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					                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept                  Description                                                                      Problem or Gap                                           Additional comment or question
                                                                                                                                                                  In "in lieu of" flow control instances LID should be
SWMM Volume 1, 2.7.2      LID Concept overall                                    In Lieu of Flow Control Policy                                                   encouraged


                                                                                 On-Site Storm Water Management
                                                                                 This Chapter presents the methods for analysis and design of on-site
                                                                                 storm water management Best Management Practices (BMPs). Many of
                                                                                 these BMPs, although being used elsewhere, are new locally. Efforts are          While low impact development includes specific on-
                                                                                 underway to further develop these “low impact development” concepts in           site stormwater management practices, LID also
                                                                                 Western Washington. Ecology will update these BMPs when local                    includes site planning and design approaches that
                                                                                 standards are established. The City will update these BMPs as                    minimize runoff generation. A more broad
SWMM Volume V, 5.1        LID Concept overall                                    information is made available by Ecology.                                        definition of LID would be useful




                                                                                                                                                                  Does not identify areas where infiltration is feasible
                                                                                                                                                                  and permitted without pre approval. Could identify
SWMM Volume I, 3.5.9      P: Hydrologic Analysis    Runoff minimization          Basin/Watershed Planning                                                         areas where LID BMP's are necessary.




                                                                                 Tacoma Watersheds - Identifies Watershed Flow Control and Quantity              Several of the basins permit no flow control.
SWMM Volume 1, 2.6        P: Hydrologic Analysis    Runoff minimization          requirements for each basin                                                     Provisions to reduce runoff should be encouraged.
                                                                                 These sections emphasize benefits of infiltration through dispersion and to
                                                                                 infiltration systems, and give clear, well-defined requirements for soil
                                                                                 analysis.
                                                                                 A shortcoming of these sections is that infiltration and dispersion "shall only
                                                                                 be used with the pre-approval of the City Engineer". This may discourage
SWMM Volume I, 3.5.5                                Maximize site infiltration   use of infiltration and dispersion in favor of conventional approaches that
SWMM Volume I, 3.5.6      P: Soil Analysis          capacity                     don't require special approval.

                                                                                 Requirements for Short Plats/Private Accessways                                  This standard requires excess impervious surface.
                                                                                 …"the minimum street section requirements for short plats                        Street widths can be reduced and permeable
                                                                                 and private accessways based on the number of lots being developed":             paving options added. The requirement for cement
                                                    Minimize Total               (from table): Pavement Width 28 feet for greater than 4 lots; 24 feet for 3 or   concrete walk on both sides of the street for
PWDS 1.030.F              P: Narrow Streets         Imperviousness               4 lots; 16 feet with an additional 4 feet graded and graveled for 2 lots.        projects with more then 4 lots could be adjusted..
                                                    Minimize Total
PWDS 4.040 A&B            P: Narrow Streets         Imperviousness               Provides Street and Lane Width Dimensions                                        Steet and Lane widths can be reduced
                                                                                 Design Speed
                                                                                 The designated speed limit for Tacoma residential streets is 25 mph which        These design speeds may be inappropriate if
                                                    Minimize Total               corresponds to a 30 mph design speed. Alleys shall be designed using a 20        narrower street design standards are adopted for
PWDS 4.010.A              P: Narrow Streets         Imperviousness               mph design speed.                                                                LID projects.




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept          Description                                                                      Problem or Gap                                           Additional comment or question
                                                                         Horizontal Curves                                                                Depending on site design considerations, a side
                                                    Minimize Total       Generally, non-arterial streets shall be designed with a standard pavement       slope (sheet flow) cross-section may be more
PWDS 4.020.C              P: Narrow Streets         Imperviousness       cross-section (2% crown) where feasible (Refer to 4.040.C).                      desirable for LID projects.
                                                                         Street Width
                                                    Minimize Total       The City of Tacoma Municipal Code defines a minimum residential street           More narrow streets are recommended for low and
PWDS 4.040.A              P: Narrow Streets         Imperviousness       width of 28 feet for new plats.                                                  moderate density residential streets in LID projects.
                                                                                                                                                          Depending on site design considerations, a side
                                                    Minimize Total       Cross Sections (Streets)                                                         slope (sheet flow) cross-section may be more
PWDS 4.040.C              P: Narrow Streets         Imperviousness       The City standard street section consists of a typical crown section…            desirable for LID projects.
                                                                                                                                                          The specified alley width is not necessarily a
                                                                                                                                                          problem, but other paving options such as
                                                    Minimize Total       Alleys                                                                           combination impervious and pervious paving will
PWDS 4.050.C              P: Narrow Streets         Imperviousness       The typical paved width of an alley in a residential area is 16 feet…            improve stormwater management for LID projects
                                                                         Figure 4-2 Standard T-Type Turnaround for Private Access and Residential
                                                                         Streets serving 3 to 4 lots.                                             Widths should be reduced for LID projects and
                                                    Minimize Total       Ingress/Egress - 32 feet wide                                            should incorporate pervious pavement where                       Should we attach a copy of the figure with
PWDS 4.060.A              P: Narrow Streets         Imperviousness       Top of "T" - 20 feet wide                                                possible                                                         mark-ups in the initial submittal?
                                                                                                                                                  Inner curb within the bulb is labelled as optional
                                                                                                                                                  and "not recommended". The not recommended
                                                                                                                                                  should be removed to promote LID techniques
                                                                                                                                                  within this area. Inner build could also be shown
                                                    Minimize Total                                                                                as a depression versus a raised island to permit
PWDS DR-06                P: Narrow Streets         Imperviousness       Minumum Standard for Cul-de-Sac                                          raingardens/biofiltration.

