Schriever_2013_I-I_Study.pdf

4P Architect-Engineer (4PAE08) Services Air Force Civil Engineer Center

FINAL INDUSTRIAL INFLOW-INFILTRATION

ASSESSMENT FOR

SCHRIEVER AIR FORCE BASE, COLORADO

August 2013

Submitted to:

Department of the Air Force

772 ESS/PKS

2261 Hughes Avenue, Suite 163 Lackland AFB, TX 78236-9861

50 CES/CEIE

Attention: Mr. Andrew Jensen 500 O’Malley Avenue Schriever AFB, CO 80912

Prepared by:

Tetra Tech, Inc.

7222 Commerce Center Drive, Suite 260 Colorado Springs, CO 80919

4P ARCHITECT-ENGINEER (4PAE08) SERVICES

CONTRACT NO. FA8903-08-D-8781, Task Order 0171

TASK ORDER NO. 0171 TETRA TECH, INC.

Final Industrial Inflow-Infiltration Assessment for Page E-1 Schriever Air Force Base, Colorado

EXECUTIVE SUMMARY

This Industrial Inflow-Infiltration Assessment for Schriever Air Force Base (AFB) documents the technical approach and methodology for providing a complete inventory and condition assessment of the wastewater system, characterization of industrial wastewater inflows, and identification of wastewater system repairs/upgrades to improve the overall function of the wastewater system on base. This report outlines the results from the wastewater asset inventory, condition assessment, industrial flow characterization, and provides recommendations based on the completed work.

Schriever AFB owns and operates a wastewater collection system to manage wastewater produced on base property. With the exception of several septic tank and leach field systems on base, the Schriever AFB wastewater system conveys all sanitary and industrial wastewater generated on base to an outfall located at the southern base boundary. This outfall discharges wastewater into the Cherokee Metropolitan District (CMD) wastewater system for treatment and disposal at a CMD owned Wastewater Treatment Plant (WWTP). In 2012, CMD observed high wastewater flow rates discharge from Schriever AFB at the outfall into the CMD wastewater collection system. CMD implied that the high wastewater discharge flow rates were attributable to storm water inflow to the Schriever AFB wastewater collection system.

The purpose of this project was to evaluate the Schriever AFB wastewater collection system to better understand connectivity and condition of wastewater assets as well as identify potential sources of high wastewater flow rates. This report does not include sanitary wastewater flows from Military Family Housing (MFH). MFH on Schriever AFB is privatized and connected to the CMD conveyance system through a dedicated collection system within MFH.

Tetra Tech, Inc. (Tetra Tech) completed a comprehensive inventory of 541 wastewater assets on base without confined space entry through the use of pole cameras and Closed Circuit Television (CCTV) investigation. The asset inventory confirmed the location, connectivity, size, material, slope, type, and invert elevations for all wastewater assets. Tetra Tech field personnel also photo documented the interior and exterior of each asset, obtained X, Y, and Z coordinates for 100 percent of wastewater assets with 84 percent of the coordinates having survey grade accuracy. Tetra Tech developed an updated geodatabase compliant with the appropriate Spatial Data Standards for Facilities, Infrastructure and Environment (SDSFIE) feature class requirements.

Tetra Tech completed a condition assessment of each wastewater asset, including 1,342 manhole components, to characterize maintenance and structural defects. Condition assessment activities were meant to identify and prioritize system upgrades. The condition assessment found that approximately 87 percent of all wastewater assets on base are in “good” or “excellent” condition and approximately 9 percent of all wastewater features on base are in “poor” or “very poor” condition. Based on condition assessment activities, there does not appear to be a significant volume of stormwater inflow into the Schriever AFB wastewater system.

During the inventory and condition assessment phase of this project, Tetra Tech identified two major sources of high flow rates within the wastewater collection system at Building 600 and Building 720.

Temporary flow meters were installed at Building 600 and Building 720 to characterize wastewater discharges from these facilities. The flow meter recorded average daily total flows up to 20,000 gallons and maximum daily peak flows reached flow rates as high as 190 Gallons Per Minute (GPM).

Using the asset inventory, condition assessment, and flow meter results, Tetra Tech developed capital improvement project recommendations as well as operation and maintenance recommendations to improve the overall function of the wastewater system at Schriever AFB.

TETRA TECH, INC. TASK ORDER NO. 0171

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Final Industrial Inflow-Infiltration Assessment for Page i Schriever Air Force Base, Colorado

