A discussion of the research performance evaluation in building and construction management discipline : the journal impact factors and SCI-index journals

The trend of diminished funding, demands for greater efficiency and higher public accountability have led to a rapid expansion of interest in the bibliometric assessment of research performance of universities. A pilot research is conducted to provide a preliminary overview of the research performance of the building and construction schools or departments through the analysis of bibliometric indicators including the journal impact factor (JIF) published by Institute for Scientific Information (ISI). The suitability of bibliometric evaluation approaches as a measure of research quality in building and construction management research field is discussed.

Ownership structure and business evaluation practices in family SMEs : evidence from empirical research in Italy

This paper presents early results from a pilot project which aims to investigate the relationship between proprietary structure of small and medium- sized Italian family firms and their owners’ orientation towards a “business evaluation process”. Evidence from many studies point out the importance of family business in a worldwide economic environment: in Italy 93% of the businesses are represented by family firms; 98% of them have less than 50 employees (Italian Association of Family Firms, 2004) so we judged family SMEs as a relevant field of investigation. In this study we assume a broad definition of family business as “a firm whose control (50% of shares or voting rights) is closely held by the members of the same family” (Corbetta,1995). “Business evaluation process” is intended here both as “continuous evaluation process” (which is the expression of a well developed managerial attitude) or as an “immediate valuation” (i.e. in the case of new shareholder’s entrance, share exchange among siblings, etc). We set two hypotheses to be tested in this paper: the first is “quantitative” and aims to verify whether the number of owners (independent variable) in a family firm is positively correlated to the business evaluation process. If a family firm is led by only one subject, it is more likely that personal values, culture and feelings may affect his choices more than “purely economic opportunities”; so there is less concern about monitoring economic performance or about the economic value of the firm. As the shareholders’ number increases, economic aspects in managing the firm grow in importance over the personal values and "value orientation" acquires a central role. The second hypothesis investigates if and to what extent the presence of “non- family members” among the owners affects their orientation to the business evaluation process. The “Cramer’s V” test has been used to test the hypotheses; both were not confirmed from these early results; next steps will lead to make an inferential analysis on a representative sample of the population.

A regional construction R&D evaluation system for China

Expenditure on R&D in the China construction industry has been relatively low in comparison with many developed countries for a number of years – a situation considered to be a major barrier to the industry’s competitiveness in general and unsatisfactory industry development of the 31 regions involved. A major problem with this is the lack of a sufficiently sophisticated method of objectively evaluating R&D activity in what are quite complex circumstances considering the size and regional differences that exist in this part of the world. A regional construction R&D evaluation system (RCRES) is presented aimed at rectifying the situation. This is based on 12 indicators drawn from the Chinese Government’s R&D Inventory of Resources in consultation with a small group of experts in the field, and further factor analysed into three groups. From this, the required evaluation is obtained by a simple formula. Examination of the results provides a ranking list of the R&D performance of each of the 31 regions, indicating a general disproportion between coastal and inland regions and highlighting regions receiving special emphasis or currently lacking in development. The understanding on this is vital for the future of China’s construction industry.

Design education online : learning delivery and evaluation

Online learning has been recognised as an effective pedagogical method and tool, and is broadly integrated into various types of teaching and learning strategies in higher education. In practice, the use of Virtual Learning Environment (VLE) in higher education has become an integral strategy for quality education. The field of design education however has not been researched extensively in regard to online learning, delivery and evaluation. This paper discusses design education from an online learning perspective. It proposes an integrated framework with three key components for online learning via VLE including an interactive delivery structure, communication channels, and learning evaluation. Additionally, the paper describes and evaluates how VLE sites for two design units were built based on an integrated framework and student learning experiences. The results indicate that online design education should be integrated with various educational values and functional features in a systematic manner, and requires designing learning evaluation protocols as part of learning activities and communicative forms within online-based learning sites.

