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9204_Wake_Sorrell_MSWLF_LFCoverMaint_FID1378510_20191205
=0 November 27, 2019 Ms. Jackie Drummond Division of Waste Management 217 West Jones Street Raleigh, North Carolina 27603 Mr. James Easthom Kennon, Craver, Belo, Craig & McKee, PLLC P.O. Box 51579 Durham, North Carolina, 27717 Reference: Landfill Cover Inspection — October 2019 Sorrell Landfill (Permit #92-04) Apex, Wake County, North Carolina S&ME Project No. 1054-07-251 Dear Ms. Drummond and Mr. Easthom: via email: jaclynne.drummond@ncdenr.gov via email:jeasthom@kennoncraver.com On October 18, 2019, representatives from S&ME, Inc. (S&ME) performed a visual inspection of the landfill cover and the storm water/surface water conveyance features at the closed Sorrell Landfill located in Apex, North Carolina. This letter report is provided to document the findings of our inspection. Services conducted by S&ME were performed in general accordance with S&ME Proposal No. P4258-07V, dated April 25, 2007, S&ME's memorandum 2079 — Landfill Cover Maintenance Cost Estimate, dated February 21, 2019, and the NCDEQ memorandum Authorization to Conduct the Spring 2019 and Fall 2079 Landfill Cover Maintenance Activities Closed Sorrell MSW Landfill, dated March 5, 2019. BACKGROUND INFORMATION Sorrell Grading Company initially operated a construction and demolition (C&D) landfill at this site, which subsequently also accepted municipal solid wastes (MSW) and similar waste materials. A Closure Plan and a Post - Closure Plan for the landfill were prepared by Stuart Jones Consulting Engineering, dated June 20, 1996 and submitted to the Section on behalf of Sorrell Grading Company. The Closure Plan provided criteria for the construction of a landfill cover consisting of a clay cap over the top 24 acres of the landfill and a vegetative layer of the top and side slopes of the landfill. The Closure Plan indicated that the side slopes were already largely constructed at that time and that the cap construction was underway. A Closure Report, dated September 7, 2001, was prepared by S&ME and submitted to the Section on behalf of Sorrell. The report detailed S&ME's evaluation of the landfill cover after the landfill had been closed and the clay cap had been placed on top of the landfill. The Closure Report described testing of the cover on the top and the side slopes of the landfill, verifying the placement and thickness of the infiltration layer and the erosion layer. Locations on the side slopes and the top of the landfill were tested. Most of the locations were found to contain adequate thicknesses of cap material. Where the thickness of the cap was insufficient, these locations were S&ME, Inc. 13201 Spring Forest Road I Raleigh, NC 276161 p 919.872.2660 1 www.smeinc.com --a Landfill Cover Inspection — October 2019 Sorrell Landfill (Permit #92-04) Apex, Wake County, North Carolina S&ME Project No. 1054-07-251 identified and repairs were to be made by the owner. Additional information on the construction and condition of the landfill cover system was described in S&ME's letter report Response to Notice of Violations, submitted to NCDENR-DWM on January 26, 2009. The May 22, 2019 landfill cover inspection was limited to an evaluation of one area of compliance: A visual inspection of the landfill cap over the top 24 acres of the landfill and the storm water/surface water conveyance features. Cutting and maintenance was performed October 14 to 16, 2019 by Carolina Outdoor Services, LLC, subcontractor to S&ME, under a separate task. S&ME personnel did not inspect the landfill side slopes which are covered by growths of pine trees, hardwoods and underbrush. OBSERVATIONS Overall, the cap and stormwater conveyance features appear to be in good condition with adequate vegetation. Three deficiencies in need of corrective measures were observed. The following features were visually identified as 1) deficient and in need of corrective measures, 2) as minor functional issues requiring monitoring or 3) as functional and not in need of corrective measures. The numbered items below correspond to the numbers on Figure 1 and to the numbered photos in the photographic log. Deficiencies A slope failure was observed on the upper portion of the steep slope on northwestern portion of the landfill property (photograph 1). The slope failure was reported in the last five cover inspections S&ME performed for the site. A small depression has formed on the landfill cap adjacent to the berm on the southeastern side of the landfill where the landfill cap is accessed (photograph 2). The depression behind the berm is preventing water from draining off the landfill, resulting in saturated soils. The depression has been degraded due to vehicle traffic while the soil is holding water and the depression has become increasingly deeper. A small depression has formed in diagonal water bar no. 1 (photograph 3). The depression formed as a result of vehicular traffic over the water bar has degraded the