ENGINEERING FEASIBILITY REPORT - EVALUATION OF POSSIBLE

Evaluation of Possible Measures for CSO Solids Control

Gowanus Canal Superfund Site

Brooklyn, New York

CONTRACT REGISTRATION NO. 20121431239

PIN: 82611BEPASFS

Prepared for:

New York City Department of Environmental Protection

59-17 Junction Blvd

Flushing, NY 11373

Prepared by:

LOUIS BERGER & ASSOC., PC

199 WATER STREET, 23RD FLOOR

NEW YORK, NY 10038

TEL. (212) 612-7900

FAX (212) 363-4341

October 3, 2012

New York City Department of Environmental Protection Assessment of Measures for CSO Solids Control for

Gowanus Canal Superfund Site, Brooklyn, NY

LOUIS BERGER & ASSOC., PC 2 October 3, 2012

Introduction

The Gowanus Canal was placed on the National Priorities List in 2010. In January 2012, the

United States Environmental Protection Agency (USEPA) issued a draft Feasibility Study (FS)

for the remediation of the Canal. The remedial alternatives developed in the FS included

removing the existing sediment in the Canal, stabilizing the underlying soft sediment, and

installing a multi-layered cap over the sediment residuals. The FS did not provide a detailed

assessment of source control although the FS states that control of existing sources, including

combined sewer overflows (CSOs), is an important part of an overall remedy.1

In a letter to the USEPA dated June 28, 2012, the New York State Department of Environmental

Conservation (NYSDEC) identified eight possible option (the “Options”) that might be effective

in addressing solids from CSOs and suggested that NYCDEP evaluate these Options in a

feasibility study which could further the Clean Water Act goals set forth in an Order on Consent

between NYCDEP and NYSDEC relating to CSOs in the Gowanus Canal and other water bodies

(the “Consent Order”). The Options focus on engineering controls for solids reduction from

CSOs RH-034 and OH-007, as these represent approximately 80 percent of the total CSO flow

volume following the water quality improvement (WQIP) upgrades currently planned or being

implemented by NYCDEP.2

The Options are as follows:

1. Optimizing the existing sedimentation trap at outfall OH-007

2. Improved maintenance program at the outfall OH-007 sediment trap

1 NYCDEP is proceeding with a work plan that will fill critical data gaps that currently exist in the Remedial Investigation/Feasibility Study (RI/FS) and are necessary for resolving the “threshold question” of whether CSOs contribute regulated CERCLA-regulated hazardous substances to the Canal at levels that pose unacceptable risks to human health or the environment. Due to the importance of this information to all stakeholders and to the ultimate remedy selection, the City emphasizes that remedy selection must be based on the results of this sampling effort. 2 Under NYCDEP’s Consent Order with NYSDEC, the City has undertaken upgrades to the Gowanus Pump Station and the Flushing Tunnel. These upgrades will reduce CSOs by 34 percent and improve water quality to achieve SD standards and are projected to meet “I” standards. Floatables control will capture 78 percent of floatables. Environmental dredging of sediments will reduce odors and improve aesthetics. Further planned upgrades include high level sewer separation and Green Infrastructure. These additional upgrades are projected to result in a total CSO reduction of 45 percent for the Gowanus Canal.




3. Installation of silt curtains and/or netting facilities at all CSO outfalls discharging to the

Gowanus Canal

4. Yearly monitoring of CSO solids deposition in the Canal

5. Development of metrics for maintenance dredging of CSO solids in the Canal

6. Additional regular sewer cleaning in the drainage area

7. Engineering evaluation of an interim or permanent sedimentation trap at outfall RH-034.

The evaluation would include possible opportunities to accelerate this work and

coordinate it with the ongoing sheet pile barrier wall for the Fulton MGP Site

8. Advance the City’s dredging of CSO mounds at the head end of the Canal to comply with

the CSO Order on Consent, while seeking synergetic opportunities to advance the

demonstration and development of remedial design protocols for dredging, dewatering,

disposal, stabilization and capping pursuant to the Superfund program.

This document discusses the potential effectiveness of the Options in reducing CSO solids and

potential costs for implementation. The timing of several other ongoing or upcoming projects in

the Canal will impact the timing for implementing the Options. In evaluating the Options, the

following assumptions were made regarding the timing of these projects:

• Reconstruction of the Flushing Tunnel scheduled to be completed in 2013.

• Environmental dredging in the Canal to remove mounds of sediment exposed under low

water conditions for odor control purposes, scheduled to be initiated within three years of

NYCDEP receiving approval of all applicable permits that period which, for purposes of

this report, was assumed to be between 2014 to 2017.

• Remediation of the Canal under CERCLA would start in 2014 or 2015 and may take up

to 8 years to complete.

Table 1 presents a summary of the evaluation results for each option, including estimated costs.

Capital and operation and maintenance (O&M) costs for the different alternatives are presented

as a present worth based on a 5 percent discount rate. O&M costs are based on a 30 year period

starting in 2013 and ending in 2042.




1. Optimizing the existing sediment chamber at outfall OH-007:

The OH-007 sediment chamber is located between the 2nd Ave Pump Station and the Gowanus

Canal (Figures 1a). As-built drawings for the sediment chamber dated August 31, 1897 indicate

that the chamber is approximately 115 years old. It appears that the chamber was designed to

intercept solids and floatables during overflow events in order to reduce the discharge of these

materials to the Canal (see Figure 1b). The main chamber measures about 8.5 ft. from floor to

ceiling with a width of 30 ft. and a length of approximately 48 ft., measured from the 12-ft wide

inlet to the baffle wall. The baffle wall has seven 36-inch diameter portals leading to a second,

shorter chamber measuring 10 ft. in length and containing a 4.75 ft. high weir. Approximately

2 ft. downstream of the weir, a second set of seven 36-inch diameter portals exit the chamber and

lead to the outfall to the Canal.

Between March 12 and March 21, 2012, NYCDEP inspected, cleaned, and repaired the OH-007

sediment chamber. The sediment chamber is now operating as designed to capture and retain

solids from CSO discharges. Through this process, NYCDEP restored the facility’s ability to

retain a portion of CSO solids and demonstrated a viable method to remove accumulated solids

from the facility using Vactor® truck equipment. NYCDEP expects that the facility will

maintain its optimal performance through the implementation of an improved maintenance

program (the subject of NYSDEC Option 2).

A thorough inspection of the facility revealed a crack along the southern (inlet) wall, as well as

some minor corrosion to the supporting columns. Inspection of the smaller compartment

(between the baffle wall and the outlet conduits) revealed cracks and missing capstones in the

overflow weir allowing tidal backwater to enter the facility. During the inspection a probe rod

was used to measure the depth of accumulated sediment within the main storage compartment.

A map of the results (Figure 1b, plan view) shows that solids had accumulated to a depth of 4 ft.

in the central portion of the chamber, while sediment depths around the perimeter of the chamber

were 0.5 inches to 1.0 ft. This accumulation pattern suggests a circular flow pattern within the

sediment chamber which is consistent with CSO flow entering along the eastern wall of the

chamber (Figure 1c).




Two Vactor® trucks were used to clean the chamber. A suction hose was lowered through each

of the six access manholes to remove the accumulated solids from the chamber. Approximately

57 tons of sediment was removed from the facility.

The integrity of the overflow weir was restored by replacing the dislodged capstones and using

gunite (dry-mix concrete sprayed with a pressurized injection nozzle) to repair cracks. Gunite

was also used to repair the crack in the southern (inlet) wall and the damaged columns. The

repair to the overflow weir prevents tidewater intrusion into the facility.

The cost for the March 2012 inspection, cleaning, and repair of the sediment chamber (estimated

at $200,000) was included as a capital cost in Table 1.

2. Improved maintenance program at the Outfall OH-007 sediment chamber

Historically, the OH-007 sediment chamber has required very infrequent maintenance. As

discussed in Section 1, NYCDEP inspected, cleaned, and repaired the OH-007 chamber in

March 2012. A previous inspection and (incomplete) cleaning was conducted in June 2006

(O’Brien & Gere, July 2006), so this sediment level represents an accumulation period of as little

as 6 years, or an annual accumulation rate of up to 9 inches (10 tons). This accumulation rate is

consistent with calculations performed by HDR|HydroQual in 2012 which estimated that the

accumulation rate in the chamber could be roughly 9.4 tons per year based on modeled flow rates

for a typical CSO year (using JFK airport 1988 rainfall records), a typical CSO solids grain-size

distribution, and a CSO solids content of 136 mg/L.

When the chamber was inspected in 2006, accumulated solids had not completely filled the

chamber. It is possible that the sediment chamber has an effective solids-holding capacity

beyond which additional solids may flush out rather than continue to be trapped; the level of

solids found during the March 2012 inspection may represent the effective solids-holding

capacity of the chamber. Because it is possible that the solids accumulation rate diminishes over

time, an annual inspection of solids levels to track solids accumulation is recommended. When

the annual solids accumulation rate diminishes significantly compared to previous periods, the

chamber would be cleaned. For example, if sediment in the chamber has accumulated to a depth




of at least 2 ft (half the level found in March 2012) and the annual accumulation rate is less than

50 percent of the anticipated annual accumulation rate, the chamber would be scheduled to be

cleaned within 6 months. It is recommended that this approach be tried for a period of two to

five years and the results monitored to determine if regular inspections improve operation of the

OH-007 sediment chamber. Following this trial period, the results should be reviewed and the

program modified as necessary to optimize sediment chamber operations.

As stated in Section 1, NYCDEP estimated that the cost of the March 2012 cleaning, inspection,

and repair was approximately $200,000. While no cost breakdown is available for the various

tasks performed during the cleaning operation, rough estimates for the associated costs are as

follows: approximately $50,000 for confined space entry; $100,000 for dewatering and removing

solids; and $50,000 for repairing the facility. On the basis of the March 2012 experience,

NYCDEP estimates that the routine cost associated with cleaning and inspecting the chamber

would be approximately $150,000 per event. For budgetary purposes, it is assumed that some

repair work will be required biennially.

Previous inspections have shown that sediment tends to accumulate in the center of the chamber.

Monitoring the sediment levels in the center of the chamber is expected to provide a conservative

measure of the accumulation rate in the chamber. While estimating the total volume of

accumulated sediment would provide a more accurate measure of the annual sediment

accumulation rate, that approach would require multiple measurements to produce a two-

dimensional map of sediment levels throughout the chamber. Unless it is suspected that such

mapping would support a less-frequent cleaning frequency, it is anticipated that monitoring

sediment levels in the center of the chamber will be sufficient to maintain the chamber’s

performance.

The most direct way to measure sediment levels is to use a rod to probe the depth of the

accumulated sediment. Four 24-inch diameter access manholes are located in the roof of the

solids-settling chamber (another two manholes provide access to the smaller weir chamber).

Unfortunately, none of the four access manholes to the chamber is located over the center of the

chamber where solids tend to accumulate. For this reason, monitoring sediment levels from




these access manholes is not anticipated to be an effective measure of the sediment

accumulation.

