FEASIBILITY STUDY REPORT

SLP4 GRADIENT CONTROL WELL DISCHARGE ST. LOUIS PARK, MINNESOTA

Prepared for

CITY OF ST. LOUIS PARK

JUNE 1987

BARR ENGINEERING CO. Minneapolis, Minnesota

FEASIBH.ITY STUDY REPORT

Str4 GRADIENT CONTROl WEU DISCHARGE ST. LOUIS PARK, MINNESOTA

Prepared for

CITY OF ST. LOUIS PARK

JUNE 1987

BARR ENGINEERING CO. Minneapolis, Minnesota

FEASIBILITY STUDY REPORT

SLF 4 GRADIENT CONTROL WELL DISCHARGE

TABLE OF CONTENTS

Page

INTRODUCTION 1

SECTION 1 - BACKGROUND 2

SECTION 2 - SURFACE WATER DISCHARGE ALTERNATIVES 5

SECTION 3 - NON-SURFACE WATER DISCHARGE ALTERNATIVES 21

SECTION 4 - EVALUATION OF COST-EFFECTIVE ALTERNATIVES 32

LIST OF TABLES

TABLE 1 COMPARISON OF SLP 4 WATER QUALITY AND CRITERIA

TABLE 2 WATER QUALITY DATA

TABLE 3 SLP 4 SURFACE DISCHARGE OPTIONS

TABLE 4 COST ESTIMATE FOR SANITARY SEWER DISCHARGE

TABLE 5 COST ESTIMATE FOR GRANULAR ACTIVATED CARBON

TABLE 6 COST ESTIMATE FOR GRANULAR MEDIA FILTRATION UP-GRADE

TABLE 7 COST ESTIMATE FOR OZONE TREATMENT

TABLE 8 COST ESTIMATE FOR REVERSE OSMOSIS

TABLE 9 NON-COST COMPARISON

TABLE 10 COST COMPARISON

LIST OF FIGURES

FIGURE 1 GRADIENT CONTROL WELL LOCATIONS

FIGURE 2 PRELIMINARY SURFACE WATER DISCHARGE LOCATIONS

FIGURE 3 SLP 4 SURFACE DISCHARGE OPTIONS

FIGURE 4 SAMPLING LOCATIONS - CH2M HILL STUDY

REITOe/346,O/msh

FEASIBILITY STUDY REPORT

SLP 4 GRADIENT CONTROL WELL DISCHARGE

INTRODUCTION

On September 4, 1986 a Consent Decree was approved between the United

States of America, State of Minnesota, City of St. Louis Park and Re^ly

Tar & Chemical Corporation. Section 7.2.1 of the Remedial Action Plan

(RAP), Exhibit A of the Consent Decree, requires submittal of "a jplan for

the feasibility study for discharge of 1,000 gallons per minute of water

from SLP 4". The required work plan submitted by St. Louis Park was

approved March 16, 1987 by the Environmental Protection Agency and

Minnesota Pollution Control Agency in a letter received March 20, 1987.

This report is submitted pursuant to the work plan.

This report examines the feasibility of discharging the water to

various surface waters as required by the RAP. It also discusses the

possible discharge to the sanitary sewer and the treatment and use of the

water for municipal water supply. The RAP only requires that the surface

water discharge options be investigated. The RAP does, however, recognize

that the quality of the water from SLP 4 might improve with time or that

the City of St. Louis Park might want to treat the water for use in the

municipal drinking water system. The options beyond surface water

discharge are included so that the public and decision makers have a more

complete understanding of the options available.

The report is divided into four sections. Section 1, Background,

describes the proposed overall remedy for the Prairie du Chien-Jordan

aquifer and the technology selected to implement the remedy. Section 2,

Surface Water Discharge Alternatives, discusses the surface water discharge

alternatives. Section 3, Non-Surface Water Discharge Alternatives,

discusses the sanitary sewer and water supply alternatives. Section 4,

Evaluation of Cost-Effective Alternatives, contains the comparison of

alternatives and the recommendation.

SECTION 1

BACKGROUND

HISTORY

The Reilly Tar & Chemical Corporation operated a coal tar refinery and

wood treating facility in St. Louis Park, Minnesota, from 1917 to 1972.

These operations resulted in groundwater and soil contamination. The

groundwater contamination affects deeper aquifers of regional concern. Six

St. Louis Park municipal drinking water wells completed in the Prairie du

Chien-Jordan aquifer, including Well SLP 4, have been closed due to the

presence of polynuclear aromatic hydrocarbons (PAH). One of the major

goals of the remedial action at this site is the management of the

migration of the contaminants in this aquifer.

The contamination in the Prairie du Chien-Jordan aquifer underlies a

large part of St. Louis Park as shown in Figure 1. Since 1969 numerous

studies have been completed which addressed this and other problems

associated with the former Reilly Tar site. These studies included the

development of various computerized groundwater flow models which were

used to develop the remedial action embodied in the RAP.

PROPOSED REMEDIAL ACTION

As a result of the numerous studies conducted over the years, most of

the remedial investigation and feasibility study work on the Prairie du

Chien-Jordan aquifer was completed prior to entering into the Consent

Decree. The Consent Decree requires that measures be implemented to

control what is believed to be one of the sources of contamination of this

aquifer. It requires that the spreading of contamination be controlled and

monitored. The Consent Decree also requires that contingent measures be

implemented if additional water supply wells are found to have levels of

PAH compounds above the health based criteria in the Consent Decree.

The source control will be accomplished by reconstructing and pumping

Well W23. This well is located on the former Reilly Tar site and is

believed to have acted as a pathway for contaminants to have been directly

Introduced into the Prairie du Chien-Jordan aquifer. The reconstructed

well will be pumped at 50 gallons per minute (gpra) to the sanitary sewer.

The contingency measure requirements for a water supply well which exceeds

the drinking water criteria include both replacing the lost system capacity

and maintaining the pumping at the well should such pumping be part of the

gradient control system.

PRELIMINARY REMEDIAL TECHNOLOGIES

There are four basic technologies that can be considered for migration

management. These are capping, contaminant barriers, groundwater pumping

and subsurface collection drains. These technologies were evaluated prior

to the Consent Decree.

Capping was found to be ineffective since the contamination was

already over 250 feet deep and covered over 3 square miles. These same

factors make it impractical to control the groundwater with containment

barriers or subsurface drains. The work done prior to the Consent Decree

therefore, focused on the design of a groundwater gradient control system.

The groundwater flow models developed in the prior work were used to

approximate the existing conditions and what would happen to the aquifer

under various pumping stresses. It was found that the spread of

contamination should be controlled by pumping SLP 10 and 15 at historic

rates, pumping the Methodist Hospital Well at historic rates and pumping

SLP 4 at approximately 900 gpm in the winter and 300 gpm in the summer.

SLP 10 and 15 are contaminated wells that were taken out of service. A

carbon adsorption system has been constructed to treat the water from SLP

10 and 15 and they have been back in service since July, 1986. The

Methodist Hospital well is used for cooling water with the discharge going

to Minnehaha Creek. SLP 4 is a municipal well which was taken out of

service due to the presence of levels of non-carcinogenic PAHs, which

although low, exceeded drinking water criteria.

The purpose of this study is to investigate the feasibility of various

options for using or discharging the water from SLP 4. This study does not

revisit the question of the design or pumping rates of the gradient control

system. It does not address monitoring of the effectiveness of the

pump-out system. It does look at the range of concerns associated with

each discharge or use option. The RAP requires that the feasibility study

be based on a 1,000 gpm pvunping rate. The actual pumping rates, expected

to approach 900 gpm from October to May and 300 gpm from May to October,

will be determined by the well and pvunp characteristics and the groundwater

system response to various pumping stresses.

REILFS/346,0/msh

SECTION 2

SURFACE WATER DISCHARGE ALTERNATIVES

DEVELOPMENT OF ALTERNATIVES

Various surface water discharge locations were identified for

receiving the SLP 4 discharge of 1,000 gpm. The surface water locations

identified are shown on Figure 2. The approved work plan requires the

evaluation of discharge to the Minneapolis Chain of Lakes, Minnehaha Creek

and the Mississippi River. Additional locations identified were Wolfe

Lake, Twin Lakes, Westwood Lake, Hannan Lake and Bass Lake in St. Louis

Park and Weber Field Pond in Edina.

The Minneapolis Chain of Lakes consists of five lakes on the western

edge of Minneapolis. Brownie Lake is connected to Cedar Lake which is

connected to Lake of the Isles which is connected to Lake Calhoun. A

pumping system from Lake Calhoun discharges to Lake Harriet which outlets

to Minnehaha Creek.

Minnehaha Creek flows from Lake Minnetonka, located west of St. Louis

Park, through the communities of Minnetonka, Hopkins, St. Louis Park,

Edina, and Minneapolis to the Mississippi River.

