Place • Charlottesville,VA 22911 Telephone (434) 984-2700 • Fax(434) 978-1444 Charlottesville •Lynchburg Page 5 of 5