It is possible that the cost of annual inspections could be reduced if suitable methods are

developed to measure the sediment levels within the chamber without performing confined space

entry. However such measures are largely untested. NYCDEP will continue to evaluate

alternative inspection methods as a way to more cost-effectively monitor sediment levels within

the chamber.

Table 1 includes the present worth of annual monitoring of the sediment chamber over a 30-year

period (assuming the program were to continue in its current form) starting in 2013. The annual

cost for confined space entry, inspection and cleaning is approximately $150,000. A biennial

cost of $50,000 for repairs to the structure of the chamber has been included in the estimate. The

estimated present worth for maintenance activities over a 30 year period is approximately

$4 million.

3. Silt curtains and/or netting facilities at CSO Outfalls:

This Option assesses the feasibility of installing silt curtains and/or netting facilities at ten CSO

outfalls in the Gowanus Canal to address suspended solids. The following analysis focuses on

outfalls OH-007 and RH-034, as these outfalls represent approximately 80 percent of the total

flow volume following the WQIP upgrades (although similar conditions would exist at other

CSO discharge points in the Canal.)

Table 2 provides a summary of the available information on the ten CSOs that drain to the Canal.

This information was used as a basis for evaluating the efficacy of silt curtains and netting

facilities to isolate solids from CSOs.




Table 2: Existing Outfall Data:

Type Outfall Outfall Size

Future Discharge

Volume (MG) per year

Number of Wet Weather

Events **

2011 Calendar year peak flow

(mgd)

Peak Flow (CFS)

Velocity (FPS) ***

CSO RH-038 144"w x 62"h 0.9 15 6.00 9.28 2.69 CSO RH-037 18" 0.5 16 3.10 4.80 3.81 CSO RH-036 18" 1.6 20 5.10 7.89 3.42 CSO RH-035 48" 3 12 43.30 66.99 7.30

CSO RH-034 4 barrels

10'x10' each 127 35 323.70 500.81 7.60 CSO RH-033 38"w x 44"h 0.2 14 2.30 3.56 2.72 CSO RH-031 72" 11 17 56.10 86.79 7.90 CSO OH-007 78" 69 47 185.56 287.08 10.35 CSO OH-006 36" 13 33 33.49 51.81 5.44 CSO OH-005 42" 0.7 5 23.64 36.57 6.35

Notes:

1. Simulated conditions reflect design precipitation record (JFK, 1988) and sanitary flows projected for the year 2045. (Red Hook

WPCP:40 MGD. Owls Head WPCP:115 MGD)

2. ** Reflects minimum modeled flow of 0.01 MGD per 5 minute intervals and minimum 12-hr inter event time.

3. 2011 Calendar year peak flows provided by HDR/Hydroqual model for 5 minute maximum flow rate.

4. ***Velocities were calculated based on an assumed pipe slope and material.

Silt curtains (i.e., turbidity curtains/barriers) are vertical, flexible structures constructed of

polyester-reinforced thermoplastic (vinyl) extending from the water surface to a specified water

depth or the bottom of the water body. The curtains are held in position by flotation material at

the top and ballast chains along the bottom. A tension cable is often built into the curtain to

absorb stresses imposed by currents and hydrodynamic turbulence.

Silt curtains are generally manufactured in standard sections (i.e., 50 or 100 ft segments) that can

be joined together at a site to provide a barrier of specified length. Traditional “off the shelf”

curtains are designed to extend 1 to 2 ft. above the bottom to allow mudflow to pass beneath

them. This would not be beneficial for the stated purpose in Gowanus Canal. Engineered

applications can be designed to provide a seal with the bottom of the waterway to prevent

sediment from migrating outside of the protected area. Anchored lines hold the curtain in a

deployed configuration that can be U- or V-shaped, or circular or elliptical, depending upon the

application. Under ideal conditions, turbidity levels in the water column outside the curtain can

be as much as 80 to 90 percent lower than those levels inside or upstream of the curtain.




Silt curtains are generally viewed as temporary measures to control suspended solids during

construction or dredging projects. In those types of applications, silt curtains are typically

inspected daily and repaired or replaced immediately if damaged. Sediment is removed when

the silt curtain is removed because the curtain is generally in service for a limited period of time.

If permanent controls were needed, it would be more common to install a sheet pile wall rather

than a silt curtain (similar to what is proposed for Option 7).

Sediment would have to be removed from behind the curtain on a regular basis (annually or more

frequently). In addition, floating debris would need to be removed following each overflow event

to avoid damaging the silt curtain and minimizing impacts associated with odors and floating

debris. If the curtain were oriented in a manner that faces the prevailing winds, anchoring

devices would need to be checked frequently.

While silt curtains will prevent suspended solids from migrating from the protected area to the

larger water body, they do have significant drawbacks.

• Silt curtains are not typically designed for the velocities associated with some CSO

events. During CSO events they may fail, releasing the captured suspended solids to the

Canal and requiring repairs before they can be returned to service. The upper limit on the

velocity for most silt curtains is 1.5 feet per second. Certain manufacturers provide

heavy duty silt curtains (e.g., Type 3) which can withstand velocities of 6.75 feet per

second (see Figure 3a). These silt curtains have 20 percent or more of the impermeable

material replaced by permeable filter fabric made of polypropylene. This fabric retains

sediment while reducing the pressure on the silt curtain.

• Silt curtains require anchoring both to maintain their position within the Canal and to

ensure a seal between the Canal bottom and the silt curtain. Existing soft sediments

throughout much of the Canal will make establishing a stable anchoring point difficult.

• Silt curtains create a physical floating barrier in the Canal which could affect aesthetics.

• Silt curtains collect floatables, including trash, preventing the natural dilution which

occurs during overflow events. This may result in odors above what is currently

experienced during overflow events.




• Silt curtains will, over time, become clogged with silt/debris which can lead to blowout

and failure, resulting in the need to replace the silt curtain.

Maintenance for silt curtains at CSO outfalls would involve removing floatables after each

overflow event using either a skimmer vessel, which hydraulically removes the floatables from

the water, or a boat and manual labor. The potential for creating backups upstream as a result of

trapped floatables is another potential issue which has not been fully examined. Conceptual

layouts for silt curtains at RH-034 and OH-007 are shown in Figure 3b.

Initially the idea of installing both a netting facility3 and a silt curtain was considered for the

CSO outfalls. The option to use both technologies together was not presented in this report for a

number of reasons:

• Netting facilities are being proposed by NYCDEP as part of the nine minimum controls

for their long-term CSO control plan.

• Installation at RH-034 would require a floating netting facility which would extend

approximately 30 feet into the Canal. A silt curtain added at this location would have to

be placed some distance from the netting facility, obstructing a large amount of the Canal

in that location.

• Installation at OH-007 would require an inline type facility. This would have to be

installed underground in line with the outfall pipe or possibly in the sediment trap located

at this outfall. The silt curtain would have to be installed in the Canal at some distance

from the outlet from the sediment chamber and would impede boat traffic.

There are two significant operation and maintenance costs associated with silt curtains: capture

and removal of floatables and removal of sediment. Skimmer vessels for removing floatables

range in cost from $300,000 to $700,000, with an annual operating cost of approximately

$75,000 to $125,000. Alternatively, the floatables can be removed manually. Given the limited

number of sites, manual removal was assumed for purposes of this analysis.

3 Netting is a commonly used floatables control technology. It is considered a screening device as the net traps the floatables within the system. Netting systems can be installed in-line, at end-of-pipe, or as a floating unit, and often can be retrofitted in existing structures.




In this application, the silt curtains would be located a distance away from the CSO outfall point

to accommodate one year of sediment loading behind the curtain. Sediment removal would

require dredging to remove the accumulated sediment. For the cost estimate, it was assumed that

approximately 200 cubic yards of sediment would be removed annually from the two locations.

The costs associated with the silt curtain option are presented in Attachment A-1. The capital

costs include the cost of the silt curtain fabric, lines, cables and anchors, and installation. The

cost to dredge existing sediment deposits at the two locations was included in the capital costs

based on the assumption that the silt curtains would be installed prior to the completion of

CERCLA remediation activities in the Canal. Maintenance costs were provided for both

floatables and sediment removal.

It was assumed that this work would be implemented in approximately 2016 following the

environmental dredging program. Current 2012 costs for the sampling program were estimated

and escalated to 2016 costs using a 3 percent inflation factor. A 30 year operation and

maintenance (O&M) period was assumed for the estimate. The future costs were discounted to a

present worth using a 5 percent discount rate. The estimated present worth for the construction

and 30 years of O&M at RH-034 and OH-007 is approximately $33,300,000.

For the reasons stated above, it is recommended that silt curtains not be considered for use at the

Gowanus Canal CSO outfalls.

4. Yearly monitoring of CSO solids deposition in the Canal:

This Option assesses the feasibility of annual monitoring of CSO solids deposition in the Canal.

To monitor the depositional patterns in the Canal, annual bathymetric survey would be

conducted. Bathymetric surveys measure the elevation of the ground surface in the Canal with

respect to a given benchmark. Comparing two bathymetric surveys prepared over different time

periods provides information which can be used to delineate depositional/erosional areas in the

Canal and the magnitude of deposition/erosion over a given period, and hence an estimate of the

rate of deposition/erosion in the Canal.




While bathymetric surveys can be used to estimate the deposition patterns in the Canal, they

cannot be used to determine the source of the solids. There are two sources of solids in the

Canal: NYC Harbor (i.e., tidal exchange and the flushing tunnel) and CSOs. To assess the

depositional patterns of solids from CSO solids only, a solids transport model can be used if the

grain size distribution of the solids from CSOs and the hydrodynamic patterns in the Canal are

known. Alternatively, a chemical pattern that is unique to solids from CSOs (i.e., a tracer) can be

used to differentiate solids from CSOs from background conditions. The City anticipates that the

sampling of the CSOs currently underway under CERCLA will be successful in identifying a

tracer for solids from the CSOs. For this option the City proposes using a tracer analysis in

conjunction with yearly bathymetric surveys to monitor the deposition of CSO solids in the

Canal.

Once the depositional areas, identified by bathymetric surveys, are delineated the City proposes

sampling these areas for chemistry (tracer analysis). The analytical results can be used to assess

the source of solids in the depositional area. It is anticipated that once the fingerprint and

common depositional patterns for the CSO solids are established it will no longer be necessary to

conduct annual tracer studies. It is recommended that the tracer analysis be conducted annually

for five years to establish baseline conditions and, thereafter, once every five years.

The annual estimated cost for monitoring the solids using the proposed method is approximately

$230,000 (see Attachment A-2) in 2012 dollars. This estimate assumes that a multi-beam

bathymetric survey for the entire Canal will be conducted annually and a minimum of

15 samples will be collected from areas identified as depositional. The cost for the tracer

analysis is based on the analytical costs provided to the City for the current CSO sampling. After

five years, the annual monitoring cost would drop to approximately $60,000 (bathymetry and

data analysis only [2012 dollars]) with the more extensive sampling conducted only every five

years. Table 1 presents the present worth for annual monitoring of CSO solids deposition.

Monitoring is anticipated to start in 2022 following the completion of remediation activities in

the Canal. Figure 4a is a process drawing for the yearly monitoring program.




