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Professional Services Agreement Little Lake Johanna and Pike Lake Stormwater Retrofit Analysis 220191 09/21/2022 Page 1 of 11 Version2.3 02052021 THIS AGREEMENT is between the City of Arden Hills (hereafter “CLIENT”) and HR GREEN, INC. (hereafter "COMPANY"). 1.0 Project Understanding 1.1 General Understanding CLIENT requires the consulting services of COMPANY to analyze the subwatersheds of Little Lake Johanna and Pike Lake within the City for potential targeted locations of specific water quality best management practices (BMP). This Stormwater Retrofit Analysis will serve to assist CLIENT in implementing targeted and prioritized practices to help meet waste load allocations for these lakes per their MS4 goals. The proposed scope of work will develop guidance to watershed management staff in implementing targeted, measurable, and prioritized water quality BMPs in the City within the watershed areas. This study will not include portions of the watersheds within the cities of New Brighton or Roseville. As identified projects come out of this study, conversations will take place with the neighboring cities on cost share opportunities to count toward multiple MS4 permits. 1.2 Design Criteria/Assumptions • Stormwater infrastructure data will be provided to the COMPANY by the CLIENT, as either a GIS shapefile or CAD File. This information will include all catch basins, culverts, pipes, pipe sizes, outfalls, ponds and ditches within the study area. • As-built surveys or construction plans of existing stormwater ponds and other best management practices will provide sufficient detail for modeling purposes. If data gaps or quality prove insufficient, assumed dimensions and hydraulic controls will be adopted, or the CLIENT will investigate the data gaps during the field reconnaissance. • City land use data will be provided to the COMPANY by the CLIENT. • The P8 Urban Catchment Model will be used for existing- and post-yield of Total Sediment and Total Phosphorus using a representative average year based on the most current 30- years of precipitation. • New proposed end-of-pipe BMPs (e.g., extended detention ponds) will be modeled to treat the drainage area leading to them but not include any newly proposed distributed BMPs upstream of it. • New proposed distributed BMPs (e.g., curb-cut raingardens) will be modeled collectively for the drainage area they serve. No feasibility study will be performed for these locations. • Conceptual, estimated construction costs for end-of-pipe BMPs will be derived at a planning-level scale with a 30% contingency. • Present Day Value costs will use spreadsheet calculators from the Water Environment Research Foundation for a 30-year period of operation. Maintenance labor, materials and frequency will be agreed upon by the COMPANY and CLIENT but may include obtaining staff rates from CLIENT. • A Technical Memorandum will be developed containing the methods and results of the study and delivered electronically. • All data used or produced in the analysis will be available to CLIENT upon request.