                                                    Minimize Effective   3705, and 3706 require curb and gutter, paving, and drainage shall be to         without LID permitted in the PWDS or the SWMMM
TMC Chapter 2.02.380      P: Minimize curb & gutter Imperviousness       minimum public works standards                                                   this requirement would discourage LID techniques
                                                    Minimize Effective   3708.1 and 2 require connection of drainage to either a street gutter or         The requirement to gain public works approval may
TMC Chapter 2.02.380      P: Minimize curb & gutter Imperviousness       storm sewer or infiltration with Public Works approval.                          discourage proposing LID techniques.

                                                                                                                                                      Curb and gutter concentrates surface flows,
                                                                                                                                                      increasing effective imperviousness. Where
                                                                                                                                                      possible, runoff should be dispersed to open areas,
                                                                         Street improvements, curb and gutter, sidewalk, and drainage for new         or diverted to infiltration facilities. Where infiltration
                                                                         developments are required according to the City of Tacoma Amendments to is not possible, runoff should be diverted to
                                                    Minimize Effective   the 2003 International Building Code (as provided in section 2.02.090 of the biofiltration areas for water quality treatment before
PWDS 1.030.A              P: Minimize curb & gutter Imperviousness       Tacoma Municipal Code) and the site-specific development conditions.         final disposal to the storm sewer system.

                                                                         All new construction other than Group R, Division 3, occupancies, shall
                                                                         install street improvements to minimum Public Works Department
                                                                         Standards and constructed in accordance with the Public Works
                                                                         Department Design Manual for the location, including, but not limited to,
                                                                         street paving, concrete curbs and gutters, storm drainage, utility elocation,
                                                                         and sidewalks on all lot frontages facing on dedicated street rights-of-way.
                                                                         When a lot adjoins an alley or street intersection, improvements shall also
                                                                         be installed at the alley or street intersection. Alleys shall be improved to
                                                    Minimize Effective   City of Tacoma standards when any access to the site is provided from the
PWDS 1.030.D 117.2        P: Minimize curb & gutter Imperviousness       alley.                                                                           see previous




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept          Description                                                                      Problem or Gap                                            Additional comment or question

                                                                         Construction of Group R, Division 3, occupancies shall require the
                                                                         development of cement concrete curb and gutter, paving, and drainage of
                                                                         all dedicated streets along the lot frontages, except, in cases where the
                                                    Minimize Effective   topography or other conditions make it impractical, the Building Official may
PWDS 1.030.D 117.3        P: Minimize curb & gutter Imperviousness       modify this street regulation.                                                see previous

                                                    Minimize Effective   Satisfactory surface drainage shall include, but not be limited to:
PWDS, 1.030.D 117.5.1     P: Minimize curb & gutter Imperviousness       Conveying all site drainage to the street gutter or storm sewer.                 see previous
                                                                         Samples of some of the requirements associated with developing new plats
                                                                         are as follows:
                                                    Minimize Effective   Concrete curb, gutter and sidewalk on all adjacent street frontages (asphalt
PWDS, 1.030.E             P: Minimize curb & gutter Imperviousness       wedge curb elsewhere).                                                        see previous
                                                                         Requirements for Short Plats/Private Accessways:
                                                                         ..."the minimum street section requirements for short plats
                                                                         and private accessways based on the number of lots being developed":
                                                    Minimize Effective   (from table): curb and gutter required on both sides for greater than 4 lots.
PWDS, 1.030.F             P: Minimize curb & gutter Imperviousness       Curb and gutter not required for 1 to 4 lots.                                 see previous
                                                                         J. Conditions of Approval of the Final Plat.
                                                                         2. Surfacing of all roadways, bike routes, and pedestrian ways with an all-
                                                                         weather surface approved by the City Engineer; this shall include the
                                                    Minimize Effective   construction of curbs and gutters of Portland cement concrete in
                          P: Minimize curb & gutter Imperviousness       accordance with the specifications of the City of Tacoma.                        see previous
                                                    Minimize Effective   “Frontage Improvements” – includes the construction of street, sidewalk,
PWDS, 1.040.R             P: Minimize curb & gutter Imperviousness       curb and gutter on all adjacent City of Tacoma right-of-way.                     see previous

                                                                         Typical Sections
                                                                         A typical roadway section shall be included on the plans for each unique
                                                                         cross section of roadway and/or at the beginning and end of a transition
                                                                         section. … The typical roadway section shall also include: the street section,
                                                                         the type and/or dimensions of the curb, the crossslope or a relationship from
                                                                         the crown to the gutter, the dimensions of sidewalk, the
                                                                         dimensions of the planter strip, the relationship to the top of the cut or the
                                                                         toe of the fill, the slope of the planter strip and sidewalk, and any other    Should add language saying that typical sections
                                                    Minimize Effective   existing or proposed improvements that reoccur and is paramount to the         will also include biofiltration/bioretention structures
PWDS, 3.060.A             P: Minimize curb & gutter Imperviousness       design.                                                                        for LID projects.

                                                                         For each cross section, the elevation and offset of the centerline and/or        Should add language saying that typical sections
                                                    Minimize Effective   crown, the meetline, both gutter lines, and the existing front of walks shall    will also include biofiltration/bioretention structures
PWDS, 3.060.B             P: Minimize curb & gutter Imperviousness       be identified where applicable.                                                  for LID projects.