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 BACKGROUND

1.2 APPROACH

1.3 REPORT ORGANIZATION

2.0 DATA REVIEW AND EVALUATION

2.1 EXISTING DATA

2.2 DATA GAPS

3.0 DATA COLLECTION

3.1 ASSET INVENTORY AND CONDITION ASSESSMENT

3.1.1 Field Guides

3.1.2 Asset Inventory

3.1.3 Condition Assessment

3.1.4 Junction Point (Manhole) Inventory

3.2 CLOSED CIRCUIT TELEVISION INVESTIGATION

3.3 FLOW MONITORING

4.0 RESULTS

4.1 GEODATABASE UPDATE

4.2 ASSET INVENTORY

4.3 CONDITION ASSESSMENT

4.4 CLOSED CIRCUIT TELEVISION INVESTIGATION RESULTS

4.5 WASTEWATER FLOW MONITORING

4.5.1 Wastewater Flow Monitoring at Building 600

4.5.2 Wastewater Flow Monitoring at Building 720

5.0 RECOMMENDATIONS

5.1 CAPITAL IMPROVEMENT RECOMMENDATIONS

5.1.1 Septic Tank Permitting or Connection to Wastewater System

5.1.2 Manhole Interior Repairs

5.1.3 Wastewater Line Slope Rehabilitation

5.1.4 Wastewater Line Repair or Replacement

5.2 OPERATION AND MAINTENANCE RECOMMENDATIONS

5.2.1 Cleaning, Closure or Abandoning of Tanks

5.2.2 Manhole Surface Maintenance

5.2.3 Manhole Interior Maintenance

5.2.4 Wastewater Line Maintenance

APPENDICES

A CONDITION ASSESSMENT GUIDE

B ARCPAD USER’S MANUAL

C WASTEWATER SYSTEM OVERALL MAP

D CONDITION ASSESSMENT MAP

E CCTV MAP AND FIELD NOTES

F CAPITAL IMPROVEMENT RECOMMENDATIONS

G OPERATION AND MAINTENANCE RECOMMENDATIONS

Page ii Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado

TABLE OF CONTENTS (Continued)

LIST OF FIGURES

3-1 GPS Field Crew Setup 3-2 GPS Point Collection Example 3-3 QuickView Camera 3-4 ArcPad Input Screen Capture 3-5 Junction Point Components 3-6 Typical FloDar Installation

4-1 Condition Assessment Results for Junction Points 4-2 Condition Assessment Results for Cleanouts 4-3 Condition Assessment Results for Septic Tanks 4-4 Condition Assessment Results for All Pipes 4-5 Condition Assessment Results for All Wastewater Features on Base 4-6 Building 600 Wastewater Flows 4-7 Building 720 Wastewater Flow Rates (Monday April 29, 2013) 4-8 Building 720 Wastewater Flow Rates (Tuesday April 30, 2013)

LIST OF TABLES

2-1 Summary of Data Review

4-1 Wastewater Asset Inventory Results 4-2 Building 600 Wastewater Flow Results 4-3 Building 720 Wastewater Flow Results

5-1 OWTS Permitting Costs 5-2 OWTS Connection to Collection System Costs

Final Industrial Inflow-Infiltration Assessment for Page 1 Schriever Air Force Base, Colorado

1.0 INTRODUCTION

This Industrial Inflow-Infiltration Assessment for Schriever Air Force Base (AFB) documents the technical approach and methodology for providing a complete inventory and condition assessment of each wastewater system asset, a Closed Circuit Television (CCTV) investigation, wastewater flow monitoring, and identification of wastewater system upgrades and maintenance recommendations to improve the overall function of the wastewater system at Schriever AFB. This document will assist Schriever AFB personnel with planning key wastewater system upgrades and improve overall wastewater conveyance system performance for the installation.

1.1 BACKGROUND

Schriever AFB owns and operates a wastewater collection system to manage wastewater produced on base property. With the exception of several septic tank and leach field systems on base, the Schriever AFB wastewater system conveys all sanitary and industrial wastewater generated on base to an outfall located at the southern base boundary. This outfall discharges wastewater into the Cherokee Metropolitan District (CMD) wastewater system for treatment and disposal at a CMD owned Wastewater Treatment Plant (WWTP). In 2012, CMD observed high wastewater flow rates discharge from Schriever AFB at the outfall into the CMD wastewater collection system. CMD implied that the high wastewater discharge flow rates were attributable to storm water inflow to the Schriever AFB wastewater collection system.

1.2 APPROACH

Tetra Tech, Inc. (Tetra Tech) performed a comprehensive inventory of the Schriever AFB wastewater system, condition assessment for each wastewater system asset, CCTV investigation, and wastewater flow monitoring to characterize the Schriever AFB wastewater system. Based on these activities, Tetra Tech developed capital improvement and maintenance recommendations to improve overall system functionality. Specific project tasks included:

Review and Evaluation of Existing Data Collect and review all available data necessary to identify wastewater system components, wastewater system data gaps, and highlight specific areas of concern related to the wastewater system.

Data Collection Perform field data collection activities at all wastewater system assets to understand system characteristics and condition, wastewater sewer connectivity, and system maintenance or structural concerns. Perform a CCTV investigation of wastewater lines with structural or maintenance defects. Perform wastewater flow monitoring using ultrasonic flow meters.

Data Analysis and Processing Using the asset inventory, condition assessment, and CCTV; create an accurate and complete Geographic Information System (GIS) database for the wastewater system according to the Spatial Data Standards for Facilities, Infrastructure and Environment (SDSFIE) framework.

Using the flow monitoring data, characterize the source and quantity of industrial and/or inflows entering the wastewater system.

Page 2 Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado

Summary Report Develop this Industrial Inflow-Infiltration Assessment to summarize results of the data review, data collection, and data analysis to provide summary of industrial inflow and/or infiltration issues and capital improvement and maintenance recommendations for improving the overall of function of the wastewater system on base.

1.3 REPORT ORGANIZATION

Section 1.0, Introduction, briefly discusses the purpose and goals of this report and Tetra Tech’s approach for developing this report. Section 2.0, Data Review and Evaluation, provides a summary of the data collection process and Section 3.0, Data Collection, provides the field data collection methodology for the asset inventory, CCTV, and flow monitoring. Section 4.0, Results, provides the results of the asset inventory and condition assessment, CCTV, and flow monitoring of the wastewater system on base.

Section 5.0, Recommendations, provides recommended capital improvement projects and maintenance activities to improve the overall function of the wastewater system on base.