An evaluation of alternative media for pebble matrix filtration using clay balls and recycled crushed glass

Protecting slow sand filters (SSFs) from high-turbidity waters by pretreatment using pebble matrix filtration (PMF) has previously been studied in the laboratory at University College London, followed by pilot field trials in Papua New Guinea and Serbia. The first full-scale PMF plant was completed at a water-treatment plant in Sri Lanka in 2008, and during its construction, problems were encountered in sourcing the required size of pebbles and sand as filter media. Because sourcing of uniform-sized pebbles may be problematic in many countries, the performance of alternative media has been investigated for the sustainability of the PMF system. Hand-formed clay balls made at a 100-yearold brick factory in the United Kingdom appear to have satisfied the role of pebbles, and a laboratory filter column was operated by using these clay balls together with recycled crushed glass as an alternative to sand media in the PMF. Results showed that in countries where uniform-sized pebbles are difficult to obtain, clay balls are an effective and feasible alternative to natural pebbles. Also, recycled crushed glass performed as well as or better than silica sand as an alternative fine media in the clarification process, although cleaning by drainage was more effective with sand media. In the tested filtration velocity range of ð0:72–1:33Þ m=h and inlet turbidity range of (78–589) NTU, both sand and glass produced above 95% removal efficiencies. The head loss development during clogging was about 30% higher in sand than in glass media.

Performance load testing and structural adequacy evaluation of road bridge decks

Many ageing road bridges, particularly timber bridges, require urgent improvement due to the demand imposed by the recent version of the Australian bridge loading code, AS 5100. As traffic volume plays a key role in the decision of budget allocations for bridge refurbishment/ replacement, many bridges in low volume traffic network remain in poor condition with axle load and/ or speed restrictions, thus disadvantaging many rural communities. This thesis examines an economical and environmentally sensible option of incorporating disused flat rail wagons (FRW) in the construction of bridges in low volume, high axle load road network. The constructability, economy and structural adequacy of the FRW road bridge is reported in the thesis with particular focus of a demonstration bridge commissioned in regional Queensland. The demonstration bridge comprises of a reinforced concrete slab (RCS) pavement resting on two FRWs with custom designed connection brackets at regular intervals along the span of the bridge. The FRW-RC bridge deck assembly is supported on elastomeric rubber pads resting on the abutment. As this type of bridge replacement technology is new and its structural design is not covered in the design standards, the in-service structural performance of the FRW bridge subjected to the high axle loadings prescribed in AS 5100 is examined through performance load testing. Both the static and the moving load tests are carried out using a fully laden commonly available three-axle tandem truck. The bridge deck is extensively strain gauged and displacement at several key locations is measured using linear variable displacement transducers (LVDTs). A high speed camera is used in the performance test and the digital image data are analysed using proprietary software to capture the locations of the wheel positions on the bridge span accurately. The wheel location is thus synchronised with the displacement and strain time series to infer the structural response of the FRW bridge. Field test data are used to calibrate a grillage model, developed for further analysis of the FRW bridge to various sets of high axle loads stipulated in the bridge design standard. Bridge behaviour predicted by the grillage model has exemplified that the live load stresses of the FRW bridge is significantly lower than the yield strength of steel and the deflections are well below the serviceability limit state set out in AS 5100. Based on the results reported in this thesis, it is concluded that the disused FRWs are competent to resist high axle loading prescribed in AS 5100 and are a viable alternative structural solution of bridge deck in the context of the low volume road networks.

The development and evaluation of a culturally affirmative counselling model for deaf clients in Australia