The Mississippi River is located east of St. Louis Park and flows

through Minneapolis.

INITIAL SCREENING OF ALTERNATIVES

Each potential location was screened for technical feasibility.

Factors considered in this initial screening were available storage, outlet

size, and distance from SLP 4.

Wolfe Lake in St. Louis Park and Weber Field Pond in Edina both were

close to SLP 4 but had storage insufficient to hold one day of 1,000 gpm

pumping. Because of the insufficient storage they were dropped from

consideration.

Twin Lakes, Westwood Lake, Hannan Lake and Bass Lake, all in St. Louis

Park had storage volumes of approximately one month for a discharge of

1,000 gpm. The distance to Westwood and Hannan Lakes was greater than four

miles and the storage volume was comparable to the other two lakes so these

options were not studied further. Twin Lakes is further from SLP 4 than

Bass Lake and they both ultimately discharge to the Chain of Lakes.

Therefore, Twin Lakes was not studied further. It was decided to consider

Bass Lake in greater detail. Bass Lake does not have a large enough volume

to be the primary body of surface water for the reception of the gradient

control discharge; however, combining Bass Lake and Lake Calhoun for the

surface waters to receive the gradient control discharge was an acceptable

alternative.

Brownie Lake, Cedar Lake, Lake of the Isles, and Lake Calhoun are four

of the five lakes in the Minneapolis Chain of Lakes. These four lakes are

connected and hydrologically act as one lake. Therefore discharging to any

of these four lakes would have the same environmental effect. Since Lake

Calhoun is closest to SLP 4, it was decided to only consider a discharge to

Lake Calhoun in greater detail.

Lake Harriet is the fifth lake in the Chain of Lakes. It is not

naturally connected to the other lakes. The outlet of Lake Harriet is to

Minnehaha Creek. There are potential discharge locations to Minnehaha

Creek that are closer to SLP 4 than Lake Harriet. The environmental

effects of discharging to Lake Harriet would be a combination of the

effects of discharging to Lake Calhoun or Minnehaha Creek. It was decided

to not consider discharge to Lake Harriet as an alternative but to evaluate

the environmental effects through the analysis of the Lake Calhoun and

Minnehaha Creek alternatives..

Discharge locations to Minnehaha Creek considered were Browndale Park

in Edina, Meadowbrook Park in St. Louis Park, and Yosemite Avenue in St.

Louis Park. The distances to these three locations are similar. Browndale

Park was dropped from consideration for Institutional reasons, since the

discharge Is not In St. Louis Park. It was decided to consider In greater-

detail the Yosemite Avenue discharge location because of Its proximity to

the waterworks facilities near SLP 6 and SLP 12. Meadowbrook Park was not

considered further because It was comparable In all features to the

Yosemite Avenue location except the proximity to the waterworks.

Two discharge locations to the Mississippi River were considered.

They were discharging to the I-35W storm sewer tunnel and the 1-394/Bassett

Creek storm sewer system. The outlets for these storm sewer systems are to

the Mississippi River. The distance from SLP 4 was similar for both

systems but the I-394/Bassett Creek option was preferable for Institutional

reasons. Minneapolis has concerns on the capacity of the I-35W storm

sewer tunnel. St. Louis Park prefers the I-394/Bassett Creek system

because It Is mostly In the City.

Four surface waters survived the Initial screening for feasibility of

discharge reception. These alternatives were Minnehaha Creek, Lake

Calhoun, Bass Lake, and the Mississippi River via I-394/Bassett Creek. The

locations of these alternatives and the routes for the discharge are shown

on Figure 3.

The alignment of the four discharge alternatives are described below.

The description Includes alignment, size and the portion of the line which

Is part of an existing system.

Bfiss Lake Alternative

The Bass Lake alternative alignment Is described first. A high

percentage of St. Louis Park stormwater Is conveyed to Bass Lake through

numerous storm sewers. Bass Lake acts as a sedimentation pond for

stormwater discharging to Lake Calhoun.

The pipe alignment assumed for the Bass Lake option is as follows,

beginning at SLP 4 location:

1,150 feet north along Natchez Avenue in new 8-inch forcemain,

Connecting to an existing 18-inch storm sewer at Natchez Avenue and Vallacher Avenue,

350 feet north along Natchez Avenue in an existing 18-inch storm sewer,

900 feet east along Excelsior Boulevard in an existing 42-inch diameter storm sewer.

1,000 feet north along Monterey Drive in an existing 54-inch diameter storm sewer.

600 feet north to Bass Lake inlet in an existing 60-inch diameter storm

The above alignment consists of 1,150 feet of new 8-inch forcemain and

2,850 feet of existing storm sewer.

A gate valve outlet near the eastern boundary of Bass Lake regulates

the amount of water discharged from Bass Lake.

Water discharged.from Bass Lake travels through an existing 42-inch

di^uneter conduit and discharges to an open ditch at Hinikahda Golf Course.

Water travels across the golf course through an open ditch and enters a

30-inch diameter storm sewer near the east edge of the golf course near

36th Street West. Water is conveyed 900 feet to Lake Calhoun.

Lake Calhoun Alternative

The Lake Calhoun alternative alignment is described next. An existing

storm sewer was located 300 feet from SLF 4 which could be used to convey

water to Lake Calhoun. The alignment for the Lake Calhoun discharge option

would be as follows, beginning at SLF 4;

300 feet south along the extension of Natchez Avenue in new storm sewer to an existing manhole,

1,850 feet east along 41st Avenue in an existing 54-inch diameter and 42-inch diameter storm sewer.

existing overflow to Weber Field Pond,

900 feet north in an existing 30-inch diameter storm sewer,

800 feet east in an existing 30-inch diameter storm sewer to France Avenue (existing storm sewer into Minneapolis),

400 feet north along France Avenue in an existing 30-inch diameter storm sewer.

700 feet east along 39th Street in an existing 42-inch diameter storm sewer.

600 feet north along Drew Avenue in an existing 48-inch diameter storm sewer.

2,000 feet east along 38th Street in an existing 48-inch and 54-inch diameter storm sewer.

700 feet north along Xerxes Avenue in an existing 54-inch diameter storm sewer.

outlet into Lake Calhoun.

The Lake Calhoun alignment consists of 300 feet of new storm sewer and

7,950 feet of existing gravity storm sewer. A dedicated pipeline to Lake

Calhoun for the SLF 4 discharge was also considered. The same alignment

was followed but the pipe was new 8-inch ductive iron pipe (DIP) with a

submerged outlet.

Minnehaha Creek Alternative

The Minnehaha Creek discharge alternative alignment is described next.

Pipe alignment for this option is proposed as follows, beginning at SLP 4:

2,500 feet west along 41st Street in a new 10-inch diameter forcemain,

700 feet south along Utica Avenue in a new 10-inch diameter forcemain.

400 feet west along 42nd Street in a new 10-inch diameter f orcemain,

400 feet south along T.H. 100 in a new 10-inch diameter f orcemain,

800 feet west along 42nd Street in a new 10-inch diameter f orcemain.

400 feet south along Yosemlte Avenue in a new 10-inch diameter forcemain.

100 feet west to SLP 6 in a new 10-inch diameter forcemain,

connect to existing storm drain at SLP 6,

450 feet south along Yosemite Avenue in an existing 30-inch diameter storm drain.

outlet into Minnehaha Creek.

The above alignment consists of 5,300 feet of new 10-inch diameter

forcemain and 450 feet of existing 30-inch diameter storm sewer. It is

also possible to connect to an existing gravity system at 42nd Street. The

10

alignment would then consist of 4,300 feet of new 10-inch diameter

forcemain and 1,450 feet of existing gravity storm sewer.

I-394/Basaett Creek Alternative

The alignment for the Mississippi River via I-394/Bassett Creek storm

sewer alternative is described next. The proposed pipe alignment for the

1-394/Bassett Creek alternative is as follows, beginning at SLF 4;

1,500 feet north along Natchez Avenue in a new 10-inch diameter forcemain,

4,000 feet northeast along Excelsior Boulevard in a new 10-inch diameter forcemain,

11,300 feet north along France Avenue and the St. Louis Park-Minneapolis boundary in a new 10-inch diameter forcemain.

connect to Minnesota Department of Transportation storm sewer near 1-394 and France Avenue.

The above alignment consists of 16,800 feet of new 10-inch diameter

forcemain. Water entering the 1-394 storm drainage system would travel

through a series of sedimentation ponds into Bassett Creek within a few

hundred feet of the mouth and into the Mississippi River.

EVALUATION OF ALTERNATIVES

The four alternatives were analyzed to evaluate technical,

environmental, public health and institutional concerns. Cost estimates

were prepared for each alternative. The results of these evaluations are

described in this section of the report.