This measure is feasible and the results of this evaluation will quantify the accumulation rate of

solids from CSOs which can guide maintenance dredging activities as needed.

5. Maintenance dredging of CSO solids in the Canal:

This Option evaluates the feasibility of regular maintenance dredging to reduce solids in the

Canal. The upper reaches of the Canal were last dredged in 1975. Since that time sediments

have accumulated in the Canal. During low tide, sediment deposits, particularly at the head of the

Canal, are above water and the odors associated with them negatively impact the community.

Under the terms of the Consent Order, in February 2012 NYCDEP submitted permit applications

for environmental dredging of the Canal. In May 2012, NYCDEP prepared a Basis of Design

Report (BODR) in support of the dredging along with a preliminary cost estimate for dredging

approximately 7,800 cubic yards of sediment from the upper 825 feet of the Canal.

At this time, no information is available on the sediment generation rate in the Canal related to

the CSOs. Because of this, it is difficult to predict the required frequency of the maintenance

dredging program or the volume that will be handled during each event. To assist the City in

their decision-making process regarding the optimum timing for maintenance dredging, a

mathematical model was developed presenting the estimated dredging costs for a variety of

dredging project sizes. In developing this model, the hourly rates presented in the BODR for

labor and equipment were converted to volume-based unit prices for dredging based on a

production rate of 45 cubic yards per hour (as specified in the BODR). This model was then

used to estimate dredging costs for various project sizes. The results of this analysis are

presented graphically to provide an understanding of the impact of size on the cost of dredging.

Figure 5a shows the estimated dredging costs (2012 dollars) for a range of project sizes – from

500 to 6500 cubic yards. To develop a range of potential costs for each project size, the

anticipated costs for a certain sized project was reduced by 5 percent to estimate the lower

boundary and increased by 15 percent to estimate the upper boundary. The upper and lower

estimated costs are also shown on Figure 5a. The 2012 project costs were converted to a cost per

cubic yard for the three price levels (upper, lower and anticipated costs) to provide a value that




can be correlated with bathymetric survey data for decision-making purposes. The cost per cubic

yards for the three cost profiles are shown in Figure 5b.

The following critical assumptions were used in developing the estimated costs:

1. Maintenance dredging would not start until after CERCLA remediation activities in the

Canal, including the initial removal of contaminated sediments, stabilizing the remaining

sediments, and capping of the stabilized sediment, has been completed. Because of this it

was assumed that the majority of debris in the sediment will have been removed and the

bulkheads surrounding the Canal stabilized. The CERCLA remediation program is

anticipated to be completed in 2022. This estimate is based on the task durations

provided in USEPA’s Draft FS (Appendix F) for the various activities.

2. Currently, there is limited information on the generation rate for CSO solids in the Canal.

For purposes of this calculation, it was assumed that maintenance dredging would be

conducted approximately every 5 to 10 years (5 years assumed for this estimate) after the

CERCLA remediation program has been completed. Therefore, 2012 dredging costs

were escalated to June 2027 based on an average annual rate of inflation of 3 percent.

3. Maintenance dredging would be conducted in the general vicinity of existing CSO

overflow points RH-034 and OH-007. The location and timing of maintenance dredging

would be based on the results of the yearly monitoring program (Option 4) implemented

by NYCDEP.

4. For comparison purposes future costs were discounted to a present worth (2012 dollars)

using a 5 percent discount rate.

5. The BODR estimate assumed a daily production rate of 45 cubic yards per hour for

mechanical dredging. This is a relatively low dredge production rate and reflects the site

conditions under which the dredging company would need to operate. These would

include numerous low bridges, a narrow canal, numerous buried utilities, and other Canal

users. Because of the low production rate, the estimated cost is conservative and actual

costs may vary.

6. The amount of capping material that will be disturbed by maintenance dredging is

unknown but will vary based on the area from which dredged solids are removed. For




this estimate, it was assumed that the amount of replacement capping material would vary

from 25 to 50 percent of the volume of dredged material.

7. The BODR included several costs that were not included in the cost model: two weeks of

standby time, coring to document cap thickness, armoring of the cap, and debris removal.

These costs were eliminated from the modeling for the following reasons:

a. Standby time is included for budgetary purposes to provide an allowance to cover

unforeseen down time. However, the BODR estimate was already based on an

8-hour work day (for production purposes) but the labor and equipment costs

were based on a 12-hour work day, or approximately 50 percent standby time.

The additional standby time was not felt to be warranted for this analysis and was

removed from the estimate.

b. Capping material is provided to maintain the integrity of the CERCLA

remediation system that would potentially be disturbed by maintenance dredging.

Coring of the cap has the potential to impact the integrity of the CERCLA

remediation system design and disturb the multi-layered cap and the underlying

the material. Instead of coring, bathymetric survey data (already included in the

project costs) can be used to document cap thickness.

c. Armoring was included in the BODR design to control erosion and its use may be

warranted, particularly at the outfall of the Flushing Tunnel. However, dredging

of the Canal would likely result in the removal of at least some of the armor

which would have to be replaced.

d. The majority of debris would be removed during CERCLA remediation so

additional costs were not warranted.

8. The cost estimate did not include either environmental monitoring during dredging

operations or wastewater treatment of water generated during sediment processing.

In October 2006, a joint venture (JV) of Greeley and Hansen, O’Brien & Gere, and Hazen and

Sawyer developed a dredging cost curve for use in the JV’s Facility Plan Report. Dredging costs

were presented on a cost per cubic yard basis as a function of the volume of material to be

dredged. Following the preparation of the original memorandum, additional information was

obtained from a dredging company with significant experience in dredging in restricted/confined




areas of New York Harbor and a second cost curve was developed. Costs for the second curve

were higher than on the first curve.

The costs from the two cost curves generated by the JV are shown on Figure 5c in 2012 dollars.

The 2006 costs presented in the memo were inflated to 2012 costs assuming a 3 percent annual

inflation rate. The present worth of the maintenance dredging program costs on a cubic yard

basis (2012 dollars) for various sized projects are also shown on Figure 5c for comparison

purposes. The present worth of anticipated dredging costs falls between the two cost curves

developed by the JV as presented in the 2006 memo. The comparison suggests that the cost

model developed for the Gowanus Canal maintenance dredging program provides a reasonable

estimate of the potential costs associated with a maintenance dredging program.

In reviewing the cost curves, it is apparent that small dredging programs have a significantly

higher cost on a per cubic yard basis compared to larger sized programs. However, the shape of

the curve (Figure 5c) suggests a declining marginal cost for projects larger than approximately

2000 cubic yards. On this basis, the recommended minimum-sized maintenance dredging

program should be approximately 2500 cubic yards. Other factors, such as depth and location of

the solids accumulation, should also be factored into the decision to conduct a dredging

operation. The actual timing on maintenance dredging will be determined based on the results of

the yearly monitoring (Option 4).

6. Additional regular sewer cleaning in the drainage area:

This Option evaluates the need for a regular sewer cleaning program in the drainage area near the

Gowanus Canal to reduce solid releases to the Canal.

Sewers are designed to convey sewage fast enough to prevent debris and sediment from settling

in the pipe and creating blockages but slow enough to prevent scouring and erosion. When

periodic obstructions do occur, NYCDEP has a Sewer Operations and Analysis Program which

combines sewer data with information on the geographic distribution of sewer backups to

identify areas that have a high frequency and density of confirmed issues. Analysts map this

data to better visualize and identify segments and neighborhoods that have recurring problems.




After the Sewer Operations and Analysis Program identifies a study area, NYCDEP closely

inspects sewer segments in the area to identify underlying factors and primary causes of

recurring sewer backups. Once a cause is identified, a remediation plan is developed, which can

include degreasing, regular cleaning, repair, and/or replacement.

One of the primary causes of sewer obstructions is the improper disposal of fats, oils, and grease

in the drain rather than in the garbage. According to the USEPA, grease accounts for nearly half

of all sewer backups. NYCDEP has a number of programs to fight the buildup of grease in City

sewers. Restaurants, hospitals, schools, and other businesses that serve food are required to

install traps to contain grease at the source. NYCDEP regularly inspects these traps to make sure

that they are properly sized, installed, and cleaned. In addition, to tackle the problem of

recurring grease buildup, a number of new degreasing products are being tested to determine

what would be most cost-effective, efficient, and environmentally sustainable.

The City currently has a sewer cleaning program, implemented by the Bureau of Water & Sewer

Operations (BWSO), which flushes and cleans the sewer system based on the pattern and

frequency of NYC-311 complaints. When a field crew responds to a customer call, they will

proactively flush or clean the sewer segment with water to ensure that it is clean and working

properly, whether or not a blockage is confirmed. From July 2011 to June 2012, NYCDEP crews

cleaned 482 miles of sewers when responding to customer calls. BWSO also responds to

NYC-311 complaints regarding clogged catch basins and street flooding. In addition, a special

rain patrol is also sent out during heavy storms to clear debris off the top of catch basins. When a

weather event is forecast, crews pre-inspect areas prone to flooding to ensure infrastructure is

operating properly.

During the 2003 through 2011 time period, BWSO responded to twenty-nine NYC-311 customer

complaints and cleaned approximately 19,000 linear feet of sewer lines. Figure 6a shows a map

that displays the sewer cleaning sites from 2003 to 2011 in the Gowanus Canal Area. The cost

of cleaning these locations was approximately $300,000. It is not anticipated that additional

sewer cleaning would have an appreciable reduction in the CSO solids in the Canal.




7. Sedimentation basin at outfall RH-34:

This Option evaluates the feasibility of constructing an in-canal sedimentation basin at outfall

RH-034. This basin would serve a similar function to the sediment chamber at OH-007 (Options

1 and 2) but would be more permanent than a silt curtain (Option 3). Sedimentation basins are

generally implemented to create a low velocity region to promote the settling of suspended

sediments. The solids removal rate for different solids size classes discharged from the CSO at

the head of the Canal is the key design parameter.

Computational fluid dynamics modeling was used to conduct a screening-level analysis of

solids-removal for a constructed solids-settling zone at the head of the Canal. Two simple

settling-zone configurations (Figure 7a) were investigated. In both configurations, a submerged

weir was used to define the solids-settling zone within the Canal. The crest elevation of the weir

was set 1 ft below mean lower low water so that the weir remains submerged, allowing some

tidal exchange of the water within the solids-settling zone while still protecting the area’s ability

to retain solids. The depth to the native sand layer was estimated at El. -18 ft NAVD88.

• In the first configuration, the submerged weir extends straight across the Canal,

approximately 100 ft from the head, so that the entrance of the flushing tunnel at

Douglass St. is just downstream of the submerged weir.

• In the second configuration, the solids-settling area extends an additional 300 ft

downstream, but only along the half of the Canal opposite the flushing tunnel. This

provides an “L-shaped” solids-settling area that is protected from disruptive currents

while still allowing the flushing tunnel flow to proceed downstream without interfering

with solids settling within the basin.

