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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D
                    UNDER THE SECURITIES EXCHANGE ACT OF 1934

         --------------------------------------------------------------
                            HILL INTERNATIONAL, INC.
                                (Name of Issuer)

                                  Common Stock
                         (Title of Class of Securities)

                                   431466 10 1
                                 (CUSIP Number)
         -------------------------------------------------------------
                                Irvin E. Richter
                          c/o Hill International, Inc.
                              303 Lippincott Centre
                                Marlton, NJ 08053
                                 (856) 810-6200

            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)
        ---------------------------------------------------------------

                                  June 28, 2006
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  that is the subject of this  Schedule  13D, and is filing this
schedule because of Sections 240.13d-1(e),  240.13d-1(f) or 240.13d-1(g),  check
the following box.

Note:  Schedules  filed in paper format shall include a signed original and five
copies of the schedule,  including all exhibits.  See ss. 240.13d.7(b) for other
parties to whom copies are to be sent.

*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for  any  subsequent   amendment   containing   information  which  would  alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).



CUSIP NO. 431466 10 1

1     NAME OF  REPORTING  PERSON  I.R.S.  IDENTIFICATION  NO.  OF  ABOVE  PERSON
      (ENTITIES ONLY)

      Irvin E. Richter

2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

      (a) |X|

      (b) |_|

3     SEC USE ONLY

4     SOURCE OF FUNDS

      OO

5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) or 2(e)

6     CITIZENSHIP OR PLACE OF ORGANIZATION

      United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

7     SOLE VOTING POWER

      7,724,271

8     SHARED VOTING POWER

      5,813,923(1)

9     SOLE DISPOSITIVE POWER

      7,724,271

-----------------
(1)  For  purposes  of  Section  13(d),  Irvin  E.  Richter  may  be  deemed  to
beneficially own an aggregate of 13,538,194 shares of common stock of the issuer
consisting of (a) 7,724,271 shares of common stock held by Mr. Richter directly,
(b)  3,365,407  shares of common stock held by David L.  Richter,  (c) 1,931,067
shares of common  stock  held by Brady H.  Richter,  and (d)  517,449  shares of
common stock held by Stuart S. Richter. Each of Messrs. Irvin E. Richter,  David
L. Richter and Stuart S. Richter is an executive officer of the Issuer. David L.
Richter and Brady H. Richter are the sons of Irvin E. Richter. Stuart S. Richter
is a brother of Irving H. E. Richter.  Mr. Irvin E. Richter disclaims beneficial
ownership of any shares of common stock held by Messrs. David L. Richter,  Brady
H. Richter and Stuart S. Richter.

                                       2


10    SHARED DISPOSITIVE POWER

      5,813,923 (see footnote one)

11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

      13,538,194 (see footnote one)

12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE
      INSTRUCTIONS)

13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

      59.4%

14    TYPE OF REPORTING PERSON

      IN


                                       3



CUSIP NO. 431466 10 1

1.    NAME OF  REPORTING  PERSON  I.R.S.  IDENTIFICATION  NO.  OF  ABOVE  PERSON
      (ENTITIES ONLY)

      David L. Richter

2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

      (a) |X|

      (b) |_|

3.    SEC USE ONLY

4.    SOURCE OF FUNDS

      OO

5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) or 2(e)

6.    CITIZENSHIP OR PLACE OF ORGANIZATION

      United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

7.    SOLE VOTING POWER

      3,365,407

8.    SHARED VOTING POWER

      10,172,787(2)

9.    SOLE DISPOSITIVE POWER

      3,365,407

----------------------
(2)  For  purposes  of  Section  13(d),  David  L.  Richter  may  be  deemed  to
beneficially own an aggregate of 13,538,194 shares of common stock of the issuer
consisting of (a) 3,365,407 shares of common stock held by Mr. Richter directly,
(b)  7,724,271  shares of common stock held by Irvin E.  Richter,  (c) 1,931,067
shares of common  stock  held by Brady H.  Richter,  and (d)  517,449  shares of
common stock held by Stuart S. Richter. Each of Messrs. Irvin E. Richter,  David
L. Richter and Stuart S. Richter is an executive officer of the Issuer. David L.
Richter is the  brother  of Brady H.  Richter  and the son of Irvin E.  Richter.
Stuart S.  Richter  is a brother  of Irving H.  Richter.  Mr.  David L.  Richter
disclaims  beneficial  ownership  of any shares of common  stock held by Messrs.
Irvin E. Richter, Brady H. Richter and Stuart S. Richter.