11

Technical Analysis

The technical analysis of the alternatives addresses concerns on the

quantity, quality and timing of the discharge from SLP 4. A continuous

discharge of 1,000 gpm is 2 cfs or a daily increase in runoff volume of 4

acre-feet. This increase in runoff volume is significant for the Bass Lake

and Lake Calhoun alternatives. Presently, the approximate storage volume

of Bass Lake is 120 acre-feet. The storage volume was assumed to equal the

volume between the outlet's invert elevation and the point of low elevation

with 1 foot of freeboard. The point of low elevation is along a berm

protecting a parking lot from flooding. The parking lot is 1.9 feet lower

than the top of the berm. The low building elevation is 2.3 feet higher

than the top of the berm. The 120 acre-feet of storage is one month of

storage with no outflow for a 1,000 gpm inflow. Storm sewer drainage to

Bass Lake would reduce this storage volume during periods of stormwater

runoff. If there was outflow from Bass Lake to Lake Calhoun the storage

volume would not be depleted as quickly. The water discharge from Bass

Lake travels through an open ditch at the Minikahda Golf Course. Members

of the ground crew from the Minikahda Golf Course indicate that water

usually flows in the ditch year round. Flooding often occurs in the spring

and during some rain storms. Based on the cross-sectional area and slope

of the ditch, the capacity is on the order of 10 to 15 cfs. The increase

of 2 cfs during the summer months could potentially create short-term

flooding. Longer term flooding could occur during the spring snowmelt.

These problems could be mitigated by utilizing the temporary storage

available in Bass Lake or increasing the ditch area. The Minikahda Golf

Course ditch (County Ditch 14) discharges to Lake Calhoun.

At the present time, the potential for flooding in the Chain of Lakes

necessitates the occasional pumping from Lake Calhoun to Lake Harriet.

However, augmentation is occasionally required to maintain present lake

levels. In addition, the Chain of Lakes is a groundwater recharge zone.

There is the potential that in the future, because of increased stresses on

the aquifer from demands such as cooling of downtown office buildings,

augmentation would be necessary to maintain present lake levels. When

augmentation is not needed, pumping to Lake Harriet would be required to

12

prevent high water problems in Lake Calhoun. Presently, a pumping system

exists between the two lakes which is capable of discharging 7,000 gpm.

The outlet from Lake Harriet is a 42-inch diameter conduit. The discharge

for a lake elevation of 846 is 15 cfs and for an elevation of 847 is 30

cfs. An increase in discharge of 2 cfs would increase the Lake Harriet

level approximately 0.2 feet. If this increase causes difficulties, the

outlet could be modified. The Lake Harriet outlet discharges to Minnehaha

Creek.

An increase of 2 cfs to the discharges in Minnehaha Creek or Bassett

Creek would cause a stage increase of less than 0.1 feet. The increase in

flow in Minnehaha Creek, Bassett Creek or the Mississippi River would not

present problems.

The winter discharge of water to surface waters in Minnesota causes

concerns with Ice formation. Ice will not form or will be weak at the

discharge points to Bass Lake, Lake Calhoun and Minnehaha Creek because

the high temperature of groundwater retards ice formation. Without proper

notices and barriers, the weak ice would create a danger to the public.

Lake Calhoun and Minnehaha Creek are presently used for Ice skating and

other recreation. Bass Lake supports limited recreational uses. To at

least partially alleviate the weak Ice hazard on Lake Calhoun, an

alternative with a submerged outlet was Included In the cost analysis. By

submerging the outlet, the Ice formation would be stronger than for the

alternative with the outlet from the existing storm sewer system.

The other major concern with Ice Is the formation of frazil Ice which

could cause partial blockage of culverts downstream. Frazil Ice Is a

slushy accumulation of Ice In water that Is too turbulent for formation of

sheet Ice. Frazil Ice has dammed flow In streams at culverts If It extends

to the bottom of the stream. This Is not a concern for the Bass Lake, Lake

Calhoun or yfilssi^lppl—River—al"ternanvesT^Mlnnehaha Creek has had

problems with frazil Ic^ resulting from fluctuating winter discharges. The

creek does have grounditater discharge and discharges from Industries with

non-contact uses w^ch are at consistent quantities. Frazil Ice has not

13

formed for these continuous discharges. Because the SLP 4 discharge would

be a low volume continuous discharge, frazil ice should not be a concern.

Environmental Analysis

At meetings with representatives of communities and public agencies,

the major concern expressed is the quality of the water to be discharged.

There appears to be a misconception that the water being pumped for

gradient control in the Prairie du Chlen is of the quality of the surficial

aquifer on the site which is highly contaminated. Table 1 shows the

quality of water from SLP 4 compared to drinking water criteria and the

surface water discharge criteria required by the Consent Decree.

Existing data on water quality of SLP 4 indicate that the

concentrations of the carcinogenic PAHs are below the Minnesota

Department of Health (MDH) drinking water recommended allowable levels and

the concentration of the non-carcinogenic PAHs is Just above the criteria

set in the Consent Decree. The data from sixteen months of sampling (July

1981 to October 1982), which were higher concentrations than the earlier

data, had a mean concentration of 0.44 ng/L carcinogenic PAHs and 340 ng/L

non-carcinogenic PAHs'.

The Consent Decree established criteria for the quality of the

discharge to surface waters. Bass Lake, Lake Calhoun, Minnehaha Creek and

Bassett Creek are public waters unclassified by the Minnesota Pollution

Control Agency (MPCA) under 7050.0430 Unlisted Waters. The MPCA considers

all unclassified waters to be of a quality that will support cool or warm

water fishery and aquatic recreation of all kinds including swimming. The

criteria were developed for the case where ;the 7-day duration low flow

discharge was zero. The criteria in the Consent Decree are set at two

orders of magnitude below the acute toxicity level for aquatic life. The

National Pollution Discharge Elimination System (NPDES) criteria are a

maximum concentration of 34000 ng/L for PAH compounds and 2000 ng/L for

phenanthrene. The criteria for the 30-day' average concentration are

one-half the maximum concentration criteria. Phenanthrene is a PAH

compound which has been found to be toxic to aquatic life above the

14

criterion. The NPDES permit also has a criterion of 10 ug/L for phenolics.

A sample was collected from SLP 4 in July 1983 and analyzed by Acurex for

PAH and phenolic compounds. The total PAH concentration was 117 ng/L,

phenanthrene was detected at 21 ng/L and no phenolics were detected. None

of the samples fromi SLP 4 has exceeded a level of one-tenth the NPDES

criteria. A review of the research on aquatic toxicity for PAH compounds

found that the low levels of PAH found in SLP 4 were not toxic to aquatic

life and did not accumulate in the organisms. A list of references

reviewed is at the end of the report.

The November 1983 CH2M Hill report, "Evaluation of Groundwater

Treatment and Water Supply Alternatives for St. Louis Park, Minnesota"

presented results of chemical analyses for six storm sewer discharges.

Four of the storm sewers were along Minnehaha Creek, one outletted to Lake

Calhoun and one outletted to Lake Harriet. These locations are shown on

Figure 4. The results of these analyses all were higher than the results

from ^the SLP 4 analyses. The carcinogenic PAHs were more than two orders

of magnitude greater for the storm sewer water while the non-carcinogenic

PAHs were two to six times greater. In addition the study analyzed samples

from surface water stations on Minnehaha Creek, Lake Calhoun and Lake

Harriet, The downstream stations are also shown on Figure 4. The data from

these analyses were all below drinking water criteria for non-carcinogenic

PAHs but the carcinogenic PAHs exceeded the drinking water criteria in the

Minnehaha Creek 4 station. The results of the CH2M Hill analyses and the

Acurex chemical analyses for SLP 4 are shown on Table 2.

The quality of the SLP 4 discharge is better than the quality of the

water in the storm sewers presently discharging to the surface waters.

Stormwater contains PAH compounds because PAH compounds are present in

tires, asphalt runoff and combustion products of fuel for vehicles,

especially dlesel fuel. The quality of SLP 4 water is comparable to the

existing quality of these waters. The discharge of SLP 4 to Bass Lake,

Lake Calhoun, Minnehaha Creek or the Mississippi River will not have an

adverse environmental effect.

15

Public Health Analysis

The surface waters evaluated as potential receiving waters of the S'LP

4 discharge are not classified for human consiunption. Incidental injestion

may occur during recreational use of the waters. Because of the low

concentrations of PAH compounds in the SLP 4 discharge there will be no

measurable increase in the levels of PAHs In the receiving water.

Therefore, there will be no increase in any public health risk from

incidental injestion.

Consumption of the fish from these waters is a second route of

exposure. The NPDES criterion of 311 ng/L of carcinogenic PAH compounds is

based on the public health risk from eating aquatic organisms from waters

with carcinogenic PAH compounds. The level of carcinogenic PAHs in the

SLP 4 discharge is 100 to 1,000 times lower than this criteria. No public

health concerns are associated with the discharge of SLP 4 to any of the

alternatives.