                                                                         Temporary vs. Permanent Improvements
                                                                         The City generally classifies a permanent street section as consisting of
                                                    Minimize Effective   concrete curb and gutter and/or sidewalk in combination with a standard          Modify to allow street sections that include
PWDS, 4.020.A             P: Minimize curb & gutter Imperviousness       residential or arterial street section (as defined in this chapter).             biofiltration/bioretention practices for LID projects
                                                                         Curb and Gutter
                                                    Minimize Effective   City of Tacoma standard cement concrete curb and gutter shall be                 Should also allow biofiltration/bioretention practices
PWDS, 4.040.E             P: Minimize curb & gutter Imperviousness       constructed unless otherwise approved (Standard Plan No. SU-03).                 for LID projects.
                                                                                                                                                          Standard Details do not provide a curb cut option to
                                                    Minimize Effective                                                                                    allow drainage to surface flow behind
PWDS SU-03, SU-04         P: Minimize curb & gutter Imperviousness       Cement Concrete Curb and Gutter, Cement Concrete Sidewalk                        curb/sidewalk.



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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept          Description                                                                     Problem or Gap                                           Additional comment or question
                                                                         Asphalt Wedge Curb
                                                    Minimize Effective   In areas where curb and gutter is not required, all new asphalt pavement        Modify to include biofiltration/bioretention practices
PWDS, 4.040.F             P: Minimize curb & gutter Imperviousness       shall include an asphalt wedge curb.                                            for LID projects
                                                                         Alleys
                                                    Minimize Effective   The typical paved width of an alley in a residential area is 16 feet, with      Modify to include biofiltration/bioretention practices
PWDS, 4.050.C             P: Minimize curb & gutter Imperviousness       wedge curbs on both sides.                                                      for LID projects
                                                    Minimize Total
TMC Chapter 2.02.380      P: Pedestrain paths       Imperviousness       3707 - requires sidewalks for all new single family or two family dwellings.    requires additional impervious surfaces

                                                                         Dead Ends                                                                       Dead ends and cul-de-sacs should be discouraged
                                                                         In general, dead-end (cul-de-sac) streets shall not be longer than 500 feet.    for LID projects. Where cul-de-sacs are
                                                                         Any dead-end street in excess of 150 feet in length shall terminate in a        unavoidable and center islands are used, the
                                                                         turnaround with a minimum curb radius of 45 feet. A center island with a        center island should include a
                                                                         maximum width of 30 feet may be constructed within the cul-de-sac. Any          biofiltration/bioretention facility.
                                                                         dead-end street with four or fewer lots accessing the street may satisfy this   T-type branch turnarounds should be allowed as an
                          P: Loop Roads in          Minimize Total       requirement with the construction of a T-type or branch turnaround              acceptable LID design standard that is NOT        Refer to Standard Plan DR-06 Minimum
PWDS 4.060                preferance to cul-de-sacs Imperviousness       subject to approval by the City Engineer. (13.04.190 TMC)                       subject to special approval.                      Standard for Cul-de-sac

                                                                         Cul-de-Sacs
                                                                         Cul-de-sacs shall be constructed where a dead end street will serve five (5)
                                                                         or more residential lots.
                                                                         Cul-de-sacs shall be designed to meet the minimum requirements set forth       Dead ends and cul-de-sacs should be discouraged
                                                                         in the Public Works Standard Plan No. DR-06 as found on the govME              for LID projects. Where cul-de-sacs are
                                                                         website under document 8/2/2004 4-11 information, standard plans.              unavoidable and center islands are used, the
                          P: Loop Roads in          Minimize Total       The construction of an inner curb as shown on the standard                     center island should include a                            Should we attach a copy of the figure with
PWDS 4.060.B              preferance to cul-de-sacs Imperviousness       plan is an option, although not recommended.                                   biofiltration/bioretention facility.                      mark-ups in the initial submittal?
                                                                                                                                                        Permeable Pavement Sections and "Country Lane"
                                                    Minimize Total                                                                                      designs could be added as possible sections for
PWDS 4.050 C              P: Alley Access           Imperviousness       Alley Section identified                                                       alleys to reduce impervious cover.
                                                                                                                                                        Under what conditions should the alley be
                                                                                                                                                        increased beyond 20 feet? What is included in the         References in the PWDS for Alleys are given
                                                    Minimize Total       “A minimum width of an alley in a residential block, when platted, shall be 20 20 feet? Can this code be modified to include             above under Narrow Streets and Minmize Curb
13.04.200                 P: Alley Access           Imperviousness       feet.”                                                                         pervious paving for LID projects?                         and Gutter.
                                                                                                                                                        No minimum/maximum driveway width standards
                                                                                                                                                        are given in the PWDS. No mention of shared
                                                                         Requirements for Short Plats/Private Accessways                                driveways (except in the case of private access
                                                                         ..."the minimum street section requirements for short plats                    roads). These issues may be covered in Title 10 or        This reference is really the only one given in
                                                                         and private accessways based on the number of lots being developed":           13 (if not, they should be).                              the PWDS for driveways that is relevant to
                                                    Minimize Total       (from table): Cement/Concrete driveway required at entrance to all private     There should also be mention of pervious paving           driveway width, length, or paving material.
PWDS 1.030.F              P: Driveways              Imperviousness       access and all residential lots                                                for driveways                                             Obviously the requirements are minimal.
                                                    Minimize Total       "Driveway width non single family residence 28' min. to 40' max. Driveway This standard driveway plan does not allow for
PWDS SU-07                P: Driveways              Imperviousness       width for single family residence/duplex 14' min to 30' max."                  smaller driveways.
                                                                                                                                                        There have been instances where the driveway
                                                    Minimize Total       "All driveways shall be in conformance with the Tacoma Municipal Code,         ordinance has not been enforced because it would
PWDS 4.050.A              P: Driveways              Imperviousness       Chapter 10.14 – Driveways."                                                    make specific projects unfeasible.
                                                                         "All driveways for other than single-family residences and duplexes shall be
                                                                         a minimum of 20 feet in width, exclusive of the radii of the returns, the
                                                                         measurement being made parallel to the center line of the street. The radius
                                                                         of all driveway returns shall be a minimum of 10 feet, except on nonarterial These minimum standards conflict with the Public
                                                    Minimize Total       streets for single-family residences or duplexes, which shall have a           Works Design Manual standard design SU-07 and
10.14.050.B.4             P: Driveways              Imperviousness       minimum radius of five feet."                                                  may not be flexible enough for LID projects




