DE PA
                                                                    Exhibit 10.2

                              SUB-LICENSE AGREEMENT

         AGREEMENT made and entered into as of the 1st day of July, 1980, by and
between INSITUFORM OF NORTH AMERICA,  INC., a corporation organized and existing
under  the laws of the  State of  Delaware,  hereinafter  referred  to as "North
America" and  Insituform  East,  Inc. of  Hyattsville,  a Delaware  corporation,
having a  principal  place  of  business  at 6525  Belcrest  Road,  Hyattsville,
Maryland, hereinafter referred to as "Operator";

                                   WITNESSETH:

         WHEREAS,  North  America has  valuable  experience  in the  practice of
certain  inventions,  know-how and  techniques  comprising the subject matter of
this Agreement and possesses valuable information with respect thereto;

         WHEREAS,   North  America  is  the  exclusive  licensee  of  INSITUFORM
INTERNATIONAL,  INC., a corporation organized and existing under the laws of the
Netherland  Antilles  having a  principal  place of  business  at P.O.  Box 840,
Curacao,  Netherland,  Antilles,  hereinafter  referred  to as  "International",
throughout the United States of America except California,  of certain know-how,
patent rights and inventions  relating to methods,  apparatus and materials used
in  the  lining  of  sewers,   tunnels,   pipelines  and  other  passageways  by
impregnating an absorbent layer with a synthetic resin, and retaining such layer
in  place  in  such  passageway  while  the  layer  cures  or is  cured  and any
improvements thereon, and

         WHEREAS,  Operator is desirous of gaining knowledge of such inventions,
know-how,  techniques, and information and an exclusive right and license within
and  throughout  the  territory  listed  on  Schedule  A herein  to use the same
together with any and all patent rights and  copyrights  relating  thereto under
which North America has or obtains the right to grant licenses therein;

         NOW,   THEREFORE,   in   consideration  of  the  mutual  covenants  and
undertakings set forth herein, the parties hereto agree, as follows:

         I.       DEFINITIONS.  As employed herein:

         A. "Territory"  shall mean that geographical area set forth on Schedule
A within which  Operator may exploit the various  inventions,  know-how,  patent
rights, techniques and information granted herein.

         B. "Subject  Matter" shall mean and include all methods,  apparatus and
materials  used  in  the  lining  of  sewers,  tunnels,   pipelines,  and  other
passageways  excepting  those used to carry aromatic  hydrocarbons  in a gaseous
state by impregnating an absorbent layer with a synthetic  resin,  and retaining
such layer in place in such passageway while the layer cures or is cured.

         C.  "Know-how"  shall mean and include all  technological  information,
ideas and techniques  relating to the Subject  Matter now owned or  subsequently
acquired by North America or which North America subsequently acquires the right
to  communicate  to its  licensees  within the United  States of America  except
California  except  any  information,  ideas  or  techniques  which  are  common
knowledge to the industry or which are readily available from sources other than
North America.

         D.  "Patent  Rights"  shall mean and  include  the  patents  and patent
applications  designated  in  Schedule B attached  hereto and made a part hereof
together with any and all other patents and patent applications  relating to the
Subject  Matter in the  Territory  under which North  America  has, or hereafter
acquires, the right to license others.

         E. "Copyrights" shall mean and include any and all copyrights at common
and/or  statutory  law within the  Territory  which relate to plans,  brochures,
instructions  or other means of expression  having to do with the Subject Matter
including  photographs,  diagrams and other visual  presentations,  or useful in
connection  with the  commercialization  thereof,  which North  America  has, or
hereafter acquires, the right to license others.

         F.  "Materials"  shall  mean  and  include  any and  all  compositions,
products,  components and other materials,  whether patented or unpatented,  for
use in the practice of the Subject  Matter.  Such Materials shall include by way
of  illustration  but not of  limitation,  the  resin  absorbent  material,  the
impervious  sheet  material,  the  thermosetting  resin  and any  and all  other
materials which go into the lining of passageways or the like in accordance with
the Patent Rights except for such fuels as may be required for energy purposes.

         G. "Apparatus" shall mean and include but not be limited to any and all
tools,  equipment,  instruments,  machines,  and  devices,  whether  patented or
unpatented, for use in the practice of the Subject Matter.

         H. "Royalty"  shall mean an amount payable by Operator to North America
equivalent  to 8% of the gross  contract  price of all  contracts  performed  by
Operator utilizing the Subject Matter as further defined herein.