Institutional Analvsis

The institutional concerns and requirements are very important for a

comparison of these alternatives. Each alternative will be evaluated

separately for this analysis because their institutional concerns are

unique.

Bass Lake would require the cooperation of many community groups and

public agencies. St. Louis Park would be involved because the discharge

utilizes existing storm sewer systems within the city and involves the

operation of the gated outlet valve. The operation of this outlet is

critical because improper operation would cause flooding of homes and

businesses. The cooperation of the Mlnikahda Golf Course is necessary

because the increase in discharge in County^ Ditch 14 could create flooding

and erosion problems for the golf course. These problems could be

addressed by enlarging the ditch capacity or by the golf course allowing

the inconvenience. The Minneapolis Park Board and the Minneapolis Public

Works Department are involved because the ultimate discharge is to Lake

16

Calhoun. The Minneapoillls Public Works Department Indicates that the

Minneapolis City Council would be involved in decisions for permits to

discharge to the storm sewers or the lakes. Bass Lake provides temporary

storage which could be utilized to mitigate impacts on lake levels or

discharges through Minneapolis storm sewers during runoff events which

could mitigate some concerns of the Minneapolis Park Board, Public Works

Department, and City Council. The Minneapolis concerns are ice problems,

pumping required to Lake Harriet and the perceived unacceptable quality of

the water. The Minnehaha Creek Watershed District would need to issue a

permit for the discharge. The Minnehaha Creek Watershed District has been

encouraging use of Bass Lake for stormwater runoff because of its

environmental effects as a sedimentation basin. A groundwater discharge

would use capacity that did not need a sedimentation pond. The Minnesota

Department of Natural Resources (DNR) would need to issue a permit for

appropriation of groundwater for all the alternatives . The MPCA would

need to issue an NPDES permit for the alternatives. The public hearing for

the NPDES permit would address water quality concerns.

The Lake Calhoun alternative requires the cooperation of many of the

groups mentioned for the Bass Lake alternative because the Bass Lake

alternative discharges into Lake Calhoun. The Minikahda Golf Course would

not be involved, but the other groups would be. However, the concerns are

not identical for the two alternatives. The Minneapolis concerns for the

gravity option are Increased flooding along the storm sewers. Ice problems,

pumping required to Lake Harriet and the perceived unacceptable quality of

the water. The dedicated line for the SLP 4 discharge addresses the first

two concerns but not the last two. The Minnehaha Creek Watershed District

would not have the concern of the sedimentation pond use for groundwater

that they would have for the Bass Lake alternative. The NPDES and water

appropriation permits would be required.

The Minnehaha Creek alternative requires a permit from the Minnehaha

Creek Watershed District, NPDES permit from the MPCA and an appropriations

permit from The DNR. Minneapolis has concerns on the frazil Ice effect on

the downstream bridges. These concerns should be addressed In the meetings

for the Watershed District permit.

17

The Mississippi River via I-394/Bassett Creek alternative requires the

cooperation of St. Louis Park because of the construction of the new

forcemaln In the city. The Minnesota Department of Transportation would be

Involved because the discharge would be to the drainage system It has

designed and will maintain for 1-394. A permit would be required from the

Bassett Creek Water Management Commission because the 1-394 drainage system

outlets Into Bassett Creek. An NPDES permit would be required from the

MPCA and an appropriations permit would be required from the DNR.

Although each of the alternatives requires many permits and the

Interaction of many communities and agencies, some of the local concerns

are harder than others to mitigate. It may be difficult to over come the

perception that the discharge water la highly contaminated.

Cost Analvsls

Costs were determined using prices from 1986 local bid tabulations.

The unit costs are shown on Table 3. The forcemalns for the Mississippi

and Minnehaha Creek alternatives were 10-Inch diameter DIP. The 10-Inch

diameter was chosen for the Mississippi alternative because of the friction

losses over the long distance and for the Minnehaha Creek alternative

because of the energy needed to pump through the treatment plant If the

discharge Is added to the municipal water supply. The forcemaln lines for

the dedicated Lake Calhoun and the Bass Lake alternatives were 8-Inch

diameter DIP because there were no extenuating circumstances. All new

gravity lines were assumed to be 18-Inch diameter reinforced concrete pipe

(RCP). The lump sum prices for jacking pipe under highways, railroads, and

four lane roadways are major expenses.

Costs for construction In the City of Minneapolis may be higher than

shown on Table 3. Some of the work performed In Minneapolis must be

performed by the City. These costs are sometimes higher than the

competitively bid prices.

18

The operation and maintenance costs Include labor for pumping and

maintenance. The pumping labor cost is for labor involved in the

maintenance of the pumps. One hour a week was assumed for the time for

maintenance of the pumps. The labor cost for maintenance is for the

placement and removal of fences at locations where weak ice conditions are

expected. The Bass Lake and Lake Calhoun alternatives include time for the

operation and maintenance of the pump from Lake Calhoun to Lake Harriet.

The pumping cost is the electricity cost. The operation and maintenance

costs were evaluated for the present worth assuming 10 and 30 years of

operation of the system. An interest rate of 5 percent was assumed.

4

A summary of the cost analysis data is shown on Table 3. The Bass

Lake alternative has a capital cost of $81,000 and an annual operation and

maintenance cost of $50,000. The present worth costs are $559,000 for 10

years and $1,017,000 for 30 years.

The Lake Calhoun alternative has two costs shown. One is for

discharging into the existing storm sewer system and the other is for

discharging through a pipeline dedicated for the SLP 4 discharge. The

second alternative would address many of the concerns of the Minneapolis

Park Board and Public Works Department. The capital costs are $15,000 for

the gravity system and $556,000 for the dedicated system. The annual

operation and maintenance costs are $49,000 for the gravity system and

$48,000 for the dedicated system. The present worth costs for the gravity

system are $472,000 for 10 years and $922,000 for 30 years. The present

worth costs for the dedicated system are $1,112,000 for 10 years and

$1,552,000 for 30 years.

The Minnehaha Creek alternative has 10-inch diameter forcemain for the

entire length to maintain flexibility of this alternative. The flexibility

allowed is the option to treat the water at the waterworks at this location

and place it in the city's water supply. This option could be Implemented

in a phased manner by deleting 1,000 feet of 10-inch diameter forcemain

shown in the cost estimate ($72,000 of capital cost). The capital cost for

implementing the project in one.phase is $419,000 and in two phases is

$347,000. The annual operation and maintenance cost is $34,000. The

19

present worth costs for non-phased system is $819,000 for 10 years and

$1,133,000 for 30 years.

The Mississippi River alternative (I-394/Bassett Creek) has a capital

cost of $1,222,000 and the annual operation and maintenance cost is

$34,000. The present worth costs are $1,785,000 for 10 years and

$2,102,000 for 30 years.

RSEC2/346,0/msh 20

SECTION 3

NON-SURFACE WATER DISCHARGE ALTERNATIVES

This section evaluates the alternatives for managing the water pvimped

from SLP 4 by means other than surface water, discharge. This work was not

required by the Consent Decree. This portion of the study was done to have

the complete range of alternatives evaluated and presented for public

discussion.

DEVELOPMENT ALTERNATIVES

Two general methods of managing the SLP 4 discharge, other than by

surface water discharge, were identified. These were: 1) discharge to the

sanitary sewer and 2) use of the water with or without treatment. Use by

an industry for process or cooling water is an option that might not

require treatment. Use by a municipality as part of the water supply would

likely require treatment.

INITIAL SCREENING OF ALTERNATIVES

These alternatives were screened based on environmental effects,

technical feasibility and cost. Based on the initial screening only use

for a municipal water supply was evaluated further. Discharge to the

sanitary sewer was dropped primarily because of the cost. Based on a 1,000

gpm pumping rate there would be a Sewer Availability Charge of $2.8

million. The annual sewer charge would approach $600,000. The present

worth of the alternative is an order of magnitude higher than most of the

surface water discharge options discussed in Section 2. The cost estimate

for the sanitary sewer option is shown on Table 4. In addition, there are

indirect adverse environmental effects. Since the water being discharged

to the sanitary sewer meets surface water quality discharge standards

without treatment, the water is needlessly using hydraulic capacity of the

treatment plant that could better be used to treat typical wastewater. For

these reasons the sanitary sewer discharge option was not evaluated any

further.

21

The use of the' water by Industrial or commercial facilities was

evaluated. The water would be acceptable without treatment for most uses

except food processing. The problem with this option is implementability.

Previous work by the City of St. Louis Park identified two potential users

of the water. These uses were primarily for cooling and air conditioning

and would not by themselves have been able to utilize 1,000 gpm in the

winter. The negotiations were terminated when one of the industries and

the City could not agree on language concerning public health liability.