The modeling analysis indicates that constructing a 100 ft x 100 ft solids-settling zone at the

head of the Canal would be effective in capturing and detaining heavier solids for the range of

CSO flow rates that would be encountered over the course of a year (Figure 7b). Lighter solids

would be captured at a significantly lower rate, and would be more easily scoured out of the

basin during higher CSO flow events. Specific results (Figure 7c) of the screening analysis

indicate that even during peak annual flow conditions, capture of sands (grain size greater than




149 µm) is expected to be at least 70 percent with little if any scouring of accumulated solids of

this size. Under the same conditions, capture of coarse silts (grain size 62 to 148 µm) is

expected to be less than 15 percent, but little if any of these solids are expected to be scoured out

of the settling area. Under peak flow conditions, capture of smaller sized solids is expected to be

minimal and analyses indicate that scouring of solids smaller than about 50 µm is likely.

Therefore, despite relatively high (nearly 50 percent) expected capture rates for smaller solids

such as fine silts (grain size 16 µm) during typical CSO flow rates of 10 million gallons per day

at RH-034, it is likely that such solids would be scoured away during subsequent high intensity

storm events. Due to the potential loss of accumulated solids due to scouring during intense

storms, accumulated solids levels in the sedimentation basin would need to be monitored and

dredged regularly to optimize solids control.

The modeling indicated that CSO flow rates significantly influence solids capture (Figure 7d)

while tidal conditions and the settling-areas configuration were generally secondary factors. As

a screening-level analysis, this modeling was not able to evaluate the impact of the following:

• The difference in density between the CSO flow and the canal water.

• The grain-size distribution of solids in discharges from RH-034.

• The variability of grain size distribution with respect to CSO flow rate.

• The impact of sediment accumulation (that is, a shallower settling-area depth) on the

tendency to scour solids in the trap.

While a sedimentation basin would be relatively effective in capturing coarse solids, there are a

number of drawbacks to the use of such a basin at RH-034:

• Overall solids accumulation rates are low, averaging less than 30 percent.

• The modeling results indicate that it is unlikely that the basin would be effective in

removing and/or retaining a significant portion of fine-grained sediments.

• Fine-grain sediments that are initially retained may be resuspended during later storm

events and scoured out of the basin during higher CSO flow events.




• The retention of sediments can be further reduced if the storm event duration is long.

• Since the Canal currently captures some fraction of the CSO solids, the actual increase in

capture rate for a sediment trap would be less than the theoretical capture rate estimated

by the model. (The actual increase in capture rate is beyond the scope of this study.) In

addition, without very frequent maintenance, the sediment trap would quickly become

ineffective.

• The proposed sedimentation basin has the potential to exacerbate, in the localized area of

the basin, the same types of water quality and odor problems that are currently observed

at the head end of the Canal.

The anticipated capital cost for the rectangular sedimentation basin and the L-shaped basin are

presented in Attachments A-3 and A-4, respectively. The estimated costs to construct a solids-

settling area at the head of Gowanus Canal would range from $4 to $15 million (present worth in

2012 dollars). These costs are based on the assumption that the sedimentation basin would be

constructed in conjunction with the remediation work in the Canal (in approximately 2015).

Following dredging in the head end of the Canal, the submerged weir would be installed.

Following weir installation, the ISS and capping work would be completed. The feasibility of

installing a sheet pile wall through the underlying deposits after the ISS process has been

completed without fracturing the ISS layer and disrupting its intended purpose cannot be

determined based on available information. For planning purposes, it was assumed that the weir

would be installed prior to the ISS process. Costs were included in the estimate to cover

additional mobilization demobilization costs due to the change in construction sequencing.

The present worth of the annual O&M costs will be based on the volume of sediment that is

captured by the sedimentation basin, which could vary substantially depending on the timing of

the dredging operations relative to storm events. To optimize solids control, it is anticipated that

the basin would need to be dredged every two to five years; for this estimate, it was assumed that

the basin would be dredged every three years, removing approximately 500 to 1500 cubic yards

of material each time. Maintenance dredging costs calculated for Option 5 were used to estimate

the O&M costs.




On the basis of the currently available information, along with the high cost to construct and

operate the system, relatively low removal rate and potential downsides, the construction of a

sedimentation basin at RH-034 does not appear to be cost effective.

8. Pilot study for remedial design:

The goal of this Option was to seek opportunities to advance the development of remedial

standards for the Gowanus Canal site by conducting studies that could be used to complement

the dredging planned for the head of the Canal. The City considered several alternatives for pilot

studies under this Option, including:

• Monitoring dredging resuspension

• Testing different cap types ( variations in carbon or permeability)

• Pore water monitoring of backfill or caps

• Collect quality of life data during dredging

o Air emissions

o Light and Noise

• Ex-situ dredged material treatment (decontamination) options

• Enhance settling techniques (baffles/deeper depths)

• Evaluation of restoration concepts

Of these alternatives, three were considered appropriate for further evaluation: pore water

monitoring for backfill and caps, decontamination options, and assessment of restoration

concepts. Because a number of studies have been conducted at other Superfund sites on the

other suggested topics and the results of these investigations are readily available in the

literature, we focused this analysis on those alternatives for which information is not readily

available.

8.1. Habitat Restoration Pilot Study:

This option evaluates the feasibility of restoring a segment of the urbanized Gowanus Canal as

a riparian restoration pilot project. An essential goal of the pilot design is to provide habitat

and an aesthetically pleasing open space in this highly urbanized area. NYCDEP has




supported this vision of restoration of the Canal, and has worked in partnership with the US

Army Corps of Engineers (USACE) toward that goal. USACE has completed several studies

of the Canal for the purpose of restoration, under Gowanus Canal and Bay Ecosystem

Restoration Project. These plans were curtailed when USEPA listed Gowanus Canal on the

NPL. However, the City still maintains that this waterway is an excellent site for an ecosystem

restoration project.

As part of the New York-New Jersey Estuary, which USEPA has designated an Estuary of

National Significance, it is important that the Gowanus Canal’s ecological potential be

considered in conjunction with the Canal’s contamination issues. Historically, the Canal

provided valuable habitat that was degraded over time as the area evolved into an industrial

corridor. Significant recovery of the Canal’s ecological conditions is impeded by an altered

hydrologic regime, hardened shorelines, extensive fill, poor benthic community structure, lack

of buffers, and contaminated sediments.

Federal, state, and local agencies, as well as local community groups, have invested energy

into developing revitalization plans for the Canal, including improved environmental

conditions and the creation of open space and recreation opportunities.

• The USACE in collaboration with the NYCDEP implemented the Ecosystem Restoration

Feasibility Study of the Gowanus Canal, which identified ecosystem restoration

opportunities for the Canal.

• The New York City Department of City Planning is developing the Gowanus Canal

Corridor Framework in response to petitions from local residents for land use changes

and the creation of open space and recreational opportunities.

• The Gowanus Canal Conservancy, an independent environmental 501(c)(3) nonprofit

organization formed in 2006, developed the Gowanus Canal Sponge Park, which is a

model for a linear park along Gowanus Canal that would provide public access and

recreation opportunities as well as improve water quality of the Canal through the

construction of retention basins and treatment wetlands.




Drawing from these efforts, the following pilot project summarizes an approach to create a

pilot riparian buffer restoration project to improve water quality and aquatic habitat and

achieve ecological uplift as well as improved public use. The proposed pilot project would

transform a section of deteriorated asphalt and bulkhead into a band of tidal marsh, scrub

shrub, and upland trees. Three potential pilot study sites were identified as part of this effort

(Figure 8-1a).

• Creamer Street Site. The Creamer Street Site is located east of Smith Street between

Bay Street and Creamer Street, just south of the I-278 bridge (see Figure 8-1b). This area

is designated “Site 1” in the USACE study for the Gowanus Canal and Bay Ecosystem

Restoration Project. The primary difference between this proposed pilot project and

USACE’s proposed project is that USACE assumed that the site would extend 20 feet

into the Canal while the City’s approach is to extend 30 feet landward of the Canal.

Contact with the property owner (listed as CF Smith, LLC) regarding site use was not

attempted; however, the presence of vegetation growing within the asphalt suggests that

this portion of the property is not frequently used.

• Huntington Street Site. The Huntington Street Site is located adjacent to the Canal, east

of Smith Street and south of Huntington Street (see Figure 8-1c). The bulkhead along this

stretch of the Canal is not maintained, making shoreline restoration efforts appealing. Its

proximity to residential areas and existing open space (i.e., St. Mary’s Park) and the

potential public access routes to the site via Huntington Street and 9th Street further

promote this location as a pilot project site. In addition, this location is strategic in its

potential to tie into future redevelopment of the area in conjunction with the cleanup of

the former Citizens Gas Works GMP Site. Implementing a pilot habitat restoration

project on publicly-owned land (listed as New York City Transit) could be less complex

than pursuing a pilot project on privately-owned land.

• Former Citizens Gas Works GMP Site. The former Citizens Gas Works GMP Site,

which the City of New York plans to redevelop as a housing complex, offers a unique

location to implement a habitat restoration pilot project. The site is located adjacent to the

Huntington Street Site, east of Smith Street and north of Huntington Street (see

Figure 8-1d). Similar to the Huntington Street Site, the former Citizens Site is




strategically located near residential areas and existing open space (i.e., St. Mary’s Park)

and is publically-owned. Public access routes could be incorporated into the pilot project

design as part of the site’s redevelopment plan.

At each potential location, the proposed restoration project would be accomplished by cutting

the existing bulkhead to a target elevation, constructing a new land side structural bulkhead,

excavating the site, and placing clean substrate to achieve elevations that experience tidal

inundation, and planting the area with native species. Additional elements such as a tidal pool

or mud flat may also be incorporated into the design. Approximately 200 feet by 30 feet of

restored habitat could be accomplished at each site. A conceptual rendering of the proposed

pilot project is provided in Figure 8-1e.

The potential for this pilot study to promote the public understanding and stewardship of the

environment is tremendous. Elements such as a boardwalk or path, interpretive signs, or

learning stations would be a valuable addition to this pilot project.

Implementation of the pilot riparian restoration project will require conducting multiple

baseline studies, coordination with stakeholders, and negotiations with landowners to change

its end use. Several baseline studies would be required to support developing permit and

construction plans, including:

• Geotechnical evaluation

• Topographic survey

• Bathymetry survey of the canal

• Characterization of soils

• Hydrologic and hydraulic analysis

• Ecological Risk Assessment.

Based on the findings of the baseline studies, permit applications and engineering plans would

be developed. Permitting of this project would likely be complicated, with numerous




approvals and certificates required. A public outreach program would be developed and

implemented to involve the local community in the program.

A preliminary cost estimate (Attachment A-5) was prepared based on restoring a 215 x 30-foot

area. Within the accuracy of this conceptual level estimate, the construction cost for all three

sites is approximately the same; actual costs may vary based on site specific conditions

identified at each site. The site specific conditions would be established through the baseline

studies conducted during the design process. Costs for monitoring, invasive species

maintenance, and replanting (first five years only) were included in the preliminary cost

estimate. Unit costs were derived from published and unpublished sources including New York

State Department of Transportation US Customary Contracts Let July 1, 2010 to June 30,

2011, Pinelands Nursery 2012 catalogue, R.S. Means, and professional judgment.