         II.  GRANT.   North  America  hereby  grants   Operator  an  exclusive,
non-transferable right and license within and throughout the Territory:

         A. To utilize the  Know-how,  to practice the  inventions of the Patent
Rights  relating  to the  Subject  Matter,  and to sell the  resultant  product;
however,  the  Subject  Matter may not be used to line  tunnels,  pipelines  and
passageways carrying aromatic hydrocarbons in the gaseous state;

         B. To use any and all  Copyrights,  if there are any,  as an adjunct to
the practice of such methods and the commercialization thereof; and

         C. To use and display  "Insituform"  as a trademark in connection  with
each and every  aspect of the  exploitation  of the  Process  including  but not
limited to all materials,  apparatus and products sold hereunder  purchased from
North  America  or a source  recommended  and  approved  by North  America,  all
equipment,  letterheads,  invoices,  advertising  signs of all types and printed
material shall bear appropriate insignia  acknowledging such products,  material
or equipment as under exclusive license from Insituform of North America, Inc.

         D. The Operator hereby  acknowledges  that the Subject Matter is a new,
specialized  and  highly  technological  process  and the  exploitation  thereof
throughout  the  United  States  will best be  served by the grant of  exclusive
licenses to carefully selected Operators for various defined  Territories in the
United States.

         E. It is  specifically  understood  and  agreed  that the grant of this
exclusive  license for the  Territory  is based upon the size and ability of the
Operator to exploit the demand for the Subject  Matter  within the Territory and
the nature  and scope of the  Territory  has been  determined  accordingly.  The
Operator further  understands and agrees that North America retains the right to
grant exclusive Licenses to other Operators in other defined Territories; and

         F. It is mutually  anticipated  that  Operator will exploit the Subject
Matter in the Territory for the benefit of the Community  involved.  If however,
the Operator  should seek to exploit the Subject Matter outside of his exclusive
Territory and in an area where an exclusive license has already been granted, he
shall pay the exclusive  licensee of such Territory a royalty of 8% of the gross
contract price of all  installations  utilizing the Subject Matter in such areas
in  addition  to the normal  royalty  payable  to North  America as set forth in
Paragraph  IX herein.  The  Operator  performing  the work must also ensure that
satisfactory  arrangements  are made to provide a full and complete  after-sales
service for the job involved; and

         G. North America is granting exclusive licenses for the exploitation of
the Insituform process in certain defined Territories,  however, it reserves the
right to vary or otherwise  modify the nature and scope of  subsequent  licenses
granted  to  subsequent   licensees  to  accommodate  specific  territories  and
population considerations and other factors.

         H. In connection with his exploitation of the exclusive license granted
herein,  Operator understands the importance of his after sales responsibilities
and agrees to provide  prompt and efficient  service to all those whether within
or outside of his Territory,  for whom it has performed any functions  utilizing
the practice of the Subject Matter.

         III.  ADEQUACY OF  CONSIDERATION.  It is  specifically  understood  and
agreed that the exclusive licenses defined in Paragraph II above relating to the
specific territory set forth on Schedule A, and the Royalty defined in Paragraph
IX shall be deemed adequate consideration for this Agreement.

         IV.  AVAILABILITY.  Since the Insituform  Process and the  installation
thereof is highly  technical,  its  success in large  part,  is  dependent  upon
quality materials made to exacting  specifications  and North America shall make
available for purchase by Operator,  Apparatus  and Materials  designated by and
for North America as required properly to operate hereunder.  Such Apparatus and
Materials which are not covered by any of the Patent Rights or Copyrights hereof
may be purchased from any source Operator desires.  However,  all such purchases
by  Operator  will be subject to North  America's  approval  of the  quality and
specifications  thereof.  North America may in its sole discretion improve, vary
or  otherwise  upgrade the  specifications  and quality  standards  to which the
Operator must abide.