The appendices presented in this report include the Condition Assessment Guide; ArcPad User’s Manual;

updated Wastewater System Map; Condition Assessment Map; CCTV Results Map and Field Notes;

Capital Improvement Recommendations; and O&M Recommendations.

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2.0 DATA REVIEW AND EVALUATION

Tetra Tech used existing base data and data from other sources to create a baseline database for wastewater assets on base.

2.1 EXISTING DATA

The data collected from base personnel established the baseline data required to support the geographical information system (GIS) database wastewater layers and a basic understanding of the current status of the wastewater system on base. Tetra Tech received a GIS geodatabase from Schriever AFB GIS and this data was used as a baseline for completing the asset inventory and condition assessment. The GIS data contained features for the majority of wastewater system assets on base including junctions, sewers, fitting points, septic tanks, oil water separators, meters, and pumps. The geodatabase also included CMD wastewater lines that ultimately convey wastewater flows from Schriever AFB. Table 2-1 summarizes the existing base data collected by Tetra Tech in support of this project. Tetra Tech also used outside sources such as the Environmental Systems Research Institute (ESRI) to develop portions of the original database.

Table 2-1 Summary of Data Review

Dataset Type Description Source

Aerial Imagery

JPG Provides aerial view of base infrastructure for reference in ArcPad

ESRI Imagery

Wastewater Infrastructure

Geodatabase Identifies junctions, sewers, fitting points, septic tanks, grit chambers, grease traps, oil water separators, meters, and pumps.

Schriever AFB GIS

CMD

Wastewater Infrastructure

Geodatabase Identifies sewer lines belonging to CMD outside the base boundary.

Schriever AFB GIS

2.2 DATA GAPS

The wastewater infrastructure dataset provided a good understanding of wastewater infrastructure on base but had several data gaps, including:

Outdated or missing wastewater components such as septic tanks, meters, pumps, etc.;

Missing invert elevations for 80 percent of manholes and sewers;

Incorrect or missing pipe diameter;

Incorrect or missing pipe material;

Missing or incorrect sewer connectivity; and

Missing condition data.

These existing data gaps can create problems for Air Force personnel in understanding the system function or planning future wastewater system maintenance and repair.

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3.0 DATA COLLECTION

Tetra Tech used three methods to collect wastewater system data at Schriever AFB. The first was an inventory and condition assessment of all assets; the second was a CCTV investigation of problem areas;

and the third was monitoring of wastewater flows at specific locations.

3.1 ASSET INVENTORY AND CONDITION ASSESSMENT

The asset inventory and condition assessment field data collection effort included obtaining GPS coordinate of all wastewater assets on base and documenting condition and attribute information to develop an updated GIS geodatabase. The following sections discuss inventory and condition assessment activities.

3.1.1 Field Guides

Tetra Tech developed two field guides that outline the methodology for standardizing the field investigation processes presented in this report. These guides are intended to assist Air Force users in replicating the field data collection process during future wastewater system updates and data collection activities. The field guides include:

Condition Assessment Guide, Appendix A; and

ArcPad User’s Manual, Appendix B.

The Condition Assessment Guide, Appendix A, provides the methodology for rating the condition, or the current level of quality, of each wastewater asset on base. The results of the condition assessment provide insight into areas of the wastewater system requiring maintenance or repair and assist in identifying regions of the base with aging infrastructure.

Appendix B provides a user’s manual for the ArcPad 8 software that guides the user through the data entry and collection process. Tetra Tech utilized ArcPad Version 8 to collect field data for each wastewater asset.

3.1.2 Asset Inventory

The first phase of the field investigation used the existing wastewater system geodatabase as a baseline for developing the comprehensive inventory of all wastewater infrastructure assets on base. The existing geodatabase was compiled into a map book of the base with aerial imagery overlaid with wastewater system assets. These maps served as a guide for field crews to use for locating structures and completing the condition assessment.

The GPS data collection was performed using single-man crews. Each crew was equipped with a survey grade GPS transmitter and Leica 1230 data collection unit attached to a surveying rod. Figure 3-1 shows a typical one-man GPS crew setup.

Final Industrial Inflow-Infiltration Assessment for Page 5 Schriever Air Force Base, Colorado

Figure 3-1 GPS Field Crew Setup

The crews used known control points on base to check horizontal and vertical GPS accuracy at the beginning, middle, and end of each day. The crews visited every wastewater system asset denoted on the existing geodatabase hard copy maps and added wastewater system features that were found in the field but may not have been identified in the existing geodatabase. This was the case for several septic tanks without access points called out in the database or cleanouts not identified in the original database. The features in this area were new and therefore had not been updated in the geodatabase. The field crews added the horizontal and vertical coordinates for each new feature, including the new features in the vicinity of this new construction.

Tetra Tech located, verified, and compiled GPS locations for each wastewater feature on base including junctions, fitting points, septic tanks, grease traps, grit chambers, oil water separators, meters, and pumps.

No GPS data was collected for wastewater lines since these features are connected to the GPS locations for their end-of-pipe features (i.e. two manholes for each wastewater line). The GPS field crews did not confirm or update feature types during the GPS data collection process. Feature types would be confirmed during the next phase of the project where field crews were equipped to open features and verify utility types.

Choosing the exact location of the survey rod during the GPS data collection effort was critical to developing consistent results. All crews used the same methodology to select the placement of the GPS unit. In general, the GPS point is the geometric center of the length of the asset. This is illustrated in Figure 3-2. Spot elevations were always measured at the surface elevation, not the invert elevation. Pipe invert elevations were measured during the full inventory process following the GPS data collection.