In Australia, there is only one, newly established, dedicated mental health service catering specifically for the signing *Deaf community. It is staffed by four part-time hearing professionals and based in Brisbane. There are currently no Deaf psychologists or psychiatrists and there is no valid or reliable empirical evidence on outcomes for Deaf people accessing specialised or mainstream mental health services. Further compounding these issues, is the fact that there are no sign language versions of the most common standardised mental health or psychological instruments available to clinicians in Australia. Contemporary counselling literature is acknowledging the role of the therapeutic alliance and the impact of 'common factors' on therapeutic outcomes. However, these issues are complicated by the relationship between the Deaf client and the hearing therapist being a cross-cultural exchange. The disability model of deafness is contentious and few professionals in Australia have the requisite knowledge and understanding of deafness from a cultural perspective to attend to the therapeutic relationship with this in mind. Consequently, Deaf people are severely disadvantaged by the current lack of services, resources and skilled professionals in the field of deafness and psychology in this country. The primary aim of the following program of research has been to propose a model for culturally affirmative service delivery and to provide clinicians with tools to evaluate the effect of their therapeutic work with Deaf people seeking mental health treatment. The research document is presented as a thesis by publication and comprises four specific objectives formulated in response to the lack of existing services and resources. The first objective was to explore the use of social constructionist counselling techniques and a reflecting team with Deaf clients, hearing therapists and an interpreter. Following the establishment of a pilot counselling clinic, indepth semi-structured interviews were conducted with two long-term clients following the one year pilot of this service. These interviews generated recommendations for the development of a new 'enriched' model of counselling to be implemented and evaluated in later stages of the research program. The second objective was to identify appropriate psychometric measures that could be translated into Australian Sign Language (Auslan) for research into efficacy, effectiveness and counselling outcomes. Two instruments were identified as potentially suitable; the Outcome Rating Scale (ORS), a measure of global functioning, and the Session Rating Scale (SRS), a measure of therapeutic alliance. A specialised team of bi-lingual and bi-cultural interpreters, native signers and the primary researcher for this thesis, produced the ORS-Auslan and the SRS-Auslan in DVD format, using the translation and back-translation process. The third objective was to establish the validity and reliability of these new Auslan measures based on normative data from the Deaf community. Data from the ORS-Auslan was collected from one clinical and one non-clinical sample of Deaf people. Statistical analyses revealed that the ORS-Auslan is reliable, valid and adequately distinguishes between clinical and non-clinical presentations. Furthermore, construct validity has been established using a yet to be validated sign language version of the Depression, Anxiety and Stress Scale-21 items (DASS-21), providing a platform for further research using the DASS-21 with Deaf people. The fourth objective was to evaluate counselling outcomes following the implementation of an enriched counselling service, based on the findings generated by the first objective, and using the newly translated Auslan measures. A second university counselling clinic was established and implemented over the course of one year. Practice-based evidence guided the research and the ORS-Auslan and the SRS-Auslan were administered at every session and provided outcome data on Deaf clients' global functioning. Data from six clients over the course of ten months indicated that this culturally affirmative model was an effective approach for these six clients. This is the first time that outcome data have been collected in Australia using valid and reliable Auslan measures to establish preliminary evidence for the effectiveness of any therapeutic intervention for clinical work with adult, signing Deaf clients. The research generated by this thesis contributes theoretical knowledge, professional development and practical resources that can be used by a variety of mental health clinicians in the context of mental health service delivery to Deaf clients in Australia.

Understanding evaluation of learning support in mathematics and statistics

With rapid and continuing growth of learning support initiatives in mathematics and statistics found in many parts of the world, and with the likelihood that this trend will continue, there is a need to ensure that robust and coherent measures are in place to evaluate the effectiveness of these initiatives. The nature of learning support brings challenges for measurement and analysis of its effects. After briefly reviewing the purpose, rationale for, and extent of current provision, this article provides a framework for those working in learning support to think about how their efforts can be evaluated. It provides references and specific examples of how workers in this field are collecting, analysing and reporting their findings. The framework is used to structure evaluation in terms of usage of facilities, resources and services provided, and also in terms of improvements in performance of the students and staff who engage with them. Very recent developments have started to address the effects of learning support on the development of deeper approaches to learning, the affective domain and the development of communities of practice of both learners and teachers. This article intends to be a stimulus to those who work in mathematics and statistics support to gather even richer, more valuable, forms of data. It provides a 'toolkit' for those interested in evaluation of learning support and closes by referring to an on-line resource being developed to archive the growing body of evidence. © 2011 Taylor & Francis.

Technology transfer evaluation in the high technology industry : an interdisciplinary perspective