         V. DISCLOSURE AND TRAINING.  Promptly upon execution of this Agreement,
Operator shall purchase the Apparatus and Materials required properly to operate
hereunder,  and North  America  thereupon  shall fully  disclose to Operator all
Know-how,  Patent Rights and Copyrights, if any, required in the practice of the
methods of the Subject Matter, and shall train at least four (4) representatives
of the Operator in the practice of the methods described above.  Further,  North
America shall provide a continuing  education program to the end that all lining
of sewers,  tunnels,  pipelines and other  passageways  in  accordance  with the
Subject Matter shall be effectively and efficiently  performed and the resultant
product of uniformly  high quality.  The content,  extent,  and frequency of the
educational  program shall be solely at the discretion of North America.  At the
request of Operator and subject to  availability,  North  America will provide a
technician  experienced  in the  operation  of the Subject  Matter to assist the
Operator and to render  advice  subject to payment by the Operator of all direct
traveling  and hotel  expenses  and a per diem rate which  shall be agreed  upon
between the parties.

         VI.  PRESERVATION OF SECRECY.  As North America  considers its know-how
and  technique  to be a key  element  in  the  successful  exploitation  of  the
Insituform  process,  it insists that the Operator exert every reasonable effort
to keep in strict secrecy the improvements  therein,  and modifications  thereof
disclosed to Operator by or on behalf of North America and all plans,  drawings,
specifications  and other data and documents relating thereto and to the Subject
Matter,  except  as may be  necessary,  and  only to the  extent  necessary,  to
exercise its rights hereunder;  and shall not reveal or communicate,  or permit,
or  cause to be  revealed  or  communicated,  the  same to any  person,  firm or
corporation,  except as above noted; and shall make diligent effort to see to it
that its officers, employees, agents, sub-contractors,  and all others under its
direction or control to whom the same is communicated  properly  pursuant to the
purposes  of this  Agreement  fully  observe  and abide by such  obligations  of
secrecy.  Such Operator will sign the form of Non-Disclosure  Agreement attached
hereto as Schedule C  contemporaneous  with the  execution  of this  Sub-license
Agreement and will cause its employees and others to execute such non-disclosure
agreement.

         VII. STANDARDS AND INSPECTION.  Operator shall maintain a high standard
of quality in all products  made with the practice of the methods of the Subject
Matter  and  in  all  other   products  sold   hereunder   under  the  trademark
"Insituform".  Pursuant to the maintenance of such standards,  North America may
periodically  inspect Operator's  practice of the methods of the Subject Matter.
Operator shall cooperate fully with North America in such  inspections and shall
promptly  put in effect  all  suggested  improvements  in its  practices  of the
methods  of the  Patent  Rights  made by North  America  which are  economically
practical and are  reasonably  calculated  to result in an improved  product and
service.  At all times  Operator  shall exert  diligent  effort to practice  the
methods  and  techniques  in  accordance  with  the  best  available   technical
information  and advice  received from North America for the general  benefit of
the Community within the specific territory.

         VIII.    IMPROVEMENTS AND MODIFICATIONS.

                  If during  the term of this  Agreement,  the  Operator  or his
employees,  develop any improvements or modifications in the Subject Matter, all
such information must be disclosed  immediately to North America and will become
the property of North America.  North America is obliged to disseminate all such
information  and material to all of its licensees  for their mutual  benefit and
the benefit of those they serve.

         IX.      ROYALTY.

         A. The Operator  will pay to North  America a gross Royalty equal to 8%
of the  invoiced  price of all  contracts  for the  installation  of the Subject
Matter  including  preparatory  and finishing  work therefor  carried out by the
Operator in his or any other  Territory,  such invoiced  price being  calculated
after adding back trade discounts and other preferences and deducting  packaging
and shipping charges and any applicable taxes,  provided however that such price
is  invoiced  at the going  commercial  rate and in the event that the  Operator
carries out installations in the Territory at other than a fair commercial price
then for the purposes of  calculation of royalty due in respect of such work, it
will be assumed that the Operator  performed such  installations  at the current
market price.

                  Within  45 days  after  the end of each  calendar  quarter  or
portion  thereof the Operator  shall submit to North America full details of all
work performed  utilizing the Subject Matter during such calendar  quarter,  the
total of amounts invoiced and a computation of the royalty due, such computation
being accompanied by payment in full in favor of North America for the Royalties
due.