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Figure 3-2 GPS Point Collection Example

The accuracy of the GPS data is less than one inch horizontally and vertically for every asset that was surveyed with the Leica 1230 survey unit. However, some system assets on base were under tree coverage or in locations where satellites were blocked. The GPS data for these system assets was collected with a handheld Trimble GeoXH, which provides sub-centimeter horizontal and sub-meter vertical accuracy.

3.1.3 Condition Assessment

The condition assessment phase was performed using two-person crews. During this phase, Tetra Tech field crews visited each wastewater system asset, obtained critical attribute information, and performed a condition assessment. Of each crew, one crew member was dedicated to operating the pole camera and one crew member was dedicated to operating the tablet data collection device. The pole camera used during field investigations was an Envirosight QuickView® camera mounted to a 25 foot extendable carbon fiber pole. Figure 3-3 shows the QuickView® camera operating in a shallow junction point. The camera is connected via cables to the tablet data collection device. The crew member operating the pole camera is able to view the interior of the pipe and zoom in, zoom out, take photos, measure distances, and inspect the pipes without entering the confined space. The QuickView® camera is limited to line-of-sight photographs; if the lines were offset or if there was a bend prior to the next manhole, the photograph was of a limited section of sewer.

Figure 3-3 QuickView Camera

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The data collection field member was equipped with a Lenovo ThinkPad Tablet 2 (tablet) with Windows 8. The tablet was equipped with a high-resolution camera and ArcPad 8.0 software. The tablet internal cameras were directly linked to the ArcPad program so that surface and interior structure photos could be taken and loaded directly into the data fields for a given asset. In addition, a micro-Universal Serial Bus (USB) connected the tablet to the pole camera for directly inserting the pipe photos into the GIS data in ArcPad.

The procedure for the field condition assessment of a wastewater feature was as follows:

1) Identify–determine the feature type.

2) Classify–characterize the interior and exterior condition of the feature and associated piping, according to the guidelines provided in the Condition Assessment Guide in Appendix A.

3) Document–photograph feature and record feature maintenance and/or structural defects according to guidelines in the Condition Assessment Guide in Appendix A.

4) Finalize–save feature data to the handheld device and mark as “complete”.

Tetra Tech used the SDSFIE to determine wastewater features and attribute data that should be collected as part of the asset inventory. The SDSFIE feature classes include:

Point features:

Junctions, Cleanouts (fitting points), Septic tanks, Grease traps, Grit chambers, Oil water separators, Meters, and

Pumps.

Line features:

Wastewater line

Based on feature attribute data provided in the SDSFIE standards, such as “pipe diameter” for a sanitary pipe, Tetra Tech developed “forms” or electronic data sheets in the ArcPad software to allow the field crew member to enter data for each wastewater feature by using drop down menus and a keyboard.

Detailed attribute data was compiled for each feature and saved to the handheld tablet computer. The ArcPad User’s Manual is provided in Appendix B. A screen shot of one of the ArcPad software “forms” for a wastewater line is provided in Figure 3-4.

Page 8 Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado

Figure 3-4 ArcPad Input Screen Capture

The field team then classified the condition of the exterior and interior of each wastewater feature on a rating scale of “excellent” to “very poor.” Photographs of the interior and exterior of the feature were taken with the handheld device and saved with the condition assessment data.

Any wastewater feature with a condition rating of “average” or worse was assigned a “defect” code for maintenance or structural issues. Interior photos for each wastewater line were taken with the QuickView® camera, which also allowed the field crews to investigate pipe defects. The following attribute data was collected for each wastewater system asset and will be available in the updated Geodatabase for wastewater system assets:

Structure Type, Structure ID, Pipe Material *, Pipe Diameter *, Pipe Type *, Invert Elevation *, Length *, Inspection Date, Weather, Interior and Exterior Photographs, Maintenance Defects, Structural Defects, Exterior Condition Rating, Interior Condition Rating, and

Comments and Narrative.

Note: * Attribute only collected for applicable features.

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3.1.4 Junction Point (Manhole) Inventory

Additionally, Tetra Tech performed a thorough inventory of each component of wastewater junction points on Schriever AFB. A typical junction point cross section is shown in Figure 3-5. For each junction point, Tetra Tech used the Lenovo ThinkPad devices to collect the wastewater feature data listed above and also junction point specific data to classify structural and maintenance defects to each component shown in the figure.

Figure 3-5 Junction Point Components

All data and photos collected during the inventory process were stored on the handheld devices. Tetra Tech processed the collected data and generated an initial update of the wastewater GIS layers. The inventory reports for each wastewater feature on base have been provided to base personnel as a supplement to this report.

3.2 CLOSED CIRCUIT TELEVISION INVESTIGATION

Tetra Tech performed line cleaning and CCTV investigation of 11,450 linear feet of wastewater line segments on base. Tetra Tech and Schriever AFB personnel selected line segments for CCTV investigation based on condition assessment activities discussed above and discussions with maintenance personnel. Prior to CCTV inspection, the line was jetted and cleaned with high pressure water to allow

Page 10 Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado the video camera to pass through the line segment and have a clear picture of pipe walls. The CCTV investigation was limited to sewers 6 inches or greater in diameter due to the size of the camera device.

