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BCC Ruling No. 99-35-691

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BUILDING CODE COMMISSION DECISION ON B.C.C. #99-35-691

IN THE MATTER OF Subsection 24 (1) of the Building Code Act, 1992.

AND IN THE MATTER OF Clause 8.7.4.2.(1)(b) of Regulation 403, as amended by O. Reg. 22/98, 102/98 and 122/98 (the "Ontario Building Code").

AND IN THE MATTER OF an application by Mr. Rick Hudson, Owner, Hudson Motorcycles Inc., Tilbury, Ontario, for the resolution of a dispute with Mr. Jim Debinham, Designated Sewage System Inspector, Windsor-Essex County Health Unit, Windsor, Ontario to determine whether, when considering an adequate daily loading rate, the Class 4 sewage system proposed without a 15 m mantle provides sufficiency of compliance with Clause 8.7.4.2.(1)(b) of the Ontario Building Code at Hudson Motorcycles Inc., Part Lot 19, Concession IV, Township of Lakeshore, Essex County, Ontario.

APPLICANT

Mr. Rick Hudson, Owner
Hudson Motorcycles Inc.
Tilbury, Ontario

RESPONDENT

Mr. Jim Debinham, Designated Sewage System Inspector
Windsor-Essex County Health Unit
Windsor, Ontario

PANEL

Mr. Bryan Whitehead (Chair)
Mr. Bill Fellner
Mr. Frank Wright

PLACE

Toronto and Windsor, Ontario

DATE OF HEARING

May 27, 1999

DATE OF RULING

May 27, 1999

APPEARANCES

Mr. Ken Dickson, Owner
Dickson Environmental Consulting
Wallaceburg, Ontario

Agent for the Applicant

Mr. Jim Debinham, Designated Sewage System Inspector
Windsor-Essex County Health Unit
Windsor, Ontario
Designate for the Respondent

RULING

  1. The Applicant

Mr. Rick Hudson, Owner, Hudson Motorcycles Inc., Wheatley, Ontario, has received a building permit under the Building Code Act, 1992 to install a new Class 4 sewage system at Part Lot 19, Concession IV, Township of Lakeshore, Essex County, Ontario.

  1. Description of Construction

The Applicant is proposing to install a new Class 4 conventional sewage system with a fully raised leaching bed to serve a proposed, 327 m2, Group E - mercantile (retail) occupancy. The proposed building is to contain six employees and will have less than 20 fixture units (12.5). The calculated total daily design sewage flow rate, based on 75 litres/per day/per employee, is 450 litres per day.

The proposed new sewage system would consist of a 3,600 litre septic tank (the minimum size allowed under OBC) that would receive effluent from the motorcycle retail operation, which would then be transmitted to a pump chamber, equipped with float operated high level alarm. The effluent would move through these components of the system by means of gravity disposal. From the pump chamber, however, it would be pumped up into the raised trenches of the disposal bed where it would be time dosed at 262 L/dose.

The fully raised disposal bed, necessary due to the presence of clay at grade, will be set back 5 m from the proposed building and will be constructed of imported sand with a percolation rate ranging from approximately 1 to 8 minutes per centimetre set on scarified native clay. The proposed raised bed is to have an area of 349 m2 (25.5 m by 13.7 m) and will be 1.5 m in height. With a total hydraulic footprint, or contact area, of 349 m2 and a daily flow rate of 450 L/d, the application, or loading, rate is calculated at roughly 1.29 litres/m2/day.

Using the T-time of 8 min/cm of the imported fill and the a daily flow rate of 450 L/d, the length of required distribution pipe was calculated to be only 18 m, but will be increased to at least 40 m to meet the minimum length of leaching tile required as per the OBC. The distribution pipe will be laid out in three parallel 15 m trench runs set at depth of 900 mm above the native clay. The trenches will be located 1.6 m apart on centre, while the 1:4 slope surrounding the raised bed will commence at distance of 1 m from the perimeter of the trenches.

The site measures 174.3 m by 103.6 m and is extremely level. The native soil is described as clayey and has a T-time of greater than 50 minutes per centimetre.