water bar, allowing water to settle. The depression has become increasingly degraded due to additional vehicle traffic while the soil is holding water and has become increasingly deeper. Minor Functional Issues Scouring below the stormwater outfall for the culvert draining the stormwater ditch parallel to the southern access road has been observed in previous inspection reports. While a previous inspection indicated that the outfall itself had experienced erosion, the outfall appears to be stable despite several significant rain events since the last inspection (photograph 4). The stormwater outfall for the pipe draining the stormwater ditch parallel to the southern access road appears to be functioning based on evidence of water flow. There appears to be an area where the pipe joints have become disconnected under the road (photograph 5). The disconnected areas within the pipe should be monitored for erosion and scouring which could impact the integrity of the road above. October 29, 2019 --a Landfill Cover Inspection — October 2019 Sorrell Landfill (Permit #92-04) Apex, Wake County, North Carolina S&ME Project No. 1054-07-251 A small slope subsidence was noted along the southern slope. The subsidence was approximately 1.5 feet deep and 2 feet wide. No trash is visible (photograph 6). Scouring was observed in the outfall ditch below the newly installed slope drains at Diversion Ditches/ Diagonal Water Bars Nos. 1 and 2 (photographs 7a and 7b). Evidence of vehicular traffic has been observed on the landfill. These vehicles appear to be accessing the landfill via an access road from an adjacent natural gas easement (photograph 8). Functional Items A depression was observed to the east of the base of the access road on the southwestern portion of the landfill cap which connects the landfill cap to the southern access road along the southern border of the landfill (photograph 9). During the previous inspection, in November of 2018, this depression was holding water several inches deep and showed signs of standing water having been present for an extended period. No evidence of standing water was observed in the May 2019 inspection, or during this inspection. A depression on the landfill cap adjacent to landfill gas vents GV-13 and VT-13 in the northeastern portion of the landfill was repaired during the May 2019 maintenance event (photograph 10a and 10b) and is now functional. 11. The landfill cap and access roads have been mowed to remove excess grass and vegetation. This maintenance item has been completed twice a year over the past several years, substantially improving the vegetative cover at the site. The grass and vegetation are currently an acceptable height (photographs 11 a-11 d). 12. The vegetation growing on the western hill slope of the landfill cap has been mowed and removed from the slope (photographs 12a-12d). 13. The vegetation growing in and clogging slope drain inlets 1 and 2 and their associated headwalls has been cut and removed. The slope drain inlets and their associated headwalls are functioning as designed (photographs 13a to 13d). 14. The vegetation previously growing in and clogging the headwall structures at the entrance of the slope drains at water diversion bars No. 1 and 2 has been cut and removed (photographs 14a-14b). 15. The vegetation growing in and clogging the drainage ditch running parallel to the landfill along the southern access road has been removed and treated (photographs 15a and 15b). The approximate location of each of the above items is labeled on the attached Site Plan drawing (Figure 1). October 29, 2019 --a RECOMMENDED CORRECTIVE MEASURES Landfill Cover Inspection — October 2019 Sorrell Landfill (Permit #92-04) Apex, Wake County, North Carolina S&ME Project No. 1054-07-251 S&ME recommends the following corrective measures for each observed item: Deficiencies The slope failure should be evaluated by a qualified professional to determine the cause of the failure and repaired according to their recommendations to prevent further damage to the landfill cap, soil erosion, or exposure of waste. The depression behind the berm, within the access road, holding water, should be stabilized by filling the depression with soil or gravel to prevent the depression from increasing in size when vehicles drive through this location when soil is saturated. The depression behind diagonal water bar No. 1, holding water, should be stabilized by filling the depression with soil to prevent the depression from increasing in size when vehicles drive through this location when soil is saturated. Minor Functional Issues: Rip rap had previously been installed within the stormwater outfall where scouring was occurring. While the previous inspections indicated that the rip rap was being relocated within the outfall during high flow events, there has been no additional scour or rip rap relocation in the outfall since the last inspection. The outfall should continue to be monitored for any further rip rap displacement or scour