Inspection of each line segment was performed in accordance with the Pipeline Assessment & Certification Program (PACP) guidelines for coding defects in sanitary sewers developed by the National Association of Sewer Service Contractors (NASSCO). The CCTV investigation recorded video of each line segment and line segment details such as material, diameter, and shape were recorded. These observations were compared to the asset inventory previously completed to ensure accuracy of sewer segment characteristics.

CCTV investigation resulted in defect codes for the entire pipe segment which provides a more comprehensive understanding of the defects within each segment of piping as compared to condition assessment using pole-cameras. The defect codes identified during the CCTV investigation were stored in an Access database and entered into the GIS database for each corresponding wastewater line segment.

The results of the CCTV investigation are discussed in Section 4.0.

3.3 FLOW MONITORING

During the wastewater system inventory and condition assessment, Tetra Tech identified two buildings with significant wastewater flows entering the wastewater system. The observed flow rates in the sewers from both of these buildings were noticeably higher than typical sanitary flow rates. The buildings included Building 600 and Building 720 inside the Restricted Area (RA).

Tetra Tech installed a flow meter (Flo-Dar) at the junction point immediately downstream of each building to characterize the flow rate and duration of these discharges. The flow meters were installed approximately 12 inches above the sewer invert. The flow meter measures the water depth in the pipe and velocity of the water passing the meter using an ultrasonic sensor. Knowing the pipe geometry, the flow meter can automatically calculated the flow rate in the wastewater line and stored flow data for a period of three days at both buildings.

Figure 3-6 shows a typical Flo-Dar installation in a wastewater manhole. The device components allow the Flo-Dar to be setup in a wastewater manhole without confined space entry.

Figure 3-6 Typical FloDar Installation

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4.0 RESULTS

The results of this evaluation provide a comprehensive understanding of the location and condition of the wastewater collection system on Schriever AFB and a quantitative assessment of high flow rate discharges from Buildings 600 and 720. The results of the asset inventory, condition assessment, and CCTV investigation are stored in an updated geodatabase included electronically with this report. The updated geodatabase and recommendations in Section 5.0 provide Schriever AFB with tools for managing and planning wastewater system upgrades, maintenance, and repair activities.

4.1 GEODATABASE UPDATE

Tetra Tech updated the existing GIS database for all wastewater infrastructure assets on base. Tetra Tech achieved this by developing a personal geodatabase for all wastewater feature classes in accordance with SDSFIE framework. Certain attributes, particularly condition rating, were not previously included in the SDSFIE standards. For these attributes, Tetra Tech developed a relational table to store and to manage the data. All SDSFIE and additional attribute fields are included in the updated personal geodatabase.

Tetra Tech used the existing base geodatabase in an ArcSDE Environment to make the necessary updates to the wastewater layers in the geodatabase. The updated geodatabase included the appropriate metadata for each update made to the geodatabase. The updated wastewater system geodatabase is included in the electronic files accompanying this report. Appendix C provides an overview map of the entire base wastewater network from the updated geodatabase.

4.2 ASSET INVENTORY

Tetra Tech inventoried and provided condition assessments for 541 wastewater system assets on Schriever AFB. Tetra Tech located, verified, and compiled the GPS locations for approximately 217 features on base. The total number of GPS points is approximately half of the total number of assets inventoried because wastewater lines did not required GPS points since these assets are geographically located based on their terminating feature types (junction points, pumps, meters, etc.)

Of the 217 features for which Tetra Tech obtained GPS coordinates, approximately 84 percent of these features had a horizontal and vertical accuracy of less than one inch. The remaining 17 percent of the assets were under tree coverage or behind buildings where satellites were blocked. For these assets, a handheld Trimble GeoXGH devices was used to obtain GPS coordinates, resulting in an accuracy of sub-centimeter horizontally and sub-meter vertically.

Table 4-1 provides an overview of the wastewater asset inventory results. The table shows the quantity of each type of structure on base.

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Table 4-1 Wastewater Asset Inventory Results

Feature Quantity

Junction Point (Manhole) 235

Cleanout (Fitting Point) 42

Sewer Line 237

Meter 2

Valve 2

Pump 4

Septic Tank 5

Oil Water Separator 5

Grease Trap 4

Total 536

4.3 CONDITION ASSESSMENT

Appendix D provides a full scale map with an overview of the wastewater pipe network and the condition rating for each pipe section. The figure in Appendix D also shows pipe sections that Tetra Tech could not access during the inventory and condition assessment phases of this project. These were features that were unable to be opened due to bolts, welds, or other factors preventing access to pipe sections.

The figure in Appendix D shows that wastewater infrastructure on base is generally in good condition.

However, the figure shows that infrastructure adjacent to the track and in several locations inside the RA are deteriorated and in need of maintenance and/or repairs. This includes junctions and sewer lines that were poorly installed or are older than other parts of the base. The remainder of base is generally in good or average condition. It should be noted that for sewer lines with two different condition ratings (either for surface versus interior, upstream versus downstream, etc.), the worst condition was used to determine the overall condition rating shown in the figure in Appendix D. Junction points have two condition ratings, designated by the bicolor circle at each junction location.

Figure 4-1 through Figure 4-5 show the results of the condition assessment for each asset inventoried as part of this project. Each figure shows the breakdown of condition ratings for the exterior and interior attributes of each type of asset. The exterior is considered every part of the wastewater feature on the visible surface of the structure including the structure itself and the surrounding surface area (asphalt, rocks, etc.). The interior of the structure is considered all portions of the structure that are below grade or inside the feature itself. For example, the interior of a manhole includes the structure walls, cone, and channel, but does not include assessment of the pipes themselves since the condition of the incoming and outgoing pipes are classified as “pipes.”