The subject dwelling is served by a well water system.

The Construction in dispute is that the Applicant is proposing to construct the subject fully raised leaching bed without a mantle in any direction. The Applicant had previously received a permit for the installation of a raised bed with a 15 m mantle in all directions but is now seeking a revision to that permit to exclude the mantle entirely.

  1. Dispute

The issue at dispute between the Applicant and Respondent is whether, when considering an adequate daily loading rate, the Class 4 sewage system proposed without a 15 m mantle provides sufficiency of compliance with Clause 8.7.4.2.(1)(b) of the Ontario Building Code. This provision of the Code requires that a 15 m mantle be constructed in any direction that effluent may move horizontally in the soil. The intent of this requirement is to ensure that the area of unsaturated soil (to a depth of 250 mm) extends beyond the raised portion of the leaching bed, especially in the direction of gravitational flow.

Since the subject site is considerably flat, it is conceivable that effluent may move, according to the Applicant, in any direction from the distribution pipes. The Applicant has interpreted this to mean that a 15 m mantle is required in all directions. A surrounding mantle was included in the original application. The mantle, however, has been completely excluded from the current proposal since the Applicant deems that the loading requirements of Sentence 8.7.5.2.(2) are being met using only the hydraulic footprint of the raised bed itself.

  1. Provisions of the Ontario Building Code

Clause 8.7.4.2.(1)(b) Construction Requirements

(1) A leaching bed comprised of absorption trenches may be constructed in leaching bed fill provided that the unsaturated soil complying with Clause 8.7.2.1.(1)(b) extends

(b) for at least 15 m beyond the outer distribution pipes in any direction in which the effluent entering the soil will move horizontally.

  1. Applicant's Position

The Applicant submitted the proposed leaching bed, without a mantle, provides sufficiency of compliance with Sentence 8.7.4.2.(1) of the Code. He argued that, when considering the small daily design flow rate of 450 L/d for the subject occupancy and the required 40 m minimum length of distribution pipe (although 45 m are being proposed), the approximate application rate of 1.29 litres/m2/day for just the raised bed alone was already on the low side. Having to provide a mantle in any direction let alone in every direction, in his view, was therefore highly unnecessary. He indicated that the imported fill of the raised bed could more than adequately absorb the effluent produced. The exclusion of the mantle, especially a surrounding mantle, the Applicant noted would allow proponents to considerably reduce the required building materials as well as the overall costs of the project.

The Applicant argued that the Building Code should allow sewage systems to be designed on the basis of application rates and their respective contact areas. By allowing systems to be based on their actual daily flow rates and the true filter medium necessary would allow, he asserted, for more appropriately designed systems that better fit the intended use of the associated occupancy. It would also prevent the construction of "overbuilt" systems such as the case at hand which, the Applicant argued, resulted from certain "minimum requirement" standards being triggered in the Code.

  1. Respondent's Position

The Respondent submitted that the subject sewage system proposed without a 15 m mantle simply does not comply with the Code, in particular Clause 8.7.4.2.(1)(b). He argued that a mantle in the direction of flow is a necessary feature of raised bed systems that enables their proper functioning by increasing the contact area. The mantle also provides additional levels of safety in the event that the bed fails. The Respondent noted that a mantle has been a long standing requirement of such raised beds. He indicated that he believed he did not have the authority to allow what, in his view, is a large deviation from the requirements of the Code.

  1. Commission Ruling

It is the decision of the Building Code Commission that the proposed 4.3 metres of leaching bed fill down gradient of the distribution pipe does not provide sufficiency of compliance with Clause 8.7.4.2.(1)(b).

  1. Reasons

(i) A 15 m mantle is required as per Clause 8.7.4.2.(1)(b).

(ii) No evidence was provided that the native soil meets the requirements of Subclause 8.7.2.1.(1)(b)(ii).

Dated at Toronto this 27th day in the month of May in the year 1999 for application number 1999-31

Mr. Bryan Whitehead, Chair

Mr. Bill Fellner

Mr. Frank Wright