                                       4



10.   SHARED DISPOSITIVE POWER

      10,172,787 (see footnote two)

11.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

      13,538,194 (see footnote two)

12.   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE
      INSTRUCTIONS)

13.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

      59.4%

14.   TYPE OF REPORTING PERSON

      IN

                                       5


CUSIP NO. 431466 10 1

1.    NAME OF  REPORTING  PERSON  I.R.S.  IDENTIFICATION  NO.  OF  ABOVE  PERSON
      (ENTITIES ONLY)

      Brady H. Richter

2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

      (a) |X|

      (b) |_|

3.    SEC USE ONLY

4.    SOURCE OF FUNDS

      OO

5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) or 2(e)

6.    CITIZENSHIP OR PLACE OF ORGANIZATION

      United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

7.    SOLE VOTING POWER

      1,931,067

8.    SHARED VOTING POWER

      11,607,127(3)

9.    SOLE DISPOSITIVE POWER

      1,931,067

------------
(3)  For  purposes  of  Section  13(d),  Brady  H.  Richter  may  be  deemed  to
beneficially own an aggregate of 13,538,194 shares of common stock of the issuer
consisting of (a) 1,931,067 shares of common stock held by Mr. Richter directly,
(b)  3,365,407  shares of common stock held by David L.  Richter,  (c) 7,724,271
shares of common  stock  held by Irvin E.  Richter,  and (d)  517,449  shares of
common stock held by Stuart S. Richter. Each of Messrs. Irvin E. Richter,  David
L. Richter and Stuart S. Richter is an executive officer of the Issuer. Brady H.
Richter is the brother of David L.  Richter and is the son of Irvin E.  Richter.
Stuart S.  Richter  is a brother  of Irving H.  Richter.  Mr.  Brady H.  Richter
disclaims  beneficial  ownership  of any shares of common  stock held by Messrs.
David L. Richter, Irvin E. Richter and Stuart S. Richter.


                                       6



10.   SHARED DISPOSITIVE POWER

      11,607,127 (see footnote three)

11.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

      13,538,194 (see footnote three)

12.   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE
      INSTRUCTIONS)

13.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

      59.4%

14.   TYPE OF REPORTING PERSON

      IN

                                       7



CUSIP NO. 431466 10 1

1.    NAME OF  REPORTING  PERSON  I.R.S.  IDENTIFICATION  NO.  OF  ABOVE  PERSON
      (ENTITIES ONLY)

      Stuart S. Richter

2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)

      (a) |X|

      (b) |_|

3.    SEC USE ONLY

4.    SOURCE OF FUNDS

      OO

5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) or 2(e)

6.    CITIZENSHIP OR PLACE OF ORGANIZATION

      United States

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

7.    SOLE VOTING POWER

      517,449

8.    SHARED VOTING POWER

      13,020,745(4)

9.    SOLE DISPOSITIVE POWER

      517,449

------------
(4)  For  purposes  of  Section  13(d),  Stuart  S.  Richter  may be  deemed  to
beneficially own an aggregate of 13,538,194 shares of common stock of the issuer
consisting of (a) 517,449 shares of common stock held by Mr.  Richter  directly,
(b)  3,365,407  shares of common stock held by David L.  Richter,  (c) 1,931,067
shares of common stock held by Brady H.  Richter,  and (d)  7,724,271  shares of
common stock held by Irvin E. Richter.  Each of Messrs. Irvin E. Richter,  David
L. Richter and Stuart S. Richter is an executive  officer of the Issuer.  Stuart
S.  Richter is a brother of Irving H.  Richter,  and he is the uncle of David L.
and Brady H. Richter.  Mr. Stuart S. Richter disclaims  beneficial  ownership of
any shares of common stock held by Messrs.  Irvin E.  Richter,  Brady H. Richter
and David L. Richter.

                                       8


10.   SHARED DISPOSITIVE POWER

      13,020,745 (see footnote four)

11.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

      13,538,194 (see footnote four)

12.   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE
      INSTRUCTIONS)

13.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

      59.4%

14.   TYPE OF REPORTING PERSON

      IN


                                       9



Item 1. Security and Issuer.

      The securities to which this statement relates are shares of common stock,
par value $.0001 per share (the "Common Stock"), of Hill International,  Inc., a
Delaware  corporation  (the "Issuer").  The principal  executive  offices of the
Issuer are located at 303 Lippincott Centre, Marlton, New Jersey 08053.

Item 2. Identity and Background.

      This Schedule 13D is filed by Messrs. Irvin E. Richter,  David L. Richter,
Brady H.  Richter  and  Stuart S.  Richter  (collectively,  the  "Filers").  The
business  address  of the filers is Hill  International,  Inc.,  303  Lippincott
Centre,  Marlton,  New Jersey 08053.  Irvin E. Richter is the chairman and chief
executive  officer of the Issuer.  David L. Richter is the  president  and chief
operating officer of the issuer. Stuart S. Richter is a senior vice president of
the issuer. Irvin E. Richter and David Richter are directors of the Issuer. Each
of the reporting persons is a citizen of the United States.