Some asset results are shown as “Unrated” or “Unknown.” Assets categorized as such were unable to access or unable to open; therefore, no condition assessment could be performed. It is possible that the upstream end of a pipe was accessed and rated, but the downstream end was not accessible and, therefore, not rated. The majority of pipes with one inaccessible end did have a condition rating at the opposite pipe end. The combined results of the condition assessment for all wastewater features on base are shown in Figure 4-5.

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Figure 4-1 Condition Assessment Results for Junction Points

Figure 4-2 Condition Assessment Results for Cleanouts

Figure 4-3 Condition Assessment Results for Septic Tanks

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Figure 4-4 Condition Assessment Results for All Pipes

Figure 4-5 Condition Assessment Results for All Wastewater Features on Base

The results in Figure 4-5 indicate that the majority (87 percent) of wastewater assets were rated “average” or better condition. Approximately 9 percent of the wastewater assets are rated “poor” and “very poor” indicating maintenance, repair, or replacement should be considered in the near future. Features classified as “excellent” condition only made up a handful of features and were located in new construction areas. Assets categorized as “Unknown” were those that the field crews were unable to access or unable to open; therefore, no condition assessment could be performed.

4.4 CLOSED CIRCUIT TELEVISION INVESTIGATION RESULTS

The CCTV investigation used more intrusive inventory and inspection techniques to further investigate areas of concern identified using the pole camera. CCTV investigation included 11,450 linear feet of wastewater line segments. Appendix E contains the CCTV investigation areas and PACP defect codes.

A copy of CCTV inspection video is included with this report.

The CCTV investigation showed several areas of concern within the wastewater collection system. The most frequent defect was “sag” in the wastewater line segment for long lengths of pipe. Sag often occurs

Final Industrial Inflow-Infiltration Assessment for Page 15 Schriever Air Force Base, Colorado in PVC pipes due to inadequate bedding material beneath the pipe during installation. The CCTV investigation observed significant sag in over 1,700 linear feet of sewer lines on base. Significant sag was defined as stagnant water in greater than 20 percent of pipe. Sag was converted to a condition assessment rating using the following scale:

New construction – “excellent” condition 0 to 19 percent full – “good” condition 20 to 49 percent full – “average” condition 50 to 74 percent full – “poor” condition 75 percent full and greater – “very poor” condition

Appendix E shows the results of the CCTV investigation. In addition to the sag defects discussed above, the following major defects were identified:

1. Rebar debris was found in SL211;

2. Manhole JP021 had significant standing water in the bottom of the manhole; and

3. Manhole JP047 had a large amount of asphalt in the manhole resulting from parking lot construction above. The asphalt was blocking flow in the manhole and associated pipes. This defect was identified during Tetra Tech’s investigation in May 2013 and after discussions with base personnel, immediate repairs were performed in the summer of 2013, prior to the finalization of this report.

Section 5 of this report provides recommendations to correct the defects identified during CCTV investigation.

4.5 WASTEWATER FLOW MONITORING

Tetra Tech installed flow meters and collected flow data at two junction points outside of Buildings 600 and 720. Flow monitoring results indicate significant quantities of wastewater discharging intermittently from these two buildings. The following paragraphs discuss flow monitoring activities.

4.5.1 Wastewater Flow Monitoring at Building 600

Flow monitoring was performed at Building 600 from 13:30 on Tuesday, May 14, to 23:59 on Sunday, May 19. Figure 4-6 presents the results of this flow monitoring event.

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Figure 4-6 Building 600 Wastewater Flows

The graph shows several significant peak flow rates of 150 to 190 gallons per minute (GPM) coming from Building 600. These are an order of magnitude higher than typical sanitary flow rates expected from a building with similar occupancy to Building 600. The daily totals, averages, and peaks are shown in Table 4-2.

Table 4-2 Building 600 Wastewater Flow Results

Total Daily Flow Volume

Average Daily Flow Rate

Maximum Daily Flow Rate

(gallons) (gallons/minute) (gallons/minute)

Tuesday, May 14, 2013 10,127* 16.2 148.6

Wednesday, May 15, 2013 14,787 10.4 83.6

Thursday, May 16, 2013 16,149 11.3 188.9

Friday, May 17, 2013 15,639 10.9 92.6

Saturday, May 18, 2013 15,585 10.8 60.6

Sunday, May 19, 2013 12,696 8.8 78.7

*Data for this day does not include any flows prior to 13:30.

The results show that a significant source of wastewater flow is originating from Building 600.

Additionally, the flow was observed during off hours, periods of no flow were recorded, and flow rates up to 190 GPM were measured, indicating a process generated wastewater. Tetra Tech and Schriever AFB personnel surveyed Building 600 and identified the cooling tower as the source of this wastewater discharge. Interviews with Building 600 personnel indicated that the discharge is associated with blow down when pressure within the system exceeds a designated threshold. The wastewater discharge passes

Final Industrial Inflow-Infiltration Assessment for Page 17 Schriever Air Force Base, Colorado through a non-function wastewater flow meter prior to discharging from the southeast corner of Building 600.