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                          LID Principle (P:) or
Code Reference            BMP:                       LID Concept                Description                                                              Problem or Gap                                         Additional comment or question
                                                                                                                                                         This standard conflicts with the PW Design
                                                     Minimize Total             "The maximum driveway width shall be 25 feet on designated pedestrian    Manual, SU-07 design. However, a maximum
13.06.510                 P: Driveways               Imperviousness             streets and 30 feet on all other streets."                               standard is desirable in a LID ordinance

                                                                                                                                                         This code should be modified to include
                                                                                                                                                         appropriate design standards for LID projects.
                                                                                “Parking facilities should be designed to contribute to an attractive    Aprpropriate standards include pervious paving,
                                                     Minimize Total and         appearance of the streetscape and to provide customers with convenient   bioretention areas, and covered parking that may
TCP DD-2                  P: Parking                 Effective Imperviousness   access to the building.”                                                 also include vegetated roofs or rainfall harvesting
                                                                                Approval factors
                                                                                In determining whether an application made for
                                                                                classification under Chapter 84.34 RCW should be
                                                                                approved or disapproved, cognizance may be taken
                                                                                of the benefits to the general welfare of preserving
                                                                                the current use which is the subject of application,
                                                                                and consideration may be given as to whether or not                      While this code applies to critical areas, a similar
                                                                                preservation of current use of the land will (a)...                      requirement with respect to vegetation and soils
                                                                                 (b) protect streams or water supplies; (c) promote                      above a set threshold infiltration capacity would go
                                                                                conservation of soils, wetlands, beaches or tidal                        far to support an LID ordinance or to establish
13.08.040                 P: Vegetation Protection   Runoff minimization        marshes...                                                               criteria for projects that are classified as "LID".
                                                                                Scope and applicability
                                                                                A. The provisions of this chapter apply to all lands,
                                                                                all land uses and development activities, and all
                                                                                structures and facilities in the City, whether or not a
                                                                                permit or authorization is required, and shall apply to
                                                                                every person, firm, partnership, corporation, group,
                                                                                governmental agency, or other entity that owns,
                                                                                leases, or administers land within the City. This
                                                                                chapter specifically applies to any activity which
                                                                                would destroy the natural vegetation; result in a
                                                                                significant change in critical habitat, water
                                                                                temperature, physical, or chemical characteristics; or
                                                                                alter natural contours and/or substantially alter
                                                                                existing patterns of tidal, sediment, or storm water
                                                                                flow on any land which meets the classification
                                                                                standards for any critical area defined herein. Such
                                                                                activities include excavation, grading, filling, the
                                                                                removal of vegetation, and the construction, exterior
                                                                                alteration, or enlargement of any building or                            This code applies only to critical areas. A similar
                                                                                structure. In addition, this chapter applies to all                      requirement with respect to vegetation and soils
                                                                                public or private actions, permits, and approvals in or                  above a set threshold infiltration capacity would go
                                                                                adjacent to a critical area and its buffer, including,                   far to support an LID ordinance or to establish
13.11.130                 P: Vegetation Protection   Runoff minimization        but not limited to, the following                                        criteria for projects that are classified as "LID".




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                          LID Principle (P:) or
Code Reference            BMP:                       LID Concept                 Description                                                                     Problem or Gap                                           Additional comment or question
                                                                                 Regulated uses/activities
                                                                                 Pursuant to the requirements of this chapter, a permit
                                                                                 shall be obtained prior to undertaking any of the
                                                                                 following activities within a wetland, stream or
                                                                                 adjacent associated buffer:
                                                                                 A. Filling, placing, or dumping any soil, loam, peat,
                                                                                 sand, gravel, rock, chemical substance, refuse, trash,
                                                                                 rubbish, debris, or dredge material;
                                                                                 B. Excavating, dredging, or clearing any soil, loam,
                                                                                 peat, sand, gravel, rock, vegetation, trees, or mineral
                                                                                 substance;
                                                                                 F. Destroying or altering vegetation through
                                                                                 clearing, harvesting, shading, pruning, or planting
                                                                                 vegetation that would alter the character of the site;
                                                                                 and
                                                                                 G. Any act or use which would destroy natural
                                                                                 vegetation; result in significant change in water level,                        Similar requirements might be considered for a LID
                                                                                 water temperature, physical, or chemical                                        standard. Obviously the code at leftattempts to
                                                                                 characteristics of the wetland or stream; substantially                         eliminate ANY changes in critical areas. Some
                                                                                 alter the existing pattern of tidal flow, obstruct the                          changes to vegetation and soils are generally
                                                                                 flow of sediment, or alter the natural contours of a                            necessary in LID projects, but reasonable
                                                                                 site. (Ord. 27431 § 24; passed Nov. 15, 2005:                                   limitations can be defined that reflect the principles
13.11.220                 P: Vegetation Protection   Runoff minimization         Ord. 27294 § 2; passed Nov. 16, 2004)                                           of this code.
                                                     Runoff quality and volume                                                                                   Does not address how LID techniques can used to
SWMM Volume I, 3.5.6      LID BMPs Overall           control                     Water Quality Minimum Requirements                                              address this minimum requirement.