         B.       Minimum Royalty Obligation

         During the year  commencing  twelve (12)  months from the date  hereof,
Operator  undertakes and agrees to pay North America a total royalty of not less
than US $115,000.00.  Should Operator fail to generate  sufficient  royalties as
per Paragraph IX A above to achieve such minimum payment, he may contribute such
additional  amounts so as to meet the minimum set forth  herein.  In meeting the
minimum  royalty  obligation  hereunder,   only  royalties  realized  from  work
performed within the Operator's  Territory will be included in such calculation.
The Operator is further  obligated,  beginning  twenty-four (24) months from the
date hereof and continuing for each and every  subsequent and successive  twelve
(12) month period during the term of this agreement,  to pay to North America, a
total Royalty of not less than US $115,000.00  subject however,  to increases or
decreases  of such amount as related to the Cost of Living  Index as compiled by
the U.S. Department of Labor for each 12 month period. Any such contribution due
from the Operator to North America to meet the minimum set forth herein shall be
made within 45 days after the end of each relevant 12 month period.

         C.       Non-Payment.

         Should  Operator fail to pay the Royalties set forth in this  Paragraph
IX herein a timely  manner,  North  America  shall  have the right  pursuant  to
Paragraph XIV hereof, TERMINATION, to terminate its agreement with the Operator.

         X.  RECORDS.  Operator  shall  keep true and  accurate  records  of all
operations of the Subject Matter. Such records shall be adequate to permit North
America to verify the accuracy of the Royalty Paragraph IX hereof and to perform
inspection called for in Paragraph VII. Such records shall be open at reasonable
times during regular  business hours for inspection and copying by North America
and its duly  authorized  agents and  representatives.  North America shall make
such periodic inspection of the records as it may consider  necessary,  provided
always  that  International,   the  owner  of  the  Patent  Rights  sub-licensed
hereunder, or North America may from time to time require a specific audit to be
carried  out on  Operator's  operations  hereunder  and in such event such audit
shall be undertaken by North America with a  representative  of International in
attendance if  International  so elects.  Such audits shall be at the expense of
the party  requiring  the audit  unless the audit  discloses a violation of this
Agreement in which event the party  requiring the audit shall be reimbursed  the
expenses of the audit by the party in violation.

         XI.      WARRANTY.

         By North America.  North America represents and warrants that it is the
exclusive  licensee of International  throughout the United States to the Patent
Rights  described on Exhibit A and fully entitled to enter into this  Agreement.
North  America  further  represents  and  warrants  that the Subject  Matter can
successfully line many types of sewers, tunnels, pipelines and other passageways
when said methods are properly  performed and that it will instruct  Operator in
such performance.  Every reasonable precaution will be taken by North America in
producing  all  Materials  and  Apparatus,  compiling  all  data,  and  offering
instructions in the methods of use of the Materials and Apparatus purchased from
North  America  for  operation  hereunder  to assure that they comply with North
America's  exacting  standards and that the ultimate lining for sewers and other
passageways maintains a high standard of quality. To the best of North America's
knowledge, all information given will be correct and the Materials and Apparatus
are believed by North America to be adequately suited to the purposes  intended.
However,  it is impossible to anticipate every possible  variation in the manner
of use or the  conditions  under which the  Operator  will apply the  Materials,
Apparatus, Know-how, data, and methods and North America makes no warranty as to
the results which the Operator will attain,  and shall under no circumstances be
held responsible for any such results that occur as a consequence of a departure
from the instructions  provided or from negligence or malfeasance on the part of
Operator except as may be contained in the specific written warranty provided by
North America with regard to any  materials  furnished by North  America.  North
America  makes no  representation  nor warranty as to the validity of any of the
Patent Rights hereof,  other than that it has no knowledge of any basis on which
any of the issued  patents is  invalid;  no  representation  nor  warranty  that
performance in accordance  with this Agreement will not infringe any existing or
subsequently  issued or pending  patent,  other than that it has no knowledge of
the  existence  of any such patent,  and no  representation  nor  warranty  that
"Insituform" is available for use as a tradename,  trademark, and/or certificate
mark in the  United  States  other than it  believes  it to be.  Further,  North
America  shall  not be held  responsible  for use by the  Operator  of any  such
Materials,  Apparatus,  Know-how, data or method in such a manner as to infringe
any patent, trademark or copyright owned by another. North America agrees not to
sell its  Materials  or  Apparatus  hereof  below its cost in  violation  of any
applicable  provision of any antitrust or unfair trade  practice  statute and to
charge all  Sub-Licensees of the Patent Rights  Royalties  according to the same
scale or formula.