The underlying objective of this study was to develop a novel approach to evaluate the potential for commercialisation of a new technology. More specifically, this study examined the 'ex-ante'. evaluation of the technology transfer process. For this purpose, a technology originating from the high technology sector was used. The technology relates to the application of software for the detection of weak signals from space, which is an established method of signal processing in the field of radio astronomy. This technology has the potential to be used in commercial and industrial areas other than astronomy, such as detecting water leakages in pipes. Its applicability to detecting water leakage was chosen owing to several problems with detection in the industry as well as the impact it can have on saving water in the environment. This study, therefore, will demonstrate the importance of interdisciplinary technology transfer. The study employed both technical and business evaluation methods including laboratory experiments and the Delphi technique to address the research questions. There are several findings from this study. Firstly, scientific experiments were conducted and these resulted in a proof of concept stage of the chosen technology. Secondly, validation as well as refinement of criteria from literature that can be used for „ex-ante. evaluation of technology transfer has been undertaken. Additionally, after testing the chosen technology.s overall transfer potential using the modified set of criteria, it was found that the technology is still in its early stages and will require further development for it to be commercialised. Furthermore, a final evaluation framework was developed encompassing all the criteria found to be important. This framework can help in assessing the overall readiness of the technology for transfer as well as in recommending a viable mechanism for commercialisation. On the whole, the commercial potential of the chosen technology was tested through expert opinion, thereby focusing on the impact of a new technology and the feasibility of alternate applications and potential future applications.

Developing a Second Life virtual field trip for university students : an action research approach

Background: Integrating 3D virtual world technologies into educational subjects continues to draw the attention of educators and researchers alike. The focus of this study is the use of a virtual world, Second Life, in higher education teaching. In particular, it explores the potential of using a virtual world experience as a learning component situated within a curriculum delivered predominantly through face-to-face teaching methods. Purpose: This paper reports on a research study into the development of a virtual world learning experience designed for marketing students taking a Digital Promotions course. The experience was a field trip into Second Life to allow students to investigate how business branding practices were used for product promotion in this virtual world environment. The paper discusses the issues involved in developing and refining the virtual course component over four semesters. Methods: The study used a pedagogical action research approach, with iterative cycles of development, intervention and evaluation over four semesters. The data analysed were quantitative and qualitative student feedback collected after each field trip as well as lecturer reflections on each cycle. Sample: Small-scale convenience samples of second- and third-year students studying in a Bachelor of Business degree, majoring in marketing, taking the Digital Promotions subject at a metropolitan university in Queensland, Australia participated in the study. The samples included students who had and had not experienced the field trip. The numbers of students taking part in the field trip ranged from 22 to 48 across the four semesters. Findings and Implications: The findings from the four iterations of the action research plan helped identify key considerations for incorporating technologies into learning environments. Feedback and reflections from the students and lecturer suggested that an innovative learning opportunity had been developed. However, pedagogical potential was limited, in part, by technological difficulties and by student perceptions of relevance.

Performance evaluation of eight contemporary passive solar homes in subtropical Australia

Subtropical south-east Queensland’s expanding population is expected to lead to a demand for an additional 754,000 dwellings by 2031. A legacy of poor housing design, minimal building regulations, an absence of building performance evaluation and various social and market factors has lead to a high and growing penetration of, and reliance on, air conditioners to provide comfort in this relatively benign climate. This reliance impacts on policy goals to adapt to and mitigate against global warming, electricity infrastructure investment and household resilience. Based on the concept of bioclimatic design, this field study scrutinizes eight non-air conditioned homes to develop a deeper understanding of the role of contemporary passive solar architecture in the delivery of thermally comfortable and resilient homes in the subtropics. These homes were found to provide inhabitants with an acceptable level of thermal comfort (18-28oC) for 77 – 97% of the year. Family expectations and experiences of comfort, and the various design strategies utilized were compared against the measured performance outcomes. This comparison revealed issues that limited quantification and implementation of design intent and highlighted factors that constrained system optimisation.

Re-engaging marginalized youth through digital music production: performance, audience and evaluation

This paper presents two case studies of marginalised youth experimenting with digital music production in flexible education settings. The cases were drawn from a three-year study of alternative assessment in flexible learning centres that enrol 650+ students who have left formal schooling in Queensland, Australia. The cases are framed in reference to the literature on cultural studies approaches to education and the digital arts. Each case describes the student’s histories, cultural background and experiences, music productions, evidence of learning and re-engagement with education. Findings document how digital music production can re-engage and extend participation among students who have left formal education. They do so by theorising the online judgements and blog comments about the digital music production as a social field of exchange. It also raises critical questions about the adequacy of current approaches to evaluating and accounting for the learning and development of such youth, especially where this has occurred through creative arts and digital production.