      During the last five years none of the  individuals  filing this  Schedule
13D have been (1)  convicted in a criminal  proceeding or (2) a party to a civil
proceeding of a judicial or administrative body of competent jurisdiction and as
a result of such  proceeding  was or is subject to a  judgment,  decree or final
order  enjoining  future  violations of, or prohibiting or mandating  activities
subject  to,  federal or state  securities  laws or finding any  violation  with
respect to such laws.

      Each of the filers is a citizen of the United States.

Item 3. Source and Amount of Funds or Other Consideration.

      On June 28, 2006, in a private  placement  transaction and pursuant to the
Agreement and Plan of Merger, by and among Hill  International,  Inc.,  Arpeggio
Acquisition Corporation and Messrs. Irvin E. Richter, David L. Richter and Brady
H. Richter (the "Merger  Agreement"),  the Filers  acquired  their shares of the
Issuer in  exchange  for their  shares of Hill  International,  Inc.  a Delaware
corporation ("Old Hill"). Pursuant to the Merger Agreement, Old Hill merged with
Arpeggio Acquisition  Corporation,  and Arpeggio Acquisition Corporation was the
surviving  company of the merger.  Immediately  upon  consummation of the merger
Arpeggio  Acquisition  Corporation changed its name to Hill International,  Inc.
("New  Hill").  The shares of common  stock of New Hill owned by the Filers were
acquired pursuant to the merger  transaction in exchange for their shares of Old
Hill,  including  shares of Old Hill which were  acquired  upon the  exercise of
options. The shares of common stock and options for the common stock of Old Hill
which the Filers owned prior to the merger were  acquired as  consideration  for
services  rendered to Old Hill,  including  as  consideration  for  founding and
establishing Old Hill.

Item 4. Purpose of Transaction.

      The  Filers  acquired  the  shares  of  common  stock  of the  Issuer  for
investment purposes.  The Filers may in the future purchase additional shares in
the open market or in privately negotiated  transactions.  The Filers may in the
future be awarded stock or options to purchase  stock of the Issuer  pursuant to
the  Issuer's  Employee  Stock  Option  Plan of 2006.  As a result of the merger
transaction  and  consistent  with  the  terms  and  provisions  of  the  Merger
Agreement,  all of the officers of the Arpeggio Acquisition  Corporation and all
of its directors  (other than Eric S. Rosenfeld and Arnaud  Ajdler)  resigned on
June 28, 2006.  Messrs.  Irvin E. Richter,  David L.  Richter,  Brian W. Clymer,
William J. Doyle and Alan S.  Fellheimer  were  appointed  as  directors  of the
Issuer. In addition, Mr. Irvin E. Richter was appointed as Chairman of the Board
and Chief  Executive  Officer of the Issuer,  Mr. David L. Richter was appointed
President  and  Chief  Operating  Officer,  Mr.  Raouf S.  Ghali  was  appointed
President,  Project Management Group  (International),  Mr. Frederic Z. Samelian
was appointed as President,  Construction  Claims Group,  Mr. Ronald F. Emma was
appointed  Senior  Vice  President  of Finance  and Mr.  Stuart S.  Richter  was
appointed  Senior Vice  President.  Reference is made to the  disclosure  in the
Definitive  Proxy  Statement (No.  000-50781)  filed by the Issuer with the SEC,
dated June 5, 2006 in the section entitled  "Directors and Executive Officers of
Arpeggio  Following  the  Merger"  beginning  on  page  112,  which  section  is
incorporated herein by reference.

                                       10


      Concurrently  with the closing of the  merger,  Messer  Irvin E.  Richter,
David L. Richter and Brady H. Richter,  on the one hand,  and Mr. Eric Rosenfeld
and Mr. Arnaud Ajdler,  on the other hand,  who  collectively  beneficially  own
together  approximately 69% of the outstanding stock of the Issuer, entered into
a voting agreement dated as of June 28, 2006. The voting agreement requires that
each individual  member of the two groups of signatories to the voting agreement
vote for the  designees  of the  other  group  as our  directors  of Hill  until
immediately  following the election at the annual meeting of  shareholders  that
will be held in 2007.  The voting  agreement  is  incorporated  by  reference as
Exhibit 7.2 to this Schedule 13D.

Item 5. Interest in Securities of the Issuer.

      (a) As of June  28,  2006  the  Filers  beneficially  and  directly  owned
13,538,194 shares of common stock consisting of 7,724,271 shares of common stock
owned by Irvin L.  Richter,  3,365,407  shares of common stock owned by David L.
Richter,  1,931,067 shares of common stock owned by Brady H. Richter and 517,449
shares of common stock owned by Stuart S.  Richter.  Each  individual  Filer has
sole power to vote and to dispose of the shares which he owns. In addition, each
Filer may be deemed to share the power to vote and dispose of those shares owned
by each of the other three Filers.