         By  Operator.  Operator  agrees to  indemnify,  defend  and hold  North
America  harmless  from any and all claims for bodily  injury  including  death,
personal injury and damage to property of Operator, North America and/or others,
which arise from the alleged  negligence or  malfeasance of Operator or from the
existence or use of Materials and/or Apparatus  acquired from sources other than
North America or which are produced by Operator.

         The Operator also agrees at its expense to procure a policy or policies
of  insurance  from an  insurance  company or  companies  satisfactory  to North
America,  providing  coverage  for the  operations  of the  Operator,  including
product and completed  operations,  with minimum  limits of Two Million  Dollars
($2,000,000.00)  per occurrence and Two Million Dollars  ($2,000,000.00)  annual
aggregate for injury to persons and Two Million Dollars  ($2,000,000.00)  annual
aggregate for damage to property. The operator also agrees to have North America
named as an  additional  named  insured  under  the  above  described  policy or
policies and to cause North America to be furnished  with a Certificate  of such
insurance  which  shall  contain a  requirement  that North  America be notified
thirty  (30) days prior to any  cancellation  or any  reduction  in  coverage or
limits.  The  insurance  required  above  shall  commence  prior to the time the
Operator  commences  operations  under  this  Sub-License  Agreement  and  shall
continue in force  throughout  the life of the  Sub-License  Agreement  until it
expires or is terminated.

         XII. DILIGENCE.  Operator  understands that the Subject Matter has been
designed  to meet the  growing  needs  of  Community  and  Commerce  within  his
exclusive  Territory  and his  license  has  been  specifically  granted  on the
understanding  that he will  use all  reasonable  endeavors  to  create a demand
within the Territory for the Insituform products, and shall fill such demand all
as good businesslike conduct requires. It is specifically  understood and agreed
that nothing herein provided shall be construed as requiring Operator to operate
in accordance with any designated marketing plan or system which, except for the
maintenance  of high  standards of quality,  the  exercise of diligence  and the
performance in accordance with the terms and conditions  hereof, are left to the
determination of Operator.

         XIII. TERM. The Term of this Agreement shall commence on the date first
above  written  and  shall  continue  for the life of the last to  expire of the
patents or the Patent Rights including any improvements or modifications thereto
extending such life, unless sooner terminated as hereinafter provided.

         XIV.     TERMINATION

         A. By Operator.  The Operator may terminate  this Agreement at any time
by service of written  notice to such effect on North  America two (2)  calendar
quarters in advance of the  effective  date  thereof and by  complying  with the
applicable  terms and conditions of Paragraph XIII C hereof.  During such period
after notice but prior to actual  termination,  Operator shall not bid or accept
any additional jobs without the written consent of North America.

         B. By North America.  In the event Operator becomes insolvent such that
his liabilities exceed his assets or files a petition in bankruptcy,  or commits
an act of bankruptcy,  or a receiver is appointed for Operator,  or in the event
Operator  breaches any material term or condition of this Agreement and fails to
correct the same within  fifteen (15) days  following  written notice thereof by
North America,  or once having been notified and having  corrected such a breach
repeats  the  same  North  America  may  then at its sole  option,  declare  the
agreement  terminated  immediately.  Further,  in the  event  Operator  fails to
provide computations of royalty or stops paying royalty within fifteen (15) days
of when  due or  Operator  fails  to meet  his  minimum  royalty  obligation  in
accordance  with  Paragraph  VIII  hereof,  North  America  may  terminate  this
Agreement  at any time by  service of written  notice of  termination  hereof on
Operator a calendar quarter in advance of the effective date hereof.

         C.  Consequences.  Upon  termination of this Agreement by either of the
parties hereto,  Operator shall immediately pay North America all Royalties then
due from it;  terminate all use by it of the word  "Insituform"  as a tradename,
trademark,  and certification  mark; avoid all subsequent use of all tradenames,
trademarks,  and certification  marks likely to be confused with "Insituform" as
well as all stationery,  invoices,  signs or other visual devices  displaying or
otherwise  associated with  "Insituform";  terminate all use of the methods,  as
well as the  manufacture,  use and sale of the  products  of the Patent  Rights,
Copyrights,  and Know-how; and assign to North America free of charge all claims
to and any and all rights arising from the use of  "Insituform",  or combination
involving "Insituform",  in the specific Territory,  and return to North America
all materials, instruction manuals, devices and other apparatus. Operator herein
agrees  to  abide  by all of the  terms  and  conditions  of the  non-disclosure
agreement despite the termination of the license agreement.