Empirical IEEE 802.11p performance evaluation on test tracks

IEEE 802.11p is the new standard for inter-vehicular communications (IVC) using the 5.9 GHz frequency band; it is planned to be widely deployed to enable cooperative systems. 802.11p uses and performance have been studied theoretically and in simulations over the past years. Unfortunately, many of these results have not been confirmed by on-tracks experimentation. In this paper, we describe field trials of 802.11p technology with our test vehicles. Metrics such as maximum range, latency and frame loss are examined.

Environmental and economic evaluation of N fertilizer rates in a maize crop in Italy : a spatial and temporal analysis using crop models

Crop simulation models have the potential to assess the risk associated with the selection of a specific N fertilizer rate, by integrating the effects of soil-crop interactions on crop growth under different pedo-climatic and management conditions. The objective of this study was to simulate the environmental and economic impact (nitrate leaching and N2O emissions) of a spatially variable N fertilizer application in an irrigated maize field in Italy. The validated SALUS model was run with 5 nitrogen rates scenarios, 50, 100, 150, 200, and 250 kg N ha−1, with the latter being the N fertilization adopted by the farmer. The long-term (25 years) simulations were performed on two previously identified spatially and temporally stable zones, a high yielding and low yielding zone. The simulation results showed that N fertilizer rate can be reduced without affecting yield and net return. The marginal net return was on average higher for the high yield zone, with values ranging from 1550 to 2650 € ha−1 for the 200 N and 1485 to 2875 € ha−1 for the 250 N. N leaching varied between 16.4 and 19.3 kg N ha−1 for the 200 N and the 250 N in the high yield zone. In the low yield zone, the 250 N had a significantly higher N leaching. N2O emissions varied between 0.28 kg N2O ha−1 for the 50 kg N ha−1 rate to a maximum of 1.41 kg N2O ha−1 for the 250 kg N ha−1 rate.

Performance evaluation of onsite sewage treatment : Evaluation of current research