4.5.2 Wastewater Flow Monitoring at Building 720

Building 720 flow monitoring was performed from 0:00 on Monday, April 29 to 23:59 on Tuesday, April

30. The results are shown in Figure 4-7 and Figure 4-8.

Figure 4-7 Building 720 Wastewater Flow Rates (Monday April 29, 2013)

Figure 4-8 Building 720 Wastewater Flow Rates (Tuesday April 30, 2013)

Page 18 Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado

As shown in Figures 4-7 and 4-8, a wastewater base flow of approximately 50 GPM occurred between 07:00 to 17:00 on both days. Several significant peak flow rates of 70 to 95 GPM were observed discharging intermittently. The daily total flow, average flow rate, and peak flow rate are shown in Table 4-3.

Table 4-3 Building 720 Wastewater Flow Results

Total Daily Flow Volume

Average Daily Flow Rate

Maximum Daily Flow Rate

(gallons) (gallons/minute) (gallons/minute)

Monday April 29, 2013 21,263 28.5 70.0

Tuesday April 30, 2013 19,495 26.1 96.2

Flow monitoring results indicate an intermittent wastewater discharge through the manhole at the southeastern corner of Building 720, however, the flow rate at this location is significantly lower than the flow rate observed at Building 600. Tetra Tech and Schriever AFB personnel reviewed as-built drawings, interviewed facility maintenance personnel, and surveyed Building 720 to identify potential sources of this intermittent wastewater discharge. Building 720 has several mechanical rooms and floor drains. All mechanical rooms were surveyed and no evidence of intermittent wastewater flow was identified.

The Utilidor entering Building 720 was also surveyed. Several sump pits and pumps were observed within the Utilidor. There was evidence of water flowing into the sump pits, including pavement staining, as well as pipes discharging directly into the sump pits; however flows could not be verified during this survey.

Final Industrial Inflow-Infiltration Assessment for Page 19 Schriever Air Force Base, Colorado

5.0 RECOMMENDATIONS

This Industrial Inflow-Infiltration Assessment for Schriever AFB documents the technical approach and methodology for providing a complete inventory and condition assessment of the wastewater system, characterization of industrial wastewater inflows, and identification of wastewater system repairs/upgrades to improve the overall function of the wastewater system on base. Tetra Tech inspected 541 features on Schriever AFB and developed a list of appropriate wastewater system upgrades and maintenance activities that will improve the overall function and performance of the wastewater system on base.

5.1 CAPITAL IMPROVEMENT RECOMMENDATIONS

Tetra Tech has identified several areas on base where capital improvement projects would improve the function of the wastewater system. A location map and table of wastewater features for each of these capital improvement upgrades are shown in Appendix F. A map for the “Sewer Line Slope Rehabilitation” recommendations is shown in the CCTV results in Appendix E.

Tetra Tech identified four categories of capital improvement projects, which are explained in the following sections.

5.1.1 Septic Tank Permitting or Connection to Wastewater System

Tetra Tech identified four operational septic tank and leach field systems on Schriever AFB. These septic systems are located at the Baseball Field, Army Air Force Exchange Service (AAFES) Gas Station, Grounds Maintenance Contractor Storage Area, and West Portal of the RA. Schriever AFB Utilities Shop personnel explained that an additional septic system located near the warehouses on the south side of the base is scheduled to be removed from service in 2013. Septic systems are considered On-site Wastewater Treatment Systems (OWTS) by El Paso County (County) Department of Public Health and must be permitted according to County’s guidelines for siting and sizing or connected to the existing wastewater collection system on base to avoid permitting.

The permitting process requires percolation testing of on-site soils, soil characterization, and sizing calculations all to be performed by a licensed Professional Engineer (P.E.). Once installed, the system must be inspected by the P.E. and the application submitted and approved by the County. Local firms specializing in permitting OWTS systems can typically perform the entire permitting process for approximately $1,500 per septic system. The total estimated cost to permit both OWTS at Schriever AFB are shown in Table 5-1. Long term maintenance costs for operating these OWTS include annual pumping of the sludge from each septic tank. Each tank is approximately 2,000 gallon capacity and vacuum trucks typically charge $1.00 per gallon of sludge, resulting in an annual maintenance cost of approximately $4,000, assuming that each tank is half full when pumped.

Page 20 Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado

Table 5-1 OWTS Permitting Costs

Description Units Unit Price Quantity Total Cost

Percolation Testing EA $500.00 1 $ 500.00 OWTS Design Calculations EA $500.00 1 $ 500.00

Inspection EA $500.00 1 $ 500.00

Total per Unit $ 1,500.00 x 2 OWTS X4

Permitting Total $ 6,000.00

Rather than permitting the existing septic systems, Schriever AFB decision makers could elect to remove the existing systems and connect to the main wastewater collection system. This alternative would require abandoning the existing septic systems and installing new wastewater lines to connect to the wastewater collection system. The estimated capital cost for removing the existing septic systems and connecting to the Schriever AFB wastewater collection system is shown in Table 5-2. The long term maintenance costs would include jetting of the wastewater lines to remove debris and buildup.