         XV.  Notices.  Any notice  required or  permitted to be given or served
upon either party hereto pursuant to this Agreement shall be sufficiently  given
or served if sent to such party by certified mail,  postage prepaid addressed to
such party as set forth below or by telex,  or to such other address as it shall
designate by written notice to the other party, as follows:

In case of notice to North America:

c/o Schulman Berlin & Davis
Professional Corporation
555 Madison Avenue
New York, New York 10022

In case of Notice to Operator:

 Insituform East, Inc.
c/o Sadur and Pelland
2000 L Street NW
Washington DC

         XVI.  SUCCESSORS AND ASSIGNS.  This Agreement shall be binding upon and
inure to the benefit of the parties hereto and their  respective  successors and
assigns with the specific  understanding that the Operator shall not assign this
Agreement  without written  permission of North America except to a wholly owned
subsidiary  and on  the  express  condition  that  the  assignor  guarantee  the
performance  of its assignee  hereto  strictly in accordance  with the terms and
provisions hereof.

         XVII. EXCLUSIVE LICENSE.  North America has herein granted an exclusive
license to the Operator  together with its Know-how,  technical  experience  and
training  program for the  exploitation  of the  Insituform  process  within and
throughout the defined  Territory.  If, despite North  America's best efforts to
maintain the  exclusivity  of its licenses and defend its Patent,  Trademark and
Copyright protections,  should such exclusivity and/or protections be terminated
for any reason whatsoever,  the Operator hereunder is nevertheless  obligated to
comply  in full  with  each and  every  term  and  condition  of this  agreement
including,  but not limited to the payment of Royalties to North America and the
maintenance of high standards of quality and service.

         XIX. EXCLUSIONS. In the event that any one or more of the provisions of
this  Agreement is, or are, held to be invalid it is agreed  between the parties
that if legally practical said provision or provisions shall be considered never
to have been  contained  herein and the Agreement  shall  otherwise  continue in
force and effect.

         XX. ENTIRE AGREEMENT.  This Agreement  constitutes the entire agreement
between  the  parties  hereto  with  respect to the  Subject  Matter  hereof and
supersedes all prior oral and written  understandings and agreements between the
parties hereto  concerning the Subject Matter.  The provisions of this Agreement
shall not be waived,  modified or amended, except by a subsequent writing signed
by both parties.

         IN WITNESS WHEREOF,  the parties hereto have executed this Agreement as
of the day and year first above written.


INSITUFORM OF NORTH AMERICA, INC.             OPERATOR

By /s/ Paul A. Church                         /s/ Arthur G. Lang III



<PAGE>


                                   SCHEDULE A

                               STATE OF DELAWARE

and the following counties in the State of Pennsylvania

Pike                         Wayne
Susquehanna                  Bradford
Tioga                        Clinton
Lycoming                     Sullivan
Wyoming                      Lackawanna
Monroe                       Carbon
Luzerne                      Columbia
Montour                      Northumberland
Snyder                       Union
Centre                       Blair
Cambria                      Huntingdon
Mifflin                      Juniata
Perry                        Delaware
Dauphin                      Philadelphia
Lebanon                      Lancaster
Schuylkill                   York
Northampton                  Adams
Lehigh                       Cumberland
Bucks                        Franklin
Berks                        Fulton
Montgomery                   Bedford
Chester                      Somerset


<PAGE>


                                    SCHEDULE
                              UNITED STATES PATENT
                                   #4,064,211


<PAGE>


                        INSITUFORM OF NORTH AMERICA, INC.

                                                     c/o Schulman Berlin & Davis
                                                     555 Madison Avenue
                                                     New York, New York 10022

                                  July 10, 1980
Insituform East, Inc.
6525 Belcrest Road
Suite 422
Hyattsville, Maryland 20782

Gentlemen:

         This is to confirm  our various  discussions  with regard to Section IX
Warranty, as described in the Sub-License Agreement dated July 10, 1980.

         North America hereby agrees to replace any faulty bag  manufactured  by
North  America  in which  there is a proven  defect  in  either  workmanship  or
material  where  Insituform  East  ("East") can provide  physical  proof of such
defect and has so notified  North America  within twelve (12) hours of discovery
thereof and allowed them to inspect such defect.

         In addition to replacing  the  defective  bag,  North America will also
reimburse  East for all of its out of pocket  costs  for  chemicals  and  resins
utilized in connection with the  installation of the bag provided such costs are
fully supported by original vouchers,  receipts,  invoices and checks in payment
thereof.