                                                                                                                                                                This discourages the use of LID techniques such
                                                                                                                                                                as permeable paving options. Boundary should be
                                                                                                                                                                reviewed. Appropriateness of soil quality for water
                                                                                                                                                                quality treatment should also be reviewed and
                                                     Runoff quality and volume   South Tacoma Ground Water Protection District - prohibits infiltration in this should consider whether soil amendments would
SWMM Volume 1, 2.6.1.3    LID BMPs Overall           control                     area without City pre-approval                                                 improve soil quality sufficiently.
                                                                                                                                                                This section also identifies that infiltration requires
                                                     Runoff quality and volume                                                                                  pre-approval. This section should encourage the
SWMM Volume 1, 5.2        LID BMPs Overall           control                     BMP and Facility Selection Process                                             use of LID BMP's
SWMM Volume 1, Table                                 Runoff quality and volume
5.1                       LID BMPs Overall           control                     Provides Suggested Stormwater Treatment Options                                 Section does not identify LID BMP's
                                                                                 Satisfactory surface drainage shall include, but not be limited to:
                                                                                 Conveying all site drainage to an approved engineered infiltration system.
                                                                                 Infiltration systems are only allowed when City storm sewers are not
                                                  Runoff quality and volume      available. Infiltration systems shall be designed per Public Works              "approved engineered infiltration system" should
PWDS, 1.030.D 117.5.2     BMP: Bioretention Areas control                        Department standards                                                            include bioretention systems.
                                                                                 Satisfactory surface drainage shall include, but not be limited to:
                                                                                 Conveying all site drainage to an existing acceptable drainage course. The
                                                  Runoff quality and volume      City of Tacoma requires prior approval to direct site drainage to drainage      "acceptable drainage course" should include
PWDS, 1.030.D 117.5.3     BMP: Bioretention Areas control                        courses.                                                                        biofiltration swale systems.
                                                  Runoff quality and volume
PWDS DR-04, DR-05         BMP: Bioretention Areas control                        Typical Street Right of Way Details                                             Sections do not promote open drainage options.




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept                 Description                                                                   Problem or Gap                                     Additional comment or question

                                                                                "Low-impact uses and activities consistent with the stream or wetland buffer
                                                                                function may be permitted within a buffer that has not been reduced
                                                                                depending upon the sensitivity of wetland and intensity of activity or use.
                                                                                These may include pedestrian trails, viewing platforms, utility easements
                                                  Runoff quality and volume     and storm water management facilities such as grass-lined swales that are
13.11.340.B               BMP: Bioretention Areas control                       used to sustain existing hydrologic functions of the critical area."         This code supports LID very well

                                                                                Minimum Requirement #5: On-Site Stormwater Management                         Where roof runoff dispersal is impractical, the
                                                                                Where infiltration or dispersion is not feasible because of very              water should be captured (and stored if necessary)
                                                                                small lot size (<8,000 square feet), impermeable soils, or where              for other uses such as landscape irrigation or toilet
                                                                                there is a potential for creating drainage problems on adjacent               flushing.
                                                                                lots, downspouts shall be connected to the City storm system.                 Roof runoff from pollutant generating impervious
                          BMP: Disperse Roof        Runoff quality and volume   If the storm system is not directly adjacent to the property, the             surfaces (e.g. roofs with unisolated HVAC systems)
SWMM Volume 1 3.5.5       Runoff                    control                     system shall be extended at the proponent’s expense.                          should be directed to a biofiltration system.
                                                                                                                                                              No slope requirements are mentioned. Dispersing
                                                                                Sidewalks                                                                     sidewalk runoff to open areas or                      Modify standard plan drawing SU-04, Cement
                          BMP: Reverse Slope        Runoff flow and volume      The standard sidewalk measures five (5) feet from front of walk to back of    biofiltration/bioretention areas, as opposed to       Concrete Sidewalk to include reverse slope
PWDS, 4.070.A             Sidewalks                 control                     walk                                                                          gutters, is the LID-preferred approach.               (and pervious surfacing).
                                                                                Requirements for Short Plats/Private Accessways:
                                                                                ..."the minimum street section requirements for short plats
                                                    Runoff quality and volume   and private accessways based on the number of lots being developed":          Pervious paving options should be encouraged for
PWDS, 1.030.F             BMP: Permeable Paving     control                     (from table): Cement concrete driveways and sidewalks are required            LID projects.
                                                                                J. Conditions of Approval of the Final Plat:
                                                    Runoff quality and volume   2. Surfacing of all roadways, bike routes, and pedestrian ways with an all-   "all-weather surface" should explicitly include
PWDS, 1.030.F             BMP: Permeable Paving     control                     weather surface approved by the City Engineer                                 pervious paving options
                                                    Runoff quality and volume
PWDS 4.040 D              BMP: Permeable Paving     control                     Pavement Sections                                                             Permeable Pavement Sections are not addressed.
                                                                                Driveways                                                                                                                      Modify standard plan drawing SU-07, Cement
                                                    Runoff quality and volume   Type I and type II concrete driveways are to be constructed where concrete    Pervious paving options should be encouraged for Concrete Approach Type I to include pervious
PWDS, 4.050.A             BMP: Permeable Paving     control                     curb and gutter is proposed or existing                                       LID projects.                                    paving.
                                                                                Private Access Ways (Serving up to 4 Lots)
                                                                                Type I or II concrete driveway provided where the private access way enters
                                                    Runoff quality and volume   onto public right-of-way where permanent concrete curb and gutter is          Pervious paving options should be encouraged for
PWDS, 4.050.B             BMP: Permeable Paving     control                     existing or proposed.                                                         LID projects.
                                                    Runoff quality and volume   Alleys                                                                        Pervious paving options should be considered for
PWDS, 4.050.C             BMP: Permeable Paving     control                     The typical paved width of an alley in a residential area is 16 feet…         LID projects.

