Detention Pond Design

Easily determine the size and configuration of effective detention ponds and their appurtenances for flood control and water quality protection. Ponds may be arbitrarily shaped and distributed around the catchment – in series, parallel or both – and may be operated according to arbitrary rules.

Sizing detention facilities and their appurtenances for flood control and water quality protection is easy in PCSWMM.

Instantly determine required storage volume (to match pre-development peak flow or other criteria) with the storage optimizer tool
Flexibly model outlet structures using either empirical rating curves or accurate, deterministic modeling of multiple physical outlet structures
Accurately model backwater effects, tailwater submergence, energy losses and more
Analyze the cumulative impact of multiple detention facilities on the larger drainage system
Compare pre and post development hydrology in graphs, HGL profiles and reports
Account for Low Impact Development (LID) practices
Create design storms for both major and minor events with the comprehensive storm distribution library in the Design Storm Creator tool, including standard SCS, Huff, AES, Chicago, etc. as well as locally-required design storm distributions
Model pond infiltration/exfiltration and evaporation
Model irrigation, routing pumped water back onto subcatchments.
Efficiently test the hydraulic design with simultaneous running of multiple design storms in the same time it takes for a single SWMM run (with multi-core CPU support)
Optimize storage and outlet parameters efficiently and easily using the unique sensitivity-based radio-tuning calibration and optimization utility
Verify pollutant removal and/or seasonal behavior through comparison of long term continuous scenarios with an unlimited number of quality constituents

Spotlight Projects

Modeling Cha-Am Municipality Wastewater Treatment Pond

Date:

February 2016

Location:

Bangkok, Thailand

Client:

Cha-Am Municipality

Consultants:

For more information:

Read the ICWMM abstract
Visit the research page
Read the news article

Discussion

Water quality in Cha-Am, Thailand is of particular concern because of the area's extensive oceanfront and its importance to the City’s tourism and real estate industries. PCSWMM was used to help improve water quality by simulating the effluent quality of the aerated lagoon system which treats municipal wastewater and consists of three ponds and a natural wetland.

The ponds were considered storage zones, and water quality sampling for Total Suspended Solid (TSS), Total Kjeldahl Nitrogen (TKN), Escherichia coli (E. coli), Chemical Oxygen Demand (COD), as well as evaporation measurements, were conducted on a bi-weekly basis for three months to calibrate the model.

Based on the observed water quality data distribution, Monte Carlo simulation was used (1,000 iterations) to receive the most probable input concentration for each pond and determine the appropriate treatment fractions for the model. Data on daily inflow rates, pump operation and bathymetric survey data also were obtained from the system operator as model input.

The dynamic wave method was used with observed inflow rates to generate a continuous water quality simulation from July 19th to September 12th, 2015. Observed mean treatment efficiency was 51.93%, 77.27%, 99.59% and 9.36% for TSS, TKN, E. coli and COD respectively; and observed concentrations at the outlet ranged between 10-25.5 mg/L, 0.98-3.92 mg/L, 0.1-260 CFU/100 ml and 48-119 mg/L for TSS, TKN, E. coli and COD respectively.

Able to accurately represent the outlet concentrations, the treatment fraction approach in PCSWWM was successful. This project has helped to protect Cha-Am’s oceanfront against pollution that threatens the City's tourism and real estate markets, and has assisted in informing individuals working toward improving water quality throughout the municipality.

Thermal Impact of Stormwater Management Ponds

Date:

September 2012

Location:

Guelph and Kitchener, Ontario, Canada

Client:

University of Guelph

Consultants:

For more information:

Read the JWMM paper

Discussion

Stormwater Management Ponds (SWMPs) are among the most popular options to control post-development peak flows, and for the effective removal of suspended solids and associated contaminants from urban surface runoff. However, there is a significant lack of information in Ontario on the potentially adverse thermal enrichment effect of SWMPs on sensitive aquatic habitats.

This study investigated the thermal effects of traditional SWMPs in southern Ontario climate conditions through monitoring and modeling. PCSWMM was used to generate inflow and outflow time series – as well as water levels in the ponds – for all events which had available temperature monitoring data.

The collected data was then used to develop PCSWMM models to represent the existing hydrologic conditions of all catchments in the Guelph and Kitchener areas. Land uses within the catchments are varied from pond to pond (residential, parking lot, combination of residential and grassland) and drainage areas also vary in size; ranging between 5 ha and 79 ha.

Inflow and outflow data extracted from PCSWMM were used to calculate the event mean temperature in different zones of the system (inlet, pond water temperature close to outlet, outlet and cooling trench) for further statistical analysis. Photogrammetric data and AutoCAD maps representing the studied areas were used to calibrate the PCSWMM model for existing conditions - as well as GIS tools and pond water level data.

Results showed that cooling trench performance was highly dependent on flow rate into the cooling trench, runoff and cooling trench volumes, influent temperature, volume of water in the cooling trench before runoff and groundwater interaction. These findings have provided an enhanced understanding of how to mitigate the potential adverse thermal effects of SWMPs, and have improved the researcher’s insight into how to better design thermal mitigation structures.

Stormwater Pond Sediment Loading and Accumulation Analysis

Date:

June 2012

Location:

Ontario, Canada

Client:
City of Hamilton

Consultant:

AECOM

For more information:

Read the JWMM paper

Discussion

Infrastructure for collecting and managing stormwater is vital to minimize flooding and erosion hazards – and maximize water quality treatment and environmental benefits – particularly when discharging to sensitive receiving watercourses such as Hannon Creek, a tributary of Lake Ontario.

The City of Hamilton, Ontario retained AECOM to provide consulting engineering services related to the design, permitting and construction of the Twenty Road regional stormwater management facility. This facility is located on city-owned property; a 2.2 ha (5.4 ac) parcel designed to service 36 ha (89 ac) of future development on primarily commercial and industrial lands.

For this project, continuous simulation was applied using a local 22-year rainfall dataset as well as a representative "average" rainfall year in order to meet specific requirements of the permitting agencies, including:

Erosion hazard impacts to the downstream watercourses were addressed by performing a flow frequency analysis of peak velocities as well as an assessment of pre-/post-project velocity frequency curves to achieve the defined erosion thresholds.
A depth duration analysis was performed to facilitate vegetation selection for the landscaping plan.
A sediment loading and accumulation analysis was undertaken to confirm the proposed detention facility achieved the prescribed long-term Total Suspended Sediment (TSS) removal efficiency.

With continuous simulation, limitations inherent in presumptive design criteria (which assume long-term sediment removal efficiencies based solely on storage volume per unit impervious area) were overcome.

The water quality module of SWMM5 was used to simulate the generation of TSS loadings from each subcatchment tributary to the pond, and the buildup and washoff of TSS generated from specific surface cover types was represented. Six mass fractions of TSS were explicitly represented to characterize the particle size distribution of sediment in stormwater runoff.

Overall, the pond removal efficiency (88% on an average annual basis) achieved the presumptive design criteria for an enhanced level of water quality protection. The resulting modeling efforts serve as a basis for confirming the facility achieves the design objectives and meets regulatory requirements aimed at minimizing adverse impacts on downstream watercourses.