These industries have since made capital investments in equipment that

greatly reduces their need for this water. Since no potential users of the

water appear to exist at this time, this option becomes too speculative to

pursue. The time frame to identify types of industries which might locate

in the City and would need this amount of water, the time to promote the

idea and the time to actually design and build the facility are well beyond

the schedule specified in the RAP. This option could be pursued at a later

date should potential users show interest in locating in the City.

The third alternative is the use of the water for drinking water

supply. When use of the well was discontinued the water quality slightly

exceeded Minnesota Department of Health (MDH) guidelines. It is possible

that since that time or at some point in the future the quality of the

SLP 4 discharge may meet the drinking water guidelines and the water could

be used without treatment. Treatment of the water is also a feasible

option. The City presently operates a carbon adsorption treatment plant

for Wells SLP 10 and 15. Preliminary discussions with the City of Edina

indicate that there may be some interest in obtaining water from St. Louis

Park. The use of the water for drinking water supply was evaluated further

because it appeared to be a potentially feasible alternative.

EVALUATION OF ALTERNATIVES

In order to evaluate the water supply alternative, certain assumptions

were made regarding the design and location of the system. It was assumed

that the water from SLP 4 would first be pumped to the SLP 6 location.

This was done for three reasons. The first reason is the very limited

22

space at the SLP 4 location. Any construction that might be needed could

be more easily accommodated at SLP 6. The second reason is that the

existing sand filters at SLP 6 can be utilized in the treatment train. The

cost of new sand filters is approximately $1.5 million. Finally, storage

is not available at SLP 4 while the SLP 6 location has existing storage.

It was also assumed that if Edina obtained water from St. Louis Park,

they would interconnect at the SLP 6 location. For each of the factors

evaluated, except institutional impacts and costs, it was assumed that the

impacts were the same for use by either St. Louis Park or Edina.

Once the water was at SLP 6 it was assumed treatment would be required

before the water could be used for water supply. If the concentrations of

PAH compounds in the water were to decrease sufficiently for no treatment

of PAH compounds to be.required, the only costs for this option would be

the forcemain between SLP 4 and SLP 6 and the associated pumping costs.

Four different treatment processes were investigated for the situation

where the PAH concentrations do not decrease. These processes were carbon

adsorption, granular media filtration, chemical oxidation and reverse

osmosis.

The carbon adsorption process evaluated was a process in which a fixed

bed of granular activated carbon serves as the adsorption media. Depending

upon the quality of water being treated, backwash or surface washing

capabilities may be required. Carbon adsorption units can be operated as a

single unit or combined in series or in parallel.

The efficiency of a carbon adsorption unit depends upon the

following:

o flow rate

o carbon bed height and diameter

o contaminant concentrations

o natural organic content of the water

o pH

23

o competition for adsorption sites by individual contaminants

o affinity of the contaminant for the carbon surface.

For full-scale" design purposes, the following conditions were

assumed:

o flow rate of 1,000 gpm

o no pre-treatment of contaminated groundwater

o two units (each containing 20,000 pounds of GAG)

o carbon burn rate of 0.01 pounds of GAG per 1,000 gallons

o located at SLP 6

The granular media filtration (GMF) process is similar to the carbon

adsorption process. The media in granular media filtration is normally a

combination of silica sand and anthracite coal. The efficiency of the

process is dependent upon the water matrix, compounds to be removed,

concentration and flow conditions. If a bench and/or pilot scale test

proved that granular media filtration were a technically feasible solution,

the existing sand filters at SLP 6 could be upgraded to granular media

filters.

The chemical oxidation process breaks large.prganic constituents down

to smaller, less harmful organic constituents. Complete oxidation would

result in the production of only carbon dioxide and water. Smaller organic

constituents may be formed due to incomplete oxidation. These may require

additional treatment. Six methods of chemical oxidation of PAH compounds

were Identified:

o ozone (0^)

o ozone/ultra-violet light (UV)

o hydrogen peroxide (H2O2)

o hydrogen peroxide/ultraviolet light

o chlorine (CI2)

o chlorine dioxide (CIO2)

24

Bench scale tests of these chemical oxidation processes were conducted

by CH2M Hill and were presented in the report "Evaluation of Groundwater

Treatment and Water Supply Alternatives for St. Louis Park, Minnesota",

which was prepared for the MPCA in November, 1983 by CH2M Hill and Barr

Engineering Co.

The tests performed by CH2M Hill were done using water from Well

SLP 15. The average total PAH concentration of the water used in the pilot

study was 7,000 ng/L. In the bench scale test, only two chemical oxidation

processes were identified as technically feasible, ozone/UV and hydrogen

peroxide/UV. Ozone/UV dosage rates of 1 mg/L and 20-minute retention time

were able to reduce the influent PAH concentration to the desired criteria.

Peroxide/UV provided good results at 5 mg/L and 60-minute retention time.

The average total PAH concentration for SLP 4 data from 1978 through

1982 was 293 ng/L and the maximum value was 1730 ng/L. The maximiom value

in SLP 4 is approximately one fourth the value used for the bench scale

test water from SLP 15 (7000 ng/L) . The lower concentration in SLP 4 would

probably require lower dosage rates and/or shorter retention times. The

necessary design criteria cannot be adequately determined from the bench

test performed by GH2M Hill.

The lower concentrations in SLP 4 may make ozone of hydrogen peroxide

alone without UV technically feasible. This cannot be determined without

additional testing. Ozone is relatively unstable and must be produced on

site at the time of use. Ozone is produced by passing dry air or oxygen

between two high voltage electrodes. The chlorine and chlorine dioxide

oxidation processes would need further testing because of the possibility

that chlorinated PAH compounds might be formed as reaction products.

Because of the many design variables, only ozone oxidation was included in

the cost analysis for comparison to the other treatment methods.

25

The reverse osmosis process can be used to remove dissolved high

molecular weight organic compounds. The compounds are filtered through a

semi-permeable membrane. Pressure greater than the osmotic pressure

(pressure produced by the dissolved materials) is applied in order to

increase the rate and efficiency of organic compound removal. The pressure

may range from 1 atmosphere to 100 atmospheres..

Typical design variables of reverse osmosis are as follows:

o membrane type

o flux (product) rate

o operating pressure

o membrane configuration

o water recovery

A bench and pilot study would be necessary to define these design

criteria for the water matrix from SLP 4.

As with the surface water alternatives, the water supply alternative

was analyzed for technical, environmental, public health, institutional and

cost concerns. Where concerns were different for the treatment options,

the differences are noted.

Technical Analvsis

The technical feasibility of treating the SLP 4 discharge for drinking

water use is well documented. St. Louis Park is presently treating

groundwater with higher levels of PAH compounds at SLP 10 and 15 to

drinking water standards. This is being done with carbon adsorption. To

determine the design parameters of the other treatment options will require

bench testing. Reverse osmosis has the lowest probability of meeting the

required standards since there is such a small difference between the

treatment goal and the influent water quality. Granular media filtration

has several unknowns since very few, if any, GMF systems have been designed

and operated for PAH removal to drinking water standards. The previously

26

referenced bench testing demonstrated that chemical oxidation will treat to

drinking water standards.

The operation and maintenance requirements for the water supply

treatment options can be quite extensive. The monitoring requirements for

a drinking water treatment system are much more extensive than for surface

water discharge treatment systems. The extent of this difference is

dependent upon the treatment process selected. The actual operation of the

various options is also quite different. The operation of the carbon

adsorption and granular media filtration are straightforward and require

minimal staff time. The ozone/UV and reverse osmosis each require about

two full-time staff to do the required operation and maintenance.

Of the four treatment options, only chemical oxidation results

directly in the destruction of the PAH compounds. With the other three

processes, it depends on how the residuals from the treatment process are

managed. In all likelihood the activated carbon will be regenerated

through incineration. This will result in the destruction of the PAH

compounds. The liquid residual from the reverse osmosis may be acceptable

for discharge into the sanitary sewer. This would result in at least

partial destruction of a percentage of the PAH compounds. A large

percentage would concentrate in the sludge and be destroyed during sludge

incineration. A small but unknown amount would pass through the treatment

plant and be discharged to the Mississippi River. This liquid could

alternatively be shipped to an off-site incinerator for treatment. The

granular media treatment option may present the most difficult residual

management problems. Since the principal design use of such systems is

fine particulate filtration, there is no need to regenerate or replace the

coal. However, when used to remove PAH compounds the media will require

regeneration. Since the coal may be mixed with sand, there will be

problems in regenerating the media through incineration. It is possible

that the media may be landfilled. More work on residual management would

have to be done before this option was selected.

One criteria to be considered in selecting a treatment option is if

the alternative can be phased. The treatment options themselves can not be

27

phased. One method of phasing the remedial actions would be the use of

temporary surface discharge to Minnehaha Creek during construction .

start-up of a drinking water treatment system. This could result in '

initiation of gradient control up to one year earlier..