below the outfall. If further damage is observed, larger rip rap should be installed to prevent further degradation of the outfall and to prevent relocation of the newly installed rip rap during high flow periods. The disconnected joint in the pipe should be monitored for evidence of scouring or erosion between the joints. Should the level of erosion or scouring reach levels where it could impact the integrity of the road, the pipe should be repaired or replaced. The small slope subsidence should be monitored for an increase in depth or size. If the area increases in size, it should be filled, graded, and stabilized with vegetation. The subsidence has not increased in size since the last inspection. The scouring below the outfalls for the slope drains in the Diversion Ditches/ Diagonal Water Bar Nos. 1 and 2 should be monitored for further erosion. Should further erosion be observed, efforts should be undertaken to stabilize the eroded areas. No further erosion has been observed since the last inspection. 8. Measures should be taken to prevent vehicular traffic from accessing the landfill via the adjacent natural gas easement. Functional Issues: S&ME recommends that the landfill cap continue to receive regular, bi-annual mowing of the landfill cap in the spring and fall to promote the health of the vegetative cover. Areas of settlement, and depressions, holding water should continue to be identified, monitored and repaired to promote water draining off the landfill cap and minimize standing water above waste. October 29, 2019 4 =0 Landfill Cover Inspection - October 2019 Sorrell Landfill (Permit #92-04) Apex, Wake County, North Carolina S&ME Project No. 1054-07-251 CLOSING S&ME appreciates the opportunity to provide these services and hopes that you find this report to be complete and informative. We would appreciate an opportunity to discuss our findings and recommendations with you. Please call us at (919) 872-2660 if you have any questions or comments, or if we can be of further assistance. Sincerely, S&ME, Inc. 0/11t 6pt�- Ashley Bentz, P.W.S Project Scientist abentz@smeinc.com Attachments: Samuel P. Watts, P.G. Senior Project Manager swatts@smeinc.com Attachment I - Photographic Log Attachment 11 - Figure 1 — Cover Inspection Site Map October 29, 2019 Attachments T 1 View of a portion of slope failure on the northwestern slope looking across the hill (looking east). small depression has developed within diagonal water bar no.1 sere vehicular traffic has degraded the water bar. 0 SWE Project No. 1054-07-251 III _ Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina 5 View of the pipe connecting the ditch north of the southern access road to the ditch south of the access road along the r r I okina southwest). .s %a iew of scouring at outfall of slope drains installed within Diversion Ditch/ Diagonal Water Bar no. 1. ;A'. 6View of small slope subsidence in landfill cap on southern slope just north of MW-8 (looking north). 7%View of scouring at outfall of slope drains installed within Diversion Ditch/ Diagonal Water Bar no. 2. S&ME Project No. 1054-07-251 Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina View of access road where vehicles appear to be entering the perimeter road and landfill footprint from an adjacent natural Oa A depression north of landfill gas vents GV-13 and VT-13 2 was repaired in May 2019 maintenance event using fill material and 0 S&ME Project No. 1054-07-251 Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina S&ME Project No. 1054-07-251 Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina �rY 9,n i S rak, _. 12biew of the recently mowed back (western) slope of the landfill cap looking downhill from the top of the cap. 12d iew of the recently mowed back (western) slope of the landfill cap looking uphill from the access road. 0 S&ME Project No. 1054-07-251 III _= Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina Ar •. 13View a of Slope Drain #1 Inlet/ Headwall, which has recently had he woody vegetation removed (looking south). I — �j Vogl _ M1 Nil 13c View of Slope Drain #2 Inlet/ Headwall, which has recently had he woody vegetation removed (looking west). 0 S&ME Project No. 1054-07-251 Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina 14a View of Diversional Ditch/ Diagonal Water Bar #1 (looking south). `µl F. K 15a Vegetation growing in and clogging the drainage ditch along the southern landfill boundary has been removed and treated. S&ME Project No. 1054-07-251 Landfill Cover Inspection Taken by: A. Bentz Date Taken: 10-18-2019 Sorrell Landfill, Apex, Wake County, North Carolina © POTABLE WELL APPROXIMATE LIMITS OF CAP APPROXIMATE WASTE BOUNDARY 49 TOPOGRAPHIC CONTOUR LINES HYDROLOGIC FEATURE FENCE LINE GRAPHIC SCALE 200 0 100 200 ( IN FEET ) rn O w Lo Lu w O N co N 2 t` m V II z 4 zLo w O Z N m LLI10 C N O z F U : z (oJ W 4g � wLL z (D UK JO w (7 wz zof (9a zu) w= rn 0 N W 00 O H O z Z J J O LL ry Q U z U �0- a= H? LJu 0 Of O (n w 0 z > O X O L7 Lu J Q J_ LL 0 z Q J FIGURE NO. 1