Efficient management of domestic wastewater is a primary requirement for human well being. Failure to adequately address issues of wastewater collection, treatment and disposal can lead to adverse public health and environmental impacts. The increasing spread of urbanisation has led to the conversion of previously rural land into urban developments and the more intensive development of semi urban areas. However the provision of reticulated sewerage facilities has not kept pace with this expansion in urbanisation. This has resulted in a growing dependency on onsite sewage treatment. Though considered only as a temporary measure in the past, these systems are now considered as the most cost effective option and have become a permanent feature in some urban areas. This report is the first of a series of reports to be produced and is the outcome of a research project initiated by the Brisbane City Council. The primary objective of the research undertaken was to relate the treatment performance of onsite sewage treatment systems with soil conditions at site, with the emphasis being on septic tanks. This report consists of a ‘state of the art’ review of research undertaken in the arena of onsite sewage treatment. The evaluation of research brings together significant work undertaken locally and overseas. It focuses mainly on septic tanks in keeping with the primary objectives of the project. This report has acted as the springboard for the later field investigations and analysis undertaken as part of the project. Septic tanks still continue to be used widely due to their simplicity and low cost. Generally the treatment performance of septic tanks can be highly variable due to numerous factors, but a properly designed, operated and maintained septic tank can produce effluent of satisfactory quality. The reduction of hydraulic surges from washing machines and dishwashers, regular removal of accumulated septage and the elimination of harmful chemicals are some of the practices that can improve system performance considerably. The relative advantages of multi chamber over single chamber septic tanks is an issue that needs to be resolved in view of the conflicting research outcomes. In recent years, aerobic wastewater treatment systems (AWTS) have been gaining in popularity. This can be mainly attributed to the desire to avoid subsurface effluent disposal, which is the main cause of septic tank failure. The use of aerobic processes for treatment of wastewater and the disinfection of effluent prior to disposal is capable of producing effluent of a quality suitable for surface disposal. However the field performance of these has been disappointing. A significant number of these systems do not perform to stipulated standards and quality can be highly variable. This is primarily due to houseowner neglect or ignorance of correct operational and maintenance procedures. The other problems include greater susceptibility to shock loadings and sludge bulking. As identified in literature a number of design features can also contribute to this wide variation in quality. The other treatment processes in common use are the various types of filter systems. These include intermittent and recirculating sand filters. These systems too have their inherent advantages and disadvantages. Furthermore as in the case of aerobic systems, their performance is very much dependent on individual houseowner operation and maintenance practices. In recent years the use of biofilters has attracted research interest and particularly the use of peat. High removal rates of various wastewater pollutants have been reported in research literature. Despite these satisfactory results, leachate from peat has been reported in various studies. This is an issue that needs further investigations and as such biofilters can still be considered to be in the experimental stage. The use of other filter media such as absorbent plastic and bark has also been reported in literature. The safe and hygienic disposal of treated effluent is a matter of concern in the case of onsite sewage treatment. Subsurface disposal is the most common and the only option in the case of septic tank treatment. Soil is an excellent treatment medium if suitable conditions are present. The processes of sorption, filtration and oxidation can remove the various wastewater pollutants. The subsurface characteristics of the disposal area are among the most important parameters governing process performance. Therefore it is important that the soil and topographic conditions are taken into consideration in the design of the soil absorption system. Seepage trenches and beds are the common systems in use. Seepage pits or chambers can be used where subsurface conditions warrant, whilst above grade mounds have been recommended for a variety of difficult site conditions. All these systems have their inherent advantages and disadvantages and the preferable soil absorption system should be selected based on site characteristics. The use of gravel as in-fill for beds and trenches is open to question. It does not contribute to effluent treatment and has been shown to reduce the effective infiltrative surface area. This is due to physical obstruction and the migration of fines entrained in the gravel, into the soil matrix. The surface application of effluent is coming into increasing use with the advent of aerobic treatment systems. This has the advantage that treatment is undertaken on the upper soil horizons, which is chemically and biologically the most effective in effluent renovation. Numerous research studies have demonstrated the feasibility of this practice. However the overriding criteria is the quality of the effluent. It has to be of exceptionally good quality in order to ensure that there are no resulting public health impacts due to aerosol drift. This essentially is the main issue of concern, due to the unreliability of the effluent quality from aerobic systems. Secondly, it has also been found that most householders do not take adequate care in the operation of spray irrigation systems or in the maintenance of the irrigation area. Under these circumstances surface disposal of effluent should be approached with caution and would require appropriate householder education and stringent compliance requirements. However despite all this, the efficiency with which the process is undertaken will ultimately rest with the individual householder and this is where most concern rests. Greywater too should require similar considerations. Surface irrigation of greywater is currently being permitted in a number of local authority jurisdictions in Queensland. Considering the fact that greywater constitutes the largest fraction of the total wastewater generated in a household, it could be considered to be a potential resource. Unfortunately in most circumstances the only pretreatment that is required to be undertaken prior to reuse is the removal of oil and grease. This is an issue of concern as greywater can considered to be a weak to medium sewage as it contains primary pollutants such as BOD material and nutrients and may also include microbial contamination. Therefore its use for surface irrigation can pose a potential health risk. This is further compounded by the fact that most householders are unaware of the potential adverse impacts of indiscriminate greywater reuse. As in the case of blackwater effluent reuse, there have been suggestions that greywater should also be subjected to stringent guidelines. Under