Environmental Analysis

The use of the discharge from SLP 4 will result in environmental

benefits. Waters in Minnesota are classified for their highest and best

use. In the case of groundwater, Minnesota Rules Chapter 7060.0400

classifies all underground waters of suitable natural quality for potable

use. The treatment and use of this contaminated water would conserve

uncontaminated groundwater for other uses. This water would replace water

presently being pumped from deeper unaffected aquifers or from

uncontaminated portions of this aquifer. There were no environmental

problems identified with the water supply alternative.

Public Health Analysis ^ ^

Since the ultimate intended use of the wat^r in the water supply

alternative is for drinking purposes, there i.k a potential public health

risk. The risk is one that results from long-term exposure to the

carcinogenic PAH compounds. The public health^risk from the treatment and

water supply options are extremely small. Historic data on water quality

of SLP 4 consistently show that the concentrations of carcinogenic PAH

compounds, are below the drinking water criteria for these compounds. The

use of the well was discontinued because the concentration of

non-carcinogenic PAH compounds was above the drinking water criteria. The

non-carcinogenic PAH compound criteria was set to provide an additional

measure of safety beyond the carcinogenic PAH criteria. Research has not

been done establishing a risk level for non-carcinogenic PAH compounds.

These alternatives all assume that treatment will be provided to remove

even the non-carcinogenic PAHs to below the drinking water criteria.

Frequent monitoring of treated water allows for early detection of any

changes in treated water quality. This will preclude or at least greatly

minimize the possibility that water not meeting the criteria is placed in

28

the munlclpaiL system. Since the health risk associated with the drinking

water criteria is based on drinking the water for 70 years, the risk

associated with any short-term exposure between monitoring events would be

very small. The public health risk associated with these alternatives

would be no worse than the risks associated with the treatment system

presently operating on SLP 10 and 15 because the quality of the water being

treated at SLP 10 and 15 is worse than that historically found at SLP 4.

Institutional Analvsis

The regulatory involvement for the water supply alternative is

primarily limited to United States Environmental Protection Agency (EPA),

MPCA and MDH. MDH has the primary responsibility for regulating public

water supplies. However, plans and specifications for any treatment system

would have to be approved by EPA, MPCA and MDH according to the RAP. The

approval of the carbon adsorption option would be the most straightforward

since it is the only treatment process of the four options being evaluated

which has been demonstrated in Minnesota.

As with all the alternatives, the DNR will have to issue a water

appropriation permit for the pumping of SLP 4. The DNR has expressed a

definite preference for use rather than discharge.

The institutional concerns involved with a sale of water to Edina are

more complicated. In recent years, interconnections between municipal

systems have become more common. One aspect of the problem is working out

logistics of the physical delivery and operation. This would also involve

the cost negotiations. In this situation, there will also be a public

perception problem. The problems with the groundwater contamination in St.

Louis Park have been well publicized for many years. Even though the water

delivered will meet drinking water criteria, there may still be many

members of the public who will not recognize this fact. Still others might

believe that any risk, no matter how small, when it involves their drinking

water is unacceptable. An arrangement whereby St. Louis Park provides

water from one of its unaffected wells and only puts the treated water in

their system might alleviate some of the public concern.

29

flQst Analysis

Cost estimates were prepared for each of the four treatment options.

The degree of certainty and completeness varies between options. As

previously discussed, bench scale tests should be done on all the options

except carbon adsorption before the facilities are designed. It is most

probable that these tests would increase the costs rather than demonstrate

that the desired level of treatment could not be obtained. It should also

be recognized that there are no costs included in the granular media

filtration for treatment or disposal of the media or costs for disposal of

the removed contaminants in the reverse osmosis options. It was decided

that these costs were too speculative and would only be important if one of

the options would receive serious enough consideration to conduct bench

tests. At the conclusion of the testing, more realistic cost estimates

could be made.

The water supply options do not contain power costs for pumping the

water from SLP 4. It was assumed that this cost would be off set by the

reduced pvimping of wells presently used.

The capital cost of the carbon adsorption system was estimated to be

$1,190,000. This includes $349,000 for the connection between SLP 4 and

SLP 6. If this amount is subtracted, the cost estimate is very comparable

to the reported cost of the system installed at SLP 10 and 15. The annual

operation and maintenance cost is estimated to be $70,000 per year. At

this time, it is too early to compare this estimated cost to the actual

annual operation and maintenance cost at SLP 10 and 15. The present worth

costs for 10 and 30 years of operation are $1,731,000 and $2,266,000,

respectively. These costs are shown in Table 5.

The capital cost of $1,001,000 for the granular media filtration is

slightly less than that of the carbon adsorption system. The annual

operation and maintenance cost of $85,000 Is slightly higher than the

carbon adsorption system. As previously mentioned, the operation and

30

maintenance cost for the GMF system does not Include any cost for media

regeneration or disposal. The 10-year present worth is $iL,,657,000 and the

30-year is $2,308,000. These costs are shown in Table 6.

The capital cost of the ozone system is estimated to be $1,386,000.

The annual operation and maintenance cost is estimated to be $175,000,

nearly double either of the first two options. This results in

significantly higher present worth cost. The 10-year present worth is

$2,737,000 and the 30-year present worth is $4,076,000. The costs are

shown in Table 7.

Reverse osmosis has the highest estimated capital and annual operation

and maintenance costs of the four options. The costs are $3,095,000 for

capital and $97,000 for annual operation and maintenance. This results in

a 10-year present worth of $4,616,000 and a 30-year present worth of

$6,123,000. The costs are shown in Table 8.

SEC3/346,0/msh 31

SECTION 4

EVALUATION OF COST-EFFECTIVE ALTERNATIVES

Sections 2 and 3 presented analyses of the technical, environmental,

public health', institutional, and cost factors for each evaluated

alternative. This section will compare the attributes of the alternatives..

Only the most important attributes will be discussed. Where there are

distinct differences between alternatives these will be highlighted so the

policy decisions are clearly identified. For this evaluation it was

assumed that carbon absorption system would be used for drinking water

treatment.

PUBLIC HEALTH COMPARISON

The public health analysis did not identify any concerns with any of

the alternatives. All the alternatives will meet the appropriate water

quality standards which take into account public health. There is no

reason to differentiate between the alternatives based on public health.

ENVIRONMENTAL COMPARISON

No environmental problems were identified in the analyses. Although

water supply alternative does more appropriately makes use of the

groundwater, this is more of an institutional factor than an environmental

concern. There is no reason to differentiate between the alternatives

based on environmental quality.

TECHNICAL COMPARISON

All the options are technically feasible. There are some distinct

differences between the alternatives. The Bass Lake and Lake Calhoun

alternative will aggravate any existing high water problems in the Chain of

Lakes. During recent years, pumping out of Lake Calhoun has been

necessary. While this can be accomplished, the SLP 4 discharge may

increase the severity and duration of the problem. The Bass Lake

32

alternative has the added problem of increased flooding at the golf course.

There should be no water level problems with the Minnehaha Creek or

Mississippi River alternatives. There were no identified technical

problems with the water supply alternative. From a technical analysis

standpoint, the water supply, Minnehaha Creek and Mississippi River

alternatives are preferred. The Bass Lake and Lake Calhoun alternatives

present the greatest problems.

INSTITUTIONAL COMPARISON

The institutional factors could play a major role in the

implementation of the selected alternative. A great deal of concern and

reluctance has been expressed by Minneapolis and the Minneapolis Park Board

with the Lake Calhoun and Minnehaha Creek alternatives. Part of this

concern relates to the technical factors already discussed. An equal or

greater concern has been expressed that is based on public perception. The

view is that St. Louis Park would simply be imposing its problem on

Minneapolis with these options. The public thinks that the groundwater is

too contaminated to leave in the ground and therefore does not want it in

the lakes or streams. This alternative would likely apply to the Bass Lake

alternative also. This is an especially difficult problem for the Lake

Calhoun alternative, where permission from Minneapolis would be required.

The same concerns would be expressed with the Bass Lake and Minnehaha Creek

alternatives., but since the city would not exercise direct control, the

concerns could be more easily addressed. There were no negative

institutional concerns identified with the Mississippi River alternative.

The preferred alternative from an institutional perspective is the water

supply option. It does not involve any local unit of government. It is

the stated preference of the DNR. It may be viewed by the citizens of St.

Louis Park as the most logical since it improves their water system rather

than pumping water to waste.

Table 9 summarizes the non-cost factors identified in the technical,

environmental, public health and institutional analysis sections.

33

COST COMPARISON

Table 10 sxuiunarlzes the capital and total present worth for 10 and 30

years of operation for each alternative. If the existing storm sewer

system can be used, the Lake Calhoun and Bass Lake alternatives have

comparable and- the lowest costs. The Minnehaha Creek and Lake Calhoun

alternative with a dedicated forcemain have comparable costs. The

Mississippi River and water supply alternatives have the highest costs

which are roughly equal.