Final Industrial Inflow-Infiltration Assessment for Page 21 Schriever Air Force Base, Colorado

Table 5-2 OWTS Connection to Collection System Costs

Description Units Unit Price Quantity Total Cost

Baseball Fields Installation of 6 inch Polyvinylchloride Pipe LF $16.77 300 $ 5,031.00

Excavation (8 feet deep) CY $6.09 89 $ 541.33 12" Gravel Utility Bedding (compacted) CY $1.80 11 $ 20.00

General Soil Backfill (7 feet deep) CY $1.85 78 $ 143.89 Compaction CY $2.85 78 $ 221.67

AAFES Gas Station Installation of 6 inch Polyvinylchloride Pipe LF $16.77 300 $ 5,031.00

Excavation (8 feet deep) CY $6.09 89 $ 541.33 12" Gravel Utility Bedding (compacted) CY $1.80 11 $ 20.00

General Soil Backfill (7 feet deep) CY $1.85 78 $ 143.89 Compaction CY $2.85 78 $ 221.67

Ground Maintenance Contractor Storage Area Installation of 6 inch Polyvinylchloride Pipe LF $16.77 700 $ 11,739.00 Excavation (8 feet deep) CY $6.09 207 $ 1,263.11

12" Gravel Utility Bedding (compacted) CY $1.80 26 $ 46.67 General Soil Backfill (7 feet deep) CY $1.85 181 $ 335.74

Compaction CY $2.85 181 $ 517.22

West Portal of the RA Installation of 6 inch Polyvinylchloride Pipe LF $16.77 550 $ 9,223.50

Excavation (8 feet deep) CY $6.09 163 $ 992.44 12" Gravel Utility Bedding (compacted) CY $1.80 20 $ 36.67

General Soil Backfill (7 feet deep) CY $1.85 143 $ 263.80 Compaction CY $2.85 143 $ 406.39

Subtotal $ 36,740.32 Mobilization (10% Subtotal) $ 3,674.03 Construction Contingencies (20% Subtotal) $ 7,348.06

Design (6% Subtotal) $ 2,204.42

Construction Total $ 49,966.83

Notes: Unit cost developed from RSMeans 2013 Quarter 3 unit cost estimates for plumbing and earthwork Excavation costs do not include sheeting or dewatering

Backfill costs assume fill material is borrowed and bottom layer is crushed stone for pipe installation

Page 22 Final Industrial Inflow-Infiltration Assessment for Schriever Air Force Base, Colorado

5.1.2 Manhole Interior Repairs

Tetra Tech identified numerous manholes with interior structural defects. Manhole defects were observed in the chimneys, cones, walls, bench, and the channel of various manholes. Tetra Tech recommends repair or replacement of these components to ensure adequate conveyance of wastewater flows through the manhole and to avoid collapse of the manhole caused by deterioration or structural failure. A location map and list of manhole interior repairs are shown in Appendix F.

5.1.3 Wastewater Line Slope Rehabilitation

Tetra Tech identified over 1,700 linear feet of wastewater line segments with significant sag. Sag within wastewater line segments could result in debris accumulation and eventually blockages. Blockages could result in wastewater backups and sanitary sewer overflows. As discussed in Section 4.4, Tetra Tech rated each sag in order to prioritize repairs. The sag rating was used to develop the repair recommendation list presented in Appendix F.

5.1.4 Wastewater Line Repair or Replacement

Tetra Tech identified numerous pipes requiring repair or replacement, particularly where the wastewater line connects to a manhole. In many cases, the pipe was deformed, damaged, dislodged, or broken at the connection with the manhole. Broken connections at junction points can allow wastewater to exfiltrate, discharging wastewater directly to surrounding soils.

For wastewater line/manhole connections requiring repair or replacement, Tetra Tech recommends removal of surface paving or vegetation and excavation of the surrounding soils to investigate the cause of the structural defect. In most cases, the existing pipes are structurally sound, but require repair to reconnect the pipe to the manhole. In these cases, the soils beneath the pipe sections should be re-graded, appropriately sloped, and compacted to minimize potential for pipe settling in the future. The installation of a pipe sleeve at the broken joint may be appropriate in cases where pipe slopes is still intact, water inside the pipe can still flow freely, and the pipe section remain structurally sound. In the event that the pipe sections are cracked or fractured, Tetra Tech recommends removal and replacement of the pipe sections. These wastewater line repair recommendations are listed in Appendix G.

5.2 OPERATION AND MAINTENANCE RECOMMENDATIONS

Operation and maintenance activities at several locations will improve the overall function of the wastewater system on base. A location map for each of the recommended operation and maintenance activities are shown in Appendix G. Tetra Tech identified four categories of operation and maintenance activities that are discussed in the following sections.

5.2.1 Cleaning, Closure or Abandoning of Tanks

Tetra Tech identified numerous grease traps, septic tanks, and grit traps on Schriever AFB that could potentially be removed. For example, the grease trap downstream of the ENT Federal Credit Union building should be reviewed. Previously, this building housed commercial food services and the grease trap was needed; however, there are currently no food service operations within the building and the grease trap may not be required. This grease trap has significant solids accumulation and should be cleaned at a minimum. If no longer required, the grease trap should be removed from service. Appendix G contains a listing of grease traps, septic tanks, and grit traps that should be reviewed to ensure these units are required.

Final Industrial Inflow-Infiltration Assessment for Page 23 Schriever Air Force Base, Colorado

5.2.2 Manhole Surface Maintenance

Tetra Tech identified numerous manholes with cracked or broken concrete surrounding the manhole cover; broken or offset cover frames; and/or poor grading surrounding the manhole. For broken concrete at the manhole surface, Tetra Tech recommends sealing cracks or replacing the concrete depending on the severity of the concrete defects. For offset frames, Tetra Tech recommends removing the soil surrounding the cover/frame and re-securing the frame and frame seal to the manhole chimney or cone.

For poor grading, Tetra Tech recommends re-grading soils to direct surface runoff away from the manhole and reinforcing with erosion control techniques. Lastly, manholes with overgrown vegetation should be cut back to provide easy access to the manhole.