Annual Inspection Report of CCR Impoundment and CCR Landfill Wenck Project # B

Transcription

1 Technical Memo To: Brian Trower, From: Peter Daniels, PE (Iowa PE# 21569) Dave Parenteau, PE (MN), Wenck Associates, Inc. Date: Subject: Annual Inspection Report of CCR Impoundment and CCR Landfill Wenck Project # B I hereby certify that this engineering document was prepared by me or under my direct supervision and that I am a duly registered Professional Engineer under the laws of the State of Iowa. Peter Daniels Jan. 15, 2016 PE # Expiration Date Dec. 31, 2016 Purpose This memorandum fulfills the requirements of 40 CFR (b) Inspection Requirements for CCR Surface Impoundments and of 40 CFR (b) Inspection Requirements for CCR Surface Landfills. Part b of both rules specifies the annual inspection by a qualified professional engineer. Background and Applicability The City of Ames, IA (City) operates a municipal power plant located at 200 East 5 th Street in Ames, IA (See Figure 1). The power plant has historically generated electricity using two coal fired units. Prior to October 19, 2015, ash from the coal burning process was sluiced to an ash pond impoundment on-site. In addition, the site operated a landfill area where coal combustion residuals (CCR) are stored for future beneficial use. Figure 2 presents a layout of the pond and landfill areas. The plant is currently being converted to use natural gas as the fuel source. This conversion will eliminate the use of coal when it is complete. As of October 19, 2015, The City ceased Wenck Associates, Inc Olson Memorial Highway Suite 300 Golden Valley, MN Toll Free Main wenckmp@wenck.com Web wenck.com

2 sluicing of CCR into their ash receiving pond (surface impoundment), and they no longer dispose of CCR in the landfill. The landfill and surface impoundment are therefore considered inactive but have not yet been closed. CCR Surface Impoundment Inspection (40 CFR ) and CCR Landfill Inspection (40 CFR ) On October 13, 2015, Dave Parenteau conducted the on-site inspection of both the CCR Impoundment and the CCR Landfill (CCR units). During his inspection the following activities were performed. Reviewed available information regarding status and condition of the CCR unit. The items reviewed are discussed below. 1. CCR unit design and construction information required by (c)(1) and (c)(1). Information pertaining to the CCR unit design and construction was obtained from an October 2012 draft report by Dewberry & Davis, LLC, titled Coal Combustion Residue Impoundment Round 12 Dam Assessment Report, City of Ames Power Plant Lime and Ash Ponds. The report included soil borings and design plans/specifications for the facility. (Results of construction quality assurance testing, construction record drawings/specs, and other information about the construction activities, are not in the report, and if ever available, were not found). 2. Previous periodic structural stability assessments required under (d) and under (d); It should be noted that does not apply as the site is not new, nor is it a lateral expansion of an existing impoundment/landfill, therefore this is not addressed. To our knowledge, previous structural stability assessments for the facility have not been performed. The City has contracted with Wenck Associates to complete this work. The field investigation was completed in Fall 2015, and upon receipt of laboratory soil strength results, the slope stability analysis will be conducted. 3. The results of inspections by a qualified person. There have been no previous inspections by a qualified person (in accordance with 40 CFR (a) and 40 CFR (a)), prior to October 19, 2015, of the facility. 4. Results of previous annual inspections. There have been no previous annual inspections of the facility. Performed a visual inspection of the CCR units to identify signs of distress or malfunction of the CCR unit and appurtenant structures. There were no observed signs of distress or malfunction on either the CCR Impoundment or the CCR Landfill and their corresponding appurtenant structures other than some minor shallow erosion on some of the inboard slopes of the south berm of the impoundment (see Figure 2). 2

3 Given the width of the crest of the embankment, the pond level at the time of the inspection and the fact that these ponds are no longer in use, this is considered to be a minor, temporary issue. The ponds will be filled in as part of the closure strategy and the inboard slopes will no longer be exposed. The slope stability analysis Wenck is conducting will verify that this does not pose an unacceptable risk of failure. Performed a visual inspection of any hydraulic structures underlying the base of the CCR Impoundment or passing through the dike of the CCR Impoundment for structural integrity and continued safe and reliable operation. There are no hydraulic structures underlying the base of the CCR Impoundment. However, there is an outlet to the adjacent Clear Water Pond that passes through the dike separating the CCR Impoundment and the Clear Water Pond. There were no signs of distress or malfunction of this pipe that passes through the dike. Given that the CCR Impoundment is no longer active, this outlet structure pipe can be abandoned during closure. CCR Surface Impoundment Inspection Report 40 CFR (b)(2) requires the following topics in italics be addressed within this report. The requirements are shown in italics with the response immediately afterwards for each item. (i) Any changes in geometry of the impounding structure since the previous annual inspection; There were no apparent changes from the geometry of the impoundment when compared to the 2012 Dewberry report or the historical construction drawings contained therein. (ii) The location and type of existing instrumentation and the maximum recorded readings of each instrument since the previous annual inspection; There are 3 piezometers present, however, since this is the initial inspection and there is no previous annual inspection (or report), there are no previously recorded readings available. As is stated in the 2012 Dewberry report; given the small size and storage volume of the pond, the need for instrumentation does not appear to be merited. (iii) The approximate minimum, maximum, and present depth and elevation of the impounded water and CCR since the previous annual inspection; This inspection is the initial annual inspection, so there is no previous annual inspection data. The approximate maximum depth of impounded water possible in the pond is 10 feet. At the time of the inspection there was approximately 4-6 feet of water present in the pond. 3

