Tom Parece, Reggie Donoghue and Mike Domenica P. R. Ammann

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1 To: From: Subject: Tom Parece, Reggie Donoghue and Mike Domenica P. R. Ammann TM #7 A STEP Effluent Has a Big Cost Advantage over a Gravity for Downtown Orleans Date: January 12, 2017 Summary In its preliminary evaluation of sewer alternatives, AECOM concluded that a hybrid gravity sewer with 8 grinder pump units was the most cost effective system for downtown Orleans. A review of the AECOM preliminary cost calculations indicates that a STEP sewer system would in fact have a significantly lower construction cost. AECOM s preliminary evaluation of sewer alternatives for downtown Orleans, dated March April 2016, was used to compare the project costs for a STEP sewer system and a gravity sewer system. Both connected the same 349 properties. Only the On-Lot and the main municipal collection systems were considered in this analysis. The total project costs for the collection systems are summarized in the next table. A STEP sewer would have two basic components and a gravity sewer would have five individual sections. At an estimated $41,820 per connection, the STEP collection system would only cost about 54% of the estimated $76,800 per connection for a gravity sewer system. An explanation of the costs is presented in the following sections. Source Estimated Total Cost Estimated Cost per Connection Gravity $26.8 Mil $76,840 STEP $14.6 Mil $41,820 Potential Savings $12.2 Mil $35,015 These results, which are based on the AECOM cost templates and methodology, illustrate the potential for Orleans to cut the initial cost of the collection system to approximately half of the cost of a gravity sewer collection system. An independent engineering analysis of the STEP sewer technology is needed to confirm the potential cost savings. STEP versus Gravity P. R. Ammann Page 1

2 Discussion I. AECOM s Preliminary (Conceptual) Gravity System The preliminary cost estimate was not supported by a significant amount of engineering detail. Preliminary costs were based on a few simple design parameters and cost estimates. The cost analysis is described briefly. 1) Municipal Collection Pipe AECOM estimated that 35,500 linear feet (6.7 miles) of gravity sewer collection pipe would be required. It is assumed that the minimum diameter was 8 inches and the installed cost was $125 per linear foot. The total project cost 1 was calculated at $9,600,000 or $27,500 per 2) Force Main AECOM roughly estimated that 15,000 linear feet (nearly 3 miles) of force main would be required. This pipe would be smaller in diameter and connect the 4 custom pump stations and 2 submersible pump stations to the next section of downstream gravity sewer pipe and ultimately the treatment facility. The total project cost 1 was calculated by AECOM at $3,800,000 and $11,150 per 3) Submersible Pump Stations AECOM estimated that 2 pump stations would be required at an installed cost of $275,000 each. The total project cost 1 is estimated at $1,600,000 which is equivalent to $4,550 per 4) Custom Pump Stations AECOM projected that 4 custom pump stations would be required as part of a gravity sewer collection system serving 349 properties in downtown Orleans. The installed cost of each pump station was estimated at $585,000. This would translate to a total project 1 cost of $5,858,000 or $16,800 per 5) Private Property Connection This component involves the extension of a 4-inch diameter, or larger, PVC pipe from a building to the nearest main collection pipe. The latter may 1 The installation cost consists primarily of materials and labor. The total project cost is approximately times the installed cost, because it includes: mobilization, overhead and profit, contingency, engineering, etc. STEP versus Gravity P. R. Ammann Page 2