In preparing the cost estimates, the following assumptions were made:

• Costs do not include design or construction of public access elements, or costs associated

with access or legal agreements with the land owner.

• Material removed from the site will be disposed in a Subtitle D landfill based on

chemical analysis. Reuse or recycling of some materials may be possible, potentially

lowering costs.

• Construction would not start until after the CERCLA remediation activities in the Canal

with the projected date for the construction of the pilot project in 2022.

This pilot study could be conducted without the need to wait for completion of CERCLA

remedial activities, since the design provides for removal of soil from behind the bulkhead and

construction of riparian habitat in an area that is not part of the Superfund site. For this

analysis, construction in 2016 was assumed. Capital and monitoring and invasive species

management costs were estimated in 2012 dollars and escalated to 2016 costs based on a

3 percent inflation factor. The future costs were then discounted to a present worth using a

5 percent discount rate. The estimated present worth for the construction and 30 years of

management of the habitation restoration pilot project is approximately $3,500,000.




8.2. Pore Water Sampling Pilot Study:

This option evaluates the feasibility of using a pore water monitoring system as a means of

monitoring the cap performance. For this analysis the primary contaminants of concern are

PAHs and BTEX.

The draft FS for the Gowanus Canal prepared by consultants for the USEPA recommended

dredging of contaminated sediments, strengthening/stabilizing the soft sediment in the Canal

using In-Situ Stabilization/Solidification (ISS), and covering the area with a multi-layer cap. A

contaminant plume underlying the Canal has the potential to leach contaminants back into the

Canal through upwelling of contaminated groundwater. The ISS is intended to minimize the

transmission of contaminated groundwater to the Canal and the cap is designed to treat

contaminants leaching from the underlying material before it is discharged to the surface water.

Historically, cap monitoring has relied on cores or sediment grab samples to assess the

performance in controlling the upward migration of contaminants from underlying sediments,

but this approach has its weaknesses in that sediment concentrations do not always correlate

with the bioavailability of contaminants in the pore water. Cores or grab samples taken from

the cap are usually analyzed as a solid for contaminants that may have sorbed onto the soil

particles and do not address the question of the contaminants contained within the pore water.

In addition, these types of samples may lose pore water during the sample collection process

resulting in a non-representative sample measured off the core. However, the contaminants in

the pore water remain an exposure route, particularly in bioaccumulation.

To address this issue, consideration is being given to more direct sampling of pore water to

assess cap performance. Pore water sampling devices fall into several general categories:

• Probe/vacuum (syringe) samplers – The types of samplers are similar to a syringe – the

probe end is placed at the depth where the sample is to be collected and a plunger or

small pump is used to create a vacuum drawing a sample into the probe. In areas where

fine-grained materials predominate, a filter pack may be required on the probe end to




prevent sediment from being drawn into the probe. The sample is analyzed using

standard laboratory methods. Several samples may need to be collected to obtain enough

pore water for the desired analysis. The Trident Probe, one example of this type of

system developed at the Space and Naval Warfare Systems Center Pacific, is available

for rental from equipment suppliers.

• Passive (or diffusion) samplers – These types of samplers are based on the transfer of

contaminants through a semi-permeable membrane or allowing contaminants to sorb onto

the sampler media. Examples of passive samplers include:

o Diffusion (dialysis) bags

o Peepers

o Semi-permeable membrane devices (SPMD)

o Polyoxymethylene extraction (POM)

o Polyethylene sheets

o Polydimethylsiloxane fibers (PDMS)

o Solid phase micro extraction (SPME)

The sampler is placed into contact with the sediment and left in place for several days to

several months, to allow the sampler to equilibrate with the surrounding conditions.

Although passive samplers have been used in groundwater monitoring for a number of

years, historically, the analytes were limited to VOCs, constrained by the ability of the

contaminant to diffuse through a membrane. Recently passive samplers have been

developed that can be used to sample PAHs and PCBs. However, many of these types of

samplers require relatively complex (and potentially expensive) laboratory procedures to

recover the sample from the sampling device. Performance reference compounds must

be preloaded onto the samplers to allow the results to be calibrated for the contaminants

of interest.

• Piezometers/monitoring wells (direct pore water sampling) – Monitoring wells and/or

piezometers can be established within the sediment to allow regular sampling of the pore

water, similar to groundwater sampling. Well points (a/k/a sand points) can be driven

into the sediment to a set depth and samples of the water at that strata sampled. In many




instances, this was the sampling method used to validate the alternative samplers and

their results. The well points can be recovered (pulled) or left in place to allow periodic

monitoring at the same location. If left in place, the riser pipe would need to extend

above mean higher high water level to prevent the well from being contaminated by

surface water inflows. Extended risers have the potential to be vandalized or create a

boating hazard. In addition, the underlying sediment must be strong enough to support

the well, well riser, and pipe support/stabilizer. Samples are analyzed using standard

analytical procedures.

The above samplers can be used to obtain information about the characteristics of the pore

water quality, but do not provide information on the rate the pore water is being discharged to

the surface water. Seepage samplers measure the flux from the sediment to surface water and

can be used with the pore water samplers to determine the rate contaminants are released to the

surface water. The Ultra Seep (Pacifica Oceanographics) is one example of a sampler used to

measure the flux across the interface allowing an assessment of the quantity of contaminants

that are being released from the sediment into the surface water.

Given the availability of equipment and apparent relative ease of the sampling approach, a

sampling program based on the use of a Trident Probe sampler could be developed, with or

without seepage monitoring. One or more sampling events could be conducted to monitor

conditions over time. The program would involve the following elements:

• Work plan and monitoring program development – Prior to the start of the study, a

work plan and other documents would be developed to establish goals and metrics for

evaluating the results. The work plan would include a field sampling plan and analytical

requirements (e.g., quality assurance project plan (QAPP)) to verify the results of the

sampling and laboratory analysis, and evaluation of the results of the sampling program.

Prior to subsequent events (if any), the work plan/monitoring program would be reviewed

and updated as necessary based on the results of the last sampling event.

• Field preparation for each sampling event – Prior to each event, the Health and Safety

Plan would be updated and arrangements made for boat and safety equipment.




Arrangements would be made to rent and ship the sampling equipment. The laboratory

selected to perform the analyses would be contacted and arrangements made for

appropriate sample bottles to be shipped.

• Sampling – During the sampling event, samples would be collected in RTA 1

(headwaters of the Canal). Samples would be packed in ice and delivered to a

commercial laboratory under contract with the City for analysis for PAHs and BTEX

under standard Chain of Custody protocols with a standard turnaround time.

• Follow up to sampling event – Equipment would be decontaminated and returned. Field

notes would be prepared and filed.

• Reporting – Once the analytical results became available, they would be incorporated

into an electronic database to facilitate analysis and documented in a brief letter report.

A conceptual cost estimate was prepared for one round of sampling (Attachment A-6). The

program was assumed to take approximately 2 to 3 days to complete and would involve

collecting pore water samples from approximately 25 locations in the head of the Canal.

Samples would be analyzed for PAHs and BTEX. This work could be conducted after the

CERCLA remediation program (anticipated to be conducted between 2014 and 2022 based on

the anticipated construction schedule), or as a pilot study for an interim dredge and cap

measure in the Canal (approximately 2014 to 2015).

If the sampling program were conducted following the CERLCA remediation program, the

contaminant levels in samples of the multi-layered cap would be tested. Contaminants

detected in the pore water would be an indication of the impact the water quality in the Canal

has on cap quality and, potentially, the degree NAPL in the underlying sediments are released

to the surface water. The time between the completion of capping operations and sample

collection would be a factor in the results of the analysis indicating the extent of contaminant

flux.

While either program would assess the performance of cover materials in isolating surface

water from underlying contaminants, it is recommended that the sampling be conducted

following the CERLCA remediation to allow an assessment of the performance of the ISS and




multi-layer capping system in controlling NAPL releases to the surface water. The longer the

time between cap/backfill placement and sample collection, the more likely contaminant

migration will be detected.

For this estimate, it was assumed the sampling would be conducted as part of an interim dredge

and cap measure in 2015. Current 2012 costs for the sampling program were estimated and

escalated to 2015 costs using a 3 percent inflation factor. These future costs were then

discounted to estimate the present worth of the sampling program assuming the project was

conducted following environmental dredging. For one round of sampling, the present worth

was estimated to be $200,000.

8.3. Dredged Material Decontamination: Sediment Washing Pilot Study

This Option assesses conducting a sediment washing pilot study to evaluate the effectiveness

of this approach as an alternative to off-site treatment and disposal of dredged materials from

the Gowanus Canal. Soil/sediment washing has been used for a number of years on materials

recovered from maintenance dredging activities. Historically, these systems focused primarily

on separating coarse- and fine-grained materials. Because contaminants do not readily bond

with coarse-grained materials (sand, gravels, and rock), this fraction can generally be reused

without further treatment. The remaining fined-grained soils and organic matter, which more

readily bond with contaminants, can then be characterized, treated as necessary, and disposed

in accordance with applicable regulations. Sale or use of the coarse-grained materials provides

a potential revenue stream or, at a minimum, reduces the volume of material that may need

treatment and/or landfilling.

Since the early 1990s, attention has been paid to developing methods for removing the

contaminants from the remaining dredged solids following the removal of the coarse-grained

materials. A number of vendors have developed sediment washing systems. Currently,

Biogenesis Enterprises, Inc. (Biogenesis) is the primary firm that is attempting to develop their

product for commercial scale operations. Other vendors have expressed interest in developing

their system for commercial operations but are not as actively pursuing this market.




John Sontag, Vice President for Engineering at Biogenesis was contacted and asked for the

cost of conducting a bench scale study of their process.4 Sontag indicated that there were three

possible options for evaluating the effectiveness of sediment washing.

Laboratory bench study: $25,000 to $45,000. Requires 30 to 50 gallons of sediment be

collected and shipped to a laboratory in Oak Creek, Wisconsin.

On-site bench study: $50,000 to $80,000. Requires 30 to 50 gallons of sediment be collected

and a small area near the site be provided to set up equipment along with access to power and

water, and a wastewater discharge point. The on-site bench study is the same as the laboratory

study but done at the client’s site to allow the client to personally evaluate the operation.

Pilot scale study: $100 to $200+ per cubic yard (~$250,000 to $500,000). Requires several

thousand cubic yards of sediment (system operates at a rate of 40 cubic yards per hour), small

area near site to set up equipment, power and water, wastewater discharge point.

The costs provided above represent the vendor costs only and do not include sample collection

and other evaluation costs. Both the laboratory and on-site bench studies require approximately

30 to 50 gallons of sediment for testing purposes. The following outlines the general approach

for implementing either the laboratory or on-site testing program.

• Work plan and monitoring program development. Prior to the start of the pilot study,

a work plan and other documents would be developed to establish goals and metrics for

evaluating the results. The work plan would include a field sampling plan and analytical

requirements (e.g., quality assurance project plan [QAPP]) for the pilot study to verify

that the process is treating the contaminants and that the reductions in contaminant levels

are due to treatment, not just internal losses within the treatment process.