OTHER CONSIDERATIONS

The only additional consideration identified was the flexibility

associated with the Minnehaha Creek alternative. With this alternative, if

the water quality at SLP 4 should improve to the degree that it meets

drinking water criteria the water could be put into the water supply system

at a minimal capital cost. This also allows the flexibility of adding a

water treatment system should the demand for water increase. If the timing

of expenditures is a concern, this alternative allows the gradient control

to begin with the surface water discharge and switch to the water supply

alternative when funds are available for treatment plant construction.

RECOMMENDATION

It is recommended that the discharge from SLP 4 be discharged to

Minneha^ Creek ajt SLP 6 (Yosemite Avenue). The institutional problems and

potential technical problems associated with the Bass Lake and Lake Calhoun

alternatives outweigh the possible cost savings. The two preferred

alternatives based on non-cost factors are the water supply and Mississippi

River alternatives. The institutional advantages of the water supply

alternative suggests that the Mississippi River alternative be eliminated.

The primary reason for recommending the Minnehaha Creek alternative over

the water supply alternative is flexibility. As discussed, the changes in

gr^und^ter quality in response to the pumping are not known. At this time'

it would be prudent to operate the system, for some time to determine what

the quality is and make better predictions on the likelihood that the water

34

may meet drinking water standards in the near future. Once the system is

operational, water treatment can be added without having incurred any

unnecessary capital expenditures, as the piping from SLP 4 to SLP 6 is

required for either alternative.

SLPS4/346,0/msh 35

REFERENCES

1. Bartell, S.M.; Gardner, R.H. and O'Neill, R.V. 1983/1984. The Fates

of Aromatlcs Model (FOAM): Description, Application and Analysis

Ecological Monitoring 22:109-121.

2. Breck, James E. and Bartell, S.M., 1985. Approaches to Modeling the

Fate and Effects of Toxicants in Pelagic Systems. Environmental

Sciences Division, Oak Ridge National Laboratory.

3. Conner, Michael Stewart, 1984. Fish/Sediment Concentration Ratios

for Organic Compounds Environmental Sciences Technologv 18:31-35

4. LaVoic, Edmond; Coleman, Daniel; Tonne, Robert; and Hoffmann, Dietrich

1983. Mutagenicity, Tumor Initiating Activity and Metabolism of

Methylated Anthracenes. Polvnuclear Aromatic Hvdrocarbons:

Formation. Metabolism and Measurement Battelle Press.

5. Staples, Carles; Dickson, Kenneth; Rodgers, John and Saleh, Farida

1985. A Model for Predicting the Influence of Suspended

Sediments on the Bioavailability of Neutral Organic Chemicals

in the Water Compartment. Aouatic Toxicoloev and Hazard

Assessment ASTM.

REREF/346,0/msh

TABLE 1

COMPARISON OF SLP 4 WATER QUALITY AND CRITERIA (concentrations in ng/L)

SLP 4 Accurex Report

Sum of Benzo(a)pyrene & 2 Dibenz(a,h)anthracene

Carcinogenic PAH Compounds

4

Other PAH Compounds 113

Phenanthrene 21

Phenolics NO

SLP 4 Avg. Cone. 7/81-10/82

0.4

340

Drinking Water Criteria

5.6

28

280

Ho Standard

No Standard

NPDES Permit Criteria

No Standard

311

17,000/34,000*

1,000/2,000*

10,000

* First nunber is 30-day average concentration. Second number is maximum concentration.

TABLI/346,0

TiBLE 2

WATER QUALITY DATA

a.p Btoni Btora Btn Btora Btora Btora mnnahriia Laka Laka 4 1 E 3 4 5 3 4 Calhoun Harrlat

DATEl m/2^m lOniVBS 1Q/iOk'B3 lOAIQ^BB 10^0^33 ICb'IIVBS 10711^33 07/21/23 07/21/23 07/21/23

ANALYSIS BVl Anurax CHEN Hill OCH HILL QCN HILL IWH HILL QCN HILL CKN HILL CWN HILL fSCH HILL QCN HILL

ANALYTICAL EDUIPNBITl BC/HB BC/NB BiyNB BG/NB BC^n BC/HB BC/m BiyHB G^NB ec/NB

tamtar

• (All valuas In ng/Ll Naphthalana BED E60 330 370 150 340 3B 1-Ha tliy I naph th ala na 180 EBO EBO 430 140 330 11 B-Hsthy Inaph thai ana 300 540 670 800 EBO 750 IB Aoanaphthylana 2 Acanaphthana 72 54 07 40 110 Pluorana a B1 31 40 35 73 Anthracana 4 87 30 E6 44 Riananlhrana SI 340 OO B30 170 35 300 E3 13 hrrana 4 130 130 110 103 5E 1E0 71 E7 3 Fluoranthana 4 EBO 170 170 160 54 130 35 14 11 Banzo(a)anthracana[*] SB 34 EB 34 E3 3.5 OiryaanaC) 2 130 83 6E 83 38 BE 8.3 Banio(b B k)anthraBana(*] 130 BE 51 BaiBo(a|pyrana(*] 2 30 Bania(a]pyrana Bamntgi h, 11pary lana E7 Indanoll •BiBrcdlpryanaC*]. , E3 D1bania(aih)anthraeana(*)

Total CarelnoBame PAHa 4 313 1BE 30 37 — 33 158 13.3 — Total "Othar- PAHa 113 1.B4E 1,733 1,780 E,113 741 E,E10 Ell EES 17

PAH enpound.

WaD/34B,a

T«i£ a ST. LOUIS nuiK vat aM

aURFAE DISHMSE DRAIN/IBE OPTmNS

LAKE CALHOUN IQrwIty Syatn)

LAKE CALHOUN (OadloBtad ^at«1

HINNnAHA nEBC Dladiarga at Hall aPS

BASS LAKE NSSISSIPPI RnBI/

BASSETT CREB I-3B4 Stora Baaar

Unit (bat II) Ouan. Eat. Eat. Eat. Ouan. Ouan. - Eat.

msaizATiaN (TBI L.B. 1846 90,39 98,90 14,49 98,810

nsraLATin lOP DIP A Httlnga L.F. B7JI0 6,39 19,19 18,800 49,89

B" DIP A Ftttlnaa UP. B1.B0 8,09 173,89 1,19 84,89

IB" RCP L.F. EC.00 39 B,B9

lir GV Eadi B30.00 8 1,89 8 3,79 8" OV Each Bsajm 1 90 3 1,69 1 90 4* m Each 1,09.00 1 1,09 1 1,09 1 1,09 1 1,09 1 1,09 Hay. Craaalng Each BE ,000 JIB • 1 86,90 1 86,000 RR CroaalnB Each eo,000.00 8 40,000 4-lana Btraat Craaalng &ch 10,000.00 8 80,90

EXCAVATSm A RBBTORATmH

Curb A Suttar Raoaa

A Raplaca L.F. 16.00 8,09 19,79 4,39 84,69 1,19 17,89 10,800 183,59 Roaora A Raplaca

gitiBlnoua Road 8.V. B.00 18,89 136,880 8,09 78,89 8,90 18,49 84,810 19,89

Raova A Raplaca Bidaalk S.F. 4J)0 3,800 14,90 7,90 9,90 Sod S.Y. 8J0 B9 8,886 1,886 4,90 8,09 80,09 Baad A Mulch B.Y. 1.9 1,39 8,09

aaar A Brub 8.Y. 8.50 89 1,860

cwsraicrin itua •

18,810 49,810 39,90 87,90 1,018,110

BBMEBIINB A AONIHIBTRATIM (i m 8,69 9,79 9,870 13,510 89,89

DRRATIDN A HAMTBIANCE

Annual Labor Puaptng

Oparatlana Hour 80.00 BB 1,380 84 1,89 9 1,09 38 1,380 68 1,09 Annual Labor Holntananca Hour ggjIO 64 1,89 18 39 IB 39 19 8,180 38 89 Annual Piaplng aP4 BBS daya L.SL 88,79 1 38,79 1 38,79 1 38,79 1 38,79 1 38,780 Annual Piaplng t Calhoun

BO daya L.8. 13,640 1 13,6« 1 13,69 1 13,59

RtanT VALUE R)R 0 A H (1=9, n^O yr) 378,130 370,19 93,700 384,830 98,170 FRSBIT VALUE FOR 0 A H (1=9, ir«0 yr) 79,79 79,90 94,870 788,39 98,89

10 YEAR OPBIAiTnil

SUBTOTAL 39,89 89,310 89,90 96,870 1,40,800

CDKTIISaCia (E91 78,79 19,89 19,69 9,19 80,69 TOTAL moiECT COST (Praaont ValuaJ 478,39 1,111,670 98,49 658,180 1,79,49

ag TEW DFBOiai SUBTOTAL. 79,89 1,89,010 844,89 347,380 1,751,89

C0KTIW9CIE8 (29) 19,90 868,800 19,89 19,470 39,380 TOTAL PROlEa COST (Praaant Value) 91,39 1,661,810 1 ,19,09 1,018,830 8,101,89

aiRDis'adB.a

TABLE 4

SANITARY SEWER DISCHARGE COSTS

MOBILIZATION (7%)

INSTALLATION 8" DIP & Fittings 18" RCF 8" GV 4' MH

EXCAVATION & RESTORATION Curb & Gutter Remove & Replace

Remove & Replace Bituminous Road

Unit Cost ($)

L.S.

L.F. L.F. Each Each

L.F.

S.Y.

21.60 22.00 530.00

1,050.00

15.00

8.00

Quantity

800 300 1 1

1,100

2,322

Extension

$4,240

17,280 6,600

530 1,050

16,500

18,580

CONSTRUCTION TOTAL ENGINEERING & ADMINISTRATION (20%)

$64,780 $12,960

OPERATION & MAINTENANCE SAC Charge L.S. Annual User Charge L.S. Annual Labor Pumping Operations ' Hour

Annual Pumping SLP4 365 Days L.S.

20.00

32,780

52

2,759,120 587,460

1,040

32,790

PRESENT VALUE FOR 0 & M (1-5%, n-10 yr.) PRESENT VALUE FOR 0 & M (1-5%, n-30 yr.)

$7,556,530 $12,309,900

10-YEAR OPERATION SUBTOTAL CONTINGENCIES (5%) TOTAL PROJECT COST (Present Value)

30-YEAR OPERATION SUBTOTAL CONTINGENCIES (5%) TOTAL PROJECT COST (Present Value)

$7,634,270 381,710

8,015,980

$12,387,640 619,380

13,007,020

SSDC/346,0

TABLE 5

COST ESTIMATE FOR GRANULAR ACTIVATED CARBON

Canltal Eouioment Quantity Unit Unit Cost Cost

Contactors 2 Each $70,000 $140,000 Carbon Inventory 40,000 Lbs. .90 36,000 Ins trumentat ion 1 L.S. 35,000 35,000 Internal Piping 1 L.S. 26,000 26,000 Electrical 1 L.S. 44,000 44,000 Building 1 L.S. 123,000 123,000 Piping from SLP4 1 L.S. 349,000 349,000 Installation 1 L.S. 44,000 44,000 Restoration 1 L.S. 18,000 18,000

DIRECT COST $ 815,000

Engineering & Administration (20%) $163,000 Contractors Fee (6%) 49,000 Contingency (20%) i63.000

TOTAL CAPITAL COST $1,190,000

Annual Cost

Labor 1,300 Hour $20.00 $26,000 Power 104,000 KWH 0.05 5,000 Maintenance 1 L.S. 5,000 5,000 Lab Analysis 12 Each 1,000 12,000 Carbon Regeneration 13,000 Lb. 0.70 9,000 Make-up Carbon 1,300 Lb. 0.90 1.000

SUBTOTAL 58,000 Contingency (20%) 12,000

TOTAL $ 70,000/yr

Present Worth (5% net annual interest rate)

10 years in operation

30 years in operation

$1,731,000

$2,266,000

SLPTBL/346,0/1

TABLE 6

COST ESTIMATE FOR GRANULAR MEDIA FILTRATION UP-GRADE

Caoital Eauioment Ouantltv Unit Unit Cost Cost

Granular Media 10,000 G.F. $17.00 $170,000 Capital Equipment 1 L.,S,. 20,000 20,000 Pilot Study 1 L.S. 20,000 20,000 Instrumentation 1 L.S. 21,000 21,000 w Internal Piping 1 L.S. 21,000 21,000 Electrical 1 L.S. 11,000 11,000 Building 1 L.S. -0- -0-Piping from SLP4 1 L.S. 349,000 349,000 Installation 1 L.S. 53,000 53,000

• Restoration 1 L.S. 21,000 21,000

DIRECT COST $ 686,000

Engineering & Administration (20%) $137,000 Contractors Fee (6%) 41,000

• Contingency (20%) 137.000

TOTAL CAPITAL COST $1,001,000

Annual, Cost

• Labor 1,300 Hour $20.00 $26,000 Power 44,000 KWH 0.05 2,000 Maintenance 1 L.S. 5,000 5,000 Lab Analysis 12 Each 1,000 12,000 Make-up Granular Media 1,500 C.F. 17.00 26,000

SUBTOTAL 71,000 Contingency (20%) 14.000

TOTAL $ 85,000/yr

Present Worth (5% net annual Interest rate)

10 years In operation $1,657,000

30 years in operation $2,308,000

SLPTBL/346,0/2

TABLE 7

COST ESTIMATE FOR OZONE TREATMENT

Capital Equipment Quantity Unit Unit Cost

Ozone Generator- (120 lbs/day) Reactor Air Dryer Ins trumentat ion Internal Piping Electrical Building Piping from SLP4 Installation Restoration

DIRECT COST

Engineering & Administration (20%) Contractors Fee (6%) Contingency (20%)

Each Each Each L.S. L.S. L.S. L.S. L.S. L.S. L.S.

$129,000 82,000 15,000 45,000 34,000 57,000

158,000 349,000 57,000 23,000

TOTAL CAPITAL COST

•Cost

$129,000 82,000 15,000 45,000 34,000 57,000

158,000 349,000 57,000 23.000

$ 949,000

$190,000 57,000

190.000

$1,386,000

Annual Cost

Labor Power Maintenance Lab Analysis

4,000 284,000

1 12

SUBTOTAL

Hour KWH L.S. Each

Contingency (20%)

TOTAL

Present Worth (5% net annual Interest rate)

10 years In operation

30 years in operation

$20.00 0.05

40,000 1,000

$80,000 14,000 40,000 12,000

146,000 29.000

$175,000/yr

$2,737,000

$4,076,000

SLPTBL/346,0/3

TABLE 8

COST ESTIMATE FOR REVERSE OSMOSIS

Canital Eauioment Unit Unit Cost Cost

Osmosis Unit 1 Each $720,000 $720,000 Instrvunentation 1 L.S. 144,000 144,000 Internal Piping 1 L.S. 108,000 108,000 Electrical 1 L.S. 180,000 180,000 Building 1 L.S. 500,000 500,000 Piping from SLP4 1 L.S. 216,000 216,000 Installation 1 L.S. 180,000 180,000 Restoration 1 L.S. 72,000 72.000

DIRECT COST $2,120,000

Engineering & Administration (20%) $424,000 Contractors Fee (6%) 127,000 Contingency (20%) 424.000

TOTAL CAPITAL COST $3,095,000

Annual qp^t

Labor 3,700 Hour $20.00 $74,000 Power 454,000 KWH 0.05 23,000 Membrane Replacement 100 Each 500 50,000 Maintenance 1 L.S. 5,000 5,000 Lab Analysis 12 Each 1,000 12,000

SUBTOTAL 164,000 Contingency (20%) 33.000

TOTAL $197,000/yr

Present Worth (5% net annual interest rate)

10 years in operation

30 years in operation

$4,616,000

$6,123,000

SLPTBL/346,0/4

TABLE 9

NON-COST COMPARISON.

Bass Lake

Technical Analvaia

High .water at golf course and Lake Calhoun

Environmental Public Health. Analysis Analysis

No problems No problems

Institutional Analysis

Public perception of poor quality water

Lake Calhoun Grayity System

High water Unsafe ice

No problems No.problems Public perception of poor quality water. Interjuris­dictional with Npls.

Lake Calhoun Dedicated System

High water No problems No problems Public perception of poor quality water. Interjuris­dictional with Mpls

Minnehaha Creek Unsafe ice No problems No proble Public perception of poor quality water

Mississippi River 1394/Bassett Creek

No problems No problems No problems No proble

Water Supply Carbon Adsorption

No proble No problems No problems No problems Preferred by DNR

T9NCC/346,0/

TABLE 10

COST COMPARISON

Bass Lake

Lake Calhoun

Gravity System Dedicated System

Minnehaha Creek

Mississippi River 1394/Bassett Creek

Water Supply Carbon Adsorption

Capital Cost

81,000

419,000

lO-Year Present Worth Value

30-year Present Worth Value

559,000 1,017,000

15,000 472,000 922,000 556,000 1,112,000 1,552,000

819,000 1,133,000

1,222,000 1,785,000 2,102,000

1,190,000 1,779,000 2,362,000

LakB Harriet

Scale In Feet

Gradient Control Well

Approximate Area of Contamination

Figure 1

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fr

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PRELIMINARY SURFACE WATER DISCHARGE LOCATIONS

0 I.

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Scale In Feet

CLOSED CONDUIT OPEN CHANNEL

Figure 3

ST. LOUIS PARK WELL SLPA SURFACE DISCHARGE OPTIONS

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© Figure 4

SAMPLING LOCATIONS CH2M HILL STUDY