                                                                                Requirements for Maintenance Access Easements
                                                                                At a minimum, accessways shall be surfaced with six (6) inches of crushed
                                                    Runoff quality and volume   rock, a minimum of 12 feet in width, or other approved all weather surface,   Pervious paving options should be encouraged for
PWDS, 9.050.C             BMP: Permeable Paving     control                     to allow year round equipment access to the conveyance facility.              LID projects.
                                                                                                                                                              Pervious Paving Options and how they are
                                                    Runoff quality and volume                                                                                 included in threshold determinations should be
SWDM Volume 1, 3.3        BMP: Permeable Paving     control                     Definitions                                                                   defined.
SWDM, Volume 1, 3.4.1                               Runoff quality and volume   New Development and Redevelopment Applicability of the minimum                Reference to how pervious paving options are
and 3.4.2                 BMP: Permeable Paving     control                     requirements.                                                                 considered in the thresholds.




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept                Description                                                                      Problem or Gap                                         Additional comment or question

                                                                               Roofs                                                                            Current code does not preclude use of vegetated
                                                                               Roof structures shall be structurally sound and free of deteriorated or rotted   roofs, but it does not explicitly include them as an
                                                                               materials. Roofing shall be weather tight and provide protection to the          acceptable roofing practice. Code revisions that
                                                    Runoff quality, flow and   interior of the building from outside elements. Roof drainage shall be           explicitly include vegetated roofs would better
2.01.070.F                BMP: Vegetated Roofs      volume control             directed to approved locations. Roofs shall be maintained in good repair.        support the LID appraoch.
                                                                               Repair Standards - Roofs
                                                                               Roof structures shall be structurally sound. Roofing                             See entry above.
                                                                               shall be weather tight and provide protection to the                             Additionally, 'approved drainage locations' COULD
                                                    Runoff quality, flow and   interior of the building from outside elements. Roof                             include LID BMPs such as rain gardens and rain
2.01.080.E                BMP: Vegetated Roofs      volume control             drainage shall be directed to approved locations.                                barrels or cisterns
                                                                               Amendment to IBC Section 1503.4 - Roof Drainage
                                                                               1503.4.1. General. Roofs shall be sloped a
                                                                               minimum of one unit vertical in 48 units horizontal
                                                                               (2 percent slope) for drainage, unless designed for
                                                                               water accumulation in accordance with Chapter 16
                                                                               and approved by the Building Official.
                                                                               1503.4.2. Roof drains. Unless roofs are sloped to
                                                                               drain over roof edges, roof drains shall be installed at
                                                                               each low point of the roof.
                                                                               Roof drains shall be sized and discharged in
                                                                               accordance with the Plumbing Code.
                                                                               1503.4.3. Overflow drains and scuppers. Where
                                                                               roof drains are required, overflow drains having the
                                                                               same size as the roof drains shall be installed with the
                                                                               inlet flow line located two inches above the low point
                                                                               of the roof, or overflow scuppers having three times
                                                                               the size of the roof drains and having a minimum
                                                                               opening height of four inches may be installed in
                                                                               adjacent parapet walls with the inlet flow line located
                                                                               not more than two inches above the low point of the
                                                                               adjacent roof.
                                                                               Overflow drains shall discharge to an approved
                                                                               location and shall discharge at a point above the
                                                                               ground which can be readily observed. Overflow
                                                                               drains shall not be connected to roof drain lines.
                                                                               1503.4.4. Concealed piping. Roof drains and
                                                                               overflow drains, where concealed within the                                      These codes may need revision if language
                                                    Runoff quality, flow and   construction of the building, shall be installed in                              addressing vegetated roofs is added to other
2.02.180                  BMP: Vegetated Roofs      volume control             accordance with the Plumbing Code.                                               section of the Tacoma code.