      (c): None.

      (d): No person other than the Filers has the right to receive or the power
to direct  receipt of  dividends,  or the  proceeds  from the sale of the Common
Stock of the Issuer.

      (e): Not Applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to
        Securities of the Issuer.

      Messrs.  Irvin E.  Richter,  David L.  Richter  and Brady H.  Richter  are
parties to Lock-up  Agreements  with  Issuer  pursuant to which each of them has
agreed that they will not sell or otherwise transfer any of the shares of common
stock of the issuer  acquired by them in the merger  until  December  31,  2007,
subject to certain exceptions, including the right to use their shares to secure
margin  loans not to exceed  20% of the value of the shares at the time that the
loans are made.

      Messrs.  David L.  Richter,  Irvin E.  Richter and Brady H.  Richter  have
entered into a voting  agreement with Messrs.  Eric Rosenfeld and Arnaud Ajdler,
which agreement  requires that the Richter  signatories to the voting  agreement
agree to vote for the designees of Messrs.  Rosenfeld and Ajdler as Directors of
the Issuer and that Messrs. Rosenfeld and Ajdler agree to vote for the designees
of the  Richter  signatories  to the  voting  agreement,  in  both  cases  until
immediately  following the election  that will be held at the annual  meeting of
shareholders  of the Issuer in 2007.  The voting  agreement is  incorporated  by
reference as Exhibit 7.2 to this Schedule 13D.

                                       11


      The Filers, together with other stockholders of Old Hill who have received
shares of the Issuer in the merger have agreed,  pursuant to the  Agreement  and
Plan of Merger, to deposit 12% of their shares of the common stock of the Issuer
into escrow.  The shares are in escrow to secure any  indemnification  claims by
the  Issuer.  Claims for  indemnification  may be  asserted  by the Issuer  once
damages exceed $500,000 and are  indemnifiable to the extent that damages exceed
that amount. However, claims with respect to taxes and certain other matters are
not subject to such threshold. Shares still in escrow on December 30, 2010, will
be released on the next business day even if claims to which they relate are not
then  resolved.  The Escrow  Agreement was attached as Annex F to the Definitive
Proxy Statement  filed by the Issuer on June 6, 2007 and is incorporated  herein
by reference.

Item 7.           Materials to be Filed as Exhibits

    Exhibit 7.1   -  Form  of  Escrow  Agreement  (included  as  Annex  F of the
                  Definitive Proxy Statement (No. 000-50781), dated June 5, 2006
                  and incorporated by reference herein).

    Exhibit 7.2   -  Form  of  Voting  Agreement  (included  as  Annex  E of the
                  Definitive Proxy Statement (No. 000-50781), dated June 5, 2006
                  and incorporated by reference herein).

    Exhibit 7.3   - Agreement and Plan of Merger dated  December 5, 2005, by and
                  among Arpeggio  Acquisition  Corporation,  Hill International,
                  Inc. and then stockholders of Hill International,  Inc., dated
                  June  5,  2006,  as  amended  (included  as  Annex  A  of  the
                  Definitive Proxy Statement (No.  000-50781) filed with the SEC
                  and incorporated by reference herein).


                                       12



                                    SIGNATURE
                           --------------------------

      After  reasonable  inquiry and to the best of my knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.

Dated: July 10, 2006                   By:

                                                   /s/ Irvin E. Richter
                                       -----------------------------------------
                                                       Irvin E. Richter

                                       By:

                                                   /s/ David Richter
                                       -----------------------------------------
                                                       David Richter

                                       By:

                                                   /s/ Brady H. Richter
                                       -----------------------------------------
                                                       Brady H. Richter

                                       By:

                                                   /s/ Stuart S. Richter
                                       -----------------------------------------
                                                       Stuart S. Richter

                                       13



                                INDEX TO EXHIBITS

    Exhibit 7.1   -  Form  of  Escrow  Agreement  (included  as  Annex  F of the
                  Definitive Proxy Statement (No. 000-50781), dated June 5, 2006
                  and incorporated by reference herein).

    Exhibit 7.2   -  Form  of  Voting  Agreement  (included  as  Annex  E of the
                  Definitive Proxy Statement (No. 000-50781), dated June 5, 2006
                  and incorporated by reference herein).

    Exhibit 7.3   - Agreement and Plan of Merger dated  December 5, 2005, by and
                  among Arpeggio  Acquisition  Corporation,  Hill International,
                  Inc. and then stockholders of Hill International,  Inc., dated
                  June  5,  2006,  as  amended  (included  as  Annex  A  of  the
                  Definitive Proxy Statement (No.  000-50781) filed with the SEC
                  and incorporated by reference herein).


                                       14