         Further, North America will also reimburse East for the labor and other
incidental  costs up to a maximum of $2,000  that may be  incurred  by East as a
result of the  defective  bag.  East shall  support  these  costs with  original
vouchers, receipts, invoices and checks. Such maximum payment of $2,000 shall be
adjusted yearly in accordance with  fluctuations,  if any, in the Cost of Living
Index as compiled by the United States Department of Labor.

         East agrees,  in addition to notifying  North  America of any defective
bag and  retaining  any  physical  proof  thereof,  to take any and all possible
action to minimize monetary or other damage resulting from such defect.

         If this letter sets forth our  agreement,  kindly  execute the enclosed
copy and return it at your earliest convenience.

                                Very truly yours,

                               /s/ Paul A. Church
ACCEPTED AND AGREED

/s/ Arthur G. Lang, III

<PAGE>

                        INSITUFORM OF NORTH AMERICA, INC.

                                                     c/o Schulman Berlin & Davis
                                                     555 Madison Avenue
                                                     New York, New York 10022

                                  July 10, 1980
Insituform East, Inc.
6525 Belcrest Road
Suite 422
Hyattsville, Maryland 20782

Gentlemen:

         This is to acknowledge our agreement that to the extent that Insituform
East Inc.  as a  sub-licensee  from  North  America  of more than one  exclusive
territory pays an amount in excess of its annual minimal  royalty  obligation in
one territory and is unable to pay its annual  minimum  obligation in another of
its territories,  the excess paid in one territory may be applied in full toward
meeting its annual  minimum  royalty  commitment to North  America,  Inc. on the
other territory.

         If this agreement confirms to our understanding,  kindly execute a copy
of this letter and return it to me.

                                Very truly yours,

                               /s/ Paul A. Church
ACCEPTED AND AGREED

/s/ Arthur G. Lang, III




<PAGE>


                        INSITUFORM OF NORTH AMERICA, INC.

                                                     c/o Schulman Berlin & Davis
                                                     555 Madison Avenue
                                                     New York, New York 10022
Insituform East, Inc.
625 Belcrest Road
Suite 422
Hyattsville, Maryland 20782

Gentlemen:

         We would refer to the Insituform Licenses granted by us to your company
and dated 10th July 1980.

         In relation to Clause IX headed  Royalty we confirm  that in  computing
the invoiced price of all contracts involving the installation of the Insituform
Process you may deduct the following:

         (a) Fees billed for preparatory  T.V. survey work but not including the
immediate T.V. survey which is recommended as part of the installation process.

         (b) Fees billed for  overpumping  provided  that these shall not exceed
$2,000 per line.

         (c)  Fees  billed  for  incidentals  including  cleaning  not  directly
relating to the  installation  but performed in conjunction  therewith  provided
these do not exceed 3.5% of the total contract price.

         We believe the above  reflects  our  understanding  of the  discussions
between us and we should be  grateful if you would  confirm  same by signing and
returning to us within 7 days the duplicate copy of this letter.
                                Yours faithfully,

                               /s/ Paul A. Church
                               P.A. Church
                               Director - Insituform of North America, Inc.




<PAGE>


STATE OF NEW YORK                       )
                                        :    SS
COUNTY OF NEW YORK                      )

         On this  10th day of July,  in the year of 1980,  before  me  Robert D.
Schulman,  a Notary  Public in and for said County and State,  residing  therein
duly commissioned and sworn,  personally appeared Arthur Lang, known to me to be
the Vice-President of the corporation that executed the attached  instrument and
acknowledged  to me that he knows  the seal of said  corporation,  that the seal
affixed to the  attached  instrument  is the said  corporate  seal,  that it was
thereunto  affixed  pursuant  to its  by-laws  as a  resolution  of its Board of
Directors and that he executed the  instrument in behalf of the  corporation  by
like authority.

         IN WITNESS WHEREOF, I have hereunto set my hand and affixed my official
seal the day and year first above written.


ROBERT D. SCHULMAN                /s/ Robert D. Schulman
                                  ----------------------------------------------
Notary Public, State of New York  Notary Public in and for Said County and State
No. 44-4602948                    My Commission Expires:
Qualified in Rockland County
Certificate Filed in New York County
Commission Expires March 30, 1982