• Field preparation. Prior to sediment collection, a Health and Safety Plan would be

prepared and arrangements made for boat, safety, and sampling equipment. In addition,

for the on-site study, the City would need to provide a site with access to power, water,

and a discharge point for wastewater generated in the treatment process.

4 During these discussions, BioGenesis was only told that the material would be recovered from maintenance dredging activities in the New York area and that the potential contaminants included PAHs, BTEX and organics.




• Sampling. The sediment sample would be collected and placed in a 55 gallon drum (or

equivalent container). Sediment grab samples would be collected using a Ponar grab

sampler or similar devise. It is anticipated that the sample collection would take one to

three day, depending on conditions. If the laboratory study is performed, arrangement

would be made to ship the sediment to the testing facility. Otherwise, the container

would be delivered to the planned site for the on-site testing program.

• Oversight and Reporting. For the on-site study, engineering oversight would be

provided during the testing. Once the results of the study became available, they would

be reviewed for the conclusions drawn regarding the use of sediment washing for the

Gowanus Canal sediment.

The full scale pilot study would require the collection of a significantly larger volume of

sediment for treatment. The Biogenesis facility is designed to operate at approximately

40 cubic yards per hour, or approximately 960 cubic yards per day. Because one of the

purposes of the pilot study is to demonstrate that the system can operate in continuous feed

mode, it would be necessary to obtain enough material for several days of continuous

operations (2,500 to 3,000 cubic yards of sediment). Generally, a full scale pilot study would

only be conducted after a bench scale laboratory study indicated that sediment washing would

significantly reduce the volume of contaminated material requiring either additional treatment

prior to disposal or costly disposal as a hazardous or toxic waste.

A conceptual level cost estimate was prepared for two firms to conduct on-site bench scale

study. Unit costs were derived from published and unpublished sources and professional

judgment. The costs were based on the following assumptions:

• Available land at a site close to the Canal would be available for the on-site bench study

at no cost to the project. Water and power would be available at the site and access to a

sewer for discharge of water from the treatment system. Estimated utility costs have been

included in the project budget.

• Sediment and treated material remaining after the on-site study would be stabilized with

cat litter or other absorbent material and hauled to a Subtitle D landfill for disposal.




The conceptual cost estimate (Attachment A-7) assumed one round of testing by two firms

would be performed at a site near the Canal. This work would be conducted during the

CERCLA remediation program for the Canal (approximately 2016 based on the anticipated

construction schedule). Costs were estimate in 2012 dollars for the sampling program and

escalated to 2016 costs using a 3 percent inflation factor. These future costs were then

discounted to estimate the present worth of the sampling program. For one round of on-site

bench scale testing by two firms, the present worth was estimated to be approximately

$600,000.

Conclusion and Recommendations

NYSDEC identified and requested the evaluation of eight Options for addressing CSO solids in

the Gowanus Canal. Table 1 provides a summary of the screening-level evaluation of these

Options in terms of effectiveness in controlling CSO solids, costs, and recommendations for

future evaluation. Of the Options evaluated, one Option has been already implemented by the

City and three Options were considered potentially feasible. The Option already implemented

by the City is:

• Option 1 – optimizing the performance of the sediment chamber through cleaning and

repair of the facility in March 2012.

The three Options suggesting some effectiveness in addressing solids from CSOs are:

• Option 2 – implementation of a program to monitor conditions in the OH-007 sediment

chamber and provide routine cleaning and repairs as necessary to maintain the optimum

performance of the chamber.

• Option 4 –monitoring of solids deposition rates from CSO outfalls. Implementation of

this option would provide additional information for future evaluations associated with

the outfalls. This monitoring is proposed to begin after completion of the Superfund

remediation project.

• Option 5 – maintenance dredging of the Canal to remove CSO-generated solids if CSO

solids are determined to have a detrimental impact on the Canal or pose navigational




problems within the Canal. If supported by the monitoring results from Option 4, a

periodic maintenance dredging program could be implemented. This monitoring is

proposed to begin after completion of the Superfund remediation project.

Three of the eight Options are not recommended for addressing solids from CSOs. These

include:

• Option 3 – installing silt curtains and/or netting facilities. This Option was not

recommended for several reasons. Silt curtains are generally considered temporary

installations and have a number of drawbacks in long-term applications. In addition, the

cost of installing and maintaining silt curtains at RH-034 and OH-007 would be in excess

of $33,300,000, while yielding little in the way of long-term CSO solids control.

• Option 6 – additional sewer cleaning. The City’s current program of sewer cleaning on

an as-needed basis has proven effective in maintaining drainage in the area and

increasing the rate of cleaning is not warranted. The sewer is designed to maintain self-

cleaning velocities in the pipelines and, except for periodic disruptions in service due

largely to inappropriate discharges to the sewer, additional cleaning is not necessary.

Additional sewer cleaning will not reduce the discharge of CSO solids to the Canal.

• Option 7 – construction of an in-canal sedimentation basin at RH-034. This Option was

not recommended for several reasons. The first is that the basin will not prevent the

discharge of solids to the Canal. While the trap may capture some of the solids, solids

may remain in suspension for extended periods and could be washed into the Canal over

the weir through tidal flow or subsequent rainfall events. Secondly, captured solids will

accumulate behind the weir resulting in the same nuisance odors and conditions that are

now present at the head of the Canal. And finally, the cost for construction and

maintenance of the basin is excessive for the expected control provided.

Option 8 was aimed at evaluating ways to seek synergistic opportunities to advance the

development of remedial standards for the Gowanus Canal site. Three possible studies were

evaluated: pore water sampling in caps, sediment washing for sediment decontamination, and

habitat restoration. All three approaches are recommended for further consideration.




REFERENCES

1897 As-Built. “Detail for the Silt and Trap Basin for the Main Relief for the Third and Fourth

Avenue Sewers, August 31, 1897.” Obtained from J. Moran, Chief, Emergency Construction

Division, NYCDEP-BWSO.

2006, O’Brien & Gere. “OH-007 Trap Basin Inspection – Owls Head Drainage Basin,”

Memorandum from Naeem Anwar to Lowell Kachalsky, O’Brien & Gere. Prepared under WP-

169, CSO-LTCP.

2012, HDR|HydroQual. “Performance Assessment of Sedimentation Basin at Outfall OH-007,”

Draft Technical Memorandum prepared July 17, 2012 by S.C. Ertman.

2012, NYCDEP. “Gowanus Canal Silt Trap Basin (Outfall OH-007) – Cleaning and

Rehabilitation,” Memorandum from James Moran, Chief Construction, Emergency Construction

Division, NYCDEP-BWSO, to Anastasios Georgelis, Director of Field Operations, NYCDEP-

BWSO, April 4, 2012

Table 1: Comparison of Alternatives for CSO Solids ControlGowanus Control Superfund Site

Brooklyn, New York

10/03/2012

1 of 2

Capital O&M1

1Optimizing the existing sediment chamber at outfall OH-007

The existing sediment chamber reduces the volume of solids discharged to the Gowanus Canal.

$200,000 $0Inspection was

completed in March 2012

The sediment chamber was cleaned and repaired in March 2012. Further optimization of the OH-007 sediment chamber based on implementation of Option 2.

2Improved maintenance program at the Outfall OH-007 sediment chamber

Program aimed at maintaining the operational efficiency of the silt trap at OH-007. Estimated removal efficiency of approximately 24% of OH-007 CSO solids.

$0 $4,000,000 Annual inspection starting in 2013

Recommend annual inspection of sediment depth in the trap and cleaning as needed based on the observed accumulation rate within the chamber. Program to be implemented for 2 to 5 years to evaluate impact on performance. Present worth cost is based on annual monitoring of sediment chamber (2013 through 2042) at a cost of $150k per year and biennial repairs to the silt trap (at a cost of $50k per round) during the same period. The City will continue to evaluate alternate inspection methods not involving confined space entry.

3Silt curtains and/or netting facilities at CSO Outfalls - RH-034 and OH-007

Silt curtains are not designed for CSO outfalls due to high velocities associated with overflow events. Failure of a curtain due to high velocities may cause accumulated solids from CSOs to disperse in the Canal. Removal rates cannot be accurately assessed because of the high potential for curtain failure.

$350,000 $33,000,000

Installation in 2016 following

environmental dredging program

Not recommended as an option for isolating solids from CSOs.

4Yearly monitoring of CSO solids deposition in the Canal

Monitoring of solids accumulation will not alter CSO solids generation in the Canal.

$0 $3,000,000

Annual monitoring following completion

of remediation activities estimated

as 2022

Recommended to evaluate the annual generation rate and location of solids generated by the CSOs. This information will allow the assessment of the feasibility of other approaches to managing solids. In 2022 through 2027, monitoring will include bathymetry (depositional areas) and chemical analysis (tracer analysis). Between 2028 and 2042, annual bathymetry survey would be conducted at a cost of $60k per year but chemical analysis (at a cost of $170k per year) only every 5 years (3 events).

5 Maintenance dredging of CSO solids in the Canal

CSO solids that accumulate near RH-034 and OH-007 will be removed periodically from the Canal. The extent of the dredging operations, volume of material removed, and interval between dredging events will be determined based on the results of yearly monitoring of the solids.

NA $11,000,000

Periodic maintenance dredging to

coordinated with the results of Option 4,

commencing in 2022

Recommended if evaluation of hydrodynamics and monitoring of deposition patterns in the Canal post WQIP identify areas where the majority of solids from CSOs will settle. Cost provided based on approximately 2500 cy of solids to be dredged approximately every 5 years. The O&M present worth assumes dredging would occur in 2027, 2032, 2037, and 2042 at a cost of $4M per event. This maintenance dredging program will be implemented if it is determined that CSO solids have a detrimental impact on the canal or present navigation problems.

Notes/ RecommendationsPresent Worth Costs

Option Title CSO Solids Control Efficiency Project Linkage/ Estimated Start Date

Table 1: Comparison of Alternatives for CSO Solids ControlGowanus Control Superfund Site

Brooklyn, New York

10/03/2012

2 of 2

Capital O&M1Notes/ Recommendations

Present Worth CostsOption Title CSO Solids Control Efficiency Project Linkage/

Estimated Start Date

6Additional regular sewer cleaning in the drainage area

Sewer maintenance activities are directed at the performance of the sewer system but will have limited impact on the discharge of CSO solids to the Canal.

$0 $0 NA Additional sewer cleaning beyond the existing program is not warranted and will not decrease the flow of CSO solids to the Canal.

7 Sedimentation basin at outfall RH-034

CSO solids from RH-034 would accumulate behind a submerged weir at the head of the Canal. Accumulated solids, particularly fine-grained solids would potentially be subject to resuspension and scour from subsequent storm events. Estimated removal efficiency of approximately 30% of RH-034 CSO solids.

$4,000,000 to $15,500,000

$7,000,000 to $13,000,000

Installation following remediation of head

end of Canal (~2015)

Not recommended as an option for isolating solids from CSOs. The basin may exacerbate existing odor and water quality problems. Screening-level modeling indicates that intense storms could scour all but the heaviest accumulated solids out of the trap and into the Canal, reducing the overall effectiveness of the system. To minimize scour/loss of solids plus prevent nuisance conditions, basin needs to be dredged every 2 to 5 years (assume every 3 years) recovering solids ranging from 500 to 1500 cubic yards in volume per event. Per cubic yard cost for dredging based on maintenance dredging cost estimate (Option 5). The O&M present worth is based on 9 rounds of dredging from 2013 to 2042 at a cost of $2M to $3.5M per event, depending on volume.