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept                Description                                                                 Problem or Gap                                          Additional comment or question
                                                                               Amendment to IBC Section 1608 – Snow Loads
                                                                               1608. Roofs shall be designed for a snow load of
                                                                               25 pounds per square foot, except that if the live load
                                                                               determined by Section 1607 is greater than the snow
                                                                               load, then the live load shall be the roof design load.
                                                                               Potential unbalanced accumulation of snow at
                                                                               valleys, parapets, roof structures, and offsets in roofs
                                                                               of uneven configuration shall be considered.
                                                                               The extra load caused by snow sliding off a sloped
                                                                               roof onto a lower roof shall be determined in
                                                                               accordance with Section 7.9 of ASCE 7-02.
                                                                               The 25-pound-per-square-foot snow load may be
                                                                               reduced by 0.125 pounds per square foot for each                            A similar specification should be added to the code
                                                                               degree of roof pitch over 20 degrees. (Repealed and                         if vegetated roofs are adopted by the code.
                                                                               reenacted by Ord. 27231 § 1; passed May 4, 2004:                            Extensive roofs generally require an additional 15-
                                                                               Ord. 26310 § 1; passed Oct. 27, 1998: Ord. 25825                            40 lbs/sq ft load capacity. Intensive roofs require
                                                                               § 1; passed Jan. 23, 1996: Ord. 25149 § 1; passed                           around 150- 200-lbs/sq ft, depending on planned
2.02.190                                                                       Jul. 21, 1992)                                                              use activities and landscaping.

                                                                               Reroofing of single family or duplex residential                            Vegetated roofs also need periodic maintenance.
                                                                               buildings, provided the existing roof is removed prior                      Whether or not permits should be required and in
                                                    Runoff quality, flow and   to reroofing and that the new roofing material does                         what circumstances needs to be considered if
2.02.030.2                BMP: Vegetated Roofs      volume control             not exceed five (5) pounds per square foot.                                 vegetated roof codes are adopted.
                                                                                                                                                           Climatic and geographic design criteria are also
                                                                                                                                                           applicable to vegetated roof design. Consideration
                                                                               Amendment to IRC Table R301.2(1) – Climatic and geographic design           should be given to including a similar table for
                                                    Runoff quality, flow and   criteria.                                                                   vegetated roof design if vegeated roof codes are   The table listed at left needs to be added as an
2.02.330                  BMP: Vegetated Roofs      volume control             TABLE R301.2(1)                                                             adopted.                                           attachment to this Gap Analysis table
                                                                               Amendment to IEBC Section A113.9 – Secondary load paths.
                                                                               EB Sec. A113.9. Secondary Load Paths. Primary or secondary framing
                                                                               supported by unreinforced masonry bearing walls or columns shall be
                                                                               provided with an independent secondary vertical load path constructed to
                                                                               support all dead and live loads. A full snow load on the roof need not be
                                                    Runoff quality, flow and   included, but a minimum ten pounds per-square-foot live load shall          This section may need revision if vegetated roof
2.02.440                  BMP: Vegetated Roofs      volume control             be assumed for the roof.                                                    codes are adopted
                                                                               Application for permit - Alley Occupancies
                                                                               d. Such structure shall be designed for a uniform live
                                                    Runoff quality, flow and   roof load of 30 pounds per square foot and a wind                           Not certain if this code is applicable to a vegetated
2.03.030                  BMP: Vegetated Roofs      volume control             load of 30 pounds per square foot.                                          roof situation. If it is, then it should be modified.




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept            Description                                                                     Problem or Gap                                           Additional comment or question
                                                                           Minimum building requirements - Foundations
                                                                           Building foundation systems shall adequately support
                                                                           the building. Those parts of the system constructed of
                                                                           wood shall be free from deterioration or dry rot.
                                                                           Concrete and masonry elements shall be integral
                                                                           without substantial fracturing or cracks.
                                                                           Exterior walls shall be supported on a continuous
                                                                           concrete or masonry foundation, or an
                                                                           engineer-designed foundation system, which
                                                                           accounts for both vertical and lateral (earthquake and
                                                                           wind) loads, shall be provided. In absence of a
                                                                           continuous masonry or concrete foundation, an
                                                                           approved skirting system shall be provided to prevent                           Current code does not preclude use of pin
                                                                           the entrance of rodents and other animals to the crawl                          foundations, but it does not explicitly include them
                          BMP: Minimal Excavation                          space or under-floor area of the building.                                      as an acceptable building practice. Code revisions
                          Foundations             Runoff flow and volume   The building shall be anchored to the foundation                                that explicitly pin foundations would better support
2.01.070.B                (aka 'pin foundations') control                  system in an approved manner.                                                   the LID approach.
                                                                           Building Permit Fees - Foudations
                                                                           Foundation permits, while being necessary in a few instances, are normally
                                                                           to be discouraged. In such cases where it is judged to
                                                                           be necessary by the Building Official, a foundation permit fee shall be
                                                                           charged to cover additional City administrative costs, and said fee shall not
                                                                           be credited as part of the building permit fee. The foundation permit fee
                                                                           shall be 10 percent of the building permit fee where the building permit fee
                                                                           is $7,618.86 or less. Where the building permit fee is over $7,618.86, the
                          BMP: Minimal Excavation                          foundation permit fee shall be $761.89 plus 5 percent of the building permit
                          Foundations             Runoff flow and volume   fee over and above $7,618.86, but in no instance shall it be less than          If pin foundations are adopted into code, it will have
2.09.050.C                (aka 'pin foundations') control                  $187.93.                                                                        to be decided if foundation permits are necessary.
                                                                           Specific standards for flood hazard protection.
                                                                           In the instance of elevation on pilings, lots are                               While this code pertains to flood protection, pin
                                                                           large enough to permit steps, piling foundations are                            foundations are also sometimes considered 'piling'
                          BMP: Minimal Excavation                          placed in stable soil no more than ten feet apart, and                          foundations. With modification, this code may be
                          Foundations             Runoff flow and volume   reinforcement is provided for pilings more than six                             applicable to pin foundations
2.12.050.3.4.b.4          (aka 'pin foundations') control                  feet above the ground level.