these circumstances the surface application of any wastewater requires careful consideration. The other option available for the disposal effluent is the use of evaporation systems. The use of evapotranspiration systems has been covered in this report. Research has shown that these systems are susceptible to a number of factors and in particular to climatic conditions. As such their applicability is location specific. Also the design of systems based solely on evapotranspiration is questionable. In order to ensure more reliability, the systems should be designed to include soil absorption. The successful use of these systems for intermittent usage has been noted in literature. Taking into consideration the issues discussed above, subsurface disposal of effluent is the safest under most conditions. This is provided the facility has been designed to accommodate site conditions. The main problem associated with subsurface disposal is the formation of a clogging mat on the infiltrative surfaces. Due to the formation of the clogging mat, the capacity of the soil to handle effluent is no longer governed by the soil’s hydraulic conductivity as measured by the percolation test, but rather by the infiltration rate through the clogged zone. The characteristics of the clogging mat have been shown to be influenced by various soil and effluent characteristics. Secondly, the mechanisms of clogging mat formation have been found to be influenced by various physical, chemical and biological processes. Biological clogging is the most common process taking place and occurs due to bacterial growth or its by-products reducing the soil pore diameters. Biological clogging is generally associated with anaerobic conditions. The formation of the clogging mat provides significant benefits. It acts as an efficient filter for the removal of microorganisms. Also as the clogging mat increases the hydraulic impedance to flow, unsaturated flow conditions will occur below the mat. This permits greater contact between effluent and soil particles thereby enhancing the purification process. This is particularly important in the case of highly permeable soils. However the adverse impacts of the clogging mat formation cannot be ignored as they can lead to significant reduction in the infiltration rate. This in fact is the most common cause of soil absorption systems failure. As the formation of the clogging mat is inevitable, it is important to ensure that it does not impede effluent infiltration beyond tolerable limits. Various strategies have been investigated to either control clogging mat formation or to remediate its severity. Intermittent dosing of effluent is one such strategy that has attracted considerable attention. Research conclusions with regard to short duration time intervals are contradictory. It has been claimed that the intermittent rest periods would result in the aerobic decomposition of the clogging mat leading to a subsequent increase in the infiltration rate. Contrary to this, it has also been claimed that short duration rest periods are insufficient to completely decompose the clogging mat, and the intermediate by-products that form as a result of aerobic processes would in fact lead to even more severe clogging. It has been further recommended that the rest periods should be much longer and should be in the range of about six months. This entails the provision of a second and alternating seepage bed. The other concepts that have been investigated are the design of the bed to meet the equilibrium infiltration rate that would eventuate after clogging mat formation; improved geometry such as the use of seepage trenches instead of beds; serial instead of parallel effluent distribution and low pressure dosing of effluent. The use of physical measures such as oxidation with hydrogen peroxide and replacement of the infiltration surface have been shown to be only of short-term benefit. Another issue of importance is the degree of pretreatment that should be provided to the effluent prior to subsurface application and the influence exerted by pollutant loadings on the clogging mat formation. Laboratory studies have shown that the total mass loadings of BOD and suspended solids are important factors in the formation of the clogging mat. It has also been found that the nature of the suspended solids is also an important factor. The finer particles from extended aeration systems when compared to those from septic tanks will penetrate deeper into the soil and hence will ultimately cause a more dense clogging mat. However the importance of improved pretreatment in clogging mat formation may need to be qualified in view of other research studies. It has also shown that effluent quality may be a factor in the case of highly permeable soils but this may not be the case with fine structured soils. The ultimate test of onsite sewage treatment system efficiency rests with the final disposal of effluent. The implication of system failure as evidenced from the surface ponding of effluent or the seepage of contaminants into the groundwater can be very serious as it can lead to environmental and public health impacts. Significant microbial contamination of surface and groundwater has been attributed to septic tank effluent. There are a number of documented instances of septic tank related waterborne disease outbreaks affecting large numbers of people. In a recent incident, the local authority was found liable for an outbreak of viral hepatitis A and not the individual septic tank owners as no action had been taken to remedy septic tank failure. This illustrates the responsibility placed on local authorities in terms of ensuring the proper operation of onsite sewage treatment systems. Even a properly functioning soil absorption system is only capable of removing phosphorus and microorganisms. The nitrogen remaining after plant uptake will not be retained in the soil column, but will instead gradually seep into the groundwater as nitrate. Conditions for nitrogen removal by denitrification are not generally present in a soil absorption bed. Dilution by groundwater is the only treatment available for reducing the nitrogen concentration to specified levels. Therefore based on subsurface conditions, this essentially entails a maximum allowable concentration of septic tanks in a given area. Unfortunately nitrogen is not the only wastewater pollutant of concern. Relatively long survival times and travel distances have been noted for microorganisms originating from soil absorption systems. This is likely to happen if saturated conditions persist under the soil absorption bed or due to surface runoff of effluent as a result of system failure. Soils have a finite capacity for the removal of phosphorus. Once this capacity is exceeded, phosphorus too will seep into the groundwater. The relatively high mobility of phosphorus in sandy soils have been noted in the literature. These issues have serious implications in the design and siting of soil absorption systems. It is not only important to ensure that the system design is based on subsurface conditions but also the density of these systems in given areas is a critical issue. This essentially involves the adoption of a land capability approach to determine the limitations of an individual site for onsite sewage disposal. The most limiting factor at a particular site would determine the overall capability classification for that site which would also dictate the type of effluent disposal method to be adopted.