8-1 Habitat restoration pilot study NA $2,900,000 $700,000

Could be constructed before completion of active remediation

(~est. 2016).

Further consideration should be given to this option to assess the ability to reestablish and maintain more natural riparian conditions in a highly industrial environment.

8-2 Pore water sampling pilot study NA $200,000 NA

Pilot study of interim measures would be possible (~2014-

2015)

Further consideration should be given to this option to assess the efficacy of the cap in isolating NAPL. This method is not as disruptive as the traditional coring method used for assessing cap performance. Also, under this option, the complete thickness of the cap can be assessed for breakthrough. In this method pore water is used as an indicator of bioavailability.

8-3 Sediment washing pilot study NA $600,000 NA

Testing during the active remediation program (~2016)

Further consideration should be given to this option to understand the options available for dredged material management.

Note: 1. Present worth based on 5% discount rate. 2. The present worth of O&M costs are based on costs for the period from 2013 to 2042. 3. See individual cost estimates for performance schedule.

Figure 1a

Location of OH-007 Sediment Chamber Gowanus Canal Superfund Site

Source: Mapquest

October 3, 2012

Figure 1b

Schematic of OH-007 Sediment Chamber Accumulated Solids Depth


October 3, 2012

Figure 1c

OH-007 Sediment Chamber Photograph of South Wall (Inlet)


OH-007 SEDIMENT CHAMBER: LOOKING SOUTH INTO INLET

October 3, 2012

Figure 3a

Type 3 Heavy Duty Silt Barrier Gowanus Canal Superfund Site

Woven Silt Filter Fabric Panels or Solid PVC

Source: www.Silt-Barrier.com

October 3, 2012

Figure 3b

Silt Curtain Conceptual Layout Gowanus Canal Superfund Site

Outfall - OH-007 Outfall - RH-034

October 3, 2012

Figure 3c

Details for Netting Facility - Outfall RH-034 Gowanus Canal Superfund Site

October 3, 2012

Figure 3d

Details for Netting Facility - Outfall OH-007 Gowanus Canal Superfund Site

October 3, 2012

Figure 4a

Monitoring of CSO Solids in the Canal Gowanus Canal Superfund Site

Annual Bathymetry Surveys

Compare Surveys to 1) Delineate Depositional Areas 2) Estimate Rate of Deposition

Analyze Depositional Areas for 1) CSO Solids Tracer

2) Grain Size

Delineate Areas where CSO solids settle

Guide Maintenance Dredging Activities as Needed

October 3, 2012

Figure 5a

Estimated Maintenance Dredging Costs (2012$) Gowanus Canal Superfund Site

$-

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

$7,000,000

$8,000,000

$9,000,000

$10,000,000

0 1000 2000 3000 4000 5000 6000 7000

Dre

dgin

g C

osts

Volume, cy

Maintenance Dredging Costs (2012$) (45 cy/hr)

Lower Estimate

Anticipated Costs

Upper Estimate

Upper Estimate – 15% over Anticipated Costs Lower Estimate – 5% under Anticipated Costs

October 3, 2012

Figure 5b

Estimated Cost per CY for Maintenance Dredging (2012$)


0

500

1000

1500

2000

2500

3000

3500

0 1000 2000 3000 4000 5000 6000 7000

Dre

dgin

g C

osts

Volume, cy

Cost per CY (2012$) (45 cy/hr)

Lower Estimate

Anticipated Costs

Upper Estimate

Upper Estimate – 15% over Anticipated Costs Lower Estimate – 5% under Anticipated Costs

October 3, 2012

Figure 5c

Estimated Present Worth Cost Comparison Gowanus Canal Superfund Site

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

500 750 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,500 6,500

$/cy

PW Cost per CY

(45 cy/hr)

Joint Venture Est (original)

Joint Venture Est (revised)

Present Worth per CY

Present worth costs based on 1 dredging event in approximately 15 years

October 3, 2012

Figure 6a

Sewer Cleaning Locations Near Gowanus Canal 2003-2011 Gowanus Canal Superfund Site

October 3, 2012

Figure 7a

Proposed Solids Settling Areas Gowanus Canal Superfund Site

10,000 sq. ft. solids-settling area

25,000 sq. ft. solids-settling area

October 3, 2012

Figure 7b

Cumulative Frequency Diagram of Discharge Flow Rates at RH-034 in 2011


October 3, 2012

Figure 7c

Solids Removal for Different Particle Sizes (Based on Example Grain-Size Distribution)


October 3, 2012

Figure 7d

Calculated Solids Removal vs. RH-034 Flow Rate Gowanus Canal Superfund Site

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10 100 1000

Rem

oval

(%)

Flow Rate (MGD)

Calculated Solids Removal vs. Flow Rate (100x100ft Settling Area, Min. During Tidal Cycle)

8 µm

16 µm

31 µm

62 µm

149 µm

October 3, 2012

Figure 8-1a

Potential Site Locations Potential Pilot Riparian Restoration Project


Huntington Street Site

Creamer Street Site

Former Citizens Gas Works GMP Site

October 3, 2012

Figure 8-1b

Proposed Site: Creamer Street (Site 1 – USACE Report) Potential Pilot Riparian Restoration Project


October 3, 2012

Figure 8-1c

Proposed Site: Huntington Street Potential Pilot Riparian Restoration Project


October 3, 2012

Figure 8-1d

Proposed Site: Former Citizens Gas Works GMP Site Potential Pilot Riparian Restoration Project


October 3, 2012

Figure 8-1e

Proposed Pilot Project Planting Concepts Gowanus Canal Superfund Site

October 3, 2012

Attachment A-1Option 3 - Silt Curtain at RH-034 and OH-007

Gowanus Canal Superfund SiteBrooklyn, New York

10/03/2012

Quantity Unit Unit Cost Cost Assumptions on Quantity and/or Approach Source of Cost

A. Trade Costs

Mobilization/Demobilization 10 Percent 2,909,750$ $290,975 Professional experienceDredging and Disposal of Existing Sediment 1,600 CY 1,800$ $2,880,000 Cost per cy taken per Maintenance Dredging Estimate (Option 5)Sit Curtain 175 LF 45$ $7,875 RH-034 - 100 LF; OH-007 - 100 LFInstallation and Anchoring 175 LF 125$ $21,875

Vendor testing Fees $160,000 Assume testing by 2 firms

Scope Development, Contingency, Additions Percentage $56,000 35% of Subtotal Trade CostsGeneral Conditions / Division 1 Percentage $32,400 15% of Subtotal Trade Costs + Scope Development, Contingency, Additions

Contractors Insurance, Bonds, OH, Profit Percentage $12,4205% of Subtotal Trade Costs + Scope Development, Contingency, Additions + General Conditions / Division 1 OHP included in Trade Costs

Subtotal Trade Costs + Additions $260,820

Public Amenities $0 15% of Subtotal Trade Costs + Additions NAReserve and Change Order $26,082 10 % of Subtotal Trade Costs + Additions + Public Amenities

Total Hard Construction Costs $286,902

B. Other Soft CostsPlanning Documents LS $75,000 Workplan, FSP, QAPP, QMP, HASPDesign/Construction Documents Percentage $29,000 10% of Subtotal Hard Construction Costs Professional JudgementPermitting and Legal Percentage $0 5% of Subtotal Hard Construction CostsProject Management Percentage $29,000 10% of Subtotal Hard Construction CostsSoft Cost Contingency Percentage $28,690 10% of Subtotal Hard Construction Costs.

Total Other Soft Costs $86,690

Total Capital Costs $373,592 Total of Total Hard Construction Costs and Total Other Soft Costs

ENR-CCI Year Estimate Developed 12,549 ENR - Construction Cost Index - NYC = 134.2 /100 times average ENR, CostWorksCurrent ENR-CCI (August 2012) 12,549 Current ENR CCI - NYC

Time to mid-pt of construction 4 Years August 2012 to August 2016 Const<1 yr

Capital Cost Estimate (Future Value) $420,481 Adjusted to August 2016 at 3% annual escalation

5% $345,931 Present Worth, 5% discount rate Discount rate=interest+2%0

C. Operation And Maintenance CostsFloatables control RH-034 127 Event 2,100 $266,700 Based on current overflow rateFloatables control OH-0007 69 Event 2,100 $144,900 Based on current overflow rateSediment removal 200 CY 3,500 $700,000 Dredging costs from Maintenance Dredging Estimate (Option 5)Contingency $333,480 30% of O&M Costs, does not include periodic replacement of silt curtainSubtotal $1,445,080

$32,958,636Present Worth, 5% discount rate, 2013 through 2043, does not include periodic silt curtain replacement as needed

$33,304,567 Sum of Capital and O&M PWTotal Present Worth Costs

Component

Present Worth- Total Capital and Other Costs Discount rate

Percentage

Present Worth -Total O&M Activities

Attachment A-2Option 4 - Annual Sediment Monitoring


10/03/2012


A. Trade Costs

Field preparation 24 HR 150 $3,600 Equipment rental, contracting, bottle arrangements, other prep/suppliesSurvey/boat fees LS $16,500 $6300/day for survey work $3900/day for mob/demob - 2 days Internal DatabaseSampling/boat fees 3 DAY 4200 $12,600 $4200/day for sampling - 3 days,Sampling 72 HR 150 $10,800 2-person sampling crew, 4 days in fieldSampling ODCS LS $2,500 Equipment rental, PPE, misc supplies, shippingAnalytical 15 Sample 1050 $15,750 Assume 16 samples at various locationsData Review 80 Hr 175 $14,000 Mapping, laboratory review

Subtotal Trade Costs $75,750

Scope Development, Contingency, Additions $26,513 35% of Subtotal Trade CostsGeneral Conditions / Division 1 $0 15% of Subtotal Trade Costs + Scope Development, Contingency, Additions NA - all work on boat

Contractors Insurance, Bonds, OH, Profit $5,1135% of Subtotal Trade Costs + Scope Development, Contingency, Additions + General Conditions / Division 1

OHP included in above costs


Public Amenities $0 15% of Subtotal Trade Costs + Additions NA - from boatReserve and Change Order $10,738 10 % of Subtotal Trade Costs + Additions + Public Amenities


B. Other Soft CostsPlannning (first year costs only) LS $75,000 Workplan, HASP, other planning expensesPermitting and Legal Percentage $0 2% of Subtotal Hard Construction Costs NAProject Management Percentage $17,717 15% of Subtotal Hard Construction Costs NA

Soft Cost Contingency Percentage $17,71715% of Subtotal Hard Construction Costs. Percentage may vary depending on the alternative.




