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                                                                   Exhibit 10.31

                               FIRST AMENDMENT TO
                   PURCHASE AGREEMENT AND ESCROW INSTRUCTIONS

         THIS FIRST AMENDMENT TO PURCHASE AGREEMENT AND ESCROW INSTRUCTIONS
("Amendment") is entered into at San Diego, California as of February 12, 2002,
between H. G. FENTON COMPANY, a California corporation which acquired title as
H. G. Fenton Material Company ("Seller"), and BIOSITE INCORPORATED, a Delaware
corporation ("Buyer"), with reference to the following

                                R E C I T A L S:

         A.       Seller and Buyer are the parties to a Purchase Agreement and
Escrow Instructions dated as of December 7, 2001 ("Agreement"), relating to that
certain real property consisting of approximately 34.7 gross acres in the
Carroll Canyon area of San Diego, California ("Land"). Initially capitalized
terms not otherwise defined in this Amendment have the same meanings as in the
Agreement, as previously amended. Pursuant to the Agreement, the parties have
established Escrow No. 51943-PM with Stewart Title of California, Inc. as Escrow
Holder.

         B.       The Contingency Date under the Agreement was the later to
occur of (i) December 14, 2001, or (ii) ten (10) Business Days after Buyer's
receipt of the CC&Rs. Buyer received the CC&Rs with all exhibits thereto on
February 4, 2002, with the result that the initially established Contingency
Date became February 13, 2002. The parties now wish to extend the Contingency
Date by two days.

         THE PARTIES AGREE:

         1.       EXTENSION OF CONTINGENCY DATE. The parties agree that
Paragraph 2.1.16 of the Agreement shall be amended to read in its entirety as
follows:

                  "CONTINGENCY DATE" means February 15, 2002.

         2.       OTHER MATTERS OF AGREEMENT.

                  (a)      This Amendment may be executed in any number of
counterparts, each of which will be deemed to be an original, but all of which
together will constitute one instrument.

                  (b)      Except to the extent modified hereby, all provisions
of the Agreement shall remain in full force and effect.

SELLER:                                        BUYER:

H. G. FENTON COMPANY, a California             BIOSITE INCORPORATED, a Delaware
corporation                                    corporation

By                                             By
    -------------------------------              -------------------------------
Its                                            Its
    -------------------------------              -------------------------------

By                                             By
    -------------------------------              -------------------------------
Its                                            Its
    -------------------------------              -------------------------------

                                      -1-<Page>

                                                                   Exhibit 10.32

                               SECOND AMENDMENT TO
                   PURCHASE AGREEMENT AND ESCROW INSTRUCTIONS

         THIS SECOND AMENDMENT TO PURCHASE AGREEMENT AND ESCROW INSTRUCTIONS
("Amendment") is entered into at San Diego, California as of February 14, 2002,
between H. G. FENTON COMPANY, a California corporation which acquired title as
H. G. Fenton Material Company ("Seller"), and BIOSITE INCORPORATED, a Delaware
corporation ("Buyer"), with reference to the following

                                R E C I T A L S:

         A.       Seller and Buyer are the parties to a Purchase Agreement and
Escrow Instructions dated as of December 7, 2001 and previously amended as of
February 12, 2002 ("Agreement"), relating to that certain real property
consisting of approximately 34.7 gross acres in the Carroll Canyon area of San
Diego, California ("Land"). Initially capitalized terms not otherwise defined in
this Amendment have the same meanings as in the Agreement, as previously
amended. Pursuant to the Agreement, the parties have established Escrow No.
51943-PM with Stewart Title of California, Inc. as Escrow Holder.

         B.       The parties wish to make certain changes to the Agreement.

         THE PARTIES AGREE:

         1.       SATISFACTION OF SPECIAL CONDITIONS. The parties acknowledge
and agree that the special conditions of Paragraphs 6.1.1, 6.1.2 and 6.1.3 have
all been satisfied or waived.

         2.       CC&RS. Buyer acknowledges having received and approved in all
material respects the CC&Rs. Seller acknowledges that Buyer may wish to propose
certain minor changes to the CC&Rs, and agrees to work in good faith with Buyer
with respect thereto; provided, however, that the parties' agreement on any such
further changes to the CC&Rs shall not be a condition precedent to Buyer's
obligations under the Agreement.

         3.       DESIGN GUIDELINES. Buyer acknowledges having received and
approved in all material respects the most recent Design Guidelines for the
Business Park. Buyer acknowledges that Seller may wish to make certain minor
changes to the Design Guidelines before the Closing, and the parties agree that
without Buyer's prior approval, Seller shall make no changes to the Design
Guidelines which would affect in any material way the design of Buyer's Project
or the development, use or occupancy of the Land.

         4.       CLOSING DATE. The definitions of Closing Date and Latest
Closing Date shall be modified to read as follows:

                           "CLOSING DATE" means a date which is thirty (30) days
         following Buyer's receipt of the latest to be delivered of (i) Seller's
         written notification of its intent to effect the Closing, (ii) the
         Grading Certifications, and (iii) Seller's delivery of the notice
         specified in Paragraph 6.1.5. The currently anticipated Closing Date is
         October 1, 2002. The Closing Date is subject to extension by Seller to
         no later than the Latest Closing Date pursuant to Paragraph 6.2.