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept   Description   Problem or Gap   Additional comment or question




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept   Description   Problem or Gap   Additional comment or question




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept   Description   Problem or Gap   Additional comment or question




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                          LID Principle (P:) or
Code Reference            BMP:                      LID Concept   Description   Problem or Gap   Additional comment or question




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                                           Suggested keyword                        LID Concept                           Regulation Type                                    Who Reviews for Gaps & What
LID Principles
Site Assessment:
Soil Analysis                              soil, infiltration                       Maximize site infiltration capacity   SW 1 Manual, Critical Areas Ordinance    AN - Critical Areas   EL - SW Man.
                                           hydrology, hydrologic, hydraulic,
Hydrologic Analysis (modeling)             modeling                                 Runoff Minimization                   SW Manual                                                                           DG, DN?
Establish Soil Conservation Areas
(infiltrative soils)                       soil, infiltration, infiltrative         Runoff Minimization                   SW Manual                                                      EL?                  DG, DN?
Establish Other Conservation Areas
(Forest, Wetlands, Riparian,               critical areas, and others shown in
Floodplains)                               parentheses at left                      Runoff Minimization                   Critical Areas zoning codes              AN
Site Planning and Layout:
Cluster Development                        development, site plan,                  Minimize Total Imperviousness         Zoning & subdivision codes               AN
Narrow Streets                             streets                                  Minimize Total Imperviousness         Zoning, subdivision codes, PWDS2         AN - codes            EL - PWDS
Minimize Curb & Gutter                     gutter                                   Minimize Effective Imperviousness     PWDS                                                           EL - PWDS
                                           sidewalks, pathways, walkways,
Pedestrain paths                           walks, paths                             Minimize Total Imperviousness         Zoning & subdivision codes               AN
Loop Roads over cul-de-sacs                road, cul-de-sacs, road network          Minimize Total Imperviousness         Zoning, subdivision codes, PWDS          AN - codes            EL - PWDS
Alley Access                               alley                                    Minimize Total Imperviousness         Zoning, subdivision codes, PWDS          AN - codes            EL - PWDS
Short Driveways                            driveway                                 Minimize Total Imperviousness         Zoning, subdivision codes, PWDS          AN - codes            EL - PWDS
Shared Driveways                           driveway                                 Minimize Total Imperviousness         Zoning, subdivision codes, PWDS          AN - codes            EL - PWDS
Vegetation Protection:
ID and protect important tree and
native vegetation stands from root
damage, soil compaction, stockpiling in    vegetation, trees, vegetation protection,                                      Critical Areas Ordinance, Fill & Grade
root zone                                  tree protection                           Runoff Minimization                  Ordinance                                AN - critical areas   EL - Fill & Grade?
Attempt to keep existing vegetation        vegetation, trees, vegetation protection,
interconnected                             tree protection                           Runoff Minimization                  Critical Areas Ordinance                 AN
Restore/Enhance existing vegetation        vegetation, trees, restoration,
areas                                      enhancement                               Runoff Minimization                  Critical Areas Ordinance                 AN

BMPs
Construction Phase:
Write a site construction plan             plan                                     Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Limit clearing, grading, construction
to dry season (summer into fall)           season                                   Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Fence vegetation and soils that are to
be protected from construction             fence, fencing, protection               Runoff Reduction                      SW Manual, Fill & Grade Ordinance

Designate stockpile areas and establish
them away from protection areas            stockpile                                Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Phase construction to limit acitivities
that can damage vegetation and soil,
this includes phasing clearing and
grading activities                         phase                                    Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Establish erosion and sediment
controls just before or immediately
after clearing and grading begins          control                                  Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Stockpile and reuse excavated soils        stockpile                                Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Cover or seed stockpiled soils to
prevent erosion                            stockpile, erosion                       Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Inspect barriers and structural controls
prior to construction                      inspect, inspections, enforcement        Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Routinely inspect and maintain controls.
Modify controls to meet changing site      inspect, inspections, maintenance,
conditions                                 enforcement                              Runoff Reduction                      SW Manual, Fill & Grade Ordinance
Perform post-construction inspection to
verify re-vegetated areas are stabilized
and stormwater management systems inspect, inspections, maintenance,
are working properly                     enforcement                         Runoff Minimization                       SW Manual, Fill & Grade Ordinance

Long-Term:
LID BMPs in general                                                          Runoff quality and volume control         SW Manual, PWDS
Bioretention Areas                  drainage                                 Runoff quality and volume control         SW Manual, PWDS                                       EL
Disperse roof run-off               drainage, dispersion                     Runoff quality and volume control         SW Manual                                             EL
Reverse slope sidewalks             slope, sidewalks                         Runoff flow and volume control            PWDS                                                  EL
Site soil amendments                soil, soil amendment                     Runoff quality and volume control         SW Manual, PWDS                                       EL
                                    paving, concrete, asphalt, all weather
Permeable paving                    surface                                  Runoff quality and volume control         SW Manual, PWDS                                        EL
Vegetated Roofs                     ????                                     Runoff quality, flow and volume control   Building Code, SW Manual(?)         AN - Building Code EL - SW Manual
Minimal excavation foundations      ????                                     Runoff flow and volume control            Building Code, SW Manual(?)         AN - Building Code EL - SW Manual
Rainfall harvesting                                                          Runoff flow and volume control            SW Manual                                              EL

1. SW = Stormwater
2. Public Works Design Standards

				
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