4 (iv) The storage capacity of the impounding structure at the time of the inspection; The combined footprint of the CCR units and Clear Water Ponds is 12.7 acres. The acreages of these units are as follows: Clear Water Ponds 2.8 Acres; CCR Landfill 3.5 Acres. The remaining 6.4 acres make up the CCR Impoundment. The storage capacity of the CCR Impoundment is approximately 65 acre feet. The Clear Water Ponds do not receive or contain CCR and are therefore not subject to the inspection requirements herein. Figure 2 presents a layout of the footprint described above. (v) The approximate volume of the impounded water and CCR at the time of the inspection; At the time of the inspection there was approximately 26 acre feet of water and CCR impounded. (vi) Any appearances of an actual or potential structural weakness of the CCR unit, in addition to any existing conditions that are disrupting or have the potential to disrupt the operation and safety of the CCR unit and appurtenant structures; and None of the following were observed that could indicate structural weakness: o Signs of slumping or rotational movement. The only movement noted was shallow erosional movement of the inboard slope in very small localized areas. o Lateral or vertical distortion of the embankment crest o Seepage on the outboard slope o Burrowing activity of varmints (vii) Any other change(s) which may have affected the stability or operation of the impounding structure since the previous annual inspection. CCR Landfill Inspection Report There were no changes noted since the 2012 inspection by Dewberry that may have affected the stability or operation of the impoundment. Observations were consistent with those noted in that report. 40 CFR (b)(2) requires the following topics in italics be addressed within this report. The requirements are shown in italics with the response immediately afterwards for each item. 4

5 Deficiencies or Releases (i) Any changes in geometry of the impounding structure since the previous annual inspection; There were no apparent changes from the geometry of the impoundment when compared to the 2012 Dewberry report or the historical construction drawings contained therein. (ii) The approximate volume of CCR contained in the unit at the time of the inspection; The approximate volume of CCR material contained in the landfill at the time of the inspection is 80,000 cubic yards. (iii) Any appearances of an actual or potential structural weakness of the CCR unit, in addition to any existing conditions that are disrupting or have the potential to disrupt the operation and safety of the CCR unit and appurtenant structures; and None of the following were observed that could indicate structural weakness: o Signs of slumping or rotational movement o Lateral or vertical distortion of the embankment crest o Seepage on the outboard slope o Burrowing activity of varmints (iv) Any other change(s) which may have affected the stability or operation of the impounding structure since the previous annual inspection. There were no changes noted since the 2012 inspection by Dewberry that may have affected the stability or operation of the impoundment. Observations were consistent with those noted in that report. 40 CFR (b)(5) and 40 CFR (b)(5) each require that if a deficiency or release is identified during an inspection, the owner or operator must remedy the deficiency or release as soon as feasible and prepare documentation detailing the corrective measures taken. There were no deficiencies or releases identified during the inspection that require remedy as soon as possible. The only deficiency noted was the shallow erosion in an isolated area of the CCR impoundment and given that the impoundment is no longer active and is intended to undergo closure by April 17, 2018, there is no apparent need for an immediate remedy. 5

6 Site Location Ames, IA Composite Aerial Photograph (Source: Iowa 2,640 1, ,640 Path: L:\3349\0001\MXD\Site Location Map.mxd Date: 10/8/2015 Time: 3:46:57 PM User: ShuJC0243 Feet ± Iowa Department of Transportation - Office of Systems Planning, Iowa Department of Transportation, USGS, Department of Natural Resources, Iowa and Nebraska counties AMES MUNICIPAL ELECTRIC SYSTEM Site Location Map JAN 2016 Figure 1

7 Ash Pond System Ash Storage Area (CCR Landfill) Ash Pond System Ash Storage Area (CCR Landfill) Ash Pond System Clear Water Basin Clear Water Basin Area of Localized Shallow Erosion of Inboard Slope 2012 Aerial Photograph (Source: ESRI) Path: L:\3349\0001\MXD\Site Layout.mxd Date: 1/15/2016 Time: 2:14:39 PM User: OlsRL0755 Feet ± Legend Dikes Inspected Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus Armes Ash DS, and USDA, Lime USGS, Pond Site AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community AMES MUNICIPAL ELECTRIC SYSTEM JAN Pond Layout Figure 2