Time to mid-point of construction from Jan 2012 10 Years August 2012 to August 2022

First Year Cost Estimate $307,148 Adjusted to August 2022 based on 3% increase in CCI

$188,562 Present Worth, 5% discount rate Discount rate=interest+2%

C. Operation And Maintenance CostsAnnual Operation and Maintenance $0 NAContingency Percentage $0 NATotal Estimated Operation and Maintenance $0

$0 Present Worth, 5% discount rate, 30 Year O&M

$3,037,656 Sum of Capital and O&M PW

Component

Present Worth - First Year Costs


Total Present Worth Costs (2013-2042)

Attachment A-3Option 7 - RH-034 In-Canal Sedimentation Basin (Rectangular)


10/03/2012


A. Trade Costs

Mobilization/Demobilization 15 Percent 276,675$ $276,675 Professional experienceCoordination/Sequencing with Remediation 15 Percent 276,675$ $276,675 Sequencing may required additional mobilizations due to weir/ISS/Cap workWeir Construction 100 LF 9,400$ $940,000 JV Bulkhead memo, updated to 2012 Professional experienceRepairs to Cap 5,000 SF 50$ $250,000

Subtotal Trade Costs $1,493,350

Scope Development, Contingency, Additions Percentage $522,673 35% of Subtotal Trade CostsGeneral Conditions / Division 1 Percentage $302,403 15% of Subtotal Trade Costs + Scope Development, Contingency, Additions

Contractors Insurance, Bonds, OH, Profit Percentage $115,9215% of Subtotal Trade Costs + Scope Development, Contingency, Additions + General Conditions / Division 1 OHP included in Trade Costs

Subtotal Trade Costs + Additions $2,434,347


Total Hard Construction Costs $2,677,782

B. Other Soft CostsPlanning Documents LS $75,000 Workplan, FSP, QAPP, QMP, HASPGeotechnical Investigation LS $250,000 Assess stability of siteDesign/Construction Documents Percentage $268,000 10% of Subtotal Hard Construction Costs Professional JudgementPermitting and Legal Percentage $134,000 5% of Subtotal Hard Construction Costs Professional JudgementProject Management Percentage $268,000 10% of Subtotal Hard Construction CostsSoft Cost Contingency Percentage $267,778 10% of Subtotal Hard Construction Costs.

Total Other Soft Costs $1,262,778

Total Capital Costs $3,940,560 Total of Total Hard Construction Costs and Total Other Soft Costs



Capital Cost Estimate (Future Value) $4,305,956 Adjusted to August 2015 at 3% annual escalation

5% $3,719,647 Present Worth, 5% discount rate Discount rate=interest+2%0

C. Operation And Maintenance CostsAnnual O&M LS $1,515,000 Cost every 3 years Professional JudgementContingency $454,500 30 % of Total O&M Activity. Subtotal $1,969,500

$7,037,017 Present Worth, 5% discount rate, 30 Year O&M


Component


Percentage


Attachment A-4Option 7 - RH-034 In-Canal Sedimentation Basin (L-Shaped)


10/03/2012


A. Trade Costs

Mobilization/Demobilization 15 Percent ####### $1,106,700 Professional experienceCoordination/Sequencing with Remediation 15 Percent ####### $1,106,700 Sequencing may required additional mobilizations due to weir/ISS/Cap workWeir Construction 400 LF 9,400$ $3,760,000 JV Bulkhead memo, updated to 2012 Professional experienceRepairs to Cap 20,000 SF 50$ $1,000,000

Subtotal Trade Costs $6,973,400

Scope Development, Contingency, Additions $2,440,690 35% of Subtotal Trade CostsGeneral Conditions / Division 1 $941,409 10% of Subtotal Trade Costs + Scope Development, Contingency, Additions

Contractors Insurance, Bonds, OH, Profit $517,7755% of Subtotal Trade Costs + Scope Development, Contingency, Additions + General Conditions / Division 1 OHP included in Trade Costs


Public Amenities $0 15% of Subtotal Trade Costs + Additions NAReserve and Change Order $1,087,327 10 % of Subtotal Trade Costs + Additions + Public Amenities


B. Other Soft CostsPlanning Documents LS $75,000 Workplan, FSP, QAPP, QMP, HASPGeotechnical Investigation LS $250,000 Assess stability of siteDesign/Construction Documents Percentage $1,196,000 10% of Subtotal Hard Construction CostsPermitting and Legal Percentage $598,000 5% of Subtotal Hard Construction CostsProject Management Percentage $1,196,000 10% of Subtotal Hard Construction CostsSoft Cost Contingency Percentage $1,196,060 10% of Subtotal Hard Construction Costs.





Capital Cost Estimate (Future Value) $17,999,029 Adjusted to August 2015 at 3% annual escalation

5% $15,548,238 Present Worth, 5% discount rate, 30 Year O&M Discount rate=interest+2%0

C. Operation And Maintenance CostsAnnual O&M LS $2,715,000 Cost every 3 years Professional JudgementContingency $814,500 30 % of Total O&M Activity. Subtotal $3,529,500

$12,610,892 Present Worth, 5% discount rate


Component


Percentage


Attachment A-5Option 8-1 - Habitat Restoration Pilot Study


10/03/2012


A. Trade Costs

Mobilization/Demobilzation LS $61,000 10% of Construstruction CostsSediment/Erosion Control LS $10,000Demolition 1,800 CY 40 $72,000 Pavement, bulkhead, misc fill and RS MeansReconstruction of Bulkheads 240 LF 1500 $360,000 Increase unit by 50% cost due to water and site access issues BYSDOTWaste Handling and Disposal 3,000 Tons 75 $225,000 Sub D Landfill - PA, 100 Mile haul WMX website, Biocycle MagaPlanting LS $110,000 For Waste disposal Pinelands Nursery 2012 Cat


Scope Development, Contingency, Additions $293,300 35% of Subtotal Trade CostsGeneral Conditions / Division 1 $169,695 15% of Subtotal Trade Costs + Scope Development, Contingency, Additions


OHP included in Trade Costs




B. Other Soft CostsPublic Outreach 5 Mtg 50000 $250,000 5 meetings @ $50,000 per meeting for staff and graphics, etsPlanning Documents LS $75,000 Workplan, FSP, QAPP, QMP, HASP Professional JudgementBaseline Studies LS $250,000 see text Professional JudgementDesign/Plans and Specifications $225,397 15% of Subtotal Hard Construction CostsPermitting and Legal LS $150,000 Professional Judgetment Professional JudgementProject Management $225,397 15% of Subtotal Hard Construction CostsEngineering Oversight and Monitoring Reports $150,000 10% of Subtotal Hard Construction Costs F -demo/const, PT-plantingSoft Cost Contingency $225,397 15% of Subtotal Hard Construction Costs.





Capital Cost Estimate (Future Value) $3,437,125 Adjusted to August 2016 based on 3% increase in CCI

5% $2,827,732 Present Worth, 5% discount rate Discount rate=interest+2%0

C. Operation And Maintenance Costs1st Year O&M LS $26,000 Estimated Value (invasive species control) Professional Judgement2nd-30th Year O&M LS $21,000 Estimated Value - invasive species control only Professional JudgementReplacement planting LS $30,000 Estimated Value - replacement planting -2 to 5 years after construction

Contingency $4,200 30% of Total O&M Activity.

$670,471 Present Worth, 5% discount rate, 30 Year O&M


Component


Percentage


PercentagePercentagePercentage

Percentage

Attachment A-6Option 8-2 - Pore Water Sampling Pilot Study


10/03/2012


A. Trade Costs

Boat mobilization/rental 5 Day 2500 $12,500 Boat and crew, including mobilization charges, 5 days event Professional ExperienceEquipment mobilization 5 Day 1000 $5,000 Trident Sampler and ancillary equipment, shipping to and from supplierSampling labor 120 Hour 150 $18,000 2 people, 12 hr days, 5 days in the field -calibration, setup, sampling, deconOther ODCs 5 Day 1500 $7,500 PPE, additional sampling equipment, containers Professional ExperienceLaboratory Analysis 25 Samples 500 $12,500 25 porewater samples in headwaters of canal Columbia Analytical Labs


Scope Development, Contingency, Additions $19,425 35% of Subtotal Trade CostsGeneral Conditions / Division 1 $11,239 15% of Subtotal Trade Costs + Scope Development, Contingency, Additions NA - work from boat


NA, OHP included in Trade Costs


Public Amenities $0 15% of Subtotal Trade Costs + Additions NA - work from boatReserve and Change Order $9,047 10 % of Subtotal Trade Costs + Additions + Public Amenities


B. Other Soft CostsPlanning Documents LS $75,000 Workplan, FSP, QAPP, QMP, HASP Professional JudgementPermitting and Legal $0 NAProject Management/QA Oversight $15,000 15% of Subtotal Hard Construction Costs NASoft Cost Contingency $14,928 15% of Subtotal Hard Construction Costs.




Time to mid-pt of construction 3 Years August 2012 to August 2015



C. Operation And Maintenance CostsAnnual O&M Costs LS $0Contingency $0 30 % of Total O&M Activity. Annual Total O&M Costs $0

$0 Present Worth, 5% discount rate

$ 192,985 Sum of Capital and O&M PWTotal Present Worth Costs

Component

Present Worth - Total Capital and Other Costs Discount rate

Percentage

Present Worth - Total O&M Activities

PercentagePercentagePercentage

Attachment A-7Option 8-3 - Sediment Washing Pilot Study

Gowanus Superfund SiteBrooklyn, New York

10/03/2012


A. Trade Costs

Boat mobilization/rental 5 Day 2,500$ $12,500 boat mobilization, demobilization and daily rental Professional experienceEquipment rental 5 Day 1,500$ $7,500 Ponar grab sample, containers, shipping container Professional experienceOther ODCs 5 Day 500$ $2,500Labor 202 Hour 150$ $30,300 Midlevel engineer or scientist on site during sampling and testingUtilities LS $10,000 power, water supplied by cityVendor testing Fees LS $160,000 Assume testing by 2 firms Email from BiogensisAnalysis of results 60 Hour 175$ $10,500


Scope Development, Contingency, Additions $81,655 35% of Subtotal Trade CostsGeneral Conditions / Division 1 $47,243 15% of Subtotal Trade Costs + Scope Development, Contingency, Additions

Contractors Insurance, Bonds, OH, Profit $18,1105% of Subtotal Trade Costs + Scope Development, Contingency, Additions + General Conditions / Division 1 NA, OHP included in above


Public Amenities $0 15% of Subtotal Trade Costs + Additions NAReserve and Change Order $19,015 5% of Subtotal Trade Costs + Additions + Public Amenities


B. Other Soft CostsPlanning Documents LS $100,000 Workplan, FSP, QAPP, QMP, HASP, Contracting with BiogenesisPermitting and Legal LS $0 NAProject Management/QA Oversight $40,000 10% of Subtotal Hard Construction CostsSoft Cost Contingency $59,899 15% of Subtotal Hard Construction Costs.







C. Operation And Maintenance CostsAnnual O&M LS $0 Estimated ValueContingency $0 30% of Total O&M Activity.

$0 Present Worth, 5% discount rate

$554,855 Sum of Capital and O&M PW

Discount rate

Percentage

Total Present Worth Costs

Component


Present Worth- Total Capital and Other Costs

PercentagePercentage