3 either be in the street of along a common property line. AECOM assumed An installed cost of $7,800 per property (connection). The total project cost 1 is calculated at $5,885,000 which is equivalent to $16,870 per AECOM Cost Estimate for Downtown Orleans Gravity Collection System Source AECOM Cost Cost per Connection Collection Pipe $9.6 Mil $27,500 Force Main $3.9 Mil $11,150 Submersible Pump Station $1.6 Mil $4,550 Custom Pump Station $5.9 Mil $16,800 Gravity Connection $5.9 Mil $16,870 Total $26.8 Mil $76,840 6) Comment As AECOM proceeds with engineering design work, the design will refine the number of pump stations and the lengths of pipe that would be needed. Therefore it is expected that the cost estimate may change and possibly decrease. For example, as of January 2017, the AECOM determined that only three custom pump stations would be needed rather than four. II. A Conceptual Cost Estimate for a STEP System Based on the AECOM Cost Framework. AECOM prepared a preliminary a STEP sewer system with capacity to serve 349 properties/connections in the downtown area of Orleans. This estimate was modified to eliminate a pump station that would not be needed with modern STEP pumps. Also a slight adjustment has been made in the installed unit cost for the collection pipe to account for the fact that there would be no need for manholes. 1) Municipal Collection Pipe (Force Main) AECOM estimated that 37,500 linear feet (7.1 miles) of collection pipe would be needed. [In contrast, the gravity sewer system was projected by AECOM to require a total of 50,500 linear feet (9.6 miles) of collection pipe and force main.] Although AECOM did not did not indicate the pipe STEP versus Gravity P. R. Ammann Page 3

4 diameters, it is expected that a large amount of pipe will be in the range of 2, 3 and 4 diameter. AECOM used a unit cost of $100 per linear foot for the installation; an installed cost of $80 was used instead since no manholes would be required. In addition, bid documents dated in 2012, with all costs escalated to late 2016 using the ENR cost index, and 2016 indicated that costs for the installation of force mains with diameters of 2 to 8 could be in the range of $60. The total project cost 1 was estimated at $5,485,000, or $18,580 per 2) Custom Pump Station AECOM assumed that one pump station at a cost of $585,000 would be needed. In consultation with Orenco it has been assumed that a pump station would not be required if the collection pipes were properly sized. 3) Private Property Connection [STEP Unit] AECOM estimated that the average cost of a STEP installation was $10,750. Therefore the total project cost 1 for 349 connections was calculated at $8,119,000 and $23,240 per AECOM Cost Estimate for Downtown Orleans STEP Collection System Source AECOM Cost Cost per Connection STEP Force Main $6.5 Mil $18,580 STEP Connection $8.1 Mil $23,240 Total $14.6 Mil $41,820 4) Comment If an engineering firm with expertise and interest in finding the optimum design for a STEP collection system in Orleans were to study the engineering drawings and topography, there is some chance that a lower cost design might be found. For example there might be areas in Orleans where a cluster of properties located on a slope might be connected by a Septic Tank Effluent Gravity (STEG) configuration to a common pump station (dual pumps) at a lower cost than multiple STEP connections. STEP versus Gravity P. R. Ammann Page 4

5 Conclusion The simple review of the AECOM cost methodology reveals two significant advantages to a STEP/STEG collection system that could save the Town of Orleans approximately $12 million just for the downtown area, as shown in the next table. These are: 1. Collection Pipe System. The total cost for the gravity sewer collection system is based on pipe and pumps stations. The cost is estimated at $20.9 million. The estimated cost for the STEP collection pipe, based on AECOM methodology, is calculated at only $4.9 million because no pump stations are needed and manholes are not used with STEP collection pipes. 2. On-Lot Connections. The cost for the gravity sewer pipe connection from the street to each building is estimated at $5.9 million. In contrast, the STEP connections are estimated at a slightly higher cost of $8.1 million. Source Total Project Cost STEP Gravity Connection Cost STEP Gravity Collection Pipe $9.6 Mil $27,500 Force Main $3.9 Mil $11,150 STEP Force Main $6.5 Mil $18,600 Submersible Pump Station $1.6 Mil $4,550 Custom Pump Station $5.9 Mil $16,800 Gravity Connection $5.9 Mil $16,860 STEP Unit & Connection $8.1 Mil $23,240 Total $14.6 Mil $26.8 Mil $41,820 $76,840 STEP versus Gravity P. R. Ammann Page 5