                           "LATEST CLOSING DATE" means March 31, 2003, which
         shall be extended day-for-day, to a maximum extension of six (6)
         months, for each day of Unavoidable Delay that is caused by
         restrictions on grading or other Pre-Closing Improvements incident to
         storm-water runoff requirements.

                                      -1-
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         5.       OTHER MATTERS OF AGREEMENT.

                  (a)      This Amendment may be executed in any number of
counterparts, each of which will be deemed to be an original, but all of which
together will constitute one instrument.

                  (b)      Except to the extent modified hereby, all provisions
of the Agreement as previously amended shall remain in full force and effect.

SELLER:                                        BUYER:

H. G. FENTON COMPANY, a California             BIOSITE INCORPORATED, a Delaware
corporation                                    corporation

By                                             By
    -------------------------------              -------------------------------
Its                                            Its
    -------------------------------              -------------------------------

By                                             By
    -------------------------------              -------------------------------
Its                                            Its
    -------------------------------              -------------------------------

                                      -2-EXHIBIT 10.47

 

ENDORSEMENT NO. 12

 

Attached to and made a part of

AGREEMENT OF REINSURANCE

NO. 7448

between

GENERAL REINSURANCE CORPORATION

and

PAULA INSURANCE COMPANY

AGRI-COMP INSURANCE COMPANY

 

IT IS MUTUALLY
AGREED that, as respects new and renewal policies of the Company becoming
effective at and after 12:01 a.m., July 1, 2000, sub-paragraph (c) in Article
II - GENERAL CONDITIONS, DEFINITIONS AND INTERPRETATIONS of this Agreement is
amended to read as follows:

 

“(c)   Company Retention

 

The Company
and its underlying reinsurers shall retain for its own account the entire
amount set forth as the Company Retention; however, this requirement shall be
satisfied if such amount is retained by the Company or its affiliated companies
under common management or common ownership of both.”

 

IN WITNESS
WHEREOF, the parties hereto have caused this Endorsement to be executed in
duplicate this 14th day of May, 2001.

 

	
   

  	
  GENERAL
  REINSURANCE CORPORATION

  
	
   

  	
  /s/ Anthony
  J. Anastanio

  	
   

  
	
   

  	
  Anthony J.
  Anastanio

  
	
   

  	
  Senior Vice
  President

  
	
   

  	
   

  
	
  Attest:

  	
   

  
	
  /s/ Melinda
  Kawanura

  	
   

  	
   

  
	
  Melinda
  Kawanura

  	
   

  
	
   

  	
  PAULA
  INSURANCE COMPANY

  
	
   

  	
  AGRI-COMP
  INSURANCE COMPANY

  
	
   

  	
  /s/ James A.
  Nicholson

  	
   

  
	
   

  	
  James A.
  Nicholson

  
	
  Attest:

  	
   

  
				

 

GENERAL REINSURANCE CORPORATION

 

 

ENDORSEMENT NO. 13

 

Attached to and made a part of

AGREEMENT OF REINSURANCE

NO. 7448

between

GENERAL REINSURANCE CORPORATION

and

PAULA INSURANCE COMPANY

AGRI-COMP INSURANCE COMPANY

 

IT IS MUTUALLY
AGREED, that as respects new and renewal policies of the Company becoming
effective at and after 12:01 A.M., July 1, 2001, and policies of the
Company in force at 12:01 A.M., July 1, 2001, this Agreement is amended as
follows:

 

I -            Section 4 of Exhibit A is amended to
read:

 

“Section 4 -           REINSURANCE PREMIUM

 

The Company
shall pay to the Reinsurer:

 

(a)                                  For
the First Excess Cover, a net rate of         
% of the Company’s earned premium for Workers’ Compensation and
Employers’ Liability Business;

 

(b)                                 For
the Second Excess Cover, a net rate of         
% of the Company’s earned premium for Workers’ Compensation and
Employers’ Liability Business.”

 

II -                                 Section
4 of Exhibit B is amended to read:

 

“Section 4 - REINSURANCE
PREMIUM

 

The Company
shall pay to the Reinsurer          % of
the Company’s earned premium for Workers’ Compensation and Employers’ Liability
Business.”

 

IN WITNESS
WHEREOF, the parties hereto have caused this Endorsement to be

 

 

executed in duplicate this 13th
day of June, 2001.

 

	
   

  	
  GENERAL
  REINSURANCE CORPORATION

  
	
   

  	
  /s/ Anthony
  J. Anastanio

  	
   

  
	
   

  	
  Anthony J.
  Anastanio

  
	
   

  	
  Senior Vice
  President

  
	
   

  	
   

  
	
  Attest:

  	
   

  
	
  /s/ Melinda
  Kawanura

  	
   

  	
  PAULA
  INSURANCE COMPANY

  
	
  Melinda
  Kawanura

  	
  AGRI-COMP
  INSURANCE COMPANY

  
	
   

  	
  /s/Jeffrey
  A. Snider

  	
   

  
	
  Attest:

  	
  Jeffrey A.
  Snider

  
	
  /s/ James J.
  Muza

  	
   

  	
   

  
	
  James J.
  Muza

  	
   

  
						

 

Endorsement No. 13

